Dr Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage passes 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, director of the Pauley Heart Center at VCU Health in Richmond, Virginia. Well, Carolyn, this week's feature article really starts to look at micro-circulatory dysfunction and abnormal coronary perfusion during exercise that can be associated with myocardial ischemia. I hear you're anxious to hear about it, but why don't we go to your article first.
Dr Carolyn Lam: Here we go. This first paper I'd like to tell you about reports a novel cardiac kinase as a potential regulator in heart failure.
Dr Greg Hundley: Now remind me, Carolyn, I got to take me back a little bit. What are cardiac kinases?
Dr Carolyn Lam: Ah, I thought you would ask. Cardiac kinases are known to play a critical role in the development of heart failure and represent potential trackable therapeutic targets. Now to identify novel cardiac kinases involved in heart failure, the corresponding authors, Dr Hind Lal from University of Alabama at Birmingham and colleagues, employed an integrated transcriptomics and bioinformatics analysis and identified homeodomain-interacting protein kinase 2 or HIP kinase 2, as a novel candidate kinase. Now this is the first study to define the role of HIP kinase 2 in cardiac biology. In essence, they performed a series of mouse experiments that showed that cardiac HIP kinase 2 expression is elevated in adults compared to embryonal and neonatal stage of mouse experiments, but down regulated in failing hearts.
Deletion of HIP kinase 2 in the cardiomyocytes led to decreased cardiac function in adulthood. The cardiac effect of HIP kinase 2 correlated to its gene expression level and impaired ERK signaling was discovered as the main driver of HIP kinase 2 deficient phenotype by enhancing apoptosis. Taken together these findings really suggest that cardiomyocyte HIP kinase 2 is required to maintain novel cardiac function via ERK signaling.
Dr Greg Hundley: All right, Carolyn, my favorite question, what does this mean for us clinically?
Dr Carolyn Lam: Two points, first since HIP kinase 2 is protective in cardiomyocytes, gene therapy using HIP kinase 2 could be a potential therapeutic method of heart failure treatment in future. Secondly, because inhibition of HIP kinase 2 has been proposed as a therapeutic approach for certain cancers and for renal fibrosis, these results suggest that caution needs to be taken for the potential cardiotoxicity of HIP kinase 2 inhibition in the adult heart. Interesting.
Dr Greg Hundley: Yeah. Very nice. Well, I'm going to switch gears a little bit Carolyn and talk about ablation for atrial fibrillation. And the corresponding author of this paper is Jason Andrade from Vancouver General Hospital. In his study, they randomly assigned 346 patients with drug-refractory paroxysmal atrial fibrillation to A, contact force guided RF ablation, B, four-minute cryoballoon ablation or C, two-minute cryoballoon ablation and they followed the patients for 12 months. Now the primary outcome was time to first documented recurrence of symptomatic or asymptomatic atrial tachyarrhythmias, whether that be AFib, aflutter, atrial tachycardia, between days 91 and 365 after the ablation or a repeat ablation procedure at any time. And the secondary endpoints included freedom from symptomatic arrhythmia and AF burden.
Dr Carolyn Lam: Interesting clinical question. What did the results show?
Dr Greg Hundley: One-year freedom from atrial tachyarrhythmia defined by continuous rhythm monitoring, was 54, 52 and 52% with each of those therapies respectively. One-year freedom from symptomatic tachyarrhythmia defined by continuous monitoring was 79, 78 and 73% with those therapies respectively. No difference statistically in either.
Dr Carolyn Lam: Right. No significant difference in those outcomes but what about AF burden or side effects?
Dr Greg Hundley: Right, Carolyn. Well, compared to the pre-ablation monitoring period, AF burden was reduced by a median of 99%, 99.9% and 98.4% in each of the three therapies. No significant difference. And serious adverse events occurred in two patients in the CF-RF group, in six patients in Cryo with four minutes and in seven patients with Cryo in two minutes. Again, no significant difference between those groups.
Dr Carolyn Lam: Greg, were there any significant difference in these techniques?
Dr Greg Hundley: Well, Carolyn, that contact force RF group at a significantly longer procedure duration but a significantly shorter fluoroscopy exposure. And the P was 0.001 versus the cryoballoon group. In summary, in this multicenter, randomized, single blinded trial, contact force RF ablation, and two different regimens of cryoballoon ablation, resulted in no difference in one-year efficacy, which was 53% by time to first recurrence, but 98% burden reduction as assessed by continuous cardiac rhythm monitoring. A new study in patients with ablations looking at these new techniques and for many reasons they're very similar.
Dr Carolyn Lam: Very interesting. My next paper also has to do with atrial fibrillation. Now we know that numerous skills exist for classification of major bleeding events in patients with atrial fibrillation who are anticoagulated. Now there are limited data comparing the most commonly used bleeding scales within a single at-risk cohort of patients with atrial fibrillation. And so Dr Bergmark from the TIMI study group and colleagues analyzed bleeding outcomes according to the ISTH, TIMI GUSTO and BARC bleeding scales in the ENGAGE AF-TIMI 48 trial of edoxaban versus warfarin. And they found that among patients with atrial fibrillation at risk for stroke, there was an approximately four-fold difference in the frequency of the most severe bleeding events across these commonly used bleeding scales. Further, the relative safety of edoxaban as compared with warfarin tended to increase with greater severity of bleeding.
Dr Greg Hundley: Interesting Carolyn. Tell me, what's the take home message from this study?
Dr Carolyn Lam: This analysis reminds us that the currently available and commonly used bleeding scales differ in important ways. The analysis shows us that one size does not fit all and that the most appropriate bleeding scale really depends on the clinical setting and the intervention being investigated. For patients particularly concerned about bleeding, these results should provide additional reassurance about the safety of the DOX. Finally, this analysis also illustrates how the differential effect of edoxaban compared to warfarin on bleeding, impacts the assessment of net clinical benefit. Now this is discussed in an editorial by John Alexander and Adam Nelson who highlight that one of the most interesting findings was the statistically significant and graded amplification of edoxaban safety compared to warfarin with more severe bleeding.
Greg, perhaps now's a good time, tell us what else is in this issue of the journal?
Dr Greg Hundley: Happy to do so. Ben Freedman from the University of Sydney discusses in a white paper concurrent thoughts from the AF, another atrial fibrillation paper, AF screen international collaboration, which summarizes existing evidence and knowledge gaps on searching for an AFib post-stroke using ECG monitoring. And Carolyn, our own James de Lemos suggests in an on my mind piece that subdividing type two MI into different based on etiology could lead to improved forecasting of events. In a perspective article, Tommy Wang from Vanderbilt revisits the polypill and discusses why we need population-based approaches in the precision medicine era.
Dr Carolyn Lam: Wow. Super interesting. And how about letters? What's in the mailbox?
Dr Greg Hundley: Oh gosh, Carolyn. It's really full this week. There are multiple letters ranging from science, to responses, to prior inquiries. It is really interesting to read these responses and the authors going back and forth and having that open discussion for us. And so Brody Slostad first has his own research letter that reviews unicuspid aortic valves, the demographics, comorbidities, and echocardiographic features and long-term outcomes. Darren Casteel from UC San Diego discusses blood pressure lowering by the antioxidant resveratrol is counterintuitively mediated by oxidation of the cyclic GMP dependent protein kinase. And there's a nice response by Dr Joseph Burgoyne from Kings College London. Finally, there's a letter by Daxin Wang and his associates from Yangzhou University regarding the article targeting filament A reduces macrophage activity in atherosclerosis and there's a corresponding response from Levent Akyürek event accurate from the Institute of Biomedicine. Great mailbox this week, Carolyn. How about now we go on to our feature discussion?
Dr Carolyn Lam: Oh boy, I can't wait. Thanks Greg.
How does coronary microvascular dysfunction relate to exercise physiology or inducible myocardial ischemia? Well, we are going to be talking all about that in the next few minutes and that's because our feature paper this week is the first study to really directly assess coronary blood flow during exercise in patients with microvascular dysfunction. And to compare these changes with high resolution perfusion imaging. We're really pleased to have with us the first and corresponding author, Dr Divaka Perera from Kings College London, as well as our associate editor Dharam Kumbhani from UT Southwestern. Welcome gentlemen and Divaka. Could you start by telling us what makes your study unique? What did you do? What did you find?
