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. And I am joined today by our Editor of Digital Strategies, Dr. Amit Khera from UT Southwestern, as well as three wonderful fellows in training. Yes, you've guessed it, it's our FIT Podcast and I'm just so thrilled to be here again.
Dr Carolyn Lam: Amit, any words of introduction before we start?
Dr Amit Khera: Thank you Carolyn. I think, for both of us, this is our favorite podcast, or two podcasts, that we do, a year. It reminds us of how bright the future is, with superb cardiology fellows in training around the country, and it really is a testament to how important we find fellows in training, to Circulation, to our mission, and how much we learn from them.
So we're really excited about this group, today, and thank them for participating.
Dr Carolyn Lam: Absolutely. So, why don't we start, now, with ladies first? Let's hear from Dr. Elizabeth Hill.
Dr Elizabeth Hill: Thanks for having me today. My name is Beth Hill, and I'm a first year cardiology fellow at Scripps Clinic, in La Jolla, California. I've a particular interest in sports and exercise cardiology, which brings me to the article I picked today about sudden cardiac death and hypertrophic cardiomyopathy, hot topics in the field and in general.
And so, today, I'm excited to be discussing the EVIDENCE HCM study, looking at the hypertrophic cardiomyopathy of risk, sudden cardiac death model.
Dr Carolyn Lam: Nice. So tell us a little bit about what really struck you about the paper and, perhaps, how that may apply to where you practice?
Dr Elizabeth Hill: What I really liked about the paper is that, when I see patients in clinic with hypertrophic cardiomyopathy, prior to having this risk stratification tool, we didn't really have a way to objectively risk stratify our patients with hypertrophic cardiomyopathy and really guide the discussion about who may benefit from an implantable cardiac defibrillator or ICD. And so, I've been using this a little bit with my patients. While it hasn't made it fully into the AHA or ACC guidelines yet, I'm using it as a tool.
Dr Carolyn Lam: Great. You know, these are seven risk factors, isn't it? I'm always struck by that survival curve that really shows that those with a predicted 6% risk stand out. Is that what you use, as well, to guide your decisions?
Dr Elizabeth Hill: Yeah. I think, as the authors noted, they picked this somewhat arbitrarily so that they could study their risk model. But I think what they found is that it seemed to fit well with the observed high risk of sudden cardiac death cohort, such that those that were seen and observed, about 9% risk of sudden cardiac death in five years, were in that greater than 6% cohort. So I think that population should receive ICDs, and that is one factor that I used to guide my decision making as well.
Dr Amit Khera: Beth, this sort of interest that you've had for a long time, in sports cardiology, I've noted you've done some prior work in EKG screening and other screenings. In terms of this article specifically, as you pointed out, this is a really helpful tool because I still remember back when I was a fellow in training, there was, sort of, this thought that everyone was high risk with hypertrophic cardiomyopathy, and I think we realized that's not true at all. The overall incidence of sudden death was only 2.4% in this cohort.
The question I have for you, in terms of application, is, as Carolyn pointed out, these are reasonably simple variables, but as we sometimes are now using cardiac MRI and genetics and other more advanced tools, where do you think they fit in, in the current paradigm, since this is a bit of a more simplistic score?
Dr Elizabeth Hill: The seven risk factors they put into this tool were noted to be independently associated with an increased risk of sudden cardiac death, and those are well known factors, entricular tachycardia, maximum wall thickness. But I really do think that other factors will come into play soon and are part of my discussion, and colleagues' discussions, including the late gadolinium enhancement on MRI, genetic factors, and I really think this may be a place for tools like machine learning. These authors, O'Mahoney and colleagues, they really did, kind of a tour-de-force, going back to the 1970s, but there is still a decent amount of data missing. So maybe we can partner with the machines and help them go back into these records, a little bit more effortlessly, and look at genetics, maybe some wearable device data, and really refine our risk stratification tool moving forward. But that's definitely something I use in risk stratification in some of my intermediate risk patients.
Dr Amit Khera: Those are great points. I think your point about machine learning and novel algorithms will definitely take foot in the future.
Maybe a follow-up, again, given your background interest, I think it's a trade-off where we're trying to, of course, avoid sudden death, but you also don't want to overtreat. Especially, when you think about athletes getting ICDs and how that changes, or anyone, for that matter, about maybe telling someone they're at high risk, or giving them an ICD when perhaps they don't need it. I guess that comes to, what's the threshold? Here they use 6%, but that ends up being a bit arbitrary, in terms of what threshold we use. And how do we decide, when we talk to our patients, about what threshold's a right threshold to apply an ICD?
Dr Elizabeth Hill: Yeah. That's a great question. Like you mentioned, these devices come with inherent risks, such as unnecessary shocks, increased risks for infection, and sometimes there's restrictions with athletic sport, although that's been changing recently.
But, I think that's where the shared decision-making process comes into play, where you put current data on the table with the patients and, perhaps, their families as well, and have a risk-benefit discussion. Perhaps gather a little bit more data about the patient, maybe follow them over time, but I guess I wouldn't jump to put an ICD in, in every patient and, especially, the lower-risk cohort. And what number that is, I'm not quite sure. Here they say maybe less than 4%, but, again, somewhat arbitrary, I think.
Dr Carolyn Lam: Thanks Beth. I mean, as Amit said, it's just so inspiring to see how the papers are being used in practice. Really loved those perspectives.
Now, from sunny San Diego all the way to snowy New Zealand. We have Dr. Mesfer Alfadhel. And Mesfer, tell us a little bit about yourself, and the paper that you've chosen?
Dr Mesfer Alfadhel: Thank you very much. I'm thrilled to be part of this podcast. I'm a second-year cardiology fellow-in-training at the Needham Hospital, in Needham City, New Zealand, where it's snowing at the moment. I'm also a clinical lecturer at the University of Otago School of Medicine. I do have great interest in general cardiology, as the rest of my colleagues, but also am passionate about interventional cardiology and structural heart disease.
The paper I've chosen is really quite relevant to everyone in cardiology, and perhaps extends to other colleagues in other health professions impacted by automated external defibrillator use on survival and functional outcomes in shockable observed public cardiac arrest. The aim of the study was to determine the association of bystander automated external defibrillator use, the survival and function of outcomes in shockable observed out of hospital cardiac arrests. The study was from 2011 to 2015 and the Resuscitation Consortium prospectively collected detailed information on all cardiac arrests at nine regional centers, six in the United States and three in Canada.
They also found that among nearly 50,000 out of hospital cardiac arrests, 8% were observed public out of hospital cardiac arrest, of which 61% were shockable. Overall, a remarkable one in five of shockable observed public out of hospital cardiac arrest were bystander shocked. Now the bystander automated external defibrillator observed, shockable observed public out of hospital arrests were associated with increased odds of survival and full or near full functional recovery almost 2.6 and 2.7 odds ratio than when compared to emergency medical service defibrillation. What's also interesting is that the longer the wait for the emergency services, the higher the benefits from a bystander observed shock.
Dr Carolyn Lam: You know, Mesfer, I appreciate that you chose this one as well. What struck out to me immediately was that more than 60% of out of hospital cardiac arrests were shockable. And when we think about the number of lives that could potentially be saved, therefore, that's quite astounding, isn't it? But can I ask you something? So these are in the US and Canada, how applicable do you think this is to New Zealand?
