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Circulation on the Run

Oct 29, 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. This week's issue provides much long awaited healthcare resource utilization and cost implications in the MOMENTUM 3 randomized controlled trial of a magnetically levitated cardiac pump in advanced heart failure. All of this coming right up after these summaries.

                                                The first original paper this week provides important mammalian data on the acute effects of phosphodiesterase type 1 inhibition on the heart. Now phosphodiesterase type 1, or PDE1, is known to hydrolyze cyclic AMP and cyclic GMP in the heart. However, what's important to understand is that data from rodents may not be applicable to humans because rodents express mostly the cyclic GMP favoring PDE1A isoform, whereas human hearts predominantly express PDE1C isoform which has a balanced selectivity for cyclic AMP and cyclic GMP.

                                                In today's paper, first author Dr Hashimoto, corresponding author Dr Kass from Johns Hopkins University School of Medicine and colleagues, determined the acute effects of PDE1 inhibition on PDE1C expressing mammals, dogs and rabbits, in normal and failing hearts. They found that selective inhibition of PDE1 with ITI-214 induced positive inotropic, lusitropic, chronotropic, and arterial vasodilatory effects in dogs and rabbits. These effects occurred via cyclic AMP modulation and were observed in failing hearts. ITI-214 contractile increase was insensitive to beta adrenergic blockade or heart rate increase, but inhibited in vivo by adenosine receptor inhibition. Furthermore, isolated myocytes revealed differences between PDE1 and PDE3 inhibition. Wherein PDE3 inhibition, augmented beta receptor agonism and calcium transients, whereas PDE1 inhibition enhanced function without calcium increase. These findings have important clinical implications for ITI-214 which has completed phase 1 trials and may provide a novel therapy for heart failure.

                                                We know that macrophages are involved in foam cell formation in atherosclerotic plaques, but our next paper tells us we may now have a way to therapeutically modify this. Co-corresponding authors Dr Wei and Schober from Ludwig Maximilian's University Munich elucidated the role of microRNA generating enzyme Dicer in macrophage activation during atherosclerosis. They showed that Dicer deletion in macrophages accelerated atherosclerosis in mice, along with enhanced inflammatory response and increased lipid accumulation in lesional macrophages. In vitro, alternative activation was limited, whereas lipid filled foam cell formation was exacerbated in Dicer deficient macrophages due to impaired mitochondrial fatty acid oxidative metabolism. MicroRNA biogenesis promoted the degradation of fatty acids by mitochondrial respiration in macrophages, which in turn reduced intracellular lipid storage and limited atherosclerosis. Thus, reducing foam cell formation in atherosclerotic arteries by enhancing energy metabolism through microRNA mediated fatty acid oxidation may be a promising approach for the treatment of atherosclerosis.

                                                The next study evaluates how aortic stiffening relates to resting cerebral blood flow and cerebral vascular reactivity in older adults. First and corresponding author Dr Jefferson from Vanderbilt Memory and Alzheimer's Center and her colleagues studied participants free of clinical dementia, stroke, or heart failure, including 155 older adults with normal cognition and 115 mild cognitive impairment. They found that greater thoracic aortic stiffening quantified by cardiac magnetic resonance was associated with lower cerebral blood flow in cognitively normal older adults. Aortic stiffening was associated with reduced resting cerebral blood flow in the presence of preserved reactivity and associated vasodilatory capacity, particularly among participants without hypertension. ApoE4, a well-known genetic susceptibility risk factor for Alzheimer's disease, modified the results with stronger effects among carriers in the temporal lobes, where Alzheimer's disease pathology is known to first evolve. In summary, greater aortic stiffening related to lower regional cerebral blood flow and higher cerebral vascular reactivity in cognitively normal older adults, especially among individuals with increased genetic predisposition for Alzheimer's disease. Understanding the association between higher aortic stiffness and compromised brain health, including cerebral hemodynamics, may allow for earlier detection and targeted interventions to prevent or mitigate the onset of more serious cerebral vascular damage associated with greater aortic stiffening.

