Oct 14, 2019
Dr Carolyn Lam: Welcome to Circulation On The Run, your weekly podcast summary and backstage pass to the journal and it's 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 from the Pauley Heart Center in Richmond, Virginia at VCU Health.
Well, Carolyn, we've got a great feature article to discuss later in our interview today. We're going to compare surgical versus percutaneous aortic valve replacement, but now with coronary artery revascularization. So, very exciting results from the SURTAVI trial.
So, Carolyn, do you have a couple papers to discuss?
Dr Carolyn Lam: For sure. Actually, it's exactly a couple, and it's a couple of GWAS papers. The first is a GWAS of the cardiac magnetic resonance imaging derived left ventricular phenotypes of the UK bio bank. It comprises almost 17,000 European-UK bio bank participants without prevalent myocardial infarction or heart failure. So this was led by professors Petersen and Monroe from Queen Mary University of London, and colleagues who found that prognostically important left ventricular imaging phenotypes were highly heritable, with a heritability of 22 to 39%. A total of 14 genetic susceptibility low PSI, eight of which were unique, enriched in the cardiac developmental pathways and regulation of contractile mechanisms were discovered, and the polygenic risk scores of left ventricular phenotypes were predictive of heart failure events independently of clinical risk.
Dr Greg Hundley: Well, Carolyn, knowing me and MRI, something I really am interested in. So tell us a little about what are the clinical implications?
Dr Carolyn Lam: Well, the findings not only enhance our understanding of the genetic basis of prognostically important left ventricular phenotypes in the general population, but they also underscore the intricate genetic relationship between these endo phenotypes and the pathogenesis of heart failure. The prioritized genes in the genome whites significant load size should be followed up in the functional studies to aid the development of potential novel therapies in future. The polygenic risk scores of left ventricular phenotypes may have a role in personalized risk stratification. But this, of course, is dependent on further validation of the clinical robustness in future studies.
I want to skip onto my second GWAS paper, and this time dealing with bicuspid aortic valve. So, first a little reminder that bicuspid aortic valve disease is a congenital defect that affects 0.5 to 1.2% of the population, and is associated with comorbidities including ascending aortic dilatation and calcific aortic stenosis. To date, while a few causal genes have been identified, the genetic basis for the vast majority of bicuspid aortic valve cases remains unknown. Today's paper from Dr Lipschultz from Medical University of South Carolina reports novel human genetic based models, which developed bicuspid aortic valve and aortic stenosis with high penetrance.
Dr Greg Hundley: Very interesting. So, how did the authors do this, Carolyn?
Dr Carolyn Lam: Yeah, it is interesting. What they did is they performed a GWAS and replication study using cohorts of more than 2,000 patients with bicuspid aortic valve and more than 2,700 controls, which identified the primary Celia genes as associated with the bicuspid aortic valve phenotype. Specifically the most associated snips were identified in or near genes that are important in regulating Ciliogenesis through the exocyst, which is a shuttling complex that chaperone Celia cargo to the membrane. Genetic dismantling of this exocyst resulted in impaired Ciliogenesis through the XO CIS, disrupted Ciliogenic signaling, and resulted in a spectrum of cardiac defects in zebra fish and aortic valve defects including bicuspid aortic valve, valve stenosis, and Velveeta calcification in murine models as well. So this data really supports that the exocyst is required for normal Ciliogenesis during aortic valve morphogenesis and really implicates the disruption of Ciliogenesis, and its downstream pathways may contribute to bicuspid aortic valve and its associated comorbidities.
Dr Greg Hundley: Wow. Very interesting. Learning more and more about bicuspid valves through our journal. I'm going to shift Carolyn and talk about an article from Dr Marc Sabatine from the TIMI study group at Brigham and Women's hospital. This study performed a systematic review and a trial level meta regression analysis of three classes of lipid lowering therapies that reduce triglycerides to a greater extent than they do LDLC. Fibrates, Niacin, and Marine derived Omega-three fatty acids and key inclusion criteria were a randomized, controlled trial that reported on major vascular events. The study also incorporated data from a previous Meta-regression of 25 Statin trials, and the main outcome measure was the risk ratio for major, vascular events associated with absolute reductions in lipid parameters.
Dr Carolyn Lam: Oh, very interesting. So did the study show that it was beneficial to lower triglycerides or not?