Dr Mesfer Alfadhel: We do have a small population, just over four million. The number of cardiac arrests here is around 2,000 out of hospital cardiac arrests. And I think probably half of them in the latest reports were shockable. The emergency response time in the urban areas is around six minutes, which I think is acceptable, but we have about 20% of population living in rural areas. And the emergency response time exceeds 10 minutes almost all the time. I think that probably a group that we need to direct intervention to in New Zealand.
Dr Amit Khera: It's really an important article. I should say that June for the American Heart Association is AED and CPR month so great choice to remind us of the value of these and especially, the one thing that was amazing, obviously this is an observational study, but the absolute change, not relative, was about 14% meaningful recovery and so that's quite impressive in terms of the number needed to treat if you will. Maybe an adjunct to Carolyn's question is, when we think about strategies to enhance bystander AED use for strategies, essentially get the AED there faster. As you know if the EMT time was not delayed it wasn't necessarily better for the bystander.
We had a paper in Circ sometime last year looking at drones and then also geocoding and other people in some countries have looked at apps where you essentially can train a group of people and then they can be texted for a sudden cardiac arrest in their area. I'm curious about any creative things, there's always training and AEDs, I think in this place it was public areas in industry, but what do you think are some creative things or things that we need to be doing to help enhance the ability for bystander or early AED use.
Dr Mesfer Alfadhel: I think this is one area in medicine in general that where technology is really going to advance how we deal with this problem. There's an app that's available, it was launched in the UK a few years ago and it’s become available in New Zealand in the last two weeks called, the Good SAM. SAM stands for smartphone activated medics. And it's become available in New Zealand two weeks ago and I downloaded it and still yet wait for it to be activated. And the way it works is you can activate a medical emergency using the app and it dials the emergency response but what it also does is it activates the nearest three people with CPR training nearest to you and it tells you how far they are from the emergency. Now if you don't have the app and you call 911 or the equivalent, the operator can activate it to the nearby personnel who have that experience. And I think it's going to reduce the time markedly.
Now the other end of the question where some of what strategies could be used I think we had a good report from Denmark where they made changes in 2007 in Denmark and then followed by the rest of the country in 2010 where they made CPR or resuscitation education as compulsory at school but also when getting a driving license they made courses available for free that increased the number of defibrillators available in public places and they shared that information with public. They’ve redone, audited their work, and compared to prior to intervention prior to 2007 and after that and they found an increase number of using the AEDs increased from somewhere around 2% to 15%, which is really encouraging. I think we are following Denmark in that regard probably at slower rate.
Dr Amit Khera: Thank you those are excellent insights.
Dr Carolyn Lam: Amit, don't you see that I just love learning from these fellows during these podcasts. We should do more of these. This is awesome.
Dr Amit Khera: I completely agree.
Dr Carolyn Lam: Thank you Mesfer, enjoy the skiing. But now from snowy New Zealand we're going all the way to Nashville Tennessee. Welcome Dr. Vineet Agrawal. So tell us a bit about yourself and your paper.
Dr Mesfer Alfadhel: So my name is Vineet Agrawal. I'm a second-year cardiology fellow at the Vanderbilt University Medical Center. My background is as a physician scientist and as a general cardiologist. My long-term goals are in understanding mechanisms underlying heart failure with preserved ejection fraction.
With that in mind I was really taken by an article that was recently by Margaret Redfield's group from the Mayo Clinic in Circulation, titled “Global Pulmonary Vascular Remodeling and Pulmonary Hypertension Associated with Heart Failure and Preserved or Reduced Ejection Fraction.” I found this article to be a very interesting, hypothesis-generating article.
In a nutshell what they did was they took an autopsy cohort of patients in the Mayo Registry and those who had heart failure with both preserved and reduced ejection fraction, normal controls, and those who had a primary pulmonary venous occlusive disease, and looked at the lung specimens of these patients. And interestingly what they found was there was a significant amount of pulmonary venous remodeling that had occurred in patients who had both preserved and reduced ejection fraction. This correlated not only with their right heart cath findings, so those who had elevated pulmonary pressures and elevated transpulmonary gradients, but also differed from the primary pulmonary venous occlusive disease in the sense that the histologic appearance of these vessels was quite different.
And while as an autopsy study this is not necessarily an article that would immediately change practice, what I think it does do though is it forces us to think about these conditions in a different context and particularly with an eye towards future therapeutics. Heart failure with preserved EF as a disease, as I'm sure we all know, is sorely missing therapies that could alter the disease progression and potentially even alter mortality in these patients. And this article in my opinion really sheds light on at least anatomically a new location for us to think about as a therapeutic target when we try to better understand this disease and find therapies for these patients.
Dr Carolyn Lam: Vineet, can I just say you're singing to the choir here. I'm such a fan of this work as well for obvious reasons. But hey, could I ask you, in your clinical practice, do you see a lot of these patients with HFpEF and pulmonary hypertension and wonder how to treat them? And along those lines, how has this paper helped you think about these patients more?
Dr Mesfer Alfadhel: I would say when I first started residency as a medical student this was not necessarily a condition that was really something that I had learned much about or felt like I had been exposed to; however, as a resident I felt like most of the patients, or at least half of the patients, I was seeing with heart failure had a component of diastolic heart failure or they had a preserved EF but very symptomatic from the standpoint of heart failure. And I struggled to treat them, particularly in some part due to the fact that many of the risk factors that contribute to HFpEF, diabetes, uncontrolled hypertension, obesity, are chronic problems that are difficult to manage as a clinician regardless.
And second because I feel that there just weren't any data to support any treatments that we were pursuing at the time and so we would try and apply what we had learned in other types of heart failure to these patients with limited results. If I could talk about what I think this article may change in terms of my practice today, one thing that we've always thought about in terms of pulmonary vascular remodeling in heart failure is that it's just a passive process that as fluid builds up you back up into the lungs and as the fluid builds up and backs up into the lungs you get remodeling.
I think one thing that this article shows is that it may actually be a bidirectional process, which would suggest that perhaps we may need to reconsider looking at pulmonary-specific therapies in this population. But more importantly I think it does confirm that chronic elevating filling pressures do have an effect and a deleterious effect on the pulmonary vasculature. Particularly when you look at other trials such as the CardioMEMS trial, the CHAMPION trial in which the data pretty convincingly showed that as clinicians we don't do the best job of reducing left-sided filling pressures in our patients with heart failure as much as we think we do. This article really drives home the point to me that I really need to make sure that when I see these patients that I'm doing everything I can to reduce their left-sided filling pressures because the consequences of not doing so can affect the lungs, which can then in turn affect the heart as well.
Dr Carolyn Lam: Vineet, that's really words of wisdom. Couldn't agree more. And these are the first sort of autopsy, histological evidence that we have, which is so important. I think if I could just add a couple of perspectives too, it makes me think about making sure that I rule out PVOD in these patients sometimes. We now keep thinking about HFpEF we forget that we need to also rule out PVOD and the other thing much as we now think about not just the filling pressures but the remodeling it's good to note that they found it more in the venous than the arterial system, which also comes therefore with a warning message that we can't just extrapolate I suppose all the PAH therapies that we know about. What do you think about that?
Dr Mesfer Alfadhel: I absolutely agree with that. It's really interesting that all of our therapies from heart failure standpoint and from a PAH standpoint have focused on the myocardium, the neural hormonal cascade, and then the arterials. The pulmonary main artery and arterials. I don't think anyone really understands the biology of pulmonary veins and yet they're actually a pretty significant part of our everyday practice in cardiology. Pulmonary veins are thought to be the source of atrial fibrillation. We look at pulmonary vein inflow when we evaluate patients with echoes. And yet we understand so little about the biology and the mechanisms by which pulmonary veins are affected in both diseased and healthy patients.