Dr Divaka Perera: As you said, microvascular dysfunction is being recognized as quite a common cause of angina. In fact, about 40% of patients who present to the Cath lab for a diagnosis of angina are found to have nonobstructive coronary artery disease, and a significant proportion of these are thought to have microvascular dysfunction. The definition of microvascular dysfunction has been based on demonstration of impaired coronary flow reserve, but what we haven't known is whether the Cath lab measurements that are made actually correlate with exercise maladaptation. Bearing in mind that these patients experience symptoms during exercise and whether there's actually demonstrable ischemia in these patients who don't have obstructed coronary artery disease. Our study's unique in that we were able to measure directly exercise physiology during cardiac catheterization and we were able to stratify patients upfront on the basis of their coronary flow reserve and then in a blinded fashion assess whether these patients who did or didn't have augmentation of flow reserve had ischemia.
Dr Carolyn Lam: Divaka, could you give us a detailed picture of what that meant? These patients were sitting with catheters and then riding bikes or give us a picture of what you did.
Dr Divaka Perera: Right. This is a setup we've been working on for the last 10 years or so to make sure that we have a reproducible and safe protocol that can be carried out in a Cath lab. A patient who was referred for diagnostic angiography, this may have been the first investigation they were having, or they may have had some form of noninvasive testing beforehand. These patients would undergo angiography via the right radial artery with their arm extended out to the side. And then during angiography when the time was right to assess this condition, they would carry out supine bicycle exercise. And that was a bike that was mounted onto the Cath lab table. During all of this, we would measure intracoronary pressure and flow velocity using this combo tipped wire which could give us distal coronary pressure and Doppler flow velocity and we were able to do this throughout the condition of exercise.
Dr Carolyn Lam: That's cool, but then how did the MRI come in then?
Dr Divaka Perera: Right. The MRI was actually done at a different visit and in that situation, we only carried out vasodilator testing. We also do exercise patients in the MR scanner, but we haven't included any of those data in this current paper. Patients would have two visits at least as part of this research protocol.
Dr Carolyn Lam: Maybe now with that background, tell us what you found.
Dr Divaka Perera: The first and most important finding was that patients are classified in the Cath lab on the basis of a coronary flow reserve below 2.5. The flow reserve threshold of 2.5, actually have demonstrable ischemia on a stress profusion myocardial magnetic resonance imaging scan. 82% of patients in the MVD group, the microvascular dysfunction group had inducible ischemia compared to just 22% of controls. This was mirrored by quantitative myocardial profusion reserve data as well, where the ability to augment overall myocardial blood flow was significantly diminished in patients with MVD. And perhaps most interestingly, their exercise pathophysiology was dramatically different to that of controls.
In the healthy heart, the heart actually becomes more efficient during exercise. We were able to quantify the proportion of accelerating and decelerating waves by carrying out a technique called wave intensity analysis on the data I've just described, on the physiology data that I've just described. And by doing that we were able to quantify the proportion of accelerating waves to decelerating wave energy. In the healthy heart, as we exercise the proportion of accelerating wave energy increases and we've termed that profusion efficiency. Now in stark contrast when you have MVD, the heart actually becomes less efficient and the profusion efficiency decreases. This is a normal finding and really told us that cath lab measurement based on the response to vasodilators seems to identify a population who have maladaptation during exercise and demonstrable ischemia on scanning.
Dr Carolyn Lam: Wow. Dharam, could I now ask you to help frame these results in the context of what's known or not known about microvascular disease?
Dr Dharam Kumbhani: I want to congratulate the Divaka and his group. I think this is very interesting analysis. It's really a new paradigm about what is now understood to be more and more of a common issue. It seems like a lot of work, even for the patient population that was enrolled. And I think done in an incredibly thoughtful way. Having said that, I guess what I'd like to understand as a card carrying interventionalist myself, I imagine that some of this may be perhaps in need of validation. And so do you think that this study and in some of the two distinct phenotypes that you describe that this will need to be demonstrated in other labs and other situations?
Dr Divaka Perera: Absolutely. I think we have demonstrated is a proof of concept that we can assess these patients in the Cath lab and then shown that firstly, the measurement of CFR and the classification of patients on the basis of CFR does identify a group with distinct pathophysiology, but that that doesn't tell the whole story because your CFR can be diminished for one of two broad reasons. That there's an abnormality of resting flow or an abnormality of hyperemic or flow at maximum stress. Now, the traditional paradigm of microvascular dysfunction has been that these patients will all have, or the majority will have, diminution of stress flow. Or that they might have an inability to reduce their microvascular resistance during stress.
What we have found in contrast is that actually two thirds of patients who have impaired flow reserve have impaired flow reserve because of an abnormality of rest perfusion. One third only conform to that traditional paradigm, and this, as you've rightly pointed out, is something that's going to need further investigation. It's very exciting and it might mean that we have a basis on which to try different therapies, for instance. That those therapies might be pathophysiologically stratified, but it needs a lot of work and I'm sure you won't be surprised to know that we've already embarked on that next stage of work to validate and take this forward.
Dr Dharam Kumbhani: Let's say you were able to validate this paradigm and you indeed are able to stratify patients with microvascular disease. What you have defined as a functional and a structural endotype. Do you believe that if this were validated and established further from a diagnostic standpoint in labs across other places, what kind of diagnostic testing do you imagine that this would require?
Dr Divaka Perera: At the most basic level Dharam, I think we need to get interventional cardiologists and any cardiologist doing diagnostic angiography to realize that the finding of unobstructed coronary artery disease isn't the final answer. It actually begins a whole chapter of investigation and if we can at least get people to think about doing a physiology study in a way analogous to what's happened when we find equivocal amounts of coronary artery disease that you'd reach for a pressure wire and do a functional test. If we can introduce that paradigm once we find normal or unobstructed coronary arteries in a patient with classical symptoms, that would be step number one. The next step will be that we'll have across the board a harmonized means of classifying these patients and by looking at microvascular resistance as well as coronary flow reserve, we might be able to identify endotypes that behave differently and need different forms of therapy. Once we've got that in place, then we have a basis to carry out large registries and large trials in a systematic fashion.
Dr Dharam Kumbhani: Let me just clarify that. You don't envision that let's say this all gets validated. Do you envision that labs that do CFR measurements would then in addition need to have the ability to do exercise testing as well?
Dr Divaka Perera: No, I don't think so. I think exercise testing requires a really carefully evolved set up and it's not practical to unleash this onto world at large. But it generates hypotheses and examines concepts which can then be translated. I think routine use of microvascular function testing will rely on response to vasodilators and these will be endothelium independent techniques such as an adenosine and possibly as a second stratum, endothelium dependent methods as well. Perhaps using graded acetylcholine infusions. But it would be vasodilator testing in the Cath lab rather than exercise.
Dr Dharam Kumbhani: Got it.
Dr Carolyn Lam: Fascinating. Wait, Divaka, just to be sure that the audience got this. You talked about the two endotypes, a structural and functional and the structural one is the one that has a low flow to begin with. The functional is the one that the hyperemic flow is the one that's mainly impaired. Is that correct? Just checking.
Dr Divaka Perera: Let me just clarify. Those patients that we've termed to have functional MVD have elevated resting flow, but actually essentially normal flow at stress. In contrast, those who have structural MVD have essentially normal resting flow but have an inability to augment their peak flow. The net result appears to be the same in the sense that they all have demonstrable ischemia on noninvasive testing, but the mechanisms are different and therefore the therapies that we direct towards these patients may also need to be different.
Dr Carolyn Lam: Very nicely put. Thank you. And if the audience, you still didn't get that, pick up the paper and read it. But say, one last question because you kind of teased us just now and said, actually we are going on with next steps and so on. What are the next steps? Maybe from you and then Dharam.
Dr Divaka Perera: I think the next step is to assess whether this sort of stratification allows us to treat patients more efficiently. To deliver subtype stratified therapy. And we need to assess this with reference to meaningful clinical outcomes, so quality of life, exercise-based indices, et cetera, before we get onto looking at large numbers and then looking at cardiovascular outcome data.
Dr Carolyn Lam: Great. And Dharam, maybe I'll let you have the closing words.
Dr Dharam Kumbhani: We're understanding a lot more about what is always been an enigma for clinicians as far as having patients who present with very typical symptoms, either stable or unstable symptoms and have no coronary artery disease. I want to congratulate the authors on really trying to dig deeper into this and helping us with this very difficult patient population.
