Dr Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the Journal and its editors. We're your cohosts. I'm Dr Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.
Dr Greg Hundley: I'm Greg Hundley, Associate Editor of Circulation, Director of the Pauley Heart Center at VCU Health in Richmond, Virginia.
Dr Carolyn Lam: Greg, guess what? We are going to be talking later about non-inferiority trials. Now, you're going to go like, "Huh? What?," but then we see more and more non-inferiority cardiovascular trials. And do we really know the advantages and limitations of this type of trial design? Which is so important to understand, because we need to understand the factors that may impact our confidence and interpretation of these results. So, that's going to be a really important feature discussion, coming up right after our coffee chat. Greg, what are your papers?
Dr Greg Hundley: Thanks Carolyn. Boy, I can't really wait to get to that feature discussion. That's something that we deal with all the time, and I look forward to that explanation and that discussion. I'm going to talk a little bit of basic science, with two papers right in a row.
And the first one involves catecholaminergic polymorphic ventricular tachycardia through inhibition of calcium/calmodulin-dependent kinase II. The lead author is Dr Vassilios Bezzerides from Boston Children's Hospital.
Carolyn, this paper focuses on treatment of catecholaminergic polymorphic ventricular tachycardia, an underlying diagnosis in at least 12% of pediatric patients who present with unheralded cardiac arrest. ICDs, as you know, are frequently implanted, but are problematic because of increased complication rates in pediatric patients, failure to convert ventricular arrhythmias, and the risk of fatal ICD-induced electrical storm. Modulating CaM Kinase II within the heart shows promise to treat this, but CaM Kinase II is essential in other tissues, most notably the brain.
Dr Carolyn Lam: How interesting. So, what did the study show?
Dr Greg Hundley: Well, the investigator used adeno-associated viral gene therapy, which is proven to be a safe and efficient vector for sustained gene transfer into many cell types to selectively inhibit CaM Kinase II in cardiomyocytes. They were able to express the specific CaM kinase II inhibitory peptide AIP in cardiomyocytes without significant extra cardiac expression, and an inhibition of CaM Kinase II effectively suppressed ventricular arrhythmias in a murine model of catecholaminergic polymorphic ventricular tachycardia after a single therapeutic dose. So thus, in animal models, delivery of a CaM Kinase inhibitory peptide by AAV represents a novel single dose gene therapy for catecholaminergic polymorphic ventricular tachycardia. How about that?
Dr Carolyn Lam: Wow. You've got a second paper?
Dr Greg Hundley: I sure do. So now we're going to jump into, again, looking at polymorphic VT from engineered human heart tissue. And this article is from Kevin Parker at Harvard University, "Modeling of Human Arrhythmias Using Induced Pluripotent Stem Cell-Derived Cardiomyocytes has Focused on Single-Cell Phenotypes."
With this said, it is important to realize that arrhythmias are emergent properties of cells assembled into tissues and the impact of inherited Arrhythmia mutations on tissue level properties of human heart tissue. And therefore, newer technologies are needed to develop more satisfactory therapeutic interventions. Ones that encompass all of the tissue, not just single cells.
Dr Carolyn Lam: Interesting. So, what did this particular study do?
Dr Greg Hundley: So, Carolyn, in this study, the investigators report on an optogenetically-based human-engineered tissue model of catecholaminergic polymorphic VT, which as we have discussed in the previous article is promoted by mutation of the cardiac ryanodine channel 2, which is promoted by mutation of cardiac ryanodine channel and triggered by exercise. They developed a human IPSC cardiomyocyte-based platform to study the tissue level properties and investigated pathogenic mechanisms in polymorphic VT by combining this novel platform with genome editing. The authors found that engineered heart tissue, fabricated from human pluripotent stem cell derived cardiomyocytes, effectively modeled catecholaminergic polymorphic VT caused by dominant mutations in the cardiac ryanodine receptor, including induction of arrhythmias by conditions that stimulate exercise. Using selective pharmacology and genome editing, the authors identified activation of calcium/calmodulin-dependent kinase II, or CaM Kinase II, and CaM Kinase II mediated phosphorylation of ryanodine at Serine 2814 as critical events that are required to unmask the latent arrhythmic potential of catecholaminergic polymorphic VT, causing ryanodine mutations, highlighting a molecular pathway that links beta adrenergic stimulation to arrhythmogenesis in this disease.
Dr Carolyn Lam: Wow Greg! So, two very interesting and important linked genetic papers. Well, we're going to switch tracks a little bit and talk about, well, my favorite topic: heart failure with preserved ejection fraction and the whole complex issue of the diagnosis of this syndrome. Now we know that the diagnosis is kind of complex and there is currently no consensus but several proposed definitions. So how do the clinical and hemodynamic profile of patients vary across the different definitions of HFpEF?
So, this question was answered by Dr Jennifer Ho from Massachusetts General Hospital and her colleagues, who examined consecutive patients with chronic exertional dyspnea and an ejection fraction above 50% who are referred for comprehensive cardiopulmonary exercise testing with invasive hemodynamic monitoring. They applied societal and clinical trial HFpEF definitions and compared the clinical profiles, exercise responses, and cardiovascular outcomes by these different definitions. So, of 461 patients, 416 met the ACC/AHA definition, 205 met the ESC definition, and 55 met the HFSA criteria for HFpEF.
The clinical profiles and exercise capacity varied vastly across the definitions, with peak oxygen uptake averaging 16.2 for those with the ACC/AHA definition and down to 12.7 in those satisfying the HFSA definition.
Dr Greg Hundley: Wow. What a difference from these societies.
Dr Carolyn Lam: Mm-hmm (affirmative).
Dr Greg Hundley: So Caroline, it sounds like they looked at all comers with exertional dyspnea. Now how about those that had hemodynamic evidence of heart failure with preserved ejection fraction?
Dr Carolyn Lam: Yeah, good question Greg. So, you caught me telling you that all these patients had hemodynamic cats as well, and a total of 243 had hemodynamic evidence of HFpEF, which was defined as an abnormal rest or exercise feeling pressure. Of these, 222 met the ACC/AHA criteria, 161 met the ESC criteria, and only 41 met the HFSA criteria. Over a mean follow-up of 3.8 years, the incidents of cardiovascular outcomes range from 75 for the ACC/AHA criteria to 298 events per thousand-person years for the HFSA criteria.
The application of clinical trial definitions of HFpEF similarly resulted in distinct patient classification and prognostication. So in summary, the authors demonstrated significant diversity in the number of patients meeting HFpEF criteria. And using different HFpEF classifications variably enriched for future cardiovascular events, but at the expense of not including up to 85% of individuals with physiologic evidence of HFpEF. Comprehensive phenotyping of patients with suspected heart failure really highlighted the limitations and heterogeneity of current HFpEF definitions and may help to refine HFpEF sub-grouping to test therapeutic interventions. Now, these are all discussed in an important accompanying editorial by Michele Senni, Sergio Caravita, and Walter Paulus.
Dr Greg Hundley: Wow Carolyn. It appears, depending upon the definition, we could really classify patients drastically differently.
Dr Carolyn Lam: Yeah, an important paper indeed. And again, I would strongly encourage everyone to read that editorial as well. For my second pick, we're going to switch to CPR in children.
So these authors, now led by Dr Rohan Khera from UT Southwestern, examined the prevalence and predictors of survival of children who progress from bradycardia to pulselessness in in-hospital cardiac arrest despite cardiopulmonary resuscitation. So they looked at almost 5,600 pediatric patients age more than 30 days to under 18 years of age, who received CPR at hospitals participating in the Get With The Guidelines - Resuscitation during 2000 to 2016 each CPR event was classified as bradycardia with pulse, bradycardia with subsequent pulselessness, and initial pulseless cardiac arrest. And the authors assessed for risk adjusted rates of survival to hospital discharge.
Dr Greg Hundley: So Carolyn, what did they find? This is really interesting.
Dr Carolyn Lam: Well, among hospitalized children in whom CPR was initiated, half had bradycardia with poor perfusion at the initiation of chest compressions and nearly one third of these progressed to pulseless in-hospital cardiac arrest despite CPR. Survival was significantly lower for children who progressed to pulselessness despite CPR compared to those who were initially pulseless. So, these findings suggest that pediatric patients who lose their pulse despite CPR are at particularly high risk and require a renewed focus on post resuscitation care.
Dr Greg Hundley: Very interesting, Carolyn.
Dr Carolyn Lam: Well, that wraps it up for our discussion. Let's go onto the featured discussion. Shall we, Greg?
Dr Greg Hundley: You bet.
Dr Carolyn Lam: Non-inferiority cardiovascular trials are increasingly being published and in the highest impact journals. Yet how much do we really know about these designs of the trial, of the non-inferiority trials? Well, I have to admit not much in my point of view, and I was so pleased to see our feature discussion paper really published in this week's journal, which really digs deep into non-inferiority trials and talks about time trends and perhaps some lessons that we should all bear in mind when we look at these. I'm so pleased to have the first author, Dr Behnood Bikdeli, to tell us about the study. And he is from Columbia University Medical Center, New York Presbyterian Hospital, Yale Center of Outcomes, Research and Evaluation Core, as well as the Cardiovascular Research Foundation in New York. We also have Dr Naveed Sattar, associate editor from the University of Glasgow. Behnood, could you tell us, so what made you look at this question and what did you find?
Dr Behnood Bikdeli: For a while we've been very interested in profiling the cardiovascular trials, trying to understand a little better, what are the specific characteristics of the major child that we rely upon for research but also for clinical practice? Years ago, we did some studies for surrogate outcome trials and this, let's just say subsequent piece, where we tried to look into a randomized cardiovascular trial that use a non-inferiority design. We had a series of features in terms of quality metrics and methodological metrics that we wanted to look into. The over eight almost 27-year period, we identified 111 of these trials. Reassuringly, most of these trials inherited several important quality and methodological metrics that we were looking into. However, we also saw a significant room for improvement. There were quite a few quality or methodological metrics that some of these trials were not adhering to and we think it's important because ultimately for the design reporting and last reading of these trials, knowing these pluses and minuses would help inform people.
Dr Carolyn Lam: That's great, Behnood. Now for those of us listening who don't think about this every day, could you give us some examples of the top errors perhaps to look out for?
Dr Behnood Bikdeli: For example, in the typical superiority trials, when we want to test an intervention a versus intervention B, all that matters is we do a very good and adequately sized trial and rest of it is up to the study and how it goes to see whether or not something panned out. There was a significant difference between the new intervention versus the older ones, but in non-inferiority trials we have something called the non-inferiority margin and that's very highly relevant when it comes to the outcome that you're assessing when it comes to the ultimate results of the trial.
If the investigators choose a very lenient y non-inferiority margin, they may end up calling an intervention non-inferior. They may give it a pass. While in reality the intervention has quite a lot of a risk or harmful profile compared with standard of care. But in the other side, as a clinical example, we have several interventional tools at hand, like transcatheter aortic valve replacement. Most of the indications where it's currently used came from large bell designed non-inferiority trials. Where they showed that it was almost as good as surgery, in some cases better, but also it had a lot of ancillary advantages.