I think this article for that reason raises a number of very interesting questions and may potentially change the way we think about these patients.
Dr Carolyn Lam: I keep learning, Amit, this is awesome. I could go on forever so you better stop me.
Dr Amit Khera: I should probably just be a fly on the wall. You must know Carolyn is a HFpEF, HFrEF aficionado and you guys should have a side call for another hour after this. But I do have one, maybe orthogonal question which is, it's interesting because if you look at how insights were made, they're made off areas I would argue at least that we don't, modern environment uses much which is the autopsy and probably to a large degree hemodynamics as much as probably in the old days although that's changing. I'm curious in a fellowship training program your exposure to autopsy and kind of current in-depth hemodynamic-type training, what's your experience?
Dr Mesfer Alfadhel: Our experience with looking at pathological slides, getting under the microscope, seeing tissue first hand, is somewhat limited in our fellowship training program. I would say in certain subspecialties like our heart failure, advanced heart failure subspecialties we do get a chance to see more myocardial biopsy specimens, but I think increasingly the focus has been on noninvasive methods by which we can assess some of these same things that we used to do, use the microscope for. Invasive hemodynamics I think similarly we get a lot of experience in terms of spending time in the cath lab but I do kind of wonder if we don't have the same in-depth training that we used to have in understanding all the nuances of hemodynamics that used to exist in the past.
Certainly, I think that while that's partially a reflection of the way and the direction in which medicine is heading, there is a little bit that's potentially lost there. That said, while we have the benefit of manuscripts like this that does do in-depth hemodynamics and looks at autopsy samples from a clinical standpoint, if we were to ever try and understand this in a larger population I think we would be required to try and find a way to noninvasively or maybe through potentially invasive hemodynamics better study this in live patients.
Dr Amit Khera: Appreciate that answer and I'm just for all of you, this has been outstanding. You all have served as incredible expert discussants. I know Carolyn already said it multiple times but we've learned a ton about each of these articles and great to see how they come alive and are used in practice and how they're applied in your own thinking and specifically as fellows in training with these have meant to you. We thank you all for joining us and it's really been a fantastic experience.
Dr Carolyn Lam: Amit, I can only echo your thanks and thank you listeners for joining us today. Fellows out there you are so important to us. Please, please apply to join us on the next FIT podcast as you can see it's really fun.
Don't forget to join us again next week.
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. This week's issue is so special. It is an autopsy issue. I think it's actually the first of its kind in the history of Circulation. I am so pleased to have with me today Dr Jeffrey Saffitz from Beth Israel Deaconess Medical Center, who's the content editor for Pathology for Circulation and the guest editor for this entire autopsy issue. Welcome, Jeff.
Dr Jeffrey Saffitz: Thank you.
Dr Carolyn Lam: We also have Dr Lee Goldman from Columbia University Medical Center who wrote a beautiful perspective piece on autopsy. Thank you and welcome, Lee.
Dr Lee Goldman: Morning.
Dr Carolyn Lam: Jeff, could you start us off? I mean, an autopsy issue. How in the world did this come about?
Dr Jeffrey Saffitz: I think it really began by coincidence. The journal received submissions from several authors, each involving studies of autopsies, and the editors approached me and asked if we might consider grouping them together in a special issue focused on the role of the autopsy and cardiovascular medicine. I thought that would be a very interesting idea and this evolved into actually something much greater. Two additional papers came in focusing on the autopsy and I think looking at these papers in the aggregate, they represent what we can now consider to be the contemporary utility of the autopsy in understanding the way cardiovascular disease works. So I was particularly pleased that the editors agreed to group these papers into a single issue focused on the autopsy. We were really delighted that Lee Goldman agreed to write a perspective. He has had a longstanding history of studying the role of the autopsy and I hope the readers will find this to be a really interesting and useful issue which will, I hope, chart the course for future discovery.
Dr Carolyn Lam: Just listening to you, I love the way you say it's a contemporary look at autopsy. I mean, we covered things like molecular genetic, proteomic, autopsies, even like electronic autopsies using device. That's really cool. Lee, thank you again for sharing your time and incredible perspectives with us. The long history of autopsy. Do you think it's still necessary now?
Dr Lee Goldman: Maybe give some perspective. I first got involved in this a number of decades ago, when as a junior faculty member, I was assigned to be on the medical audit committee of the hospital where I saw patients as a cardiologist. And two of the senior people in the committee got into a debate about whether autopsies were still important given the advent of CT scans and other modern diagnostic technology. And to listen to them debate for 15 or 20 minutes, I finally had the temerity to pipe in and say we can actually study this, and so we did. We looked at autopsies in three different decades: 1960, 1970, 1980, and much to everyone's surprise, I think found, A. that the rate of which autopsies found diagnoses that doctors had missed and for which treatment would almost certainly have prolonged life was about 10 percent, and it was 10 percent, 1960, 10 percent, 1970, 10 percent, 1980.
But the difference was that doctors were missing different diagnoses. The things that got missed in 1960, and where autopsies showed there were being missed led to better diagnostic approaches and those things were rarely missed in 1980. But since people stayed alive longer, they got new things that we didn't really know much about in 1960. A big difference, fewer people missed heart attacks, pulmonary emboli, and things of that sort, but far more people had missed infections, especially fungal infections that were complication of multiple antibiotics or immunosuppressive therapies.
And so, as I followed this in 1980, if you will, to now, 2018, we find this gets recapitulated over and over again. Medicine moves forward, things we used to miss, we no longer miss, but people still die, and they still die from things that we don't always diagnose. We've done statistical analyses to show that probably the rate of misdiagnosis is going down a little bit, but it's still substantial and we still estimate that thousands of people each year die in the U.S. from things that are not what the doctors thought they had, and if that diagnosis had been made, the patient would have lived longer.
Dr Carolyn Lam: Lee, I just love that perspective. I have to say, it's really humbling. I mean, 1960s and so on would predate me as well, so I'm really humbled, and I love that reminder. Jeff, in fact, quite a number of our papers illustrate exactly what Lee said. We have four papers just dealing with sudden cardiac death, and that is still what diagnosis was struggled with. Could you tell us a little bit more about those?
Dr Jeffrey Saffitz: Yes, of course. I think we all recognize that sudden death remains a huge public health issue. We also realize that most people who die suddenly and unexpectedly don't do so in the hospital when they're being followed and monitored; rather, they die out in the community, and in many cases, these are individuals in whom major risk for coronary disease or other potentially lethal cardiovascular conditions was really not known. So I think it remains a major public health issue, and we still have a great deal to learn. So perhaps it's not surprising that four of the five papers involved autopsy studies of sudden death victims of individuals who died out in the community. A couple of them focused on sudden death in young people.