                                                Aortic valve replacement for aortic stenosis is usually timed according to the development of symptoms, but could the timing be too late once irreversible myocardial scar has developed? Co-first authors Drs Musa and Treibel, corresponding author Dr Greenwood from University of Leeds and their colleagues found that in patients with severe aortic stenosis, focal myocardial fibrosis determined by cardiac magnetic resonance imaging was present in over 50% of patients and was associated with a two-fold higher late mortality. Focal scar was independently associated with all cause and cardiovascular mortality, after both surgical and transcatheter aortic valve replacement. In severe aortic stenosis, late gadolinium enhancement appears to be a useful biomarker of left ventricular remodeling, and its presence is associated with worse long-term outcomes following aortic valve intervention. Thus, in severe aortic stenosis, late gadolinium enhancement may be a useful biomarker of left ventricular remodeling, and its presence may be associated with worse long-term outcomes following aortic valve intervention.

                                                The next study suggests that endogenous factor Xa activity may be irrelevant pharmacodynamic marker to guide Edoxaban dosing in future. First author Dr Yin, corresponding author Dr Giugliano from TIMI Study Group, Brigham and Women's Hospital in Boston, and their colleagues, describe the value of endogenous factor Xa activity as a pharmacodynamic marker, linking Edoxaban concentrations and clinical outcomes in the ENGAGE AF-TIMI 48 trial. They showed that the extent of inhibition of endogenous factor Xa activity was influenced by Edoxaban dosing and clinical characteristics, and was associated with both antithrombotic benefit and risk of bleeding. The implications are that this approach of linking endogenous factor Xa activity to clinical outcomes may be used to guide dose selection in future clinical trials, to monitor patients in certain clinical scenarios, or to define the doses of oral factor Xa inhibitors in patients who require precise anticoagulation therapy.

                                                The next paper describes a novel multi-protein complex that plays a critical role in regulating cardiomyocyte survival. First author Dr Zhang, corresponding author Dr Yan from University of Rochester School of Medicine and Dentistry and colleagues, showed that phosphodiesterase 1C is activated by transient receptor potential canonical channel-3 derived calcium, thereby antagonizing adenosine A2 receptor cyclic GMP signaling and promoting cardiomyocyte death or apoptosis. Targeting these molecules individually, or in combination, may represent a compelling therapeutic strategy for potentiating cardiomyocyte survival.

                                                The final paper demonstrates a molecular link between two well-recognized biomarkers of fibrosis, Galectin-3 and Osteopontin. First author Dr Shirakawa, corresponding author Dr Sano from Keio University School of Medicine and their colleagues, showed that Osteopontin was almost exclusively produced by Galectin-3 high CD206 positive macrophages, which specifically appear in the infarct myocardium after a myocardial infarct. The interleukin-10-STAT3 Galectin-3 axis was essential for Osteopontin producing reparative macrophage polarization after myocardial infarction, and these macrophages contributed to tissue repair by promoting fibrosis and clearance of apoptotic cells. These results therefore suggest that Galectin-3 may contribute to reparative fibrosis in the infarct myocardium by controlling Osteopontin levels. And that brings us to the end of this week's summaries, now for a feature discussion.

                                                Left ventricular assist devices have truly revolutionized our management of advanced heart failure. In fact, these devices have allowed us to keep patients not just as a bridge to transplantation, but as destination therapy. The devices get better and better but also more and more expensive, and the problem is, that places a lot of strain on our healthcare systems. A lot of us are crying out for information on the cost effectiveness of these newer devices, and guess what? We have answers this week with our featured paper.

                                                I am delighted to have with us the first and corresponding author Dr Mandeep Mehra from Brigham and Women's Hospital in Boston, Massachusetts, as well as our senior editor Dr Biykem Bozkurt from Baylor College of Medicine in Houston, Texas. Hello, Mandeep and Biykem! I am so pleased to be talking about a subject really close to all our hearts. Mandeep, could you start by maybe sketching out the actual issue, and maybe reminding our audience what's the difference between the different types of left ventricular assist systems that you compared.

Dr Mandeep Mehra:       The era of left ventricular assist devices took a major therapeutic shift when we recognized that we could usher in continuous flow devices. These are devices that generate no peripheral pulse, they do not have systole and diastole. And these devices are small in profile, have very few moving parts, and there are several commercially available devices, two in the United States and up to three worldwide, that bear these characteristics.

                                                The HeartMate II device, which is a continuous flow device that flows blood in an axial format. The HeartWare, or HVAD device, which is a centrifugal flow pump, where the blood comes in and then is ejected at a 90 degree angle. The Jarvik 2000 pump that is still used in some areas, in many regions experimentally, and then the new kid on the block, the HeartMate 3 device, which is a centrifugal flow pump with some very unique technological characteristics.