Dr Carolyn Lam: Thanks, Behnood. And you know here, I just want to call out to the readers. You have to look at this paper. Look at the tables and figures which are really so helpful. And Naveed, can I bring you in on this now? I mean, I just love this paper. It's such an important topic and I've never seen it addressed like this before. Could you tell us a little bit about what the editors discussed when we looked at this?
Dr Naveed Sattar: I've been involved in a few non-inferiority trials and some of the factors that many of us discuss and some of course associated, sort of our clinical trials, and I've been involved normally in superiority trials, but increasingly we have cut our teeth in non-inferiority trials. So, some of the points that the paper picks up resonated well with us in terms of, one of the examples was Behnood and his team found that around about 40% of trials didn't even justify what their non-inferiority margin was. And that's something I've actually had detailed discussions involved in various trials with. And that's a really important point, but it isn't a, you have to be able to justify why you choose particular margin and what that margin would mean to the community. Otherwise you potentially could just pick something out there which really doesn't allow you to make a really strong non-inferiority claim. And I think that's one of the factors that you found, Behnood. Is that correct?
Behnood Bikdeli: Absolutely. And that's a great point. Thank you. To us, there were two things about it. One was whether or not they provided any detailed justification for it exactly as you said, not that they're just picking up something because that's the sample size that they could achieve or that's the number that they felt comfortable with. But also the second piece of it, a respective of how they calculated or came up to the number, their readers have a right to know how this was calculated or were this came from, so it's the reporting part of it. Sometimes they reported both in the published paper and a study protocol or a design paper. Sometimes it was only in one of them. Sometimes as you mentioned, it was not mentioned in either, which puts the reader in a very difficult situation.
So we think, and these were the best of the best trials in the highest impact journals. Probably if we look high and low elsewhere it's going to be even more challenging. So, we think there's a lot of room for improvement for the readers to expect cleaner, more comprehensive papers to come, but also for the trialist to report them with more clarity.
Dr Naveed Sattar: And going forward, issue a nice figure that shows that the trend is that we are going to see more of these trials probably because you've got lots of better treatments now. So, you know it's getting harder, in the sense, in many areas of cardiovascular medicine to show superiority. So, there is a need for more trials which actually show benefits beyond just perhaps the main outcome in ways that you've explained in the particular paper.
Do you think the FDA does enough in this particular area in terms of this helping investigators decide what the non-inferiority margins are? Or is that something in terms of the quality of the trials that needs a bit more investigation? I think your papers partly are pushed to say, "Actually we need to do these better. We need to justify them better. We need to look at them better." Because actually they do have a greater influence going forward.
Dr Behnood Bikdeli: First, I cannot agree more. We are going to see a lot more of non-inferiority trials sort of, maybe because we have reached a ceiling effect when traditional intervention for superiority, but there's a lot of room to find interventions that are at least as safe or as good but have a lot of side advantages and ancillary benefits that's happened with some of the anticoagulants among other therapies available.
In terms of the regulatory aspects, one of the things we were fortunate about was within our team, we had people with expertise on the trialist side while communicating with the regulatory bodies and also from people who were consulting to the FDA for assessment of non-inferiority trials. So, we were fortunate to look into several of the methodological or quality metrics that were being thought of and we consulted with the in-source guidelines and FDA guidelines. That said, I completely agree that, for example, the suggestions that you provided in one of the tables could hopefully help shape some of these trials in a more rigorous way. Or at least a reporting, which is also an important piece, would be more transparent ultimately for the readership.
Dr Naveed Sattar: Absolutely. And transparency is really pivotal so that the readers completely understand what was done, what was predefined, and what was found so that they can make a proper judgment. And probably the final question I have in terms of, you make a good point that actually if the trials are not done well and there's a bit of slippage either in terms of loss of data or methodological issues, that then really pushes a trial towards a "no", in a sense you get a false reassurance of non-inferiority, but partly because the methodology wasn't robust enough. And it's really very critical for these trials, perhaps at least as critical as they are in superiority trials, but perhaps even more so. Is that a fair judgment?
Dr Behnood Bikdeli: No, no, no. You're absolutely right. That's another very important point in the typical superiority trial, if any bias drives the results toward no difference. Investigators are naturally guarding against that because it's going to be very problematic in non-inferiority trials. Depending on the effect measure that they choose, it could actually falsely favor the intervention of interest because it might show a false assessment of non-inferiority, and there are ways to work around it. There are ways to correct for it, such as choosing both absolute and relative effect measures, which practically addresses this concern. Again, gets back to the importance of appropriate design and appropriate transparency to report the results in a robust way, both intentions to treat and has treated or per protocol, both relative effect measures and absolute effect measures.
Dr Naveed Sattar: My sense of and getting back to you, but I think this will be a really seminal paper for the community to look at and really help us as a community to improve our conduct of such trials in the future because there will be more of these coming forward.
Dr Carolyn Lam: And I couldn't have said that better, Naveed. I think the take home message is right there. Pick it up, have a look and especially have a look at those tables and figures. It's really going to help you read many, many journals.
Thank you so much, Naveed and Behnood. Thank you audience for joining us on Circulation on the Run. Talk to you next week.
This program is copyright American Heart Association 2019.
Dr Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. We're your co-hosts, I'm Dr Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.
Dr Greg Hundley: And I'm Greg Hundley, Associate Editor at the Pauley Heart Center at VCU Health in Richmond, Virginia.
Well Carolyn, did you ever wonder whether cardiovascular drug effects could be investigated through natural variation in the genes for the protein targets? In our feature discussion today, investigators from the British Isles, Germany, and the United States use this approach to explore the potential side effects and repurposing potential of antihypertensive drugs. Sound interesting? Well listeners, we look forward to the results later in our program, but Carolyn, how about we chat about some of the other papers in this issue?
Dr Carolyn Lam: You bet Greg. So, have you ever asked yourself "What is the role of protein glycosylation in regulating LDL metabolism?"
Dr Greg Hundley: That was going through my mind when we were playing basketball just the other night.
Dr Carolyn Lam: Well this is truly a great study from Dr Holleboom at Academic Medical Center Amsterdam and Dr Lefeber from Radboud University Medical Center, both in the Netherlands. And their colleagues will study 29 patients of the two most prevalent types of Type 1 Congenital Disorder of Glycosylation, and these are the ALG6 and PMM2 types. They also study 23 first and second-degree relatives with a heterozygote mutation and measured their plasma cholesterol levels. LDL metabolism was studied in three cell models. They found that patients with type 1 congenital disorder of glycosylation have hypobetalipoproteinemia through increased LDL receptor expression. Carriers of the mutation in glycosylation enzymes affected in this syndrome had decreased LDL cholesterol levels compared to controls, and defects in glycosylation enzymes could play, therefore, an important role in LDL cholesterol metabolism.
Dr Greg Hundley: Boy, this is pretty insightful I think, Carolyn. So, what are the clinical implications?
Dr Carolyn Lam: Well, given that LDL cholesterol was also reduced in a group of clinically unaffected heterozygotes, the authors propose that increasing LDL receptor mediated cholesterol clearance, by targeting N-glycosylation in the LDL pathway, may therefore represent a novel therapeutic strategy to reduce LDL cholesterol, and of course prevent cardiovascular disease.
Dr Greg Hundley: Very interesting work. You know, we just keep learning more and more about LDL. I'm going to switch and jump back with Empagliflozin. And this is a study in diabetic mice that really has an interesting in-vivo imaging component. As an imager, I was really excited about this. The article is from Dr Kengo Kidokoro from Kawasaki Medical School. And we don't often talk about it, but listeners, if you have a chance, there's a very interesting video-enhanced file associated with this article, and if you can download it, it's really just so cool with multiple image clips demonstrating an operative mechanism of SGLT2 inhibition on renal function. And it really gives us an opportunity to revisit renal function.
Quick quiz Carolyn. In diabetic kidney disease, is glomerular hyperfiltration good or bad?
Dr Carolyn Lam: Bad.
Dr Greg Hundley: Yeah, absolutely. So, hyperfiltration is characteristically observed at earlier stages of diabetic kidney disease and involves activation of the renin-angiotensin-aldosterone system at the efferent arteriole and tubuloglomerular feedback mechanisms, especially at the afferent arteriole. So, as they go through this, just picture in your mind that glomerulus and afferent is arriving, and efferent is leaving.
So, SGLT2 upregulation in diabetes is thought to play an important role in TGF signaling by increasing sodium reabsorption at the proximal tubule, thereby decreasing distal delivery to the sodium sensing macula densa at the juxtaglomerular apparatus. This decline in distal sodium delivery is interpreted as a decline in effective circulating volume, leading to inappropriate afferent vasodilation in an effort to preserve intra-glomerular pressure and GFR.
In diabetes, these TGF effects lead to intra-glomerular hypertension and hyperfiltration. You got that quiz right, Carolyn. Which promotes diabetic kidney disease progression and impaired kidney function, ultimately increasing overall cardiovascular risk and mortality. Conversely, blocking SGTL2 pharmacologically reduces renal hyperperfusion and hyperfiltration in animals and humans, which may preserve renal function, thereby reducing risk associated with diabetic kidney disease progression.
Dr Carolyn Lam: You know what, Greg? I kind of had an unfair advantage in this quiz. I work with a lot with the SGLT2 inhibitors, but I just love that you asked us to picture it and look at that video. Anyways, so this article really allows us to review SGLT2 inhibition at the glomerular level, which is truly hot. So, tell us what did they find?
Dr Greg Hundley: So, this is the first report of changes in renal hemodynamic function by SGLT2 inhibition using direct in-vivo visualization techniques in a diabetic animal model. The videos, they're spectacular, and they're excellent so that you can download them for educational purposes. Afferent arteriolar vasoconstriction, and reduced hyperfiltration occurred within a few hours after a single dose of a SGLT2 inhibitor. And Adenosine signaling, through tubuloglomerular feedback, is a key pathway to prevent diabetic hyperfiltration via SGLT2 inhibition.
Clinically, Carolyn, now I know you would ask me about that, so I got ready, this study highlights another potential mechanism for the benefits of SGTL2 inhibition. The SGLT2 inhibitor-related mechanism's responsible for reducing cardiovascular risk in clinical trials may be due to protection against diabetic kidney disease progression, thereby attenuating risk factors for heart failure, such as volume overload and hypertension.
Dr Carolyn Lam: Ah. That is just so cool, and really just so consistent with the clinical data that's emerging too. Thank you, Greg. So, have you ever asked yourself this other question, what role do platelets play in ischemia reperfusion injury? So, I'm not going to quiz you. I'm actually kind and loving and a good person. And so, I will tell you about ischemia reperfusion injury, which is a common complication of cardiovascular disease.