Dr Carolyn Lam: Thank you, Dharam. Thank you Divaka. And thank you listeners 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 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, Associate Editor, Director of the Poly Heart Center of VCU Health in Richmond, Virginia.
Well, Carolyn, this week's feature articles, very interesting, discussing hypertrophic cardiomyopathy and sudden death in young individuals. But, let's save all the details for later and start in on our coffee chat. So, Carolyn, have you got a paper that you'd like to start with?
Dr Carolyn Lam: I have, and it's a basic science paper. It's one that details the contribution of get this, M-C-U-B. Now this is a paralogue of the poor forming sub-unit MCU in mitochondrial calcium, uniporter regulation and function. Now, this paper shows, for the first time, MCUB's relevance to cardiac physiology, and it's from corresponding author Dr Elrod from Center of Translational Medicine, Louis Katz School of Medicine at Temple University in Philadelphia, and their coauthors, who showed, in a series of elegant work, that MCUB is absent from the uniporter complex in the homeostatic heart. But it's incorporated into the mitochondrial calcium uniporter following ischemic injury and thus represents an endogenous mechanism to limit mitochondrial calcium overload during stress.
Interestingly, the increased incorporation of MCUB into this mitochondrial calcium uniporter is too little and too late to limit acute cell death following ischemic reperfusion injury but may limit cell loss during chronic stress.
Dr Greg Hundley: So Carolyn, tell me what are the clinical implications of this important finding?
Dr Carolyn Lam: Well, simply put, MCUB represents a novel therapeutic target to modulate mitochondrial calcium uptake in disease states speech during mitochondrial calcium overload such as myocardial infarction and heart failure.
Dr Greg Hundley: Very nice, Carolyn. Well, I've got another basic science paper and it involves Protein Kinase N and how that promotes stress induced cardiac dysfunction through phosphorylation of myocardin-related transcription factor A and disruption of its interaction with actin. This comes from the corresponding author Mikito Takefuji from Nagoya University Graduate School of Medicine. So Carolyn protein phosphorylation of course, is a major and essential intracellular mechanism that mediates various cellular processes in cardiomyocytes, in response, extracellular and intracellular signals. The RHOA-associated protein kinase, or ROCK Rho-kinase, in effect, are regulated by the small GTPS RHOA causes pathological phosphorylation of proteins resulting in cardiovascular diseases. RHOA also activates Protein Kinase N, however, and the role of PKN in cardiovascular disease remains unclear.
Dr Carolyn Lam: Ah, okay. So with that background, what did these authors find, Greg?
Dr Greg Hundley: Great question, Carolyn. What they found is that PKN inhibits the binding of MRTFA to G-actin by phosphorylating MRTFA and activating SRF mediated expression of cardiac hypertrophy and also fibrosis associated genes. Also, they showed that cardiomyocyte specific PKN1 and PKN2 double deficient mice are resistant to pressure overload and ANGII induced cardiac dysfunction.
Dr Carolyn Lam: Wow. There's a lot of letters in what you just said. So could you just tell us how does this impact heart failure research and management?
Dr Greg Hundley: So Carolyn, this PKN family appears to play a role in regulating hypertrophy and fibrosis in the heart and therefore could serve as a unique target for therapeutic interventions for heart failure in the future. And so maybe it's going to make its way your way.
Dr Carolyn Lam: Well, okay, well this next paper definitely is making its way my way and it focuses on the Sodium Glucose Co-transporter two inhibitors or SGLT-2 inhibitors, which we know lower cardiovascular events in patients with type two diabetes, but whether they promote direct cardiac effects as in that we can see in cardiac structure and function actually remained unknown until today's paper. And this is from Dr Subodh Verma and Dr Kim Connelly, these co-corresponding authors from St. Michael's Hospital and University of Toronto and their colleagues.
And they sought to determine if empagliflozin causes a decrease in left ventricular mass in patients with type two diabetes and coronary artery disease. So this was a six month double blind randomized placebo controlled trial. If individuals with type two diabetes, coronary artery disease and relatively normal left ventricular mass index. The primary outcome was six month change in left ventricular mass index to body surface area from the baseline and measured by cardiac magnetic resonance imaging and they found that the empagliflozin allocated group exhibited a significant reduction in left ventricular mass index compared with the placebo group.
Dr Greg Hundley: Wow, Carolyn. We have been hearing a lot about empagliflozin in the last several issues. How does this article differentiate what we do or maybe even change our practice?
Dr Carolyn Lam: Well, you know what? It enhances our understanding which is important. We knew about the events. Now we perhaps understand a little bit more of what it may be doing actually to the heart in terms of cardiac structure and function. The so the decrease in left ventricular mass associated with empagliflozin may explain and contribute to the cardiovascular benefits observed in patients with type two diabetes and coronary artery disease who are treated with SGLT-2 inhibitors. Now it's interesting the way we've gone like reverse translation in this, haven't we? Observing the events and then trying to find the mechanism. And this is in fact discussing an editorial by Mark Petrie and titled SGLT-2 Inhibitors: Searching for Mechanisms in the Wake of Large Positive Randomized Trials.
So Greg, after that, maybe you could tell us what else resides in this week's issue.
Dr Greg Hundley: Oh my goodness, Carolyn. Well, there's quite a bit. First Paola Erba from Pisa, Italy provides a nice In-Depth review of the use of echocardiography, radioisotope imaging and computed tomography for the assessment of patients with endocarditis. In another article, Wayne Batchelor and Rebecca Ortega and their colleagues discuss a Perspective piece, several strategies to improve enrollment of racial and ethnic minorities into clinical cohorts and trials addressing cardiovascular disease.
And of course we have our mailbox. And first is Dr Diamantis Tsilimigras from The Ohio State University, and he responds to a letter by Moris et al regarding the article: Effects of Arteriovenous Fistula Ligation, or cardiac structure and function in kidney transplant recipients.
Barry Borlaug from Mayo clinic discusses the importance of right ventricular volume loading and high output heart failure with arteriovenous fistulas.
And Carolyn, our own Joe Hill and a first author Dan Tong coauthor a letter pertaining to whether female sex is protective in a preclinical model of heart failure with preserved ejection fraction.
And then finally Toby Coates from Australia responds to several inquiries related to a prior publication regarding a published article involving the effects of arteriovenous fistula ligation on cardiac structure and function, again in kidney transplant recipients.
There's an On My Mind piece from Dr Heinrich Taegtmeyer from McGovern Medical School at The University of Texas Health Science Center at Houston, or UT Health, relating to characteristics of past prominent investigators. What makes them tick? What contributes to their long-term success and sharing their catch with others? And it's interesting Carolyn, because he compares the vast community of cardiovascular investigators to those that are like anglers or fisherman. Their passion is kind of like the allure of catching just one more. And in so doing, they like to share their catch with others.
Dr Carolyn Lam: That is hilarious. I don't think I've ever wanted more to be a fisherman or angler myself. Well that's great, Greg. Thanks and let's carry on with our feature discussion, shall we?
Dr Greg Hundley: Absolutely.
Welcome everyone to our feature discussion and we're going to discuss hypertrophic cardiomyopathy and sudden cardiac death and the relationship to exercise. And our study comes from Ontario and our lead investigator is Dr Paul Dorian from St. Michael's Hospital, and we also have our associate editor Mark Link from Dallas, Texas. Welcome gentlemen. And Paul, I'll start with you, tell us a little bit, what was the hypothesis and what were the aims that you were trying to accomplish with this particular study?
Dr Paul Dorian: Our hypothesis was that the likelihood of sudden death in patients with hypertrophic cardiomyopathy may be less than has previously been supposed. In brief, the community that looks after patients with HCM, we'll call it for short, is faced with a major challenge in knowing what the actual rate of sudden cardiac death is and it seems to be a little bit of a moving target. Over the last decade, I think that most clinics that look after these patients were faced with what appears to be a less and less frequent likelihood of sudden death in these mostly young patients that we follow. And because we have the opportunity to study this using a well-established prospective coroner database with autopsy results in all sudden deaths in Ontario in young individuals, that we have the opportunity to test our hypothesis that this sudden death rate is lower than had previously been suspected.
Dr Greg Hundley: It sounds like younger patients and trying to investigate the cause of sudden cardiac death. Can you tell us a little bit more about your study population and what was your study design?
