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Circulation on the Run

Nov 26, 2018

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. We will be discussing accelerated diagnostic protocols for chest pain, a very, very important issue in Cardiology with very important new safety and effectiveness data on one such protocol provided in our feature paper this week. Coming right up after these summaries.

                                                Our first original paper this week identifies a new link between specific gut bacteria and atherosclerosis. Co-First authors, Dr Yoshida and Emoto, corresponding author, Dr Yamashita, from Kobe University Graduate School of Medicine, and colleagues recruited patients with coronary artery disease and controls without coronary artery disease but with coronary risk factors. They then compared gut microbial composition using 16S ribosomal RNA gene sequencing in fecal samples. Subsequently, they used atherosclerosis prone mice to study the mechanisms underlying the relationship between such species and atherosclerosis. Their analysis of gut microbial profile in patients with coronary artery disease showed a relative depletion of bacteroides vulgatus and bacteroides dorei compared to controls with coronary risk factors. Gavage with live bacteroides vulgatus and bacteroides dorei decreased fecal and plasma lipopolysaccharide levels and protected against atherosclerosis in apoE deficient mice. Fecal lipopolysaccharide levels in patients with coronary artery disease were significantly higher compared to controls. These findings suggest that bacteroides treatment may serve as a novel and effective therapeutic strategy for suppressing lipopolysaccharide-induced inflammatory response in coronary artery disease.

                                                The next paper identified a potential novel molecular target in the treatment of myocarditis. Co-First authors, Dr Chen and Zeng, Co-Corresponding authors, Dr Song from Fuwai Hospital in Beijing, and Dr Yang from Shenzhen University School of Medicine, and their colleagues aim to elucidate the role of BCL2 Like protein 12 in the pathogenesis of biased T Helper-2 response in myocarditis. Using a combination of mouse models of myocardial inflammation and human hearts from patients undergoing heart transplantation, the authors found that CD4 positive T-cells isolated from hearts in myocarditis at the end stage of heart failure expressed high levels of BCL2 Like protein 12, which was required for the development of aberrant T Helper 2 polarization in the heart. Thus, BCL2 Like protein 12 may be a novel target in the treatment of myocarditis, as well as other T Helper 2 biased inflammatory processes.

                                                Could vaccination against LDL be a way to prevent atherosclerosis? Well, the next paper brings us one step closer to this dream. First author, Dr Gisterå, corresponding author, Dr Hansson from Karolinska School University Hospital and colleagues developed T-cell receptor transgenic mice to study LDL autoimmunity in a humanized hypercholesterolemic mouse model of atherosclerosis. A strong T-cell dependent E-cell response was induced by ODL leading to production of anti-LDL IgG antibodies that enhanced LDL clearance and ameliorated atherosclerosis. Results show that anti-LDL immuno-reactivity evoked three atheroprotective mechanisms, namely 1) antibody-dependent LDL clearance, 2) increased cholesterol excretion, and 3) reduced vascular inflammation, thus targeting LDL-reactive T cells may enhance atheroprotective immunity, and vaccination against LDL components may be an attractive way to prevent atherosclerosis.

                                                MicroRNAs regulate nearly all biological pathways and dysregulation of MicroRNAs is known to lead to disease progression. However, are there cell type specific effects of MicroRNAs in the heart? Co-First authors, Drs Rogg and Abplanalp, corresponding author, Dr Dimmeler from Goethe University Frankfurt, and colleagues assessed MicroRNA target regulation using MicroRNA 92a3p as an example. Their data showed that MicroRNAs have cell type specific effects in vivo which would be overlooked in bulk RNA sequencing. Analysis of MicroRNA targets in cell subsets disclosed a novel function of MicroRNA 92a3p in endothelial cell autophagy and cardiomyocyte metabolism. These findings may have clinical applications for the fine tuning of autophagy and metabolism to mitigate tissue damage in patients with cardiac disease.