We know that these individuals often will have familial diseases, and the autopsy has been one mechanism for studying these individuals, so one of the papers from Michael Ackerman at Mayo Clinic, advanced the concept that they started many years ago, the so-called molecular autopsy in which they apply a whole exome sequencing in cases of sudden unexpected death in young people defined here as age under 40, and they identified some rare variants which were likely to be of potential pathogenic significance in sudden death. A related paper from Junttila et al in Finland looks at the finding of myocardial fibrosis in young victims of sudden death. They identified several cases in which that was the only structural change in the myocardium, and when they applied next gen sequencing, the identified variance that we typically associate with the familial non-ischemic cardiomyopathies, arrhythmogenic, dilated, and hypertrophic cardiomyopathy. But the key insight here is that we traditionally think of these diseases as having rather characteristic structural changes which we can recognize at autopsy. What they showed is that those structural changes might be limited to nothing more than some fibrosis. And so the key here is that this expands our potential opportunity to recognize these familial cardiomyopathies, and the overarching idea is we use the autopsy to serve the living. This is a way to gain information at autopsy that we can then use to help family members and other individuals by virtue of the insights gained at autopsy.
Dr Lee Goldman: When we did the estimates in my editorial, and I estimated that roughly 28,000 people die each year in America with diagnoses that doctors missed and for which treatment would have been different if they hadn't missed it, that's really based on, I'll call traditional autopsy methods, which are anatomical, include microscopic evaluation, include culture, but it's not historically included genetic testing. I believe, as these articles show, that the advent of genetic testing, which you could argue could have been done while the patient was alive, but we're not quite there yet in terms of testing everyone's genome, now help you autopsies find even more things that might've been missed. And as you just heard, also can have important information for the family. So, one of the issues you often get into in autopsies is what's in it for the family, and one of the problems here is that the pathologists don't get paid. For the family members, it's mostly an aggravation. The doctors are worried they're going to get sued if something that gets found. And so, to make this work you need to bring in some incentives. Doctors not getting sued if they find things because they should get credit for trying to learn more, some way to reimburse reasonably pathologists and hospitals who do the autopsies, and the understanding of family members that they not only will perhaps be more reassured about what happens to the loved one, but also may learn things that will affect their future, because certainly, these cardiomyopathies, instead of them being diagnosed, are familial and oftentimes will lead to testing and hopefully interventions in family members that'll be to their benefit.
Dr Carolyn Lam: Lee, what great comments about bringing this into the clinical perspective and I just love what you said, Jeff, about autopsy for the living. That is just a quotable quote. That's so cool. I noticed that you did ask Dr Judge to write an editorial specifically about bringing autopsies into the molecular genetic era. So I just want to encourage all our listeners to make sure you read that as well. But Jeff, back to you about the other two papers.
Dr Jeffrey Saffitz: Well, I think one that I found particularly significant is this idea that nowadays, patients come to autopsy with implantable cardiac electronic devices, and the point of this paper is that interrogation of these devices postmortem can provide really important information about the cause and timing of those deaths. I think the reality is that most pathologists who do these autopsies are entirely unprepared or ill equipped to do such interrogations, and so I think the point of this paper is simply to encourage pathologists who do these autopsies to develop partnerships and relationships with cardiologists who are able to get this type of information from these devices. And again, it not only provides information about what happened to that one individual and what the death was all about, but it provides important information to the family and potentially information that allows the family to recognize particular risks that might impact the living members. So I thought this was just another really interesting example of how information that is potentially available at autopsy may not be fully utilized, and I hope that this paper will have an impact in that regard.
Dr Carolyn Lam: That's great. Lee, did you have any perspectives on devices and its role in autopsy now?
Dr Lee Goldman: I guess that the point that I would just reinforce would be that diagnostic technologies, including the ability to monitor someone's heart rate, have helped us diagnose things that were missed in previous eras, but medicine is always pushing the frontier forward, and as long as we develop new therapies, develop new devices, there'll be new things to learn. I want to make one other point about what I'll call overconfidence in diagnoses. The published statistics for the accuracy of most diagnostic tests are based on what doctors think the diagnosis ends up being, not the autopsy, which is the ultimate gold standard. So, if you actually go through some not-so-complicated arithmetic, you'll find that many of the tests that we think are almost perfect at finding things really aren't because the people who die with those things found that autopsies that the test missed. There's something called a virtuous circle, there's also a vicious cycle. There's a bit of a vicious cycle here that if you don't do autopsies to be sure you aren't missing things, you become overconfident in the tests that you think are finding them, and therefore think you already know everything and don't need to do an autopsy. To me, in some ways, that's the most perverse result of the plummeting autopsy rate, which, by the way, can be linked directly to changes in how hospitals get accredited, that in prior years there was a minimal autopsy rate required for accreditation. When that was removed, not surprisingly, autopsy rates plummeted, and now, most autopsies done in the US are not done in hospitals because doctors aren't sure what's going on. They've done by medical examiners as part of the laws for autopsies least being considered and people who die without having had a medical attention to some degree.
Dr Jeffrey Saffitz: You are exactly right on all of these points. I'll just say this is the point of one of the other papers from Tseng et al. This was a prospective autopsy study of sudden death in the city and county of San Francisco, and what they showed here is that only about half of the deaths that were considered to be sudden cardiac deaths as defined by the conventional criteria actually turned out to be deaths due to a rhythmic disorder. So Lee's point is exactly right. Doctors think they know a lot of things, but they're not always right about that, and the autopsy is probably one of the best ways to bring some quality control to this, and to really provide, I think, objective data that often is the case flies in the face of what the previous thinking was, and I think this paper in this issue of Circulation really brings that point home very clearly.
Dr Carolyn Lam: Yikes. OK, so here I am, I practice in Asia, and I think the autopsy rates are even lower, so this is a great wake up call for me just listening. Let's switch gears a little bit. How about the paper by Dr Herrington? Now this goes to a proteomic bisection almost of maybe preclinical disease and atherosclerosis. Would you like to comment on that on, Jeff?
Dr Jeffrey Saffitz: In the perspective that I wrote with Gaetano Thiene, in addition to looking at the history of the autopsy, we looked to the future and just considered briefly what role will the autopsy play going forward, and I think the paper by Herrington is a great example of how we can use the autopsy to learn so much more about the way human disease works. The basic idea here is that something like coronary artery disease or atherosclerosis, we think of as being a disease that only involves the blood vessels, and we tend not to recognize it until it is rather advanced and clinically manifest, but we recognize that these diseases begin decades before they become clinically manifest. We really don't know how to identify the earliest antecedents, and without knowing that we really, I think, very much limit our ability to identify the disease way early before it becomes clinically manifest, and then be able to practice preventive measures and intervene to prevent the disease from occurring.
So, what this paper showed is that it's an application of high-throughput proteomics looking at coronary artery and aortic samples obtained at autopsy, and these authors identified particular changes in proteins that they then were able to show in a prospective independent clinical cohort were able to predict the development of coronary artery disease. So I think going forward, we are going to redefine our understanding of human disease by learning about its earliest expressions and its full systemic distribution, and in doing so, we'll be much better prepared to diagnose earlier and intervene and prevent disease. So I think this was a great example of how the autopsy can help in that effort.
Dr Carolyn Lam: I feel like we are going full circle in history and going back to learn about how to go forward. I don't know if I expressed that well, but I am just in awe of what I've learned from both of you. Thank you so much, Jeff, for putting together this amazing issue, and thank you so much, Lee, for sharing your perspectives. Thank you, audience, for joining us this week. You've been listening to Circulation On The Run. Don't forget to tune in again next week.
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. Today's feature discussion revolves around important hemodynamic and echo data from the reprise three trial, comparing the lotus and core valve transcatheter aortic valves in patients with high surgical risk. Can't wait? Well it's coming right up after these summaries.