Dr Paul Dorian: We had the fortune of being able to use the Coroner of Ontario database. Ontario has about 13 million population and by the longstanding design, almost all patients under the age of 45 who suffer out of hospital, sudden cardiac death receive a full coroner investigation and then 90% of them, it's an autopsy which includes a cardiac autopsy by a qualified forensic pathologist. And in the case of cardiac hypertrophy, the cases are re-reviewed by a specialized cardiac forensic pathologist. So we have very extensive, if you like, detective work, CSI-type information on virtually everybody who dies out of hospital suddenly including those individuals among them who have hypertrophic cardiomyopathy.
And what we did was we reviewed every single case of unexpected sudden death, looking for the specific diagnosis of cardiac hypertrophy or HCM. We verified the accuracy of our numbers by also using, for at least portions of our follow-up, the complete emergency medical services database for about 7 million people, mostly from Toronto. And this included all patients who had a 9-1-1 call for documented cardiac arrest. So we were able to verify that we missed essentially no patients without a hospital cardiac arrest who then died suddenly.
Dr Greg Hundley: Give us a little bit more about the numbers. So what was the age range of your study population, perhaps the gender and breakdown, things like that?
Dr Paul Dorian: We looked at individuals under the age of 45 but the median age was 36 for all of our patients. About 85% of the patients with documented HCM were male, 83% to be precise. And a pretty small minority of them. Had comorbidities that we would expect including hypertension, diabetes, et cetera. 11% were on beta blockers, and a small proportion had atrial fibrillation. So these are generally healthy individuals, or at least they had had relatively little interaction with the healthcare system and about half of these individuals had previously been diagnosed clinically with HCM and the rest had not been diagnosed as far as we could tell, or at least there was no medical record of them having been diagnosed with HCM.
Dr Greg Hundley: And what was the total number of individuals in this study? And then tell us a little bit about your study results.
Dr Paul Dorian: The total number of individuals who had definite HCM was about 45 we had 31 patients who were not known to have HCM who had definite HCM, which we defined as having myocardial disarray on cardiac microscopy and another 13 who are not known to have HCM. And then we had about another 10 patients who we thought had possible HCM because they had autopsy with hypertrophy but didn't have disarray. And a few patients that were diagnosed with HCM but didn't have autopsy. So the total population was approximately 50 patients and this is out of a total population of estimated population of about 140,000 HCM person-years using the widely estimated prevalence of HCM of one in 500.
Dr Greg Hundley: And what did you find?
Dr Paul Dorian: The bottom line, if you like, is that the annual incidence of unexpected sudden death, this would be out of hospital sudden death, was many folds lower than would've been expected based on prior publications and on prior risk calculators that are used by many physicians who for these patients. If your readers or the listeners just want single numbers, the total number of both definite probable and possible HCM related sudden death, this is the most sort of conservative estimate, would be approximately 0.4 per thousand person-years. So this would be less than one per thousand. This would be one half of one 10th of 1% so less than one per thousand per year. Patients with HCM will have sudden death. If we take the most conservative definitions.
Dr Greg Hundley: Now, could you tell whether these sudden deaths were related to exercise? That was sort of one of the feature questions.
Dr Paul Dorian: Absolutely. That's how we were of course, very interested so we defined both exercise as somebody died or doing sport or observed during exercise. I should emphasize that the coroners do extremely careful digging if you like into the circumstances. They interview paramedics, police, they have the police and paramedic report, they interview physicians, relatives, so they do a very thorough assessment of course as best as could be told after the fact. 65% of the sudden deaths occurred at rest and 18% occurred during light activity and about 10% occurred during exercise.
Dr Greg Hundley: Very good. I want to turn over to Mark now. This is Dr Mark link from University of Texas Southwestern in Dallas. Mark, how can we put the results from this study in the context of other studies relating to implementation of defibrillators in patients with hypertrophic cardiomyopathy?
Dr Mark Link: This study brings up a lot of issues and I want to applaud Paul and his gang for doing this. The data is very good. The autopsies are very good. So the quality of the data is excellent and the incidence of sudden death for a hypertrophy is lower than any other study that we've seen. And there are a number of possible reasons for that. Well, you know, one is that the Toronto group was using autopsied determined HCM or most other studies were kind of a mixed bag of clinical and autopsy and newspaper reports and all sorts of things. So the Toronto data is going to be probably the most accurate. The other issue, or the other question I think that could lead to a low incidence, is the denominator, in that there were estimated to be more hypertrophy in Toronto than there actually are. They use the commonly accepted one in 500 and I think that's a reasonable number across all sorts of populations that we see, but is it possible that maybe the one in 500 number isn't true for Toronto?
You know, I've heard one person explain this is that patients with HCM can't stand the cold weather. So they left Toronto, but it is a much lower number than we've seen in regards to sudden death. A couple of other things I think are very interesting in this study. One is that if you looked at the individuals that got ICD shocks for ventricular arrhythmias is there was about as many people as died suddenly, arguing that the Toronto physicians can actually in many ways predict who would benefit, predict which hypertrophy would benefit from an ICD. Since many of these hypertrophies didn't have appropriate ICD shocks. And I also found fascinating that more of the deaths occurred during rest or light activity than exercise. We all tend to think that HCM causes its sudden death with exercise. And what this study's telling us is that's not true that more sun deaths are during rest and light activity. So there's a lot of very interesting insights that come out of this manuscript in this data.
Dr Greg Hundley: Just following up on your last point, are there any inferences regarding activity in this patient population that we should take away from these study results?
Dr Mark Link: I think if you look at the early newspaper reports and they're in there as reports of the incidence of HCM, sudden deaths during sports. So it was because of that, that everyone associated HCM with death during sports. But you have to remember those studies didn't include athletes that died at night. Athletes that died during dinner. They only included athletes that died during sports. So we were missing a large percentage of the hypertrophs dying. And I think we sort of infer that it was exercise that was dangerous, but in fact there's really not that much data that would support that exercise is dangerous for patients with HCM.
Dr Greg Hundley: Interesting. So I'll maybe ask Mark first and then come back to you, Paul. Do you think there are tools that could be available, either blood testing or perhaps other imaging that could help identify which HCM patients may benefit from a defibrillator? Do these results help us in any way make that decision?
Dr Mark Link: Unfortunately, I don't think this study offers us any clues into which patients should get defibrillators. And clearly there are other data that look at risk factors for sudden cardiac death in hypertrophic cardiomyopathy. And one of the things that has come out over the last 10, 15 years is that magnetic resonance imaging, and in particular the scar burden magnetic resonance imaging may actually offer additional prognostic information to our traditional respect for stratification grade CM.
Dr Greg Hundley: Paul, do you have anything to add?
Dr Paul Dorian: Just a couple of things if I may. I think on that last point I completely agree with Mark. Of course we didn't have data on MRI, but the greater the scar burden, the greater our index of suspicion. It is interesting that 57% of the cases of sudden death had asymmetric septal hypertrophy, so we can at least hypothesize that it is possible that patients with septal hypertrophy as opposed to concentric hypertrophy may be at higher risk.
The one thing I might want to highlight for the listeners is that it would seem to me based on our data and based on our suspicions, is that there's probably a difference in the risk in patients who are discovered incidentally. In other words, somebody has an echocardiogram or an ECG for reasons unrelated to their heart and then HCM is discovered and these might be asymptomatic patients as opposed to patients that tend to be followed in specialized clinics who often are sent there because they have some symptoms or there's some specific signal that they have a clinically evident HCM. So I wouldn't want listeners to conclude that the risk is necessarily this low in patients that are transferred to a clinic because of disarray or atrial fibrillation or electro regurgitation or some other manifestation of a hypertrophic cardiomyopathy.
Dr Greg Hundley: Paul, I want to start with you first. What study do you think should follow yours? What's the next study?
Dr Paul Dorian: What I'd like to see, and this is technically feasible although practically challenging, is to use the big data approach and combine in one large database, all echocardiograms done in a large geographic area. All electrocardiograms done in a large geographic area with supplemented with clinical information and do, over a long period of time, a prospective study looking at all patients with cardiac hypertrophy, particularly asymmetric hypertrophy or suspected to have HCM to look at the long-term outcomes. And this should be feasible because most echocardiograms today are uploaded if you like, into a database.
Dr Greg Hundley: Very nice and Mark, how about you?