Now, resolution of the detrimental effects of ischemia reperfusion injury generated prothrombotic and proinflammatory responses, is essential to restore homeostasis. Now, although platelets are known to play a crucial role in the integration of thrombosis and inflammation, their role as participants in the resolution of thrombo-inflammation is really under-appreciated. And hence, this other paper that I chose today, and it's from Dr Gavins from Louisiana State University Health Sciences Center Shreveport, and her colleagues, who used pharmacological and genetic approaches, coupled with murine and clinical samples to uncover key concepts underlying this role for platelets.
Dr Greg Hundley: So Carolyn, what did they find?
Dr Carolyn Lam: Well, they found that exacerbation of thrombo-inflammatory responses occurred in ischemia reperfusion injury mouse models of middle cerebral arterial occlusion, as well as lower plasma levels of the anti-inflammatory pro-resolving protein Annexin A1. And this was a lower plasma level of this Annexin A1 among patients with acute ischemic stroke.
Administration of Annexin A1 promoted cerebral protection against thrombo-inflammation and the development of subsequent thrombotic events post-stroke. Annexin A1 was also able to reduce platelet activation and thrombosis, via the suppression of integrins. So, overall, these data reveal a novel multi-faceted role for Annexin A1 to act both as therapeutic and prophylactic drug via its ability to promote endogenous pro-resolving anti-thrombo, anti-inflammatory circuits in the cerebral ischemia reperfusion injury. And collectively, these results further enhance our understanding in the field of platelet and ischemia reperfusion injury biology.
Dr Greg Hundley: Oh wow. So, another important insight from this author group on platelet activation and thrombosis in key clinically relevant syndromes. Well, my last paper is going to be talking about a risk prediction score for life-threatening ventricular tachyarrhythmias. And they're going to study this in laminopathies, and the lead investigator is Dr Karim Wahabi from Cochin Hospital in France.
To estimate the risk of life-threatening ventricular tachyarrhythmia in patients with LMNA mutations, and thus select candidates for implantable cardiac defibrillators, the investigators evaluated 444 patients of about 40 years in age in a derivation sample. And then, 145 patients that are about the same age, 38 years, in a validation sample, for the occurrence of a) sudden cardiac death or b) ICD-treated or hemodynamically unstable ventricular tachyarrhythmias.
Dr Carolyn Lam: Oh. Very important. These laminopathies are really not that uncommon. So what did they find, Greg?
Dr Greg Hundley: Carolyn, predictors of events included male sex, non-missense LMNA mutations, first-degree and higher AV block, non-sustained ventricular tachycardia, and LVEF. The authors developed a new score to estimate the 5-year risk of life-threatening ventricular tachyarrhythmias in patients with LMNA mutations. And compared to the current standard of care, the proposed risk prediction model offered more accurate prediction of life-threatening ventricular tachyarrhythmias, and correctly re-classified almost 30% of the patients in the study.
Nicely, the authors have made this available, and the score can be derived from readily collected clinical and genetic parameters and estimated using an online calculator that's provided in the journal. But, it's https://lmna-risk-vta.fr.
Future prospective studies should focus on the estimation of the clinical benefit conferred by the use of this score in terms of sudden cardiac death prevention.
Dr Carolyn Lam: That is super cool, Greg. But, I am so excited now to move to our feature discussion. Shall we?
Dr Greg Hundley: You bet.
Dr Carolyn Lam: Can we use natural variations in our genes for the protein targets as a way to look at cardiovascular drug effects? Man, this is going to be such an important and exciting discussion, because this is what our feature paper talks about. I am so pleased to have with us our corresponding author, Dr Dipender Gill from Imperial College London, as well as our Associate Editor, Dr Wendy Post from Johns Hopkins.
So, first of all, Dipender, please, could you give us a background on what you did? This is really very novel in approach.
Dr Dipender Gill: It was also a lot of fun to conduct. I think, currently, we're living in an era where there's been a recent explosion in the availability of genetic data, and this really inspired us to think about how we could use that to learn more about commonly prescribed drugs. The implementation of genetics, or genetic variance, to study drug effects isn't entirely novel. It's actually been undertaken for some years now.
Most of the work has been related to lipid lowering drugs, for example, statins, where people can take genetic variance, or versions of genes, corresponding to the drug effect, and study these to investigate what effects these drugs might have, both on the intended target, but also potential side effects. To my knowledge, this hadn't previously been done for anti-hypertensive drugs. But yet, the data for this was available. And therefore, we thought that actually we could very well go ahead and do this, and perhaps find some interesting things.
Dr Carolyn Lam: Oh, that's so interesting thing, Dipender. You know, there was this term in your abstract, and mentioned multiple times, Mendelian randomization. Now, for those of us that don't think about this every day, could you tell us a little bit what that means?
Dr Dipender Gill: Yeah. So, I'll actually give a little bit of background. One of the main limitations of traditional epidemiological research is that any association, it's sometimes difficult to infer causation. They can be confounded by environmental factors, lifestyle factors. In the Mendelian randomization technique, what we do is we use randomly allocated genetic variants to study the effect to an exposure.
So, we select these genetic variants because they are related to the exposure of interest. And because these genes are randomly allocated at conception, they're not subject to confounding from environmental or lifestyle factors. Whether you have a gene or not, is not necessarily related to your lifestyle or your environment. And therefore, the association of these genetic variants with certain outcomes isn't subject to confounding.
Dr Carolyn Lam: That makes so much sense, and I suppose that, not to allow cause and effect to be determined. So please, tell us, in this particular case of the anti-hypertensive drugs, what did you do and what did you find?
Dr Dipender Gill: First, we decided specifically which drugs we wanted to look at, and we thought, actually, let's start off with the most commonly prescribed anti-hypertensive drugs. So, we short-listed these based on recent consensus guidelines, and we looked at ACE inhibitors, beta-blockers, calcium channel blockers, thiazide type diuretics. And then, we went back to various online databases to identify which genes correspond to the target protein of these drugs.
We took these genes, and we then identified genetic variants at their specific genetic loci, their specific region of the genome, and we identified the variants in these regions that were also related to systolic blood pressure. And in this way, we inferred that genetic variants, at the protein coding targets of these genes, that were also related to systolic blood pressure, likely represented the effect of variations in these proteins that also implicated blood pressure, and therefore, could serve as proxies, or instruments, to study the effect of these drug targets.
We then went ahead to validate the selection of these genetic variants by forming Mendelian randomization, and specifically, we checked whether people that have genetic variants that correspond to, say, ACE inhibitor activity, or beta-blocker activity, or calcium channel blocker activity, if they also have correspondingly lower risk of coronary heart disease and stroke, to the same degree that we would observe in randomized control trials against placebo.
And indeed, we found that actually, the results were fairly similar, and this gave us confidence. And studying these genetic variants that mimic the effect of these drugs could be used as a proxy or as a surrogate to study their clinical effect of taking these drugs. So, that was the first phase.
Dr Wendy Post: Dipender, congratulations to you and our team. This is a really exciting paper, and the editors were especially interested in the novelty, and the potentially impactful findings, especially of the second part of the study, which I think you'll describe briefly next. And that was using an approach that many who are listening may not have heard about too much before called PheWAS, or a phenome wide association study. And maybe you could tell us briefly what you found in that part of the analysis.
Dr Dipender Gill: The first part, it was very cool, because it allowed us to identify versions of genes that corresponded to the effect of these drugs. But in itself, it didn't tell us anything novel. It didn't tell us anything new. So, the real question was, how could we use this new information to make progress towards helping patients? So, we went back and we thought, "So okay." So, we knew that these drugs are used for certain conditions already to prevent heart disease, to prevent stroke.
But, what about their side effects? What about their repurposing potential? How could we use our new approach to study that a little bit more carefully? As you alluded to, when we used this new technique, relatively new technique called phenome wide association study, and we essentially investigated the association of our genetic variants for each respective anti-hypertensive target with all clinically relevant outcomes throughout the phenome, using the UK bio-back cohort, which was the main population used for this PheWAS, this phenome wide association study.
We were actually able to rapidly investigate over 900 disease outcomes, and their association with our genetic risk score for these drugs. And this was very exciting for us, because it allowed us to very rapidly, efficiently, and cost-effectively explore the potential repurposing opportunity and side effects of these very commonly prescribed drugs, which to our mind, offered significant advantage over previous approaches.
We all know that sometimes randomized control trials can be very expensive and time-consuming, and of course, traditional observational research can be limited by reverse causation, assessment-vise confounding. And so, what we were able to do here had several important advantages, and not to mention the efficiency by which it allowed study of these outcomes.
Dr Wendy Post: Dipender, tell us what you found in your PheWAS study.
Dr Dipender Gill: We identified genetic variants for 3 commonly prescribed anti-hypertensive targets. The first were ACE inhibitors, second, beta blockers, and the third were calcium channel blockers. When performing PheWAS for all of these drug targets, we identified associations with common cardiovascular disease that are related, or implicated in hypertension, specifically hypertension itself, but also circulatory diseases, things like atrial fibrillation, coronary heart disease. They all came up.
And this actually gave us a lot of confidence because that's exactly what we'd expect. We know that these medications prevent or reduce risk of these diseases, and therefore, this served as kind of a positive control that our approach was doing it what it was supposed to do. The novel finding came when we investigated the genetic risk score, or the genetic variants for calcium channel blockers, in this PheWAS approach.
And we actually identified an association which we weren't expecting. We showed that blood pressure reduction through the genetic risk score for calcium channel blockers was an association with an increased risk of diverticulosis, a condition not conventionally thought to be associated with blood pressure. We were very excited and interested by this, and we went on to investigate it further using some other techniques as well.
Dr Wendy Post: The really impactful part of this, many things, but especially this association with diverticulosis. So, maybe you can briefly summarize what you think the potential clinical implications are, and what the next step should be.
Dr Dipender Gill: The first question we had was whether this was related to blood pressure alone, the effect of calcium channel blockers, or perhaps some other effect of these drugs. We investigated the genetic risk score for systolic blood pressure generally and found that this itself wasn't associated with risk of diverticulosis, which suggested that the effect isn't really mediated by blood pressure alone, but it's some other property of calcium channel blockers.
We know that sometimes calcium channel blockers can be associated with constipation, and it may be through this mechanism that they're having consequent effects on risk of diverticulosis. Other possible mechanisms might be through effects on blood flow, through the vasa recta in the bowel. But, what was very interesting was that we went forward with this finding, and investigated, observed, drug use in the UK bio-bank.
Specifically, we looked at people taking non-dihydropyridine, and dihydropyridine calcium channel blockers at baseline, and found that those taking non-dihydropyridine calcium blockers only were known to have a higher risk of diverticulosis as compared to those taking other anti-hypertensive classes, which further added support for our findings. The interesting point here is that looking at the genetics doesn't allow us to discriminate between these drug classes.
That was only possible with the observed data, and that was because the genes for these drug classes were the same.