The first original paper this week provide experimental data showing that the endothelium controls cardiomyocyte metabolism and function via notch signaling. Corresponding author, Dr. Fischer, from German Cancer Research Center in Heidelberg, Germany, and colleagues, studied fatty acid transport in cultured endothelial cells and transgenic mice with endothelial specific notch inhibition, or wild type mice treated with neutralizing antibodies against the Notch ligand. They showed that notch signaling in the endothelium controlled blood vessel formation and fatty acid transport in the adult mouse heart. Inhibition of Notch signaling in the vasculature led to expansion of the cardiac vasculature and impairment of fatty acid transport to cardiomyocytes. This resulted in metabolic reprogramming and heart failure.
Together, these data provide compelling evidence for a central role of Notch signaling at the coordination of nutrient transport processes in the heart. These findings help to explain how pharmacological inhibition of Notch signaling, for example, in oncology could lead to heart failure. The findings also help to identify the signals and molecules involved in endothelial transport capacity and show how these could offer new targets for the treatment of heart failure.
The next paper raises the prospect of new treatment options to combat ischemic heart disease and its progression to heart failure. Ischemic injury to the myocardium is known to trigger a robust, inflammatory response, which is an integral part of the healing process, although much effort has been directed at tempering the inflammatory response in hopes of achieving clinical gain. Major efforts have focused on individual cytokines, the complement cascade, and antibodies to adhesion molecules preventing leukocyte invasion.
In contrast, relatively little effort has focused on macrophages. Although macrophage transformation is known to be crucial to myocardial repair, the events governing this transformation are poorly understood. In today's paper, co-corresponding authors of the trial in Hill, from UT Southwestern Medical Center, performed an elegant series of experiments and showed that release of DNA from necrotic tissue during myocardial infarction, triggered in macrophages a recently described innate immune response known as the GMP-AMP synthase-stimulator of interferon genes pathway or cGAS-STING pathway.
This response in turn promoted an inflammatory macrophage phenotype. Suppression of the pathway promoted emergence of reparative macrophages, thereby mitigating pathological ventricular remodeling. These results therefore reveal for the first time, that the cytosolic DNA receptor, GMP-AMP synthase, functions during cardio ischemia as a pattern recognition receptor in the sterile immune response.
Furthermore, this pathway governs macrophage transformation, thereby regulating post injury cardiac repair. As modulators of this pathway are currently in clinical use, these findings raise the prospect of new treatment options to combat ischemic heart disease and its progression to heart failure.
Cigarette smoking is a well-known risk factor for atherosclerotic cardiovascular disease. However, less is known about the risk for heart failure. First author, Dr. Kamimura, corresponding author, Dr. Hall, from University of Mississippi Medical Center, and their colleagues investigated 4129 black participants without a history of heart failure or coronary heart disease at baseline in the Jackson Heart Study.
They examined the relationship between cigarette smoking and left ventricular strength and function by using cardiac magnetic resonance imaging. They found that current cigarette smoking status, smoking intensity in terms of cigarettes per day, and smoking burden in pack-years, were independently associated with higher left ventricular mass, lower left ventricular strain, higher brain natriuretic peptides, higher BNP levels and higher risk of incident heart failure hospitalization in blacks.
These relationships were significant after adjustment for coronary heart disease, suggesting mechanisms beyond atherosclerosis may contribute myocardial dysfunction and increased risk of heart failure in smokers. In summary, these findings suggest that smoking is associated with structural and functional left ventricular abnormalities that lead to heart failure in blacks and that smoking cessation should be encouraged in those with risk factors for heart failure.
What happens to the risk modifying effects of exercise in individuals with increased genetic risk of cardiovascular disease. Drs. Tikkanen, Gustafsson, and Ingelsson from Stanford University School of Medicine performed the study in about 500,000 individuals from the UK Biobank and reported and compared the association's objective and subjective measures of fitness and physical activity with prospective cardiovascular disease events and all-cause death.
They found consistent and robust inverse association, particularly between objective measures of fitness and physical activity and six cardiovascular outcomes and total mortality. Using genetic risk scores for coronary heart disease and atrial fibrillation, they showed that these inverse associations were present in each genetic risk category, suggesting that elevated genetic risk for these diseases can be compensated for by exercise.
The knowledge that lifestyle choices have substantial effects on disease risk could encourage individuals to initiate a healthier lifestyle to reduce their overall risk. In the longer term, identifying subgroup space on genetic risk that benefit most from lifestyle interventions, could help personalize preventive strategies for chronic diseases.
Well, that wraps it up for our summaries, now for our feature discussion.
Today's featured paper deals with transcatheter aortic valve replacement, which we are all going to recognize has rapidly emerged as a treatment of choice in inoperable patients and, it's a reasonable alternative to surgical aortic valve replacement in high- and intermediate-surgical-risk patients. However, the success of this technology is in large part due to the rigor with which quantitative echocardiography by core laboratories has been used to assess the native and prosthetic aortic valve function.
Today's feature paper gives us such important data from the REPRISE III trial, which compares the Lotus and the CoreValve transcatheter aortic valve in patients with high and extreme surgical risk. I'm so pleased to have the corresponding author, Dr. Federico Asch, from MedStar Washington Hospital Center, as well as our associate editor, Dr. Dharam Kumbhani from UT Southwestern. All right Federico, please help me here, so as a noninterventionist and a person who doesn't deal with all these different types of valves every day, please tell us what was the motivation of looking so closely at the echocardiographic data from REPRISE, because the REPRISE III trial results were already published?
Dr Federico Asch: The most interesting aspect of this analysis is really that there is a very methodic, blinded comparison of two different valves. The valve that is being tested and that the reason why Boston Scientific has sponsored the study, is the Lotus valve, the Lotus System is, if you want, a new valve that is not clinically approved in the United States yet, that basically, it's a completely repositionable bovine pericardial valve that comes in different sizes.
The three sizes that were tested in here are what we would call the small, or 23 millimeters, the medium, 25 millimeters, and the large, 27 millimeters. Each patient, at the moment of randomization, or at the moment of inclusion, were randomized to the small, medium, or large Lotus valve vs the clinically approved CoreValve, which is a Medtronic product. Obviously, this is taken as the control group because this is one of the valves that is widely clinically available nowadays in the United States and worldwide.
This is exactly the motivation here. On one side, to prove whether this valve was as good as CoreValve or not and whether it was as safe as the CoreValve as well, and that, the study was about. Every three patients that were randomized, two were randomized to the new valve, the Lotus, and one was randomized to the CoreValve.
An important note to make here is because the control arm included clinically available valves at the beginning of the study, the previous generation of CoreValve was used and then about halfway through the trial, the Evolut valve was the one being used, so there's two different valves on the CoreValve system that were tested in this trial while Lotus was a single earlier generation valve.
We focus here on the hemodynamic implications, that meaning, the gradients and the degree, if you want, of obstruction that these valves could have over time, and the amount of regurgitation that these two valves and how they compare to each other.
Dr Carolyn Lam: That's great. Could I ask if you had any hypothesis going in, because as I recall, the Lotus valve actually met the non-inferiority comparison, but it did have significantly higher rates of new pacemaker implantation and valve thrombosis, right? So, was that perhaps a hypothesis going in and what did you find?
Dr Federico Asch: So, the initial hypothesis of the trial overall was that this new valve was one that was designed to have less paravalvular regurgitation, which is something as you probably know, has been of significant concern in the cardiology world ever since the initial clinical trials for Tyler with Partner and CoreValves.