Dr Mark Link: I have similar opinion. Any one of the most important things in HCM is being able to predict who would benefit from a defibrillator, and currently our ability to risk stratify is woefully inadequate. It lacks sensitivity and specificity. And so with a larger population of HCM patients, and I think Paul's correct followed prospectively, not retrospectively, with the kind of data that we would want to be complete, including echo. Now, MRIs would be fantastic, but there's just no way that's practical, but to have echoes and EKGs and clinical factors and be followed prospectively really to hone down which patients would benefit from a defibrillator, and which patients would not benefit.
Dr Greg Hundley: Well listeners, this has been a great discussion and we want to thank Dr Paul Dorian from the St. Michael's hospital for providing this paper to Circulation and sharing these results with us and also our associate editor, Dr Mark Link from Dallas, Texas and both have emphasized in this study that those individuals with HCM, while we often see them on the sports programs and whatnot, having their, experiencing their event during activity, they also occur within activity.
For Carolyn and myself, we wish you a great week, and we look forward to talking with you next week in our next chat. Bye now.
Dr Carolyn Lam: 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, associate editor, director of the Pauley Heart Center at VCU Health in Richmond, Virginia.
Dr Carolyn Lam: Greg, we are going to have a great discussion coming right up regarding intensive versus standard ambulatory blood pressure control and its effects on cerebrovascular outcomes in older people. It's the INFINITY trial, but that's all I'm going to tell you for now because I want to hear all about your picks for this week's journal first.
Dr Greg Hundley: Absolutely Carolyn and I can't wait to hear about that discussion regarding hypertension. My first paper though is about titin and it comes from Dr Charles Murry from the University of Washington. The giant sarcomere protein titin is important in both heart health and disease as mutations in the gene encoding for titin are the leading cause of familial dilated cardiomyopathy. The uneven distribution of these mutations within titin motivated the authors of this article to seek a more complete understanding of this gene and the isoform it encodes in cardiomyocyte sarcomere formation and function.
Dr Carolyn Lam: Cool. What did these investigators find?
Dr Greg Hundley: Using genetically engineered human induced pluripotent stem cell derived cardiomyocytes, the authors experimentally confirmed that the gene encoding for the giant sarcomere protein titin includes an internal promoter and start site. This internal start site encodes for the isoform Cronos, which the authors demonstrate support some sarcomere formation in these human induced pluripotent stem cell derived cardiomyocytes.
Dr Carolyn Lam: Oh, nicely summarized. What are the clinical implications Greg?
Dr Greg Hundley: Well, Carolyn identification that Cronos titin, a previously unstudied form of titin is necessary for normal human cardiomyocyte function could be contributing to some of these titinopathies that are relevant for some patients with dilated cardiomyopathy.
Dr Carolyn Lam: Cool. Mine has to do with heart failure as well and presents new results regarding heart failure and heart failure related outcomes from the EXSCEL trial.
Dr Greg Hundley: Carolyn, what was the EXSCEL trial? What did it find?
Dr Carolyn Lam: Ah, so as a reminder, EXSCEL was the largest glucagon-like peptide-1 receptor agonist or GLP-1 receptor agonist trial reported to date where once weekly, exenatide had a neutral effect on hospitalization for heart failure with no differential treatment effect on major adverse cardiovascular events or MACE, by baseline heart failure status. However, the question remains, what about exenatide's effects on secondary endpoints based on the heart failure status? This is from Dr Rob Mentz and colleagues from Duke Clinical Research Institute who aim to explore the effects of exenatide on secondary outcomes in patients with and without baseline heart failure and test the effects of exenatide on recurrent heart failure hospitalization events.
Now they found that out of more than 14,750 EXSCEL participants, 16% had heart failure at baseline and when stratified by the presence or absence of baseline heart failure, there was no observed reduction in all cause death with exenatide in patients with baseline heart failure. While the risk of mortality was reduced with exenatide in the no heart failure group. And that was a significant interaction P value of 0.031. Similar results were observed for the combined outcome of all cause death or heart failure hospitalizations.
Now regarding recurrent heart failure hospitalizations, 450 patients experienced at least one hospitalization for heart failure, but there were 713 hospitalization heart failure events in total. The effect estimate that included the recurrent events was separately, statistically significant while the primary analysis based on just first events was not.
In conclusion in EXSCEL, the use of exenatide in patients with or without heart failure was well tolerated, but the benefits of exenatide on reduction in all cause death and first heart failure hospitalization were attenuated in patients with baseline heart failure. Now this is accompanied by a great editorial by Bruce Neil and Claire Arnett who caution against using post talk subgroup analysis, but the interaction of exenatide tout with baseline heart failure, it's interesting, although should be treated with caution until confirmed by findings from another trial.
Dr Greg Hundley: Very nice Carolyn, especially a nice issue regarding heart failure and I'm going to steer a little bit away from that and talk about atrial fibrillation duration and CHA2DS2-VASc scores. Putting those two together and this article comes from Rod Passman from Northwestern University. Studies of patients with cardiovascular implantable electronic devices show a relationship between atrial fibrillation duration and stroke risk though the interaction with a CHA2DS2-VASc score is poorly defined. The objective of their study was to evaluate rates of stroke and systemic embolism in those patients with cardiovascular implantable electronic devices as a function of both the CHA2DS2-VASc2 score and A-fib duration.
Dr Carolyn Lam: Interesting. What did the authors do?
Dr Greg Hundley: They had 21,768 non-anticoagulated cardiovascular implanted electronic device patients from the Optum electronic health record, de-identified database from 2007 to 2017 and they link those to the Medtronic CareLink TM database of CIEDs capable of continuous AF monitoring. Now the age averaged about 69 years and 63% were men and they found that increasing a fib duration, and of course increasing CHA2DS2-VASc2 score were both significantly associated with annualized risk of stroke and systemic embolism. These rates were low however, in those individuals with CHA2DS2-VASc2 scores of zero to one, regardless of the device detected a fib duration.
Dr Carolyn Lam: Ah. Were there any particular threshold values that seemed important?
Dr Greg Hundley: Great question, Carolyn. Yes, the stroke risk crossed an actionable threshold defined as greater than 1% per year in those with CHA2DS2-VASc2 score patients of two or more with greater than 23 and a half hours of a fib or those patients with CHA2DS2-VASc2 scores of three or four with greater than six minutes of a fib duration or finally in those individuals with CHA2DS2-VASc2 scores greater than five even if they had no atrial fibrillation.
Dr Carolyn Lam: Wow. Very nice clinically relevant conclusions here. Thanks Greg. I'm going to tell you what else is in this issue. There's also a research letter by Dr Rosenmeier entitled, “Aerobic Exercise Induces Cardiac Fat Loss and Alters Cardiac Muscle Mass Through an Interleukin 6 Receptor Dependent Mechanism.” And this is a cardiac analysis of a double blind randomized controlled trial in abdominal obese humans. We have an on my mind paper by Dr Delbridge entitled “HFpEF, It's Time to Explore the Role of Genetic Heterogeneity in Conferring Phenotypic Variability.” And this discusses among other things, the role of induced pluripotent stem cells and functional studies of bioengineered HFpEF patient derived cardiac micro tissues that could potentially enable several important questions to be answered for the first time. There's an ECG challenge as well by Dr Naru Kanya, and it's really interesting. It's a hiccup artifact. If you haven't heard about that, you should take a look. And finally cardiology news by Dr Kuhn and it's entitled, “Nourishing Native American Communities by Increasing Access to Traditional Food.” A very interesting paper right there.
Dr Greg Hundley: Carolyn, I have a few papers. Robert Gerszten provides a perspective piece regarding emerging affinity reagents for high throughput proteomics, sort of an emerging field, everyone doing proteomic studies, we have to pay a special attention to the reagents that are being used. And then Andrew DeFilippis from University of Louisville as well as Johns Hopkins reviews important concepts related to the definition of MI.
Dr Carolyn Lam: Is this pertaining to that fourth universal definition of MI?
Dr Greg Hundley: Yes, Carolyn. Absolutely. And basically in this white paper, the authors review the epidemiology, risk factor associations and diagnostic tools that may assist in differentiating between non-ischemic myocardial injury, type 1 MI and type 2 MI. And then finally from Suowen Xu from the University of Rochester, there's a letter discussing the CCN family of matricellular proteins CCN 1, CCN 2 and CCN 3, that are mechano-sensitive proteins that are differentially regulated by sheer stress, the frictional force exerted by blood flow in our vessels. Well Carolyn, that's a great issue. How about we move on to our feature article?