Dr Carolyn Lam: Well, congratulations. Wow. I'm just so intrigued listening to all of this. Wendy, I would love if you could help put all of this in context for us. The US, the novel information, and the approach that could potentially go way beyond just anti-hypertensive.
Dr Wendy Post: So, this is a very exciting new approach to doing genetic studies that can help us to understand potential targets for therapy in the future, and understanding more about causality, which as Dipender explained, can sometimes be confusing, as it may be confounded by environmental factors. So, using these genetic approaches through Mendelian randomization, and what we heard about today, which is PheWAS, or phenome wide association study, we can learn much more about how the potential observational analyses can be related to new discoveries through mechanisms, or potential side effects, as we heard about here of calcium channel blockers.
So, wanted to congratulate Dipender again with his impactful paper here.
Dr Carolyn Lam: Thanks, Wendy. And then if I could, I'm just going to steal minutes here, because this is so interesting. Where do you think the field's going to go next? And Dipender, with these findings of diverticulitis and diverticulosis, what next? How do we apply this?
Dr Dipender Gill: There's 2 main points to cover here. The first is what we do specifically with the findings we got for calcium channel blockers and diverticulosis. I should emphasize that on their own, I don't think that this should currently change practice. But, I think it should inspire and capitalize further research into this association. If we're able to replicate and validate it further, then perhaps there might be some implications for the drugs that we prescribe with patients at risk of diverticulosis.
The second point I wanted to make is more generally, what does this mean for research, and particularly, genetic research. I think we're living in very exciting times, and there's a lot of really great work that's going to come out using these types of approaches. I think 2 areas that we could expand further is what else we can do with our genetic instruments, or our genetic variants that proxied these drugs. How do we look at other targeted refocusing potential? Can we try and explore other side effects? Can we investigate efficacy for other disease outcomes? Specifically, for these anti-hypertensives.
And the other thing is, which other drugs can we identify genetic variants to proxy? We've been thinking about looking at diabetes medicines. There's a variety of other drugs that correspond to specific gene targets, and proteins. And in theory, these could also be studied using genetics. So, there's a lot more work to come out from this.
Dr Carolyn Lam: Thanks so much, both of you, for joining us today. This was just such an exciting discussion.
Thank you for listening to Circulation on the Run. Don't forget to tune in again next week. This program is copyright American Heart Association, 2019.
Dr Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. We're your co-hosts, I'm Dr Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.
Dr Greg Hundley: And I'm Dr Greg Hundley: Hundley, Associate Editor from the Pauley Heart Center in Richmond, Virginia at VCU Health. Well Carolyn, our featured article this week addresses the age at which to initiate clinical screening of relatives for hypertrophic cardiomyopathy. Our guidelines suggest screening of relatives from age ten and onwards but data are lacking to substantiate this suggestion. I look forward to the authors' discussion of their findings regarding initiation of screening in children. For now though, do you have an article that you'd like to share?
Dr Carolyn Lam: You bet, Greg. So, the first paper I chose really demonstrates that patients inducible pluripotent stem cells or IPSC cardio derived myocytes can be used as a disease modeling platform to delineate the functional mechanisms that underlie cardiac hypertrophy and in this particular case they looked at Noonan Syndrome and showed that how these techniques can be subsequently used to identify novel molecular and genetic therapeutic targets. So, Greg, here's your quiz. The genetics of Noonan Syndrome.
Dr Greg Hundley: I remember it was on our board exam.
Dr Carolyn Lam: Let me tell you about it. So more than 90% of patients with Noonan Syndrome have a mutation in the hinge region CR2 domain of Raf-1 and they exhibit severe hypertrophic cardiomyopathy for which there is no treatment. Authors, Dr Jaffrey from Cornell University and Dr Kontaridis from Masonic Medical Research Institute in Utica in New York and their colleagues used Noonan Syndrome Raf-1 patient and CRISPR corrected IPSC cardiomyocytes to recapitulate the Noonan Syndrome cardiac phenotype.
These Noonan Syndrome IPSC derived cardiomyocytes exhibited the same hypertrophy and myofibrillar disarray that's really observed in Noonan Syndrome patient hearts, so mechanistically the authors showed that activation of mitogen-activated protein kinase or mech-1 or -2, but not the extracellular regulated kinase, which is ERK1 or 2 triggered abnormal cardiomyocytes structure and conversely ERK5 mediated increased cell size in these Noonan Syndrome mutant IPSC derived cardiomyocytes.
RNA sequencing further identified genes dysregulated in the Noonan Syndrome cardiomyocytes that may underlie hypertrophic cardiomyopathy downstream if the mech-1 or -2 and ERK5 genes.
Dr Greg Hundley: So, Carolyn, that's a lot of genetic information, so what can I take home as I think about this further and what may come down the line as we manage patients with Noonan Syndrome?
Dr Carolyn Lam: Thanks, Greg. The real take home message is that these pathways could serve as novel therapeutic targets to treat hypertrophic cardiomyopathy in patients with Noonan Syndrome and Raf-1 mutations. Overall, the elucidation of rare disease mechanism of hypertrophic cardiomyopathy may further unravel and reveal causes of other more common idiopathic congenital disorders and hypertrophic diseases.
Dr Greg Hundley: Oh, very good. Well, I'm going to switch gears and talk a little bit about infective endocarditis prophylaxis and this article comes from Pallavi Garg at the London Health Scientist Center. Carolyn, as you may recall, given the lack of proven efficacy and concerns about the perceived risks of antibiotic prophylaxis like development of antibiotic resistance, the American Heart Association in 2007 and the European Society of Cardiology in 2009 published revised guidelines recommending cessation of antibiotic prophylaxis prior to dental procedures for patients at moderate risk of infective endocarditis while continuing the practice in high risk patients. This Canadian study was conducted from 2002 to 2014 among all adults and those at high and moderate risk for infective endocarditis and they were stratified by age. Prescriptions for antibiotic prophylaxis were obtained from the Ontario Drug Benefit Database for adults 65 and older and outcomes regarding antibiotic prophylaxis prescription rates and the incidents of infective endocarditis related hospitalization were assessed.
Dr Carolyn Lam: Ooh, interesting. What did they find?
Dr Greg Hundley: The authors found a sustained reduction in antibiotic prophylaxis prescriptions among individuals at moderate risk for infective endocarditis that coincided with the change in guidelines. In contrast, while there was a decreasing trend in antibiotic prophylaxis among individuals at high risk of infective endocarditis and a minimal drop following the guidelines released, the overall rates of prophylaxis prescribing in this group continued to climb since early 2007, and collectively, these findings suggest that appropriate uptake of the revised AHA guidelines occurred.
Furthermore, over the thirteen-year study period, the authors identified an increase in hospitalizations for new episodes of endocarditis approximately three years after the AHA guidelines were revised. This timeline along with the rise of endocarditis incidents in both the high and moderate risk groups suggests that this observed increase in endocarditis is likely unrelated to the change in the prescribing practice of antibiotic prophylaxis. This conclusion is further supported by the overall decrease in endocarditis cases attributable to streptococcal infections over time, a finding contrary to what might be expected as a result of the reduction in antibiotic prophylaxis.
Dr Carolyn Lam: Oh, very interesting, Greg. At first a little bit scary and then after when you described it more, it does seem a little bit more reassuring. Very interesting. Well, thank you. My next paper deals with functional tricuspid regurgitation, which as you know is really common in heart failure with reduced ejection fraction or HFrEF and mostly consequent to pulmonary hypertension. However, what is the access mortality associate with functional tricuspid regurgitation in HFrEF? Well, this paper from Dr Maurice Serrano from Mayo Clinic and colleagues looked at all Mayo Clinic patients from 2003 to 2011 diagnosed with heart failure stage B and C and an ejection fraction less than 50% who had functional tricuspid regurgitation grading and systolic pulmonary artery pressure measured by Doppler echocardiography.
Now among more than 13,000 patients meeting these inclusion criteria, functional tricuspid regurgitation was detected in 88%. Functional tricuspid regurgitation was independently associated with more dyspnea, more impaired kidney function, and lower cardiac output. For the long term outcomes, the higher the degree of functional tricuspid regurgitation compared with a group with trivial tricuspid regurgitation was independently associated with a higher mortality hazard. The five year survival was substantially lower with increasing severity of tricuspid regurgitation so it was 68% on average for trivial functional tricuspid regurgitation versus 34% for severe functional tricuspid regurgitation.
Importantly, this access mortality observed with moderate or severe functional tricuspid regurgitation was independent of pulmonary hypertension and any other clinical characteristics.
Dr Greg Hundley: Hmm, interesting but Carolyn, wouldn't we expect this?
Dr Carolyn Lam: You know what, you may expect it, but this is really the largest series, I think, that has shown this and shown this in the systematic way that functional tricuspid regurgitation in and of itself may play an important pathophysiologic role and thus, may represent a potential therapeutic target in HFrEF. In other words, the present study really advocates for a trial to test treating functional tricuspid regurgitation in patients with HFrEF.
Dr Greg Hundley: Oh wow, you really put that in great perspective, Carolyn. Well, your reward is going to be a quiz.
Dr Carolyn Lam: Oh my gosh, Greg.
Dr Greg Hundley: We're going to talk about ...
Dr Carolyn Lam: What now?
Dr Greg Hundley: Caveolin-1, an atherogenesis and nitric oxide and this is from Professor Carlos Fernandez Hernando at the Yale University School of Medicine. Okay, multiple choice. What are caveolae? Now I'm going to give you some choices, you get to pick A. Are they crypts within the walls of vessels. B. Crypts within the membranes of endothelial cells. Or C. Crypts within the border zones of infarcts.
Dr Carolyn Lam: Wait a minute, Greg. I'm not even sure we're pronouncing it the same. You're asking about caveolae like ... Potato potata. They're invaginations of cell membranes, that's all I know.
Dr Greg Hundley: Oh wow, fantastic. This study focused on the effect of Caveolin-1, a protein integral to the formation of caveolae. The investigators found in a series of mouse experiments that A. The athero-protection observed in mice lacking Caveolin-1 is independent of endothelial nitric oxide synthase activation and nitric oxide production. B. Endothelial Caveolin-1 controls lipoprotein infiltration in vascular inflammation in early stage atherosclerotic lesion. C. Endothelial Caveolin-1 promotes pro-atherogenic matrix deposition leading to endothelial cell activation in atheroprone regions of the aorta and finally, D. Atheroprone regions of the aorta are characterized by increased intracellular and basolateral caveolae distribution in endothelial cells compared to athero-resistant areas.
Dr Carolyn Lam: Wow, I like the way you broke that down into four points, but could you summarize what it means clinically?
Dr Greg Hundley: Yeah, so I think if you had to summarize all of this in a sentence, perhaps the suppression of Caveolin-1 expression in endothelial cells might prevent the progression and promote the regression of atherosclerosis so in the future perhaps an interesting target to treat atherosclerosis. Well, now Carolyn, I guess we should proceed to that talk with our featured discussion.