Patients with more significant paravalvular leak did have worse outcome over time, so, one of the main goals of this valve itself, was to prevent that paravalvular regurgitation. So, that was the initial idea behind this product I would say, not just the clinical trial and obviously, this clinical trial tried to prove that, indeed, as I mentioned before, the primary effectiveness end point was mortality, disabling stroke, and paravalvular leak, the main driver on the difference between the two valves there was indeed a much lower paravalvular regurgitation on the Lotus valve compared to CoreValve.
There was also lower stroke rate, but the most important difference was on the paravalvular aortic regurgitation. Of course, when you think of any of these devices, for them to be able to prevent paravalvular leak, they have to have some kind of skirt or cushioning around the valve, an adaptive seal, which in the case of the Lotus valve, that would prevent any flow around the stent, but one of the risks of that of course is that by trying to seal the valve, you're actually, you may be decreasing a little bit the effective orifice area, so it was actually very important to understand whether gradients with this valve were higher and whether the potential differences in the gradients did turn into any difference in clinical outcomes.
Dr Carolyn Lam: That is super clear now. What did you find?
Dr Federico Asch: I would say, the findings from a hemodynamic standpoint, we can briefly summarize them in two aspects of it. No surprise, the paravalvular leak was significantly lower for Lotus compared to CoreValve, and that was true for any of the three sizes, for the small, medium, and large size in all of them, the rate was significantly lower for Lotus. It was actually under 1% of the patients with moderate or higher paravalvular leak, as opposed to an average of 6.7% on the CoreValve, but on the other side of the spectrum, the gradients and the effective orifice area, and the dimensional index were all significantly better on the CoreValve compared to the Lotus.
The bottom line is, we have two valves that each of them has a specific strength. On one side, Lotus has less paravalvular leak. On the other hand, CoreValve has a better gradient profile than Lotus. I would say in two lines, that's the findings of this study. We did take these findings further and compared among different valve sizes and we saw that these differences were consistent at each of the valve size, so if we would compare the small Lotus with the small CoreValve or the large Lotus with CoreValve, the findings were very similar.
They were always significant, and what is important is that while there was a difference, both for paravalvular leak and for gradients and other hemodynamic parameters, the reality is that when it came to clinical outcomes, there was no significant difference among the two.
Dr Carolyn Lam: Dharam, you have to weigh in now as an interventional cardiologist, what does this mean to you.
Dr Dharam Kumbhani: First of all, Federico, congrats to you and Ted and the rest of the group. I think this is obviously a very important trial and I think this hemodynamics paper, I think definitely moves, helps understand the differences a little bit better, so I think this is a very valuable contribution. I think you said it exactly right. I think what is really interesting is that you have a significant introduction into the paravalvular leak, but yet you have, because of difference in valve design, one being annular vs the other being super annular, you have higher gradients with the Lotus valve compared with the CoreValve, so you wonder if the two differences can cancel themselves out in some way, because you don't see any difference in clinical end points at one year, and also, I guess, what we've learned from the Partner data and other CoreValve data is it would be really helpful to see how this evolves over time, whether there will be any late separation of the curves or just a long-term follow-up, whether that will still be important.
I think that is the really interesting insight that we glean from this analysis. I want to make two other points. I think the other interesting thing about the design of the Lotus valve, and probably having such a great seal for the paravalvular leak reduction and having higher radial strength, I would think, at the annulus, I suspect that that's probably also the reason why the pacemaker rate is higher with this, compared with CoreValve, so it's almost 30% in this trial. About 20%, 18% already had an existing pacemaker, so particularly I guess, as we move to lower-risk population, I think that will certainly, balancing the two and deciding probably one valve doesn't fit everybody and we may have to have strategies to figure out which may be the best valve for a given patient based on this.
The other point I'd like to make is the question about stents or valve thrombosis and I know that your group has been heavily invested in that research, because I know in the JAMA paper, there was a report of few valve thrombosis events and you also bring that home here in this hemodynamics paper. Is there anything you want to elaborate on that or any insights that you feel would be helpful for the next set of trials and next generation of the Lotus valve?
Dr Federico Asch: Yeah, you're bringing two very, very important points. Let me address the thrombosis one first. As you very well described, we have been working a lot on multiple different valves and understanding why this is happening. It's clearly something of concern. In this study in particular, we did not have data collected to detect subclinical thrombosis, which is what most of us have been talking mostly about over the last few years. The diagnosis of thrombosis here was not so clinical. These were patients that mostly, because gradients were going up, were detected. They were image ... there was one or two cases with TE and the other ones with CTs and then they were given anticoagulation and those results, and based on that is that the diagnosis of thrombosis was made. All those cases, nine cases, indeed, happen on the Lotus group. The CoreValve is one in that overall has shown to have lower rates of thrombosis in general and I'm not just talking about our own report. Our report was consistent with that.
That may be something related to the fact that it's a super annular valve and the flow through the valve may be better, if you want, but we don't know that. The rate of thrombosis, again, clinical thrombosis, in this case, for the Lotus valve was 1.5%, which is still low, but it's impossible to compare to all those new reports that are coming out because those are mostly subclinical, which is not the case here.
One could argue that if would have done CTs on every patient here at 30, 45 days, we would have found much higher rates in both valves, but we don't know that. We don't have the data to address that.
Dr Dharam Kumbhani: As I remember, almost all of them, I think seven out of eight of those reported, were in the 23 valve, right? They were not ... I think the larger valves ...
Dr Federico Asch: Exactly. There were nine cases overall, eight of them were on the small valve, on the 23 millimeters, and one was in the middle size, on the 25 millimeters. You are completely right.
Dr Dharam Kumbhani: I don't know what to make of that, but that was an interesting observation as well.
Dr Federico Asch: Yeah. It's interesting because when you look at reports of subclinical thrombosis, actually some of the reports suggest that this is more common in bigger valves than in smaller valves. Registries, I'm talking about, but that didn't seem to be the case here, but again, we need to understand the limitations. This was not a study geared towards detecting sub clinical thrombosis or thrombosis overall. These are just clinically reported cases that were analyzed thoroughly but they were triggered by some kind of clinical event, what's mostly an increase in the gradient.
That's all that I would make out of the thrombosis. I think there is definitely more that we need to learn about it. We know that both CoreValve and Lotus have been reported to have cases of thrombosis, but in general, CoreValve seems to be of all the type of devices, the one with the lowest incidents.
Dr Dharam Kumbhani: Maybe your studies will help in understanding the influence of hemodynamic profile, patient-prosthesis mismatch, to the risk of thrombosis. I think the interactions are not well understood. I think that will be very interesting going forward.
Dr Federico Asch: Exactly. And the other comment that I wanted to make, Dharam, regarding your first impression about the pacemakers and the gradients, a couple of observations that I want to make out of that, one is that the difference in gradients between Lotus and CoreValve seem to be the highest early and then over months, that difference seemed to get smaller and smaller, still significant though, even at one year, but one could argue that if, as we continue following up these patients, maybe the difference starts getting smaller and smaller to the point that to become irrelevant, but we don't know that. That is just the impression that we get at looking at the curves over time.
The pacemaker, obviously, as you can imagine, this is something that is of concern for everybody. It's a high rate, the newer Lotus generations are geared towards having lower paravalvular leak, like the head Lotus Edge and so we would expect that in the future that would be the case, but we don't know. The same way that it is important to mention that CoreValve has been addressing their initial concern, which was paravalvular leak.