Dr Greg Hundley: Let me tell you a little more about it. The study encompass 374,358 patients that sustained 46,180 major cardiovascular events, and in their multi-variable Meta-regression model, that included terms for both LDLC and triglyceride surrogates for LDL and VLDL. The risk ratio was 0.8 per one millimole per liter reduction in LDLC, and 0.84 per one millimole liter reduction in triglycerides. Therefore, a reduction in non-HDLC, a measure of atherogenic LDL and VLDL particles, is strongly associated with lower risk of major vascular events regardless of the lipid lowering drug class, and triglyceride lowering is associated with a lower risk of cardiovascular events, but to a lesser extent per absolute amount of reduction then with LDLC. Interesting, Carolyn one study reduce it and impacted the study results, and nearly all non-statin trials did not achieve significant non-HDLC lowering to detect a clinical difference in major vascular events. Now how about in regards to Omega- three dose?
Well, each one gram per day of EPA administered was associated with a 7% relative risk reduction in major vascular events, whereas there was no significant reduction in major vascular events with DHA. So the benefits of Marine-derived Omega-three fatty acids, particularly high dose EPA, appear to exceed their lipid lowering effects.
Dr Carolyn Lam: Wow. Interesting. So Greg, take it home for us. What should we do clinically about this information?
Dr Greg Hundley: Carolyn, developing drugs that achieve large reductions in VLDL and triglycerides and are targeting patients with high baseline levels of triglycerides would likely increase the probability of showing a meaningful clinical benefit, and fibrates could be considered in patients needing further non-HDLC lowering, being mindful of side effects, as they should offer clinical benefit proportional to the degree of non-HDLC lowering, and if a disproportionate relationship between lipid lowering and cardiovascular risk reduction is validated in ongoing high dose Omega-three fatty acid trials, it will support the hypothesis that confers a unique benefit of this class of agents beyond simply their lipid lowering.
How about that?
Dr Carolyn Lam: Very nice Greg and I think very balanced and good clinical take home messages. Tell us what else is in the mailbag.
Dr Greg Hundley: We have so many interesting articles in Circulation and let me just run through a quick list of those that are also in this issue. First, Dr Jere Mitchell, from UT Southwestern, reviews the 50th anniversary of the Dallas Bedrest Study that involve five 20-year-olds that underwent several weeks of bedrest, and he discusses how this informs many of our thoughts regarding the benefits of activity today, and one of his major coauthors is Dr Ben Levine. Our own Josh Beckman reviews the ongoing efforts of physicians to understand the role of paclitaxel coated stents for those undergoing peripheral arterial interventions. Dr Berlinde von Kemp, in our case series, identifies that not all cardiomyopathy, after delivery, is simply postpartum cardiomyopathy. In another article, Dr Anurag Agrawal discusses what's on their mind regarding the use of spirometry as a cardiovascular disease risk assessment tool, should it be incorporated into existing cardiovascular disease risk models.
Then, we have a great letter back and forth discussion from Dr Junfeng Wang, Dr Daxin Wang, and our own Naveed Sattar in three separate letters that discussed the relevance of age of onset for type two diabetes relative to cardiovascular risk. Then, finally our own Carolyn Lam reviews the role of biomarkers in heart failure and preserved ejection fraction.
Dr Carolyn Lam: Let's hop on to our feature discussion, shall we?
Dr Greg Hundley: Absolutely.
Dr Greg Hundley: Welcome everyone to the discussion of our featured article today where we're going to review an excellent study comparing TAVR versus SAVR in patients with aortic stenosis, but also now considering simultaneous coronary artery revascularization. Discussing our article today we have Dr Thomas Engstrøm and then our own associate editor, Dharam Kumbhani. Well Thomas, welcome to our podcast featured article discussion. I wonder if you could start us off with a little background regarding your study. What were your hypotheses, and then tell us a little about your study population and your methods.
Dr Thomas Engstrøm: Now, as you know, up to 50% of patients that are treated for aortic stenosis have coronary artery disease, and this may be considered as a bystander disease to develop disease, but definitely also adds to the prognosis for the patients. A priority guideline recommends that if you do SAVR, you'll also have significant coronary artery disease. What we don't know is if the complete percutaneous approach is as good as a surgical approach. Maybe do TAVR plus PCI comply with fiber plus CABG. That's the background for the study.
Now, the population involved in this study is the population from the search TAVR trial, which as you know compared TAVR to SAVR in patients that were clinically at intermediate risk and in patients that had severe aortic stenosis. If patient had additional coronary artery disease with a syntax called Bob 22, they were excluded from the trial. We are talking about intermediate risk patients with low syntax score. Of the patients in the TAVR trial, 20% had additional coronary artery disease and were resterilized. In the paper, we compare TAVR plus PCI versus SAVR plus CABG in those patients with significant coronary artery disease.
Dr Greg Hundley: How did you define the presence or absence of coronary disease? Just real quickly before we get to your results.
Dr Thomas Engstrøm: This was at the discretion of your operator to define where the patients had coronary artery disease or not. In the paper, patients were defined as having significant diseases. More than 70% of stenotic lesions were present in one or more coronary arteries.