Dr Carolyn Lam: Absolutely. Thanks, Greg.
Hypertrophic cardiomyopathy is an inheritable myocardial disease with age-related penetrance. Current guidelines recommend that clinical screening of relatives start from the age of ten years onwards by the European Society of Cardiology and twelve years onwards by the American College of Cardiology or American Heart Association. There are of course caveats for earlier screening but the clinical value of this approach has really not been systematically evaluated. That is until today's feature paper and we are so pleased to be here discussing it. This is Greg Hundley and Carolyn Lam and we're your co-hosts for Circulation on the Run. So happy to welcome Dr Juan Pablo Kaski who's the corresponding author of today's feature paper from Great Ormand Street Hospital in London and we also have Dr Gerald Greil, Associate Editor from UT Southwestern.
Welcome, everyone. Juan, if you don't mind, could you start by summarizing this very important study of yours?
Dr Juan Pablo Kaski: Thank you very much. Hypertrophic cardiomyopathy is a genetic muscle condition that is characterized by hypertrophy and is most commonly inherited as a dominant trait. Previous studies have suggested that in familial disease at least ventricular hypertrophy doesn't usually present until adolescence and this has led to the current guidelines which do not recommend routine screening of children below the age of twelve according to the American guidelines below the age of ten and the European guidelines for hypertrophy cardiomyopathy but own clinical experience was different and suggested that perhaps sarcomeric disease and familial disease could present in younger children, so what we aimed to do with this study was to assess the validity of this approach and tried to assess the yield of clinical screening in children from families of hypertrophic cardiomyopathy.
Dr Juan Pablo Kaski: We took our collective experience in our institution over a period of many years and recruited just on the 1,200 consecutive children all aged less than eighteen years at the time of initial assessment coming from just under 600 families and these were children who were referred for clinical screenings because a first degree relative had been diagnosed with hypertrophic cardiomyopathy. What we found was that in 5% of these children and in fact, in 8% of the families that we screened, we were able to pick up early phenotypic features of hypertrophic cardiomyopathy. In 72% of patients, we made a diagnosis before the age of twelve, so before current clinical screening guidelines we'd recommend and importantly, a third of these patients during follow up had a change in their management as a result of the diagnosis. Their medication was commenced, they underwent procedures or implantations of defibrillators.
Dr Greg Hundley: Juan, this is Greg Hundley and I was wondering when did the participants that were enrolled experience events? Did those that were say under fourteen or even under twelve, did they experience events relative to those that were a little older?
Dr Juan Pablo Kaski: The events that our participants experienced were relatively few. Many of these occurred during the childhood age but some occurred once the children had transitioned into the adult age. We did look to see whether there was any difference in terms of early diagnosis and subsequent events, but we didn't find anything, we didn't identify two separate populations in that respect.
Dr Greg Hundley: And then did you perform genetic analyses? I know you described phenotypic characterization of the patient population but how about genetically? What results did you find there?
Dr Juan Pablo Kaski: The main aim of the study really was to determine a yield of clinical screenings, so this is a reflection of a real-world practice where genetic testing may not necessarily be routinely available. Having said that, we did have genetic data in a third of our families and in fact, in maybe 70% of those children who made clinical diagnosis of hypertrophic cardiomyopathy was made and what we find in those individuals who have undergone genetic testing is that the vast majority of those had mutations in sarcomeric protein genes and pathogenic or likely pathogenic variants in sarcomeric genes in just under 70% and these were well characterized mutations that are very similar to those that are seen in adolescence or adult onset hypertrophic cardiomyopathy.
I think what was interesting about these genetic results is that we seem to have identified a population of early onset sarcomeric disease that genetically appears to be indistinguishable from a sort of later onset adult disease but with the clinical presentation and natural history curve shifted somewhat to the left.
Dr Greg Hundley: Gerald, just switching over, can you tell us some of your thoughts about how the results of this study will impact clinical practice, both in the European countries as well as U.S.?
Dr Gerald Greil: I mean, I was obviously delighted to see the study being submitted to circulation because there's a very important message particularly for pediatric cardiologists which is potentially influencing the guidelines and Dr Kaski may comment on this as well as the next step meaning that it seems like screening patients older than ten or twelve years and once again, there's a slight discrepancy between the European and U.S. guidelines, seems to be ... Can be questioned and potentially we should screen these patients earlier.
Another amplification of this study is that we should think about how much genetic screening can be an essential tool in our methods in looking at these patients and I want to point out that because of these discrepancies we also initiated an editorial letter for this publication done by Dr Ommen and by Dr Mital kind of pointing out there needs a lot of work to be done maybe even including rewriting the current guidelines.
There's another paper that came out recently in European Society Cardiology, the European Heart Journal about a similar topic so it's something which is very, very heavily discussed in our community. We think how we are looking at these patients and how we're following them up.
Dr Greg Hundley: What would you suggest are next steps for the world community in this space in regards to modifying those guidelines?
Dr Gerald Greil: I think there's now enough literature around which suggests that we should look at these patients earlier and screen them earlier on both sides in European, in the U.S., in the Asian world, and ideally these two groups should sit together and write combined guidelines. It's still interesting that the European and U.S. guidelines are slightly different in that we're talking about a similar group of patients, so I'm very, very delighted to see that this is coming up in the national literature as a new topic and I think everything is open now to rethink this topic and rewrite these guidelines.
Dr Greg Hundley: Do you think prospective studies would be necessary because I believe, and Dr Kaski please weigh in here, this was a retrospective review, and do you think there could have been triggering circumstances that prompted early screening? I mean, would a next step be some sort of prospective registry?
Dr Gerald Greil: I mean definitely that's the next step. I think we have enough data material around once again to rethink the strategy which age these patients should be looked at. A prospective registry and Dr Kaski can probably comment on it better than I can, I think that something which is a logical next step and there may be even something being on the way to make this happen.
Dr Juan Pablo Kaski: I agree. I think further validation and confirmation of these data from prospective studies would be extremely helpful. I think one of the things that we need to bear in mind is the potential cost implications of expending screening to ever increasing populations and so perhaps an additional further step would be to try to refine the screening tools so that we are able to identify clinical by a chemical of those individuals who are more likely to present in childhood and perhaps set a target screening towards that population.
I can just go back to one of your sort of previous points also about a potential bias and it is true that these patients were referred for clinical screening at a time when clinical recommendations do not suggest that this is necessary and although we didn't specifically in this cohort look at those that would have fulfilled current early screening criteria, the vast majority of the patients were asymptomatic at the time that they were referred. We also looked to see whether there was any link between those individuals who had a family history of early onset disease and an early diagnosis, and that was the only factor that came up as potentially significant so perhaps the current guidelines that do recommend considering earlier screenings if there's a family history of childhood disease are still applicable.
Dr Carolyn Lam: That was just an amazing interview, by the way. I've learned so much and thank you so much for publishing this very important paper with us.
You've been listening to Circulation on the Run. Don't forget to tune in again next week.
This program is Copyright American Heart Association 2019.
Dr Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. I'm Dr Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.
Dr Greg Hundley: And I'm Greg Hundley, also Associate Editor from the Pauley Heart Center at VCU Health in Richmond, Virginia.
Dr Carolyn Lam: I'm so excited about our feature discussion today, Greg, because it is about a familiar but very important problem of hypertension, and we will be looking at trial results of a new drug, a first in its class type of drug. And tackling a problem that is particularly important perhaps in black patients with hypertension. Well, more very soon. First, let's discuss some papers, shall we? Do you have one?
Dr Greg Hundley: My paper is from Joseph Burgoyne from King's College in London and pertains to resveratrol. Now, resveratrol is a non-flavonoid polyphenolic compound that has been found in the skin of several fruits, with the most notable being grapes. The compound exhibits beneficial effects, including the prevention of cardiovascular neurologic diseases, cancer, metabolic syndrome, as well as it promotes bone and eye health. And in this study, the investigative team explains how resveratrol may mediate its numerous beneficial effects including lowering of blood pressure by direct thiol oxidation. Also, they demonstrate that resveratrol can counter-intuitively induce direct protein oxidation, a process that is enhanced under pro-oxidative conditions associated with disease. The oxidation of cyclic GMP dependent protein kinase 1 alpha, or PKG1 alpha, by resveratrol lowers blood pressure in hypertensive mice.
Dr Carolyn Lam: Okay. But what does that mean for us clinically, Greg?
Dr Greg Hundley: Well, the results demonstrate how blood pressure can be lowered by using resveratrol, and targeting cysteine 42, or PKG1 alpha, may provide a new class of anti-hypertensive agents. In addition, identifying additional proteins modified by resveratrol may provide new targets for therapy to treat cardiovascular disease. Carolyn, how about your first paper?
Dr Carolyn Lam: We are going to look at the further results of the ODYSSEY OUTCOMES trial. And as a reminder, ODYSSEY OUTCOMES was a double-blind randomized comparison of the PCSK9 antibody Alirocumab with placebo in almost 19,000 patients who had an acute coronary syndrome 1-12 months previously and elevated at the atherogenic lipoproteins despite intensive statin therapy.
And that trial found that Alirocumab reduced the risk of the primary composite outcome of coronary heart disease, death, ischemic stroke, myocardial infarction, or unstable angina requiring hospital admissions. The current paper looked further at the effects of Alirocumab on death.
Dr Greg Hundley: So Carolyn, what did they find?
Dr Carolyn Lam: Well, there are quite a number of findings here. The first, there were fewer deaths in total that occurred with the PCSK9 inhibitor Alirocumab versus placebo, and this resulted from a non-significantly cardiovascular and non-cardiovascular deaths with Alirocumab. The second finding was that in a pre-specified analysis of more than 8,200 patients eligible for 3 or more years of follow-up, Alirocumab reduced death.
And then, the third finding was that patients with non-fatal cardiovascular events were at increased risk for both cardiovascular and non-cardiovascular deaths, and a post-Hoc analysis found that compared to patients with a lower LDL, those with a baseline LDL above 100 had a greater absolute risk of death, and a larger mortality benefit with Alirocumab. In the Alirocumab group, all cause death declined with a lower achieved LDL achieved at 4 months of treatment to a level of approximately 30.
So in summary, Alirocumab added to intensive statin therapy, has the potential to reduce death after acute coronary syndrome, particularly if treatment is maintained for 3 or more years, and if baseline LDL is 100 or more, or if achieved LDL is low.
Dr Greg Hundley: That's great, Carolyn. My next paper is going to talk a little bit about endothelial cells. And what I think we're going to learn is that not all endothelial cells are alike. This comes from Dr Rajat Gupta from Brigham and Women's Hospital, and I really thought this was an interesting article that used single-cell RNA sequencing to make it possible to identify and characterize cellular sub-populations.
Dr Greg Hundley: The investigative team performed enzymatic dissociation of 4 whole mouse aortas, followed by single-cell sequencing of over 10,000 cells.
Dr Carolyn Lam: Wow. What did they find?