I mentioned before that the control arm in this clinical trial included CoreValve classic, earlier generations from roughly half of the patients, and the paravalvular leak in that group was a little bit over 10%, while the second group, which was the Evolut R had already a much lower rate of paravalvular leak, but was still significantly higher than Lotus, but was definitely better.
I think what this points out to, is that all these devices are so early in their life, in their history, that all the efforts that each of these companies are making into fixing the specific problems that each of them have, really turn into a next generation that addresses more aggressively all these things. In the case of CoreValve, definitely the paravalvular leak is one and they are making very good progress in the care of Lotus, the permanent pacemaker is one and we expect in subsequent generations to improve as well.
Dr Carolyn Lam: It's been very enlightening for me and I'm sure for all our listeners. Thank you for joining us today listeners. Don't forget to tune in again next week.
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, associated editor from the National Heart Center and Duke National University of Singapore. This week's feature paper reports results of the SWAP-4 study, which is the first study to evaluate the pharmacodynamic impact of the timing and dosing of clopidogrel administration when de-escalating from ticagrelor therapy. Extremely important take-home messages for clinicians looking after patients with coronary artery disease and a must listen to. Coming up right after these summaries.
In the first original paper this week, chondroitin sulfate, well known in the context of the monogenic disease mucopolysaccharidosis type 6 may actually represent a novel therapeutic approach for the treatment of general heart failure. First author Dr Zhao, corresponding author Dr Foo, from Genome Institute of Singapore studied changes in myocardial chondroitin sulfate in non-mucopolysaccharidosis failing hearts and assessed its generic role in pathological cardiac remodeling. They found that failing human hearts display an abundant accumulation of chondroitin sulfate proteoglycans in the extracellular matrix largely localized to fibrotic regions.
The main component of chondroitin sulfate glycosaminoglycan chains in human hearts was chondroitin 4 sulfate. TNF alpha was a direct binding partner of glycosaminoglycan chains rich in chondroitin 4 sulfate. Modification of the chondroitin sulfate chain with the recombinant human arylsulfatase B, which is an FDA-approved treatment for mucopolysaccharidosis type 6 that targets chondroitin 4 sulfate, actually ended up reducing myocardial inflammation and overall fibrosis in vivo. In two independent rodent models of pathological cardiac remodeling, this recombinant human arylsulfatase B treatment prevented cardiac deterioration and improved functional recovery. Thus, targeting extracellular matrix chondroitin sulfate represents a novel therapeutic approach for the treatment of heart failure.
The next paper focuses on the subcutaneous ICD, which is an entirely subcutaneous system that does not require intra-procedural vascular access or endovascular defibrillator leads or coils. Now the subcutaneous ICD has a novel mechanism of defibrillation and is associated with an increased energy requirement for defibrillation when compared to traditional transvenous ICDs. Thus, ventricular fibrillation or VF conversion testing at the time of subcutaneous ICD implantation is a class 1 recommendation.
Yet, what is the current adherence to this recommendation? Well, today's paper addresses this question from first and corresponding author Dr. Friedman from Duke Clinical Research Institute. He and his co-authors studied first time subcutaneous ICD recipients between 2012 and 2016 in the National Cardiovascular Database Registry ICD Registry to determine the predictors of use of conversion testing, predictors of an insufficient safety margin during testing and in-hospital outcomes associated with the use of conversion testing.
Results show that use versus non-use of VF conversion testing after subcutaneous ICD implantation in the US was more related to physician preference than patient characteristics. The study also identified several patient characteristics associated with an insufficient defibrillation safety margin. That included increased body mass index, severely decreased ejection fraction, white race, and ventricular pacing on the pre-implantation ECG. Use of VF conversion testing after subcutaneous ICD implantation was not associated with a composite of in hospital complications or death. These data may inform ICD system selection and a targeted approach to conversion testing.
We know that elderly patients are at elevated risk of both ischemic and bleeding complications after an acute coronary syndrome and display higher on clopidogrel platelet reactivity as compared to younger patients. Does prasugrel at five milligrams compared to clopidogrel reduce ischemic events without increasing bleeding in the elderly? Today's paper addresses this question from corresponding from corresponding author Dr Savonitto from Manzoni Hospital Italy and his colleagues.
These authors performed a multicenter randomized open label blinded end point trial comparing a once daily maintenance dose of prasugrel five milligrams with the standard clopidogrel 75 milligrams in patients more than 74 years old with acute coronary syndrome undergoing percutaneous coronary intervention. The primary end point was a composite of mortality, myocardial infarction, disabling stroke and re-hospitalization for cardiovascular causes or bleeding within one year. Enrollment was interrupted due to futility for efficacy according to pre-specified criteria after a planned interim analysis when 1,443 patients had been enrolled with a median follow-up of 12 months.
At this point of interruption, there was no difference in the primary end point between reduced dose prasugrel and standard dose clopidogrel. The results of this Elderly ACS 2 study therefore could not show overall clinical benefit of prasugrel five milligrams versus clopidogrel in elderly ACS patients undergoing early PCI.
The final study is the first to define the cellular and molecular mechanisms of cardiac valve inflammation and fibrosis occurring in the setting of systemic inflammatory disease. First author Dr. Meier, corresponding author Dr Binstadt from University of Minnesota used T-cell receptor transgenic mice which spontaneously developed systemic auto antibody associated autoimmunity leading to fibro inflammatory mitral valve disease and arthritis.
They identified a critical population of CD301b/MGL2 expressing mononuclear phagocytes that orchestrated mitral valve inflammation and fibrosis in this mouse model. They further demonstrated an analogous cell population was present in human inflammatory cardiac valve disease. Finally, they defined key inflammation molecules that drove mitral valve disease in this model, thus providing multiple potential therapeutic targets that are required for mitral valve inflammation and fibrosis.
Dr Carolyn Lam: That wraps it up for your summaries. Now for our feature discussion.
Searching between different classes of P2Y12 inhibitors including de-escalation from ticagrelor to clopidogrel commonly occurs in clinical practice. However, what are the pharmacodynamic profiles of this strategy? Well, today's feature paper is going to provide a lot of insights. I am so pleased to have the corresponding author of the SWAP-4 study, Dr. Dominick Angiolillo from University of Florida College of Medicine Jacksonville, as well as our associate editor Dr. Gabriel Steg from Hôpital Bichat in Paris, France. Dominick, now this is SWAP-4. That means there was a SWAP 1, 2, 3. Could you just paint the background and rationale for SWAP-4 and tell us what you found?
Dr Dominick Angiolillo: We performed this study on the background of a line of research that we've been conducting over the past number of years of switching antiplatelet therapies. There's so many different types of switches that can occur and one of them is that which is defined as a de-escalation which is that from a more potent P2Y12 inhibitor to a less potent and one of those that occur frequently in clinical practice is the switching from a ticagrelor to clopidogrel and this was essentially the rationale for conducting the SWAP-4 study.
Now I want to start off with saying that the reason for doing this study is not to advocate switching because we always recommend that individuals follow guideline recommendations but we performed this study because we wanted to provide clinicians with some additional insights that if you're going to switch particularly from ticagrelor to clopidogrel, which would be the modality which is associated with, put it this way, with the smoothest transition one drug to another.