                                                The next paper establishes a mechanism by which cardiac inflammation may be initiated in response to hemodynamic stress, but in the absence of significant cardiomyocyte cell death. Co-First authors, Drs Suetomi and Willeford, Co-Corresponding authors, Drs Brown and Miyamoto from University of California San Diego, and their colleagues used conditional cardiomyocyte-specific calcium calmodulin-regulated kinase Delta all CaM kinase II Delta knockout mice to demonstrate that cardiomyocytes generate inflammatory chemokines and cytokines and are the initial site of NLRP3 inflammasome activation. They further identified a causal role for CaM-Kinase II Delta-mediated activation of NLRP3 inflammasome and inflammatory responses in macrophage recruitment, cardiac fibrosis, and development of heart failure induced by pressure overload. Their elegant mouse experiments revealed sites and mechanisms of proinflammatory gene and inflammasome activation within cardiomyocytes which could serve as targets for early intervention or disease prevention.

                                                Are there different metabolomic effects between PCSK9 inhibitors and statins? First author, Dr Sliz, Corresponding Author, Dr Würtz from Nightingale Health Limited in Helsinki, Finland, and their colleagues quantify 228 circulating metabolic measures by Nuclear Magnetic Resonance Spectroscopy for over 5300 individuals in the PROSPER Trial at six months post randomization. The corresponding metabolic measures were also analyzed in eight population cohorts, including more than 72,000 individuals using a specific PCSK9 inhibitor SNP as an unfounded proxy to mimic the therapeutic effects of PCSK9 inhibitors. Scaled to an equivalent lowering of LDL cholesterol the effects of genetic inhibition of PCSK9 on these 228 metabolic markers were generally consistent with those of statin therapy. Alterations of lipoprotein lipid composition and fatty acid distributions were also similar. However, discrepancies were observed for very low-density lipoprotein or VLDL lipid measures where genetic inhibition of PCSK9 had weaker effects on lowering VLDL cholesterol compared with statin therapy. Genetic inhibition of PCSK9 showed no significant effects on amino acids, ketones, or a marker of inflammation, where a statin treatment weekly lowered this marker of inflammation. Thus, if VLDL lipids have an independent causal effect on cardiovascular disease risk, the observed discrepancy on VLDL lipid lowering could contribute to differences in cardiovascular risk reduction between statins and PCSK9 inhibitors for an equivalent reduction in LDL cholesterol. Moreover, these results exemplify the utility of large-scale metabolomic profiling with genetics and randomized trial data to uncover potential molecular differences between related therapeutics.

                                                The final original paper this week demonstrates a novel biomarker discovery paradigm to identify candidate biomarkers of cardiovascular and other diseases. Co-First authors, Dr Mosley and Benson, co-corresponding authors, Dr Wang from Vanderbilt University Medical Center and Gerszten from Beth Israel Deaconess Medical Center, and their colleagues employed a virtual proteomic approach linking genetically-predicted protein levels to clinical diagnosis in more than 40,000 individuals. They used genome-wide association data from the Framingham Heart Study to construct genetic predictors for more than 1100 plasma protein levels. They validated the genetic predictors for 268 proteins and used them to compute predicted protein levels in more than 41,000 genotyped individuals in the eMerge Cohort. They tested associations for each predicted protein with more than 1100 clinical phenotypes. These associations were validated using directly-measured protein levels and either LDL cholesterol or subclinical atherosclerosis in the Malmo Diet and Cancer study. Using this virtual biomarker strategy the authors identified CLC1B and PDGFR Beta as potential circulating biomarkers of atherosclerosis and validated them in an epidemiologic cohort. Thus, these results demonstrate that a virtual biomarker study may efficiently identify potential biomarker disease associations, and that wraps it up for our summaries. Now for our feature discussion.