Dr Greg Hundley: And so can you tell us, Thomas a little about the results of your study?
Dr Thomas Engstrøm: First of all, the patients that had additional coronary artery disease had a poor prognosis than those that only had valve substitution, which is probably not a surprise. Within those that also had coronary artery disease, TAVR plus PCI appeared to be as good as CABG plus SAVR in terms of the primary endpoint, which was all because mortality or disabling stroke after two years. Then, if you dive more deeply into the endpoint and the number of secondary endpoints were pre-specified, there were no differences regarding any stroke myocardial infraction and in total no differences between what you could call major heart end points. If you look more into detail of the secondary endpoint, there are subtle differences. Patients that were in the SAVR plus CABG had more atrial fibrillation as they also had more acute kidney injury following that treatment. Whereas, in the TAVR plus PCR, more patients had vascular complications and of course had the need for pacemaker implantation. There are differences between the outcome in the two groups, but not in regard of pre-specified primary and more important secondary endpoints.
Dr Greg Hundley: Dharam, I was wondering if you could help us think about what this means for the field in terms of both from aortic valve replacement, and then also the concomitant management of coronary disease in patients that require aortic valve replacement.
Dr Dharam Kumbhani: As Thomas just pointed out, I think this is a very important question. This comes up all the time in patients with severe aortic stenosis, being evaluated for best options, and the guidelines have stayed true to this that if somebody has concomitant coronary artery disease, then the guidelines typically would recommend SAVR as the first option because then they can have CABG at the same time. This study really seeks to address a very important knowledge gap in the field, and as he very well pointed out, this does restrict itself a little in terms of the population, because they couldn't have a high syntax score, actually an intermediate or high syntax score, and they need in the trial...I think the main syntax score was eight or nine. I think that is important, but having said that, more than 50% of the patients had multi-vessel disease, and it was really impressive that nearly 15 or 17% still had three vessel PCI even in this arm.
I think it's important for people to recognize that although this was the lowest syntax score, multivessel PCI was still pursued. I think that's definitely an important takeaway from the strike. It's a really important trial. It's one of the very few pieces of information that we have that is prospectively done under the auspices of a big trial like SURTAVI, and with low risk approval in and what this means for patients going forward I think will be very exciting to see how this few devolves.
Thomas, as this field matures, could you walk us through, in terms of did you do the valve first and then the coronaries, or where the coronaries worked on first and then the valve? That's sort of the first question. Can you walk us through how you make those decisions?
Dr Thomas Engstrøm: It was up to the discretion of the operator whether to do a concomitant procedure, both PCI and TAVR, or to state the procedures in that way that PCI was done first, and this could be done up to seven days before the TAVR. If you compare those two groups, and now numbers become a little bit few, so we can't be conclusive here. It appears that patients that had stage procedures did poorer than those that had concomitant procedures done. Of course, it raises some questions. The prioritization as to do it in one way or the other was that through concomitant procedure, you may introduce too much of stress to the patient. Otherwise, if you do a stage procedure, it's best to do the PCI first, because the actual appearance of the valve may make it more difficult and cumbersome to address the coronary arteries. To sum this up, in the patients that we have, it appeared that a concomitant procedure is safe.
Dr Greg Hundley: Dharam, tell us, what do you think is the next step forward for this field? What do see as the next study moving forward here?
Dr Dharam Kumbhani: I think this study really sets the stage for, I think future trials where perhaps we would have... So I'm doing this in this trial. The stratification was done based on whether or not they need to revascularization. I think going forward, again with LOTUS approval here and proliferation of the number of TAVR procedures that are being offered everywhere, I think it will be helpful. This study would set the stage for future studies, where I think you would prospectively have patients with needing an aortic valve replacement and perhaps even complex revascularization, and how that was kind of actually the randomization, which is the stratification strategy, which again was very helpful. These are really among the first few data that we have of this, but I think this kind of sets the stage for future investigations in this space. And then as I briefly alluded to, I think this may help evolve or this may help in the evolution on the guidelines as well.
Thomas, would you like to add anything to that?
Dr Thomas Engstrøm: Yeah, I completely echo that. Going back to the old syntax trial, it would be very interesting to see if PCI holds through, even in high tunes, syntax scores with newer drug eluting stents, and also of course the question of the diabetics is totally unsolved in this cohort. CABG plus SAVR may turn out to be the best solution, but we still are waiting to see data that can support any of the two strategies in those patient cohorts.
Dr Greg Hundley: We want to thank Thomas Engstrøm and also our own Dharam Kumbhani. We look forward to seeing you next week.
Dr Carolyn Lam: This program is copyright American Heart Association, 2019.