Dr Carolyn Lam: Let's go Greg.
For our feature discussion today we are talking about intensive versus standard ambulatory blood pressure control and that effect on cerebral vascular outcomes in older people or the INFINITY trial. Very, very important stuff and I'm so pleased to be with the corresponding author, Dr William White from Calhoun Cardiology Center in University of Connecticut School of Medicine. Dr White, thank you so much for being here. Could you maybe set up already the background of what you were thinking when you started this trial? Especially given the results that we know from SPRINT and SPRINT mind. Could you perhaps comment on how this INFINITY trial is different?
Dr William White: We started work in this area about 15 years ago and we initially were interested in interactions among vascular risk factors including ambulatory blood pressure, lipids and other sort of thrombotic factors and so forth with the development of small vessel disease in the brain that led to these fairly classic images on MRI called white matter hyperintensity lesions. And we learned from a prospective cohort study that we started about 15 years ago, that there was a very strong relationship between ambulatory blood pressure and the development and progression of these white matter hyperintensity lesions on MRI, but not very nice relationship with the clinical blood pressures measured in the standard office practice.
We decided to pursue a clinical trial, a randomized clinical trial in which we would evaluate different levels of ambulatory blood pressure versus the development of the small vessel disease as imaged by MRI, but very importantly we also wanted to link it to functional outcomes because this was in older people, typically in their late seventies, eighties and even nineties in which cognitive impairment begins to develop. There's problem with mobility, bladder function and things of that nature. And since our funder was always the National Institute of Aging of the NIH, there's a great deal of interest in more than just the vascular risk factors and even the cerebral vascular disease that we would detect on the MRI. That was the background of why the study got developed the way it did.
Dr Carolyn Lam: That's so interesting. You've already pointed out ways that this was very different from SPRINT OR SPRINT MIND in looking at ambulatory instead of clinic blood pressure and I suppose in the population you selected, out of curiosity, you mentioned that your prior work showed a relationship between white matter hyperintensity on MRI and perhaps future dementia. In which direction? And is there any basis to suspect low, too low blood pressure may also be bad in these older people who already have microvascular brain disease?
Dr William White: Absolutely. Very important point. When we look at our prospective cohort which was about a 100 older people, we followed for four years without any intervention. This was just a mixture of normal tensive and hypertensive individuals. Some on meds, some not on meds. But we did show that when you got too low or if you stay too low during those four years with a systolic blood pressure of under 115 on a 24-hour blood pressure monitor, it seemed like there was an almost like U shaped relationship with progression of white matter disease. Below 115 there was more accrual of white matter disease. Above 150 there was a systolic blood pressure, there was also a greater accrual, but in between about 125 and 145 we weren't really sure if there was going to be a difference. And that there was the target is that everybody's talking about for clinical measurement, so we decided to pursue that in this study to determine if we could figure out whether or not there was a sweet spot for the desk blood pressure without getting into trouble with hypotensive symptoms.
Dr Carolyn Lam: Nice. Thank you for drawing that up so nicely. Now I get it that you chose the targets that you did, which just for everyone, just a reminder, it was a 24 hour mean systolic blood pressure by ambulatory blood pressure control and the two targets were 130 millimeters mercury and less versus 145 millimeters mercury and less. With that, could you please tell us the results?
Dr William White: Right. We called the 130 or less systolic group, the intensive treatment group and the 145, the standard group. We focused on the primary endpoint was changes in mobility parameters in conjunction with changes in white matter hyperintensity lesion growth. And after a period of about three to four months of randomization, post randomization, we achieved a 24-hour systolic blood pressure about 128 millimeters of mercury in the intensive treatment group and 144 in the standard group. And we maintained a pretty good separation in blood pressure, ambulatory blood pressure throughout the three years of treatment. Now the changes in gait speed, which was one of our primary parameters for mobility actually turned out not to be different between the treatment groups. That is intensive versus standard. However, the changes in the accrual of light matter hyperintensity volume was smaller in the intensive treatment group of a 0.29% versus a 0.48% in the standard treatment group. That was significant at a P value of 0.03.
We actually also had a pre-specified sensitivity analysis, sort of a per protocol analysis that allowed us to look at people who stayed in their sort of assigned treatment groups based on blood pressure throughout the three years of the trial. And in that circumstance, there was actually a stronger separation because these are people who stayed clearly at 130 or less than about 145 throughout the three years and now the differences were approximately 0.23% in the intensive group and 0.58% in the standard group. And now the P value is smaller, .0028.
I think we proved in the study that maintaining a systolic blood pressure on the ambulatory recorder over 24 hours of 130 or less benefited patients by reducing the accrual of white matter hyperintensity lesions by about 40% relatively speaking compared to a standard ambulatory blood pressure value of a 145. One of course caveat is that after that happened within three years, but we did not see the expected benefit on mobility or on most of the cognitive parameters either. And while we were a little bit surprised about that, when we went back and analyzed our situation with where people started from as far as this particular cohort of patients, they might've been a little on the healthy side compared to some other studies. A very educated group, very compliant with everything that they did. And probably three years was just not long enough to show the result of this white matter hyperintensity benefit on some of the functional outcomes.
Dr Carolyn Lam: That's really interesting and I'm glad you sort of tackled head on that sort of apparent dissociation between the clinical end points and the MRI end point. Could I also ask, wouldn't those findings also be consistent with SPRINT and SPRINT MIND?
Dr William White: In many ways our results were consistent with SPRINT MIND, a sub-study on the SPRINT MRI sub-study. Of course, just let me mention the differences between the two studies. Of course, SPRINT was very large but there are sub-studies were not as large as the parent study. The MRI study had about 300 plus patients randomized into it, but the measurement of blood pressure was done in the standard clinical fashion and used that digital device that was able to take measurements without somebody present in the exam room. Though they were a bit lower than what I would have seen on an ambulatory monitor during the day time. And their goals were 120 systolic versus 140, whereas ours were an ambulatory systolic of 135 and 145.
But the results were actually comparable because they showed a benefit with regards to lesser accrual of white matter hyperintensity volume in the intensive group versus this banner treatment group. But they also showed no differences after 3.4 years in the incidence of dementia. And they also showed in a separate study, no differences in gait speed in the population who are in intensive versus standard treatment. One would say that results were really actually comparable despite the age differences and the blood pressure measurement differences. And I think both studies really point to the fact that lower systolic blood pressures in older people should be our target because it's safer actually then than maintaining people in the 140s.
Dr Carolyn Lam: Maybe the follow-up period was not long enough. Could it be possible too that maybe blood pressure control should start earlier in life. Could that be it? And then also, could you give us an idea of the kinds of changes, the magnitude of the change on MRI that you see for those of us that don't think about this all the time, is this a big change considered for your cohort or is it a little change?
Dr William White: I think it's true that these people started out around 81 years old in this trial and so by the time they got to that age and had systolic hypertension for probably as many as 20 years, that some of the damage that was done was obviously permanent and we don't really know how long it took for that to accrue. What we did know is that with three years of intensive treatment, we benefited patients by reducing the continued growth or confluency of these small vessel lesions in the brain. Now the range in the amount of damage varies from about half a percent of the overall brain volume to about 5%, so a 10-fold magnitude difference in our cohort.
And as a result of that, certainly somebody who's got about two to 3% of their brain occupied by better hyperintensity lesions or damage is going to have a great deal more functional disability than somebody who's .5%. I think we have to look at the outliers as well as the mean and median changes that we saw. The mean changes are not huge. The difference between 0.2 and 0.6% for example, in our protocol analysis, 0.4% to me it's clinically relevant because I know that that means that there are some people who went up by a percent or two over the years versus the standard versus the intensive treatment group. That's a big difference in an individual over that period of time.
Dr Carolyn Lam: Yeah, I'd hate to think that I'm losing 1% of my brain.
Dr William White: Yeah. Plus it's also where it's located because the lesions are typically around the ventricles of the brain and it's exactly where neurons are going sort of posteriorly to anteriorly to transmit information. For example, from the visual center to the sort of spatial motor cortex. And when those are interrupted, even if it's in one or 2% of the tissue, it can cause substantial difficulties for people. And it's for both the flow of cognitive information as well as this flow of a mobility and balance. I think that it is very relevant, but the gray matter is affected much less by this compared to the white matter. But there are still studies that show that gray matter sort of follows in line with that so that of course also enhances thought processes and cognitive function as well.
