Jun 11, 2018
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.