                                                Accelerated diagnostic protocols for testing are used everywhere. They're designed to improve the quality and value of chest pain risk stratification. However, many of them lack sufficient prospective safety and effectiveness data. We're so pleased to have a paper today that provides such important data on one of these accelerated diagnostic protocols for chest pain, and it's the HEART Pathway. To discuss this, I've got the corresponding author of today's featured paper, Dr Simon Mahler from Wake Forest School of Medicine, as well as our Associate Editor, Dr Deb Diercks from UT Southwestern. Simon, could you start by just telling us, what is the HEART Pathway?

Dr Simon Mahler:             Sure. Yeah, it's an accelerated diagnostic protocol. It's based on an accelerated diagnostic protocol called the HEART Score. We use a modified version of the Heart Score. We actually use a HEAR score, and that stands for the history, EKG, Age, and risk factors. That is combined with two troponin measures at 0 and 3 hours. We also factor in whether or not the patient has had prior coronary artery disease or has an acute ischemic EKG. So, to be low-risk you have to have a HEAR score of 0-3. HEAR is an acronym. You get points for each of those categories. If you have less than 3 points that's a low score. You have to have a low score, a non-ischemic EKG, no history of prior coronary disease, and two troponins less than a 99th percentile at 0 and 3 hours to be considered low risk and recommended for early discharge. If you don't meet any of those criteria then you are considered non-low risk and appropriate for further in-hospital evaluation.

Dr Carolyn Lam:                That's great. Could you just tell us what you did to give us some real-world safety and effectiveness data on this.

Dr Simon Mahler:             Yeah, so we had done a single-site randomized controlled trial. That was published in 2015 in Circulation: Quality and Outcomes, and really showed some promising results. We received some funding to do an implementation trial. So, this is the results of our implementation study. It's a before and after study. What we did was we sought to implement a HEART Pathway as a clinical decision support tool, integrated fully into our electronic medical record so that when providers see the patient with chest pain and order a troponin they interact with a HEART Pathway tool that guides them through the HEART Pathway risk assessment and then provides real-time decision support regarding their treatment and disposition decisions based on whether or not the patient has a low-risk assessment or a non-low-risk assessment. The design of the study was we collected data on all patients with chest pain and troponin order for one year while we worked on how we were gonna build this tool and embed it, and then we had three month watching period where we built the tool into the electronic health record across our three sites. Then, we had one year where we were post implementation where we collected data and looking at the difference in outcomes, particularly looking at both safety and utilization outcomes before and after use of the HEART Pathway.

Dr Carolyn Lam:                That's just such a clever design. Just give us a summary of the results before I ask Deb to chime in here.

Dr Simon Mahler:             There's a few really important things that we found. Probably the most important thing was the safety data that came out of this study. We had some good safety signals on prior studies. They didn't have enough sample size to really have a good precision around the safety point estimate, so in this study we had over 4000 patients in our post-implementation cohort, and about 31%, 30.7%, of those patients were classified as low-risk by the HEART Pathway. Among those patients that were classified by low-risk, the rate of death and MI, the composite outcome at 30 days, was 0.4%. Typically for these accelerated diagnostic protocols we want them to have an adverse cardiac event rate less than 1%, so a finding of 0.4% with a confidence in our role that doesn't extend beyond 1% that was a really important finding that really confirms the safety of this strategy.

                                                The other thing that we found which was interesting was that the use of the HEART Pathway was actually associated with detecting more myocardial infarctions during the index visit, which means that possibly the HEART Pathway use improved the recognition of those patients that were presenting with MIs. It's possible that without using the HEART Pathway some of those cases may have been missed. Finally, we were able to demonstrate that use of the HEART Pathway as a clinical decision support tool was able to decrease hospitalizations and some other utilization metrics such as stress testing and possible length of stay.

Dr Carolyn Lam:                Oh, that's awesome, Simon. I said it earlier. I'm gonna say it again. Thank you so much for publishing this wonderful work with Circulation. I really think that implementation, science, and decision support tools you've got that all in this paper, just beyond even the actual topic. Deb, take us behind the scenes a little bit with how we reacted as editors to this paper, please.