Dr Carolyn Lam: Wow. I love the way you explained that. Very important question would of course be the safety and tolerability of this more intensive approach. Any comments there?
Dr William White: Our sponsor, the National Institute of Aging did recruit a data safety monitoring board that was independent from the study for all the years. Impressively over the course of this trial, even though there wasn't a large sample, it was a 199 people, we saw a significant benefit in the intensive group for cardiovascular events, so there were less admissions for heart failure. There were less myocardial infarctions, there was less strokes. All these kinds of things that we worry about in our patients as they get older with vascular disease was reduced by about 75% in the intensive treatment arm versus the standard arm. As far as the events that we were concerned about, such as falls and syncope and presyncope and things of that nature, they were virtually identical in the intensive treatment group and `the standard treatment group. When you take that into consideration, along with the fact that you're reducing the accrual of small vessel disease in the brain, it's clear that this population, even though they're older, would benefit from a lower systolic blood pressure.
Dr Carolyn Lam: Oh my goodness. Thank you so much, Dr White. That was a beautiful summary. That is the take home message right there.
Listeners, I'm sure you agree with me. Thank you so much for joining us this week, and 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 Dr Greg Hundley, associate editor from the Poly Heart Center at VCU Health in Richmond, Virginia.
Dr Carolyn Lam: Greg, this issue is super exciting. It's the ESC simultaneous publication issue, isn't it? So the original papers were simultaneous publications at the European Society of Cardiology meeting this year.
Dr Greg Hundley: Oh, wow. Carolyn can't wait to get to these. So Carolyn, later we're going to listen to the authors of this feature discuss the association between ICD use and all-cause mortality in a contemporary heart failure reduced ejection fraction cohort and examine relevant subgroups. So Carolyn, I'm going to get started with my first paper and it's a randomized trial of one hour, one-hour deponent T protocol and suspected acute coronary syndromes and it's a rapid assessment in emergency rooms and it's from professor Derek Chew from Flinders Medical Center. High sensitivity troponin assays promise earlier discrimination of MI, yet the benefits and harms of this improved discriminatory performance when incorporated within rapid testing protocols with respect to subsequent testing and clinical events has not been evaluated in an in-practice, patient level, randomized study. So this multicenter study evaluated the non-inferiority of a zero to one hour, zero to one-hour, high sensitivity troponin T protocol compared with a more traditional zero to three-hour mask, high sensitivity troponin T protocol in those suspected with ACS.
Dr Carolyn Lam: Interesting. So what did the study show?
Dr Greg Hundley: So participants in the zero to one-hour arm were more likely to be discharged from the ED quicker and that would be expected. So 45% versus the standard arm, which was 32%. Also their median ED length of stay was shorter, and we would expect that. Four and a half versus five and a half hours. Those randomized to the zero to one-hour protocol were less likely to undergo functional cardiac testing. The zero to one-hour high sensitivity troponin T protocol was not inferior to standard of care and among patients discharged from the ED, the zero to one-hour protocol had a negative predictive value of 99.6% for 30-day death or MI. So Carolyn, how about your first study?
Dr Carolyn Lam: Well, from MI risk stratification to heart failure risk stratification. I'm going to tell you about a paper describing the TIMI Risk Score for heart failure in diabetes, which is a novel integer base clinical risk score for predicting hospitalization for heart failure in patients with type two diabetes. This is from Dr Mark Sabatine and the TIMI study group who developed a clinical risk score for heart failure hospitalization in more than 8,200 patients with type two diabetes in the placebo arm of saver TIMI 53, as well as externally validated this score in more than 8,500 patients with type two diabetes in the placebo arm of declare TIMI 58.
They found that five clinical variables were independent risk predictors of heart failure hospitalization. These were prior heart failure, history of atrial fibrillation, coronary artery disease, estimated GFR, and urine albumin-to- creatinine ratio, a simple integer base score from zero to seven points. Using these predictors identified a more than 20 full gradient of heart failure hospitalization risk in both the derivation and validation cohorts with high SES statistics. Although the relative risk reductions with dapagliflozin were similar for patients across the risk scores, the absolute risk reductions were greater in those with higher baseline risks.
Dr Greg Hundley: Wow, Carolyn. So tell us what are the clinical implications of this really thorough study?
Dr Carolyn Lam: In summary, the risk score had excellent discrimination in two large clinical trial cohorts. It was well calibrated, and it identified a strong gradient of increasing absolute reduction in risk of heart failure hospitalization with the SGLT two inhibitor dapagliflozin. So by using this TIMI Risk Score for heart failure in diabetes, which is a simple validated clinical risk score, clinicians could better educate patients about their risk for heart failure hospitalizations and could perhaps better identify those patients who have a greater absolute risk reduction in heart failure risk with SGLT two inhibitors.
Dr Greg Hundley: Very good, Carolyn. Well, I'm going to go back to the world of troponins and talk about a paper from Nicholas Mills from University of Edinburgh. And in this study, they evaluated the safety and effectiveness of risk stratification thresholds of high sensitivity troponin in patients with suspected acute coronary syndrome. 48,282 consecutive patients with suspected ACS were enrolled in a multicenter trial from 10 hospitals within Scotland and they're pre-specified secondary and observational analyses. They compared the performance of the limit of a detection of less than two nanograms per liter versus the optimized stratification threshold of less than five nanograms per liter using the Abbott high sensitivity troponin I assay. Patients with myocardial injury at presentation with less than two hours of symptoms or with ST segment elevation myocardial infarction were excluded and the negative predictive value was determined in all patients in subgroups for a primary outcome of MI or cardiac death within 30 days. And they had a secondary outcome that was MI or cardiac death at 12 months.
Dr Carolyn Lam: Nice. So Greg, which threshold of troponin was the optimal one?
Dr Greg Hundley: So the negative predictive value for the primary outcome was 99.8% and 99.9% in those with cardiac troponin I concentrations of less than five or less than two nanograms per leader respectively. At both thresholds, the negative predictive value was consistent in men and women across all age groups. Although the proportion of patients identified at low risk fell with increasing age. Compared to patients with cardiac troponin I concentrations of greater than five nanograms per liter but less than the 99th percentile, the risk of MI or cardiac death at 12 months was 77% lower in those with less than five nanograms per liter and 80% lower in those with less than two nanograms per liter. So in conclusion, use of risk stratification thresholds for high sensitivity cardiac troponin I identified patients with suspected acute coronary syndrome in at least two hours of symptoms at low risk presentation irrespective of both age and sex.
Dr Carolyn Lam: Very nice. Well, more risk stratification in this next paper, which really evaluated the application of the 2018 ACC AHA Cholesterol Management Guideline recommendations for additional lipid lowering therapies in patients with established atherosclerotic cardiovascular disease and residual dyslipidemia despite maximum tolerated Statin who were enrolled in the ODYSSEY OUTCOMES trial. Now, just as a reminder, the 2018 US Cholesterol Management Guidelines recommend additional lipid lowering therapies for secondary prevention in patients with LDL above 70 or non-HDL above a hundred despite maximum tolerated Statin therapy.
Such patients are considered at very high risk based on a history of more than one major atherosclerotic cardiovascular disease event or a single event and multiple high-risk conditions. So in this paper from Dr Matt Roe from Duke Clinical Research Institute and colleagues, they found that in the ODYSSEY OUTCOMES trial, patients classified as very high risk by these 2018 ACC AHA guidelines and either because of a history of multiple atherosclerotic cardiovascular events or a single event, which is a trial qualifying acute coronary syndrome and multiple high risk conditions, these very high risk patients had more than double the risk of recurrent cardiovascular events as compared to patients classified as not very high risk.
They further looked at the association of Alirocumab with outcomes and found that Alirocumab was associated with a consistent relative risk reduction in both risk categories. But the absolute risk reduction for major adverse cardiovascular events was numerically greater, although not statistically different, in the very high-risk group versus those not at very high risk and among patients at very high risks with multiple prior events versus a single prior event.
Dr Greg Hundley: Wow, Carolyn. Can you put all this together? This is a lot of information in this study.