Dr Greg Hundley: Well using cluster analysis of gene expression from the aortic cells, they identified 10 populations of cells representing each of the main arterial cell types. There were fibroblasts, vascular smooth muscle cells, endothelial cells, immune cells, including monocytes, macrophages, and lymphocytes. And importantly, there were 3 distinct endothelial cell sub-populations with differences in them driven by major functional gene programs including adhesion and lipid handling.
Comparison of aortic single-cell RNA sequence data sets from normal and Western diet-fed mice suggested that these sub-populations exist under both dietary conditions and have some unified responses to diet alteration. Also, immunofluorescence using single marker genes to identify endothelial cell sub-populations showed that the VCAM1 positive population was spatially located in regions of disturbed flow like the lesser curve of the aorta.
Dr Carolyn Lam: Okay. So bring it home for us, Greg. What does this mean clinically?
Dr Greg Hundley: Yeah exactly, Carolyn. So, characterizing functional sub-populations may serve as a novel method for understanding endothelial health in patients with vascular disease. And although aortic endothelial cell sub-populations demonstrate some unified responses to vascular disease relevant stimuli, like a Western diet, functionally different sub-populations may contribute differentially to vascular diseases, enabling sub-population targeted therapies to perhaps be implemented in the future.
Dr Carolyn Lam: Cool. So Greg, cardiomyopathies have often been seen as genetic in origin, but what about potentially modifiable causes? So, this next paper that I picked looked at that, and it's from corresponding author Dr Rosengren from Sahlgrenska University in Gothenburg, Sweden, who with her colleagues, sought to investigate a potential link between obesity in adolescence and being diagnosed with cardiomyopathy in adulthood.
So, this was a nation-wide register-based prospective cohort study of almost 1 million 690,000 adolescent men who were enlisted for compulsory military service from 1969 to 2005. Now at baseline, body mass index, blood pressure, and medical disorders were registered, along with test results for fitness and muscle strength. Cardiomyopathy diagnosis was then identified from the National Hospital Register and Cause of Death Register.
So, they found that during a median follow-up of 27 years, 4,477 cases of cardiomyopathy were identified, of which 59% were dilated, 15% were hypertrophic, and 11% were alcohol or drug-induced. Increasing body mass index, or BMI, was strongly associated with elevated risk of cardiomyopathy, especially dilated cardiomyopathy, starting at levels considered normal, meaning a BMI of 22.5 to less than 25 kilograms per squared meters.
And this was even after adjusting for age, years, center, and baseline comorbidities. There was a more than 8 fold increased risk of cardiomyopathy at a body mass index of 35 and above, compared with a BMI of between 18.5 and less than 20.
Dr Greg Hundley: So, it sounds like BMI elevations and cardiomyopathies don't go together. So, what are the clinical implications?
Dr Carolyn Lam: This really shows that even mildly elevated body weight in late adolescence may contribute to being diagnosed with cardiomyopathy in adulthood. So, the already marked importance of weight control in youth is really further strengthened by these findings, as well as the greater evidence for obesity as a potential important cause of adverse cardiac remodeling that is independent of clinically evident ischemic heart disease.
Dr Greg Hundley: Outstanding. So, BMI, not good.
Dr Carolyn Lam: Nope, Greg. High BMI, not good. That was fun, Greg. So, shall we move on to our feature discussion?
Dr Greg Hundley: Absolutely.
Dr Carolyn Lam: For our feature discussion today, we are talking about a familiar problem, but just so very important, and that is hypertension. And guess what? Our feature paper discusses a new first in class centrally-acting renin-angiotensin system blocker that has such remarkable initial results. I am so pleased to have with us the corresponding author for the paper, Dr Keith Ferdinand from Tulane University School of Medicine, as well as our Guest Editor, Dr David Calhoun from University of Alabama and Birmingham.
Keith, could you start by telling us a little bit about the kinds of patients you see there in New Orleans that struggles with hypertension control perhaps? And then, please tell us about Firibastat.
Dr Keith Ferdinand: I'm in New Orleans. In fact, I'm a native New Orleans. And as you know, most of the south and southeast and part of the United States has a high proportion of African American or US blacks. This population has higher rates of hypertension, increased prevalence, more severe hypertension, and more uncontrolled hypertension.
We also note in the south that there tends to be an increase in obesity, which is a powerful risk factor for all patients with hypertension, regardless of race or ethnicity. And unfortunately, the rates of obesity appear to be increasing. So based on the fact that we have an increase in obesity, we have many patients whose blood pressures are not controlled, and some of the previous data have suggested less response to first step or monotherapy with ACE inhibitors and angiotensin receptor blockers, I initiated a trial with a first in its kind oral active brain aminopeptidase A inhibitor.
Dr Carolyn Lam: Wow. Could you tell us a little bit more about brain aminopeptidase, and this new drug Firibastat?
Dr Keith Ferdinand: Most people don't know anything about this molecule, because this is something that was discovered by some French physiologists. They approached me to design the clinical trial here in the United States. And what it does is, it blocks the conversion of angiotensin II to angiotensin III in the brain. Angiotensin III is actually the active component of the renin-angiotensin system centrally, and if you block angiotensin III production, it has a triple therapy effect.
One is that it causes the diuresis. It decreases sympathetic tone, and it stimulates the carotid artery, such that you have, again, a decrease in sympathetic tone. Now, why choose it for patients who are obese, and why want to include a large proportion of non-Hispanic blacks here in the United States? Well, the reasons are that when you look at some of the bench research using rats, it appears to have a more beneficial effect in DOCA-salt rats, which is a model for salt-resistant hypertension.
Salt-resistant hypertension is more common in blacks, more common in patients with obesity, and may indeed be one of the reasons why monotherapy or first-step with conventional renin-angiotensin system agents, specifically ACE inhibitors and ARBs, have not been as effective in the past.
Dr Carolyn Lam: Gosh. That is so interesting, and it's really making me think about my patients too here in Asia, where we have a lot of salt-sensitive hypertension. Now, could you please tell us about the trial you did, and what you found?
Dr Keith Ferdinand: We looked at a cohort of patients. All of the patients were overweight and obese. They were washed out for 2 weeks, and had a systolic blood pressure of 145-170, and a diastolic of less than 105. We wanted to get at least 50% self-identified blacks or Hispanics, and I suspect that any patient who meets this phenotype, and that would include Asians, or even Whites, may respond similarly.
We then placed them in an open label format, and I can discuss why we used an open label, with monotherapy with Firibastat. After 2 weeks, we then titrated the dose level from 250 twice daily to 500 twice daily if needed, and we had a low dose thiazide and hydrochlorothiazide 25 mg addition, if needed, for escape, if patients had a blood pressure greater than 160/100.
The other thing that was interesting and unique about this particular trial is that we used the automatic office blood pressure, where the blood pressure was taken 6 times. The first time was discarded, and then averaged, without a particular doctor or a nurse being there to do the blood pressure. We felt that this was a valid means of getting blood pressure loaded. It tends to mimic, to a large extent, what you see in 24 hour inventory daytime systolic blood pressure.
So, this was a valid means of measuring blood pressure loads. This was a relatively high risk patients. And these were patients whom, previously, probably would not have responded as well to monotherapy with ACE inhibitors or ARBs.
Dr Carolyn Lam: That's really clear, and clever design. I would love to hear a little bit more about why the open label, and of course, the results.
Dr Keith Ferdinand: Well, that's one of the criticisms of this study, but actually, we presented to the FDA when we were discussing designing this trial, perhaps doing a placebo control trial. And we were told by the FDA that if you use a valid means of measuring blood pressure load, so that would be ambulatory blood pressure, or automated office blood pressure, that a placebo would not be necessary, because those means of checking blood pressure load would be considered a true valid means of finding a blood pressure effect.
The other thing is, dealing with minority patients, and really dealing with patients in general, for blood pressure, if they have substantial hypertension, the message has been out there that this is a killer and cause of cardiovascular disease. It would probably have been very difficult to enroll the patients, you've got 254 patients in a national study. It would have been very difficult to enroll these patients, who would have known easily that they had substantial elevation of blood pressure, and we said, "You know, 50% chance you're going to get a sugar pill that has no effect."
Dr Carolyn Lam: Right. Right. Very nice. The results?
Dr Keith Ferdinand: Well, the results were a robust 9.7 mm reduction in systolic blood pressure. At day 56, the p-value was less than 0.0001. And when you do a sub-group analysis of patients who were in the study, it was effective for persons who are under 65, or over 65, male or female. All patients were overweight, and the patients who were obese, with a BMI of 30 or above, had a trend towards even a better blood pressure effect, which again, is not seen with first step with conventional ACE and ARBs.
We also did an analysis based on black and non-black, and there was no difference, again with the trend towards the black patients actually doing fairly well. So, the take home from the particular study was this is the first in its kind, new approach to central Ras blockage with aminopeptidase A inhibitor, that was effective in a population which was overweight and obese, with over 50% minority, and showed substantial blood pressure reduction using a valid means of checking blood pressure, the automated blood pressure in the clinic.
Dr Carolyn Lam Keith, congratulations. A very important study. David, could I bring you in here? What were your thoughts as you were managing this paper, and what do you think are the future steps here?
Dr David Calhoun: Looking at the submission, I was obviously excited about the results and the potential implications. I think, like Keith, in treating a lot of resistant or obesity-related hypertension, we're frustrated that control rates are not better, that the initial response to monotherapy is not better, and that's particularly true of Ras blockers. I think many of us are investigating the initial use of Ras blockers for a variety of reasons related to outcome benefit and reduction in incident and diabetes.
So, I know I like to start with such an agent. I'm particularly excited that there may be, firstly, a new opportunity to block the Ras system, and potentially comparable or even better in the most difficult patients to treat. That is, the African American and the Hispanic patients, who often have very severe hypertension. So, my initial reading was I was very excited to see the potential, and that was brought out by the reviews as well. They shared my excitement. So, I'm looking forward to Keith advancing this compound.
Dr Carolyn Lam: Indeed. Keith, I'm sure everyone's thinking now, wow, remarkable results. What's the drawbacks? How well-tolerated was this drug?
Dr Keith Ferdinand: One of the drawbacks is that the structure of Firibastat included a sulfhydryl group. And we saw with early studies with captopril, which also has a sulfhydryl group, some skin rash, and we saw those similar changes with some of the patients in this particular study. At least 2 of them were suggested to potentially have erythema multiforme, although this was not proven. This was an investigator initiated adverse event.
So, I don't know if we're going to be able to structure a similar type of aminopeptidase inhibitor without a sulfhydryl group. The other thing is that in its presence formulation, it's given twice daily. We know optimally you'd like to have a long-acting agent that can be given once daily. And I don't think we need a placebo control trial, but we may need to do a trial where patients are on 2 or more medications, and then, you add the Firibastat versus adding placebo. But, I don't think at this particular point, we need to get some of these more difficult to treat patients, and just place them on placebo, and watch and see what happens.