Dr Carolyn Lam:                Nice! And now drumroll, please tell us what you found in your brilliant study this week.

Dr Mandeep Mehra:       First, I'd like to remind the audience that the MOMENTUM 3 trial which randomized patients to the HeartMate II versus the HeartMate 3 device, was called MOMENTUM 3 and was a two-year study. We presented the pivotal two year trials results in 366 randomized patients earlier this year in The New England Journal of Medicine, and this study showed that the HeartMate 3 was superior on the primary endpoint when compared to the HeartMate II. The primary endpoint was survival, free of a disabling stroke, or the need to replace the pump surgically for a pump malfunction. And much of that, Carolyn, was driven by the need for replacement of the pump because the HeartMate 3 pump has some unique features that reduce its proclivity for pump thrombosis.

                                                The HeartMate 3 pump is a frictionless pump. It's completely, magnetically, dynamically, born in the rotor. It has wider blood flow paths, so we don't see hemolysis with this pump. And this pump also has an artificial intrinsic pulse that has been created, that pulsates the pump in a 40 beats per minute configuration. So this was the primary trial result, and one of the lucky foresights that we had when we designed the trial was to embed, prospectively, economic analysis within this trial. We recognized that the cost effectiveness related issues and cost configurations with these devices would become very, very important as we scale into today's day and age of healthcare transformation. And the paper that is being presented in Circulation this week, really speaks to the health resource utilization and cost outcomes between the two devices.

                                                We found that the HeartMate 3 pump is actually a cost minimization device, and what that means, Carolyn, is that we have become very used to thinking of new technology as providing incremental costs. So we think that, "Oh, well, what incremental costs should society bear for the benefits as we allocate new technology?" And in this particular trial, what we found is that while the costs of the pump itself, the HeartMate II and the HeartMate 3, were kept the same, which means its operational implant costs were the same, pretty much. We found that the HeartMate 3 pump was associated with a reduction in healthcare resource utilization over two years and with a marked decrease in cost. And in fact, our estimate of cost reduction was in the range of about 65 thousand dollars less, compared to the HeartMate II, in favor of the HeartMate 3.

Dr Carolyn Lam:                Wow, Mandeep, first of all, congratulations on these remarkable findings. Biykem, I really have to bring you in here. What do you think of the implications of this?

Dr Biykem Bozkurt:         First, I would like to congratulate the authors for a very innovative approach. As Mandeep has stated, they prospectively collected very challenging billing data from the hospitals, and then also did a very complex analysis including the VRG, as well as looking at payer reimbursements for public versus private. And did a variety of subgroup analysis, which I thought was quite helpful in sorting out that perhaps the cost effectiveness was concurrent both from the Medicare, the public, as well as the private, or regardless of the intent for destination versus bridge to transplant.

                                                Probably the most important concept when you look at these close analysis is incremental cost effectiveness ratio, per quality of adjusted life year gained. Now, I do realize the current analysis doesn't allow us to infer the ICER benefit or the incremental cost effectiveness, which I think the investigators are planning to do with a thousand and more patients over a course of two years, which is going to be probably the more definitive. But as it currently stands, with what is provided by Dr Mehra and his colleagues is, we're probably reaching that sweet spot of what is construed as the cost effectiveness ratio of a cost.

                                                Let's say 100 thousand dollars over the course of a year, then I would like to ask Mandeep whether on the prediction will reach that threshold of less than 100 thousand dollars. Because the former studies, looking at the ICER ratios, or incremental cost effectiveness ratios for the DT destination therapies, usually we select somewhere around 200 thousand dollars. And I know that usually that is seen as a prohibited cost, and there was a discussion whether we would be able to reduce the cost by about half, either doing index admission and add subsequent hospitalizations. With the data Dr Mehra and his colleagues have shown, it looks like the re-hospitalization cost is about, approximately half, or reduced by 50%. Mandeep, any thoughts on that, on that sweet spot?

Dr Mandeep Mehra:       Yeah. I think, Biykem, you have articulated this extraordinarily well. And for the audience, since it's worldwide, I'd like to place a few things in perspective on how to think of economic modeling. First of all, the point I would make is that this is the first prospectively collected data that we have in the field, and as you pointed out, it was very, very difficult to pull this data together and is still very complex. But let's just think about what ICER really is. It all starts with what we consider to be health utility.