This is the rationale. What we did was do a pharmacodynamic, conduct a pharmacodynamic study taking patients who were on standard treatment with dual antiplatelet therapy aspirin and clopidogrel and they had a run-in phase with ticagrelor. And the reason why we took patients on the back part of aspirin and clopidogrel is because we then wanted to look at the effects after switching to compare it with a baseline. There have been some discussions about drug-drug interactions. And patients were randomized to either continue with treatment with ticagrelor to switch with a loading dose of clopidogrel, 600 milligrams 12 hours after last dose of ticagrelor. 24 hours after last dose of ticagrelor or directly switch with a maintenance dose. So, the randomization was into four groups.
Essentially to keep a long story short, what we observed was that when de-escalating from ticagrelor to clopidogrel we did see an increase in platelet activity obviously as expected. But the use of a loading was not able to mitigate this increase but there were no differences according to timing of administration of the loading dose clopidogrel 12 or 24 hours. We had anticipated in our study design that with the administration of the loading dose 24 hours after last maintenance dose we could have achieved a smoother transition, but this was not the case.
Nevertheless, the overall conclusions of our study are supported by the pharmacodynamic data in terms of you still achieve a better transition when you give a loading dose than without a loading dose. I was also want a little bit cautious and I think during the review process of the journal and feedback from the editors we kind of phrased in a very cautious way the suggestion for a drug-drug interaction, in fact we suggested because there are other ways to look into this phenomenon in more detailed manner. For example, doing some specific pharmacodynamic analysis which was not done in this study. Nevertheless, the take-home message from a clinical perspective remains unchanged.
Dr Carolyn Lam: Thanks so much, Dominick. That was a very important framing of the paper that you gave us at the start that this trial was not designed to try to say who should be de-escalated or not and that should be in line with the guideline recommendations and yet such an important just take-home message that if there is a need that the 600-milligram loading dose of clopidogrel should be used. You know, Gabriel, you've thought a lot about this and especially the drug-drug interaction question. What are your thoughts there?
Dr Gabriel Steg: Yeah, well first of I think this is an extraordinary, important study even though it's a pharmacodynamic study, which many clinicians might look at and then quickly read the abstract and turn the page I think this is actually one of the most interesting papers we've published in recent months. The reason for this is this is tackling a very common clinical scenario, which is having or desiring or wanting to de-escalate the intensity of platelet therapy after a PCI or ACS from a potent agent such as ticagrelor to a less potent agent such a clopidogrel. And as nicely explained in the paper, there are multiple reasons why this can occur.
A common clinical scenario is that cost is a major issue. Because of the cost patients or physicians may want to switch to clopidogrel, a generic drug as opposed to a branded drug. Another scenario which is fairly common is side effects. Either nuisance bleeding or maybe dyspnea with ticagrelor may prompt some physicians and patients to want to deescalate to clopidogrel. To a less intensive therapy which may not have dyspnea or may not cause as much nuisance bleeding. And finally, sometimes it's done on purpose because some believe that within a few weeks or months following PCI or ACS the benefits of more intensive patient therapy is less, the risk remains the same and therefore maybe we could proposedly de-escalate therapy to clopidogrel and get away with it and there have been a number of randomized studies and observational studies that suggested that this might be feasible although these studies have weaknesses. They're often open label. They're often fairly small and somewhat underpowered.
So, we don't have a definitive answer. Nevertheless, this happens on an everyday basis in most large clinical centers and we don't know exactly how to do it and what the best way to do it and I really want to credit Dominick's team for doing a rigorous series of investigations, including this one, which is the latest one but not the only one in trying to really map out how exactly we should as clinicians manipulate these agents to achieve the best safety and efficacy for our patients. And I think the message here is very clear. Yes, you can de-escalate but you have to be careful on how you do it. And I think you really need to use a loading dose, a 600-milligram loading dose of clopidogrel if you're going to deescalate from ticagrelor to clopidogrel to avoid a gap in protection that might be deleterious to patients.
That does not address all of the questions that are raised by de-escalation and as I pointed out I think outcome trial data are really of paramount importance here, but I think this really important because it has major practical implications for clinicians worldwide on how to do this. So, I think this is a great study. I really want to congratulate Dominick.
Dr Dominick Angiolillo: Thank you.
Dr Carolyn Lam: You looked at the genetic status as well. Could you tell us about your findings there?
Dr Dominick Angiolillo: We in the spirit of trying to perform the most comprehensive possible assessment we have also looked at the genetic background of our patients and in particular looking whether the presence of a loss of function allele for CYP2C19, which is involved with clopidogrel metabolism, could have affected the outcomes. And the reason why we did this there've been a lot of studies clearly showing that if you have a loss of function allele for CYP2C19 you do have higher levels of platelet reactivity. Therefore, we want to see if those carriers would have had even a greater increase in platelet reactivity. And again, we did all this in the spirit of really trying to define again this from a pharmacodynamic standpoint, if there could be any potential safety hazards with such an increase in platelet reactivity with the de-escalation.
When we did our analysis, we did not find any impact of a CYP2C19 on our data. However, I think it's important to underscore that we did not have too many patients with a loss of function allele so clearly the study was not designed or nearly closely powered to look into this assessment. So, I think that aspect does need to be interpreted with caution.
Dr Carolyn Lam: Thanks so much, Dominick. Were there perhaps caveats that clinicians listening in should pay attention to? For example, this study was conducted in stable patients with coronary artery disease. What about patients with recent acute coronary syndrome?
Dr Dominick Angiolillo: That's a great point. The reason why we conducted this study in a more stable setting was largely driven by two aspects. Well first of all, we wanted to have a run-in phase of patients switching from clopidogrel to ticagrelor to have some sort of baseline to reference to after the switch. And this would have been mostly ACS patients that would be less likely to be on clopidogrel. The second is purely a safety issue. We know that patients with acute coronary syndromes are associated with higher levels of platelet reactivity and in the context of a study where we do not know the pharmacodynamic profiles associated with de-escalation or better off we don't know the details.
And so, there was a safety consideration there which is why we did it in stable patients. But what we can say is tied with Gabriel's comment before in all the studies out there are not powered or do not have the rigor of a mega trial. Although we give our suggestions and recommendations, practical recommendations on how to switch, there is an increase in platelet reactivity and we stress in our manuscript that if you are going to switch, please try to delay this as much as possible because those increases in platelet reactivity for example, in a patient with an ACS for example, immediately after PCI, something that we probably would not want for our patients. I'm very happy actually that we conducted the study in the more stable cohort because we had less confounders. This is kind of the reason behind all this.
Dr Gabriel Steg: The last question maybe I would ask Dominick is whether he believe that results would be different if we had the patients on a maintenance therapy for longer with clopidogrel, do you believe that the risk of rebound or drug-drug interaction are the same early on after institution of therapy or later on? Is there any reason to expect a difference?
Dr Dominick Angiolillo: That's a great question. My personal opinion would be that with longer duration the platelet reactivity would have gone back down to baseline. We actually continue to study out up to around 10 days following the switch which we thought would have been sufficient time to get back to baseline and it was not the case particularly in the patients whose switch was a 75 milligram. The answer's probably yes. Probably yes. To redesign the trial again maybe having that 30-day time point as well would have been obviously of added value.
Dr Carolyn Lam: Thank you so much, Gabriel and Dominick. This has been extremely insightful. Fun as always.
You've been to Circulation on the Run. Don't forget to tune in again next week.