We know what happens. The blood pressure goes up. Many of them may have acute heart failure, or progression of renal failure. And I just don't think it's necessary. And the FDA doesn't think it's necessary to prove that hypothesis.
Dr Carolyn Lam: David, what do you think about that? Do we need a placebo control trial? And that use of ambulatory blood pressure, that's novel aspects of this trial too.
Dr David Calhoun: I think use of placebo comparison has been for the traditional or conventional approach. I think most investigators, most clinicians, sort of anticipate seeing the placebo corrected effect. So, I think the results would have been, or will be potentially, more compelling if that's done. But, I can also appreciate Keith's contention, and it sounds like the FDA, that in this day and age, with use of automated office blood pressure measurements tend to minimize that white coat effect, and particularly true of ambulatory monitoring, that it may be that not using a placebo comparison maybe is compelling as well.
Dr Carolyn Lam: Indeed. I really enjoy actually just digging deep into the study like this. Keith, if I could just ask for some final words from you, learning lessons, or even what have you got planned next.
Dr Keith Ferdinand: The first lesson is, we need to continue to pay attention to hypertension. It's kind of been placed on the back burner with more interest now in diabetes and sugar, a lot of interest in lipids because of some of the new agents. But if you look across the globe, Asians, blacks, whites, regardless of race or ethnicity or geography, hypertension is the most potent cardiovascular risk factor, and I think we need to continue to address that.
In terms of this particular agent, I believe that we will have to have some sort of placebo arm, but again, I think it's going to be built on a conventional medication, and then randomized with Firibastat versus placebo on top of conventional medications. In a more severe or a more difficult to treat hypertension, I'm just not really convinced that we need to do a purely placebo arm.
Dr Carolyn Lam: Great, Keith. And David, how about yourself? Any take home messages?
Dr David Calhoun: I think when there's a new in-class compound, I think that's always exciting, particularly when it has the initial results, preliminary results, that Keith is reporting. As many agents as there are out there to treat hypertension, we still are not doing as well as we should be. I think it can only help to have additional classes of agents as therapeutic options, and I think that's particularly true with minority patients, who are, as Keith has indicated, are at the biggest need in terms of controlling blood pressure. Keith, these initial results are very exciting, and I look forward to future studies.
Dr Carolyn Lam: Completely sharing your enthusiasm here. Thank you so much, Keith, for publishing this remarkable paper with us at Circulation. Thank you, David, for helping us manage it.
And thank you, audience, for joining us today. You've been listening to Circulation on the Run. Don't forget to tune in again next week.
This program is copyright American Heart Association 2019.
Dr Greg Hundley Welcome back everyone from our week hiatus for this July 2nd issue of Circulation On the Run. I'm Dr Greg Hundley, from the Pauley Heart Center at VCU health in Richmond, Virginia.
Dr Carolyn Lam: And I'm Carolyn Lam, associate editor from the National Heart Center and Duke National University of Singapore. So good to be back, Greg.
Dr Greg Hundley Absolutely. So Carolyn, our featured articles going to focus on amyloid and transthyretin amyloid is recognized in middle age and older individuals with increases in LV mass and heart failure. And in our featured article from the United Kingdom, Dr Gilmore and colleagues are going to discuss the natural history of this disease and compare outcomes of those with acquired versus hereditary forms of the disease. But before we get to that interview, how about we discuss several other original articles?
Dr Carolyn Lam: For sure, Greg. Thanks. I want to pick two genetic papers in this issue. They're really exciting. The first one is actually the first study to consider the association between rare genetic variance in a large set of cardiomyopathy genes and the occurrence of cancer therapy induced cardiomyopathy. So this paper is from co-corresponding authors, Dr Garcia-Pavia from hospital Universitario Puerta de Hierro from Madrid, and Dr Christine Seidman from Harvard Medical School in Boston, Massachusetts. The authors studied 213 patients with cancer therapy induced cardiomyopathy from three cohorts. The first retrospectively recruited adults with diverse cancers, the second prospectively phenotyped breast cancer patients. And then the third prospectively phenotyped children with acute myeloid leukemia. They showed an increased prevalence of rare variants in cardiomyopathy genes, particularly the truncating variants of the TTN gene in both adults and pediatric cancer patients with cancer therapy induced cardiomyopathy. They confirmed the human genetic data with experimental analyses showing that anthracyclines induced protracted left ventricular dysfunction in mice with truncating variants of TTN genes but not in the wild type mice.
Dr Greg Hundley Aha. So what are the clinical implications of this study, Carolyn?
Dr Carolyn Lam: Well, the findings show that variance in cardiomyopathy genes contribute to cancer therapy induced cardiomyopathy susceptibility among adult and pediatric cancer patients. And thus the identification of genetic risk factors really opens the door to new opportunities to define patients at high risk of cancer therapy induced cardiomyopathy and associated adverse outcomes.
I want to go onto the next paper because it's so related. It's another genetic paper. This time looking further at the truncating variants of the TTN genes and a very novel approach, they aim to assess a genomics first approach to assess the consequences of these TTN variants. So, this was from corresponding author Dr Zoltan Arany from Perelman School of Medicine in University of Pennsylvania where he and his colleagues reviewed whole exome sequence data for more than 71,000 individuals to identify anyone with truncating variants of TTN genes. They further selected individuals with these variants in exons highly expressed in the heart and using a linked electronic health record, they evaluated the associations of these truncating variants of TTN genes with the diagnosis and quantitative echocardiographic measures. They also reviewed data from the Jackson Heart study to validate specific analyses for individuals of African ancestry.
Dr Greg Hundley Interesting. So we're hearing a little bit about different ancestry and TTN genes. What did they find?
Dr Carolyn Lam: So, I should have first clarified that that first look was in individuals of European ancestry. And they found there that the individuals of European ancestry identified through this genomics VERSE approach had a much greater odds of developing dilated cardiomyopathy and had lower left ventricular function than their peers, whether or not a clinical diagnosis of dilated cardiomyopathy was present. They also found that the association of the TTN variants and dilated cardiomyopathy was much weaker in individuals of African ancestry. So in summary, truncating genetic variants of TTN had a measurable effect in large clinical populations with respect to both strong associations with cardiomyopathy and with associations with quantitative differences in cardiac structure and function. Given the caveat though, that these association appeared strongest in individuals of European ancestry. So Greg, what did you have?
Dr Greg Hundley Well, Carolyn, the overlap of inflammatory processes operating in atherosclerosis and the rich presence of macrophages within plaques make macrophages a strong candidate for therapeutic targeting in atherosclerosis. And so this study comes from Levent Akyürek at the Institute of Biomedicine and involves targeting filament A to reduce macrophage activity in atherosclerosis. So filament A is a large actin binding protein that has been implicated in atherosclerosis and this study tested the hypothesis that targeting filament A in macrophages would impair atherosclerosis in vivo in mice and the investigators evaluated the expression of filament A in human atherosclerotic plaques.
Dr Carolyn Lam: Huh, interesting. So what did it show?
Dr Greg Hundley: Well, in humans, expression of filament A is increased in macrophages and advanced atherosclerotic plaques of human carotid arteries. In mice, in the absence of filament A, macrophages displayed impaired migration, proliferation and lipid uptake and secreted lower levels of inflammatory IL 6, also lack of filament A and macrophages in vivo reduced aortic plaque size and atherogenic mice.
There were additional mechanistic findings and that the C terminal fragment of Filament A produced by calpain cleavage regulated IL 6 secretion in macrophages and treatment with calpeptin, which inhibits calpain cleavage, reduced aortic plaque size and atherogenic mice. And so therefore, filament A might serve as a prognostic biomarker and atherogenesis and perhaps targeting the C terminal proteolytic fragment of filament A could be a strategy to reduce inflammation and atherosclerotic plaque development. Carolyn, I've got another paper, but guess what? This one has our first quiz of the academic new year. This is a paper about Nexclin, and it discusses a new component of junctional membrane complexes required for cardiac T-tubule formation. The corresponding authors are led by professor Zhou Shen from the University of California, San Diego. So, Carolyn in this quiz, what is a T-tubule?
Dr Carolyn Lam: Greg, that is mean! T-Tubules, something inside the cell. Something to do with membranes folding over.
Dr Greg Hundley Yeah, you know this is one of those, it's not multiple choice. It's an open ended question. You need your little blue book. You've got to write the answer. So T, or transverse, tubules are extensions of the cell membrane that penetrate into the center of cardiac muscle cells and interact with the sarcoplasmic reticulum to facilitate calcium release and thus help modulate myocardial contraction. T-tubule uncoupling and remodeling are known features of heart failure.
Dr Carolyn Lam: Alright, so that's T-tubules. Guess what Greg, I'm going to ask you before you ask me. So, what's Nexilin?
Dr Greg Hundley I read the paper like a good student of the American Heart Association. This was answered by the investigative team of Chen and his associates. Nexilin has been identified as an actin binding protein and multiple mutations in the nexin gene are associated with cardiac diseases. In this study, Nexilin was required for initiation of T-tubule invagination and overall T-tubule formation, with a loss of next sullen leading to impaired calcium handling. Clinically, these results identified Nexilin as a new possible target for T-tubule remodeling and provide mechanistic insight into molecular pathways leading to cardiomyopathy in patients with mutations in Nexilin. So Carolyn, great job on our first quiz of the academic new year. And how about we move on to that featured discussion?
Dr Carolyn Lam: Absolutely.
Dr Greg Hundley Welcome everyone to our featured article discussion on this July 2nd and we are going to discuss with Dr Julian Gilmore from London, and our editor Dr Justin Grodin from Dallas, regarding amyloid. And Julian, I understand this particular study you have investigated a natural history of transthyretin amyloidosis cardiomyopathy. Can you tell us a little bit about transthyretin amyloid as opposed to light chain amyloid? And then also I think there's two types of transthyretin amyloid, both a hereditary and then a wild type.
Dr Julian Gilmore: Amyloidosis is a disorder of protein misfolding, and there are in fact many different proteins that can misfold and form amyloid fibrils. When they form fibrils they become insoluble and tend to build up and cause damage to whichever organ they're depositing in. Two of the proteins that form amyloid fibrils in humans in vivo are transthyretin, known as TTR for short, or immunoglobulin light chains, known as immunoglobulin light chains, and those two proteins cause transthyretin amyloidosis and AL amyloidosis or immunoglobulin light chain amyloidosis respectively. Those are the main two types of amyloid that affect the heart or cause a cardiomyopathy and they behave very differently in terms of their natural history in that AL amyloidosis is a very aggressive, rapidly fatal cardiomyopathy if untreated. Whereas cardiac transthyretin amyloidosis tends to be a more gradual albeit progressive cardiomyopathy.