Dr Carolyn Lam: Yes, so it would appear that the application of the new ACC AHA 2018 guideline recommendations for risk stratification and the use of additional lipid lowering therapies in patients with established cardiovascular disease clearly identifies patients at very high risk of recurrent cardiovascular events after an acute coronary syndrome and these patients may derive substantial benefit from additional lipid lowering therapy, for example, with a PCSK nine inhibitor.
Dr Greg Hundley: Very nice, Carolyn. Well, let me just finish off with what other articles we have in this ESC featured issue of our journal. So Jonathan Stamler and John Lundberg in separate letters discuss findings related to whether hemoglobin beta 93 cystine is not required for export of nitric oxide bio activity from the red blood cell. And in additional separate letters, Doug Lewandowski and Heng-Chen Yao discuss preservation of ACL CoA and attenuation of pathological and metabolic cardiac remodeling through selective lipid trafficking. In a perspective piece, Blake Thomson from the University of Oxford discusses what Medicare for all in the United States can mean for US medical research and provides lessons from the United Kingdom. In a letter from the United States, Gregory Marcus from University of California San Francisco discusses incident atrial fibrillation among American Indians in California and then both Marco Bergonti from University of Milan and Derek Chew from University of Calgary present two separate cases in our ECG challenge feature. Well, Carolyn, what a great issue and how about we turn to our feature discussion?
Dr Carolyn Lam: Yes, let's go. Thanks, Greg.
Dr Greg Hundley: Welcome, everyone, to our feature discussion today we have Gianluigi Savarese from Karolinska Institute in Stockholm, Sweden and our own associate editor, Sana Al-Khatib from Duke University. We're going to be discussing implantable cardioverter defibrillators in their mortality and looking at a more recent take on this relative to some of the previous published studies. So Gianluigi, I'd like to start with you. Could you tell us a little bit about the hypothesis and why you wanted to perform your study?
Dr Gianluigi Savarese: Yes. Basically we design our study based on three main considerations. First one is recent studies show that the advance in heart-failure therapies have impact patients' risk profile leading to roughly 40% reduction risk of sudden cardiac death in HFrEF and RCTs on ICD use for primary prevention of sudden cardiac death and rural patients more than 20 years ago and thus, nowadays the beneficial prognostic effects of ICD may be different due to the improved risk profile in this population.
The second consideration was that efficacy of ICD patients with heart failure with non-ischemic cardiomyopathy patients receiving a contemporary heart failure therapy as being a question in Danish trial and the third consideration is that efficacy of ICD in elderly is still debated due to findings again from the Danish trial showing a significant reduction in all-cause death associated with ICD use in patients age younger versus older than 70 years old. Based on these considerations, we decided to assess the use of ICD for primary prevention propose in a contemporary and selected FRF population and to assess the association between ICD use and outcomes in such a population.
Dr Greg Hundley: So it sounds like we're doing an update on the utility of ICDs. Can you tell us a little more about your study population and your study design and then let's hear a little bit about your results.
Dr Gianluigi Savarese: Sure. First of all, I would like to first highlight of course the observational natural of this study. Our analysis is performed using data from the Swedish Heart Failure Registry, which is a large enough select court of heart failure patients, enrolling patients regardless of ejection fraction. So today we have roughly around 70,000 patients. And of course for the current analysis we select the patients with HFrEF. There were around 15,000 patients with the HFrEF who were eligible for ICD use for primary prevention according to the ESC guidelines. A study design, we used propensity score matching design in order to try to address the issue of potential compounders. Of course this is a very important point in observational studies. So basically, we amassed patients receiving the ICD versus those not receiving ICDs. And we assessed the association between ICD use and all-cause death and cardiovascular death and we accessed one year and five-year outcome.
Dr Greg Hundley: And so what were some of those results?
Dr Gianluigi Savarese: What we observed is that there was a statistically significant 25 relative risk reduction in all-cause mortality in ICD recipients versus those who didn't receive an ICD within one year and there was also a 12% reduction erased within five years. And we also serve a statistically significant 29% reduction in risk of cardiovascular mortality within one year. But we were not able to observe any association for cardiovascular mortality within five years. We thought it was particularly relevant to have subgroup analysis in our studies since there are so many questions regarding ICD use in specific subgroups, which are, for example, older versus younger patients, those with versus without ischemic heart disease, males versus the females and so on. So what we observed was that results in terms of all-cause mortality were consistent in all of the subgroups considered such as patients older versus younger than 70 years old, versus those without history of ischemic heart disease and those with versus without concurrent CRT use.
Dr Greg Hundley: What about the frequency of implanting ICDs? Was the frequency expected in your results?
Dr Gianluigi Savarese: We add that only 10% of our patients received an ICD at the baseline. This person's age is quite low in particular. If we compare these with other studies in US for example, or also in other European countries and basically, we can only speculate about the underuse of ICD in primary prevention propose. First of all, a certain proportion of ICD underuse may be explained by the fact that we could not assess whether life expectancy was longer than one year, and this is one of the eligibility criteria for ICD according to the guidelines.
Then another point is that in Sweden, the majority of heart failure patients are seen by primary care physician and general practitioners who may have less knowledge and acceptance of device therapy and then higher perception of contraindication. In our previous analysis, we showed that patients not seen by cardiologists have lower likelihood of receiving an ICD and use of devices is higher in centers who do implants, CRT, ICD. So this may be some of the explanation that I can anticipate that some more analysis will follow where we will try to assess the predictors for an under use of ICD for primary prevention.
Dr Greg Hundley: Well, thank you very much. Sana, now we're going to turn to you and help us put this study in perspective to what we have already found or observed in other prior studies related to implantation of cardio defibrillators.
Dr Sana Al-Khatib: As was mentioned earlier, I was the handling associate editor for this paper, so I really enjoyed the handling it and writing an editorial on it. The main points that I wanted to touch on are number one, the significantly low or reduced utilization rate of ICDs. So as was mentioned, the 10% of this patient population received a primary prevention ICDs. Even if you account for some of the new ones is that you can't estimate life expectancy. You can't capture granular clinical data on these patients. So of course some of the non-use of ICDs may have been appropriate. I think 10% by anyone's definition is still pretty low and I'm very encouraged to hear that there are plans to look at predictors of non-use, the characteristics of those patients and hopefully the office can build on their findings and try to implement some strategies to improve the utilization of this life saving therapy.
The other thing that I wanted to touch on is clearly the results are positive in favor of the implantable cardioverter defibrillator. Showing that it significantly reduces all-cause mortality within one year, within five years, certainly reduces cardiovascular mortality within one year. As was mentioned, the reduction in cardiovascular mortality within five years was not significant and to me that is probably mostly explained by competing causes of death in this patient population, but I also cannot rule out the possibility of some mis-classification of causes of death, which is not uncommon. I do want to commend the authors for the great and robust methods that they applied in their analysis. As was mentioned, this was a comparative effectiveness research using observational data. These kinds of analyses can be pretty challenging, but the authors defined their patient population very clearly. They used propensity score matching. In fact, they took it a step further by doing a negative control analysis, meaning looking at hospitalizations for renal failure, for pneumonia, respiratory infections, things like that that you don't expect to be affected by the ICD and they found no difference in that.
And that is amazing to kind of see this level of analysis that I believe really lends their results more credibility. It is important though to keep in mind that when you have 10% of patients getting an ICD, I suspect that this was a highly selected patient population and most likely people who were thought to benefit the most from ICDs were implanted with an ICD. And yet, as I said, that given the robustness of the methods that they use, I actually believe the results. I think the results are credible.
The one last point that I want to comment on is the subgroup analyses that were mentioned. Absolutely important subgroups to look at from a clinical perspective. But I point out the fact that when you start looking at subgroup analyses, and especially when you have a smaller sample sizes and lower event rates that it makes you start thinking about, "Well, are these results valid? Are they believable?" I mean, even honestly, in the setting of a randomized clinical trial, I look at subgroup analyses as hypothesis generating. So I liked that they included those just to kind of really emphasize the importance of looking at these subgroups. But I certainly would not put too much weight on the subgroup analysis results, but overall great results and congratulations to the authors.
Dr Greg Hundley: Fantastic overview, Sana and Gianluigi. So on behalf of Carolyn Lam and myself, we wish you a great week and we look forward to speaking with you next week.
Dr Carolyn Lam: This program is copyright American Heart Association 2019.