                                                For example, Carolyn, Biykem, and me less so, would have a health utility of 1.0, 1.0 means a perfect health utility number. And I know, Carolyn, you and Biykem are absolutely perfect so you would be a 1.0, I probably am not a 1.0. But a patient with advanced heart failure has a health utility of about .4, so that's only 40% of what is perfect. And when we place ventricular assist devices, whether you place the HeartMate 3 or the HeartMate II, the health utility actually jumps up to about .7. So it's not perfect yet, but it moves all the way up there.

                                                The incremental cost effectiveness ratios of implanting a device over time are calculated based on this health utility benefit, compared to the population of advanced heart failure. And the best current estimates of the HeartMate II are that ICER is about 200 thousand dollars, per quality adjusted life years gained, and this has been done by creating what's known as Markov modeling. A lot of that, by the way, is conjecture, it's not real information. It is predicted information, so one has to take that data with a grain of salt.

                                                Here in this health resource analysis for MOMENTUM 3, we actually looked at actual data. There are some estimates used in this analysis as well, where we did not have accurate billing forms available, but we focused on those things where we had very clear knowledge of the cost of outcomes. For example, we did not look at the costs of outpatient follow-up care. We mainly looked at the cost differences of hospitalizations. And what we essentially found here is that just looking at hospitalizations and differences between the two devices, the cost differential, whether it's Medicare which is public [inaudible 00:20:14], or whether it's commercial. It ranges somewhere between 50 to 65 thousand dollars of difference between the two devices.

                                                Now, if you assume that the ICER for the HeartMate II is accurately at about 200 thousand, and you reduce that ICER by about 50 to 60 thousand, the ICER would naturally come into the range of what you would consider to be about 135 thousand to 150 thousand dollars per quality adjusted life years gained for the HeartMate 3, compared to an advanced heart failure population. Once we look at it from that perspective, as Biykem pointed out, we are getting closer and closer to the societal norms.

                                                At one time-point, society used to think of a quality adjusted life years gained cost of 50 thousand dollars as something that would be acceptable to society, and this was seemingly based on the threshold for what dialysis provides in benefit. And now, we recognize that we have to really expand that to somewhere around 100 thousand more logically, or between 100 and 150 thousand for some technologies. The important thing I would say to you is that, that is society dependent. So what the United States considers to be a reasonable ICER, say 100 to 130 thousand dollars per quality adjusted life years gained, may not be the same that Great Britain would look at, or Sweden would look at, or another country would look at. And each country actually creates their own economic value propositions, and this will have to be taken into account as we think about this data as well.

Dr Carolyn Lam:                How cleverly and clearly articulated, thank you so much Mandeep. Just one last question for both you and Biykem, what do you think this implies for moving to less and less advanced heart failure with these left ventricular assist device systems? Biykem?

Dr Biykem Bozkurt:         It's an ever-expanding field, and as these devices are becoming smaller, lower profile with lesser complications and more affordable, probably the utilization will likely increase as we have been seeing. As you know, even the percutaneous non-durable device used, as well as our mechanical circulatory support durable devices are definitely increasing utilization. And thus, one may wonder not only the bridge to transplantation, but the destination therapy portfolio, or bridge to decision portfolio, may really increase as these devices become safer and more affordable.

Dr Carolyn Lam:                Wow, that's amazing. How about you, Mandeep, what do you think?

Dr Mandeep Mehra:       Carolyn, I couldn't have said it any better than what Biykem articulated. I do think that at least in the United States, as we reach the thresholds of cost effectiveness that we as a society accept, we will start to see a lot more widespread utilization, particularly for lifelong therapy or so-called destination therapy. I completely agree with that. I think that moving the needle to the less sicker population is still challenging, because there are complications with these devices that make that slightly difficult.

                                                There was a trial called the REVIVE-IT trial that was stopped midstream largely because of concerns about pump thrombosis, and that trial was looking at taking these devices to a less sick NYHA class 3 population and was stopped midstream. Now that the HeartMate 3 has pretty much resolved the issue of pump thrombosis, and even show a halfing in stroke rates with this device over two years, I think that that portfolio of evidence needs to be reopened. I would caution though, that until we have confirmatory randomized data in those less sick populations, the use to that population should still stay restricted.

Dr Carolyn Lam:                I don't think anyone could have said it better than both of you. Thank you so much for this very insightful and balanced conversation.

                                                Thank you so much for listening today. You were listening to Circulation on the Run, and don't forget to tune again next week.