Transthyretin amyloidosis, as you alluded to, can either be acquired, known as wild type or hereditary and in the hereditary version it's associated with mutations in the transthyretin gene of which there are more than 130 now that are recognized to cause disease. The wild type version of the disease, the non-hereditary version of the disease, is now an increasingly recognized cause of heart failure, mainly in older individuals and particularly older males. And the hereditary version essentially remains a rather rarer disease, although the mutation that is associated or it is associated with a risk of developing this disease occurs in certain populations and in particular occurs in 4% of people of African descent, as a particular genetic mutation that occurs in 4% of individuals of African descent. So and that is associated with risk of developing this hereditary transthyretin cardiomyopathy.
Dr Greg Hundley: And so, there's the UK National Amyloidosis Center. Tell us a little bit from that center, what did you do with this particular study in terms of its design and what were your results?
Dr Julian Gilmore: Essentially the UK National Amyloidosis Center is the single center in the UK, which is commissioned centrally to diagnose and type, stage, and provide treatment FYS for patients with amyloidosis. And that includes all parts of amyloidosis. We studied a large number of patients with cardiac transthyretin amyloidosis, so cardiac ATTR amyloidosis, who referred to our center and studied them longitudinally, if you like, over the course of many years. So this was a natural history study for a condition for which at the time of the onset of the study and until the end of the study there was no disease modifying treatment and essentially what we found is that there was a great delay in diagnosis amongst most patients diagnosed with the disease and in fact the median number of attendances in hospital for patients diagnosed with the disease before they were actually diagnosed with 17 which is quite amazing and unsurprisingly in a gradually progressive disease, by the time they were diagnosed, their quality of life was very poor.
We found that their quality of life symptoms gradually progressed and that they became more and more functionally impaired and had relatively poor survival with a median survival of somewhere in the region of five years. What we did find is that patients with a particular type of hereditary, ATTR amyloidosis, the type that I alluded to earlier, the mutation for which is present in 4% of people of African ancestry, he planted the V122I mutation. Patients carrying that particular mutation actually have more aggressive disease and survive for shorter than patients with the wild type disease.
So, 17 hospitalizations before diagnosis and the proceeding three years. Were there factors in your study that you could identify that we should now be looking for to try and make this diagnosis earlier?
Absolutely. So one of the reasons for not diagnosing the condition is basically the poor sensitivity and specificity of echocardiography, which is generally the first investigation that a cardiologist will request when a patient presents with symptoms of heart failure. There are some particular features on echocardiography that can provide clues such as strain measurement on tissue doppler imaging, where one can get a bullseye pattern, that's been reported in the literature. So there are particular features on echocardiography that one can look at to increase the chance of picking up this disease. And in particular the big increase in the number of diagnoses over recent years has been because of cardiac MRI scanning, which has become an increasingly used tool for the investigation of heart failure in which one gets a very characteristic picture of late gadolinium enhancement when it's performed in a patient with cardiac amyloidosis, which immediately triggers people to think, ah, here it is, we've got amyloid.
And the other sort of novel diagnostic technique as being bone scintigraphy. In the UK we use a bone tracer called DPD and in the US a bone tracer called PYP, and those bone tracers have exquisite sensitivity for cardiac amyloidosis. So if one injects these tracers in a patient with cardiac amyloidosis one gets cardiac uptake into the heart, which can't really be missed on a planar scan. So those two techniques basically, the increasing needs of cardiac MRI and the increasing use of bone scintigraphy to investigate patients with heart failure have resulted in a great increase in the number of diagnoses.
The last thing to say is that a huge proportion of patients with amyloid or transthyretin amyloid cardiomyopathy have actually had carpal tunnel syndrome previously. The median time from carpal tunnel syndrome to presentation with heart failure is about seven years, but that is another red flag, if you like, that ought to at least trigger a doctor to think could be amyloid. A thick walled heart in the context of someone whose had previous carpal tunnel syndrome. So there are a few clues there as to how one might make an earlier diagnosis, which is absolutely necessary given the nature of our data, sharing the delays that I outlined down here.
Dr Greg Hundley And Julian, last quick question before we get with Justin here. In your data, can you describe for us the importance of that earlier diagnosis related to long-term outcomes as opposed to the group that was diagnosed much later, you know, beyond your median. What was the difference in prognosis in those two groups?
Dr Julian Gilmore: There is no doubt that if patients are diagnosed earlier, they survived for longer, reflecting the natural history of the disease. So these patients, as I mentioned earlier, did not receive any disease modifying therapy and we did divide the patients into pre 2012, when patients were essentially diagnosed by endomyocardial biopsy, or the vast majority of them were diagnosed by endomyocardial biopsy, and post 2012 by which time most patients were diagnosed via an imaging, if you like, algorithm that we published in 2016 in the same journal in circulation. And the patients who were diagnosed earlier had significantly improved survival. Just corroborating really the fact that they were actually diagnosed earlier. What's particularly relevant there, is that the treatments that have been developed for this condition, and there are some recent new potential disease modifying treatments that have been developed, they find that things seem to slow progression of the disease rather than stop it or reverse it, so that if one can diagnose a patient early when their quality of life is still good and then slow progression, there's a high chance of improving quality of life quite substantially and obviously prolonging life.
Dr Greg Hundley Thank you so much, Julian. And Justin as the managing editor of this article, what struck you most in terms of its results and conclusions, and how we should manage patients today suspected of transthyretin amyloid?
Dr Justin Grodin: Well, I would say that really there are four things that in my opinion that were quite striking. The first at least as highlighted by Professor Gilmore is that the UK National Amyloid Center, they get the national case load. So this is unlike other cohorts and other centers across the world in that this is subject to less referral bias than others. So I think that's the first thing that's quite impressive. And I think Professor Gilmore really hit the nail on the head when he highlighted that this paper, that this analysis really underscores the importance of an early efficient diagnosis. And a lot of this is really through his seminal work in achieving a non-biopsy diagnosis of ATTR amyloidosis and his findings have been replicated in other cohorts as well. So I think those, I would like to say are really one and two.
And then number three, which is one that I don't think Dr Gillmor mentioned, I think he mentioned indirectly, but we were also struck by the prognostic importance or I should say the prognostic meaning of having the V122I mutation. So these are individuals like hereditary amyloidosis and they have a single mutation. This is the one that is prevalent, at least we think from population studies, in approximately 4% of the African or Afro-Caribbean population. And we really see unequivocally that the time from symptom onset to diagnosis was shorter and the prognosis was actually worse in comparison to other mutations or in individuals with wild-type amyloid. And this is an important finding really for two reasons. Number one, it is largely confirmatory from other studies, but it's important to note that those studies were subject to referral bias. And we could never ever successfully incorporate whether or not socioeconomic status had actually influenced the bad outcomes of these individuals.
And I would say that Professor Gilmore's findings are quite compelling in that regard. And then the second thing for this point is really this underscores I think the importance of genetic testing. I mean I think all the readers can take that message away. And then the fourth thing, which as Professor Gilmore alluded was the striking amounts of healthcare utilization, although it was in a minority, certainly quite compelling and really what it speaks to is multiple missed opportunities. Even in the UK where they have a centralized center of excellence, just like Professor Gilmore's, that there were delays in diagnosis and then when delayed these patients are quite ill. And I think I'm making all these points because at least in 2019, the regulatory environment about amyloidosis, specifically ATTR therapies. In The United States, it's actually changed. So a disease where we had therapies that might be off label or our therapies were largely symptomatic, where we managed the patient's signs and symptoms, we now actually have disease modifying therapies.
So, in the United States in 2018, there were two biological agents that actually silence the livers production of transthyretin or TTR and they were approved for hereditary ATTR polyneuropathy. But there is some suggestion from sub-studies that those will have the efficacy in cardiac amyloid. And then number two in the United States, we recently gained approval in May of a drug that actually stabilizes the transthyretin protein or tetramer. So in other words, just as Professor Gilmore had highlighted at the beginning of this call, it stabilizes the breaking up, if you will, of this protein, which is the rate limiting step of amyloid formation. So you take this pill and then the transthyretin molecule does not then deposit amyloid. So this is really exciting because professor Gilmore's cohort study really captures now at least the impact that these therapies might have, and in the United States and across the world and in the UK, these therapies are being studied for all types of ATTR amyloid and really they're on the horizon. So it's given us very deep insights into how these might impact our patient's lives with ATTR.
Dr Greg Hundley Julian, Justin, that was just such an impressive discussion of a very important topic and something that again, with echocardiography, we really need to start thinking about when perhaps we appreciate some LVH, diastolic dysfunction. We have apical sparing of systolic function, but abnormal basal systolic function. Could you just summarize one point, each of you, that we should be thinking about as we move forward and we're seeing patients in our clinic that might have this disorder.
Dr Justin Grodin: The first thing to say is that awareness is all important. You know, 25% of male individuals in autopsy studies over the age of 80 have ATTR amyloid deposits in their heart, and when one sees a thick walled heart in any situation, and particularly in an elderly individual, one needs to think, could this be, amyloid, that's the first thing. And the second thing I'd like to say is that if that thought occurs, which it should occur at a much earlier stage than it does probably in most cardiologists minds, then one should think about either a bone scan, which is a cheap, simple tests. The PYP scan in the US or DPD scan in the UK and or an MRI scan, which has a very characteristic picture in a patient with cardiac amyloidosis. So those would be my take home messages to try and improve early diagnosis.
You know, I'd like to dovetail what Professor Gilmore had said cause he just about took the words out of my mouth and I would like to emphasize the first point in that the diagnosis of AL, we mentioned earlier, or an ATTR amyloidosis, really necessitates a very, very high index of suspicion. What do I mean by that? When somebody has a thick heart muscle and it's not explained by something else, in other words, they don't have a lifetime history of high blood pressure and they don't have high blood pressure seeing you, or maybe they don't respond adequately to standard heart failure therapies when something is not fitting, it's always incumbent to the treating clinician to think amyloid.
I would also like to highlight some of the clues that Professor Gilmore had mentioned, that any individual with carpal tunnel syndrome or who might be hospitalized with heart failure, in other words, they have shortness of breath and swelling, and the squeeze of their heart is normal, or the ejection fraction is normal, that should increase your index of suspicion for amyloidosis. And then individuals that might've had lumbar canal surgery or really any issue impacting their tendons. And then they're now presenting with a thick heart muscle. That should be a clue. It doesn't necessarily mean it's diagnostic. In fact, the majority of those individuals might not have, or a large proportion, might not have ATTR amyloid, but it should certainly raise an eyebrow and then kind of allow the clinician to move forward with the evaluations that Professor Gilmore had mentioned.
Dr Greg Hundley Well, listeners, what a phenomenal discussion that we've had from Professor Julian Gilmore from London, and Dr Justin Grodin from Dallas, Texas, educating us on transthyretin amyloid and thinking about that early and being suspicious as we evaluate patients, particularly older individuals that are symptomatic with heart failure. Well, on behalf of Carolyn Lam, this is Greg Hundley. We look forward to seeing you next week. Have a great week.
Dr Carolyn Lam This program is copyright American Heart Association 2019