Dr Deb Diercks:                 Well, I think that overall, we were really excited about this paper. It really does add a real, real context to something we were really discussing and wondering about. I think one of the great things about the implementation, and Simon, please comment on this, is the diversity of the places that you actually used this in. I mean, most of us when we look at papers there's always a fear that it won't be able to be generalized to real-world practices. Correct me if I'm wrong, but you really applied it to just a wide variety of Emergency Departments that really support that this could be used anywhere.

Dr Simon Mahler:             Yeah, I think that's a really important point, that we did this across our system so that included a large academic busy Emergency Department that sees over 100,000 patients per year, all the way, basically to a smaller 12,000 per year, essentially almost a free-standing Emergency Department at the time that we started our study; it now has inpatient bed capacity, and then a suburban/rural hospital, as well, with about 30,000 patient visits per year. We extended beyond kind of the typical kind of comfort zone of large academic centers and into smaller community Emergency Departments as well.

Dr Deb Diercks:                 One of the things that this manuscript nicely articulated is that you kind of break it into the HEAR and then the troponin.

Dr Simon Mahler:             Right.

Dr Deb Diercks:                 Things change in the US with troponin. How do you think that's gonna impact how you guys apply this Pathway in the future?

Dr Simon Mahler:             It's a big topic of discussion right now, what to do with these Pathways. Are these Pathways still needed with the availability now of high-sensitivity troponins in the United States? I think that for many years as we've kind of followed data coming out of Europe we've been anxiously awaiting the arrival of these tests in the U.S., and there's a lot we can learn from the European data so far. Most of that data suggests that the high-density troponins are best used still in the context of a Pathway or an accelerated diagnostic protocol.

                                                I think that this particular study was conducted just using contemporary troponins, particularly given the time frame of the study in which we were accruing patients from 2013 through 2016, but I think it's still gonna be highly relevant, because I think that best practices are gonna still require us to use some sort of structured framework with high-sensitivity troponins. Now, it does remain to be seen a little bit what the best Pathway is gonna be to incorporate that. My take on this is that I believe that clinical decisions support tools or decision aids integrated with high-sensitivity troponins is going to be the best way to go. I'm a little bit skeptical about troponin-only approaches.

Dr Deb Diercks:                 That's a great summary. I don't think it's time to throw out all the value of that risk stratification tool, and I think your study showed that how it can easily be incorporated into what we do in a manner that doesn't really negatively impact the work flow, which I think is so important.

Dr Simon Mahler:             You know, we did a smaller study where we looked at the performance of the HEART Pathway with high-sensitivity assays. We studied it with both the Roche troponin high-sensitivity troponin T and the Abbott high-sensitivity I, and at the 99th percentile it actually made very little difference in terms of the performance of the HEART Pathway. What the potential advantages of incorporating high-sensitivity assays is that you probably no longer need a 0 and 3 hours, evaluation can be condensed. I think there's a lot of really interesting questions that availability of high-sensitivity troponins has created, and I think that there's gonna be a lot of emerging evidence over the next few years about new Pathways, and what are the best ways to fully take advantage of these higher-sensitive assays because, frankly, most of the decision aids that are currently in use they were developed using contemporary troponins, and they may not fully take advantage of high-sensitivity troponins. We may see modifications of our Pathway, and it will interesting to see kind of how things evolve as we study the impact of high-sensitivity troponin.

Dr Carolyn Lam:                Wow, exciting work ahead. Just one last question regarding the future. So, you followed up the patients in your study for 30 days. Am I wrong? Any plans to follow them up longer, and do you think such data are needed?

Dr Simon Mahler:             Yeah, we actually followed them for a year. Our primary analysis was through 30 days, and so we do have one-year data on all of our patients, and so we'll be doing a secondary analysis looking out to a year. Yeah, you can look forward to that coming up hopefully in the next six months or so.

Dr Carolyn Lam:                That is awesome. Thank you so much, Simon. Thank you so much, Deb. Thank you, listeners, for joining us today. You've been listening to Circulation on the Run. Don't forget to tune in again next week. This program is copyright American Heart Association 2018.