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Circulation on the Run

Each monthly episode will discuss recent publications in the fields of genomics and precision medicine of cardiovascular disease.
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Apr 10, 2017

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 issue features two exciting papers regarding heart failure in patients with breast cancer. We will be discussing this right after these summaries.

                                                Are we any closer to improving survival in Eisenmenger syndrome? Well, today's first original paper looks at contemporary trends and presents a multivariable mortality risk stratification model based on five simple noninvasive predictors of death in this population. Dr. Kempny and colleagues from Royal Brompton Hospital in London in the United Kingdom preform a large multicenter study in 1098 patients with Eisenmenger syndrome followed up between years 2000 and 2015.

                                                At the end of the study almost two-thirds of patients were on advance therapy for pulmonary arterial hypertension, while only six patients underwent lung or heart and lung transplantation. The study showed that despite advances in management, there was significant mortality amongst contemporary adults with Eisenmenger syndrome and 25.3% of patients died over a median follow up period of 3.1 years. Mortality was higher in older patients, those with a pre-tricuspid shunt, lower oxygen saturation, absence of sinus rhythm, or with a pericardial effusion.

                                                This important study is accompanied by an editorial by Drs. Lange, from Texas Tech University Health Sciences Center El Paso and Dr. Brickner from UT Southwest Medical Center in Dallas, Texas. The editorialists call for a prospective randomized control trials of the effect of current, or future pulmonary vasoactive disease targeting therapies on mortality in Eisenmenger syndrome patients, and say it's time to direct our efforts from improving risk-stratification towards improving survival.

                                                The next study provides experimental evidence of tolerogenic dendritic cell therapy as a novel anti-remodeling therapy in myocardial infarction. Tolerogenic dendritic cells are promising, potent, beneficial regulators of the post-infarct healing process via their control of T-regulatory cells and M1 M2 macrophages. Plus they have the advantage of the ease of administration and feasibility of a heart specific tolero-dendritic cell production.

                                                In the current paper by co-first authors, Drs. Choo and Lee, and co-corresponding authors, Drs. Chang and Lim, from Catholic University Korea and Chai University in Korea, authors generated tolerogenic dendritic cells by treating bone marrow-derived dendritic cells with TNF-alpha and cardiac lysate from mice with myocardial infarction. They then injected myocardial infarction mice twice with tolerogenic dendritic cells within 24 hours and at 7 days after LAD ligation. In treated animals, in vivo cardiac magnetic resonance imaging and ex vivo histology confirm the beneficial effects on post-infarct LV remodeling. Furthermore, subcutaneously administered tolerogenic dendritic cells near the inguinal lymph node migrated to the regional lymph nodes and induced infarct tissue specific T-regulatory T-cell populations in the inguinal and mediastinal lymph nodes, spleen, and infarcted myocardium, all of which elicited an inflammatory to reparative macrophage shift. The altered immune environment in the infarcted heart resulted in better wound remodeling, preserved left ventricular systolic function, and an improved survival following myocardial infarction. Thus, this study shows that tolerogenic dendritic cell therapy in a preclinical model of myocardial infarction may be potentially translatable into an anti-remodeling therapy for ischemic repair.

                                                The final paper reports results of cell therapy on exercise performance and limb perfusion in peripheral artery disease from the PACE trial, which is an NHLBI-sponsored randomized double-blind placebo-controlled phase two clinical trial, designed to assess the safety and efficacy of autologous bone marrow-derived aldehyde dehydrogenase bright cells in peripheral artery disease, and to explore associated claudication physiological mechanisms. In this paper from corresponding author Dr. Moye from UT School of Public Health in Houston, Texas and colleagues of the Cardiovascular Cell Therapy Research Network, a total of 82 patients with claudication and infrainguinal peripheral artery disease were randomized at nine sites to receive alcohol dehydrogenase bright cells or placebo. All patients underwent bone marrow aspiration and isolation of aldehyde dehydrogenase bright cells followed by 10 injections into the thigh and calf of the index leg. Results showed that there were no significant differences in the change over six months between study groups for the co-primary endpoint of peak walking time, collateral count, peak hyperemic popliteal flow, and capillary profusion measured by magnetic resonance imaging.

                                                Additionally, there were no significant differences for the secondary endpoints including quality of life measures. There were no adverse safety outcomes. Interestingly, a post-hoc exploratory analysis suggested that aldehyde dehydrogenase bright cell administration might be associated with an increase in the number of collateral arteries in participants with completely occluded femoral arteries.

                                                In summary, cell therapy did not improve peak walk time or magnetic resonance outcomes, and the changes in peak walk time were not associated with the anatomic or physiologic MRI endpoints. However, future peripheral artery disease cell therapy trial design may be informed by new anatomic and perfusion insights. These and other issues are discussed in an accompanying editorial by Drs. Breton-Romero and Hamburg from Boston University School of Medicine. Well, that wraps it up for our summaries, now for our feature discussion.

                                                We are really in the grove here in Washington, D.C. and I am borrowing the words of my very special, star associate editor, guest, Dr. Gregory Hundley, and he's from Wakefield University School of Medicine. We're discussing two very important papers and they deal with the risk of heart failure following breast cancer. Why they're so important? Well, first of all, it's about time we looked at this problem in detail, and secondly, they actually represent papers in a new section of the journal called "Bridging Disciplines," and in this case cardio-oncology. Very, very important topics.

                                                We're here with the corresponding authors of both papers, Bonnie Ky from University of Pennsylvania School of Medicine and Dr. Margaret Redfield from Mayo Clinic.

Dr Gregory Hundley:      Thank you, Carolyn. I really appreciate that wonderful introduction and also the chance to talk with Bonnie about this exciting topic.

                                                So, Bonnie, you've got a paper here, now, where you did a study in patients with breast cancer, and it sounds like you acquired echocardiograms over a period of time. Can you tell us a little bit about that?

Dr Bonnie Ky:                     Correct. So this is longitudinal prospective cohort study, it's an NIH-funded R01, whereby we are enrolling patients from the breast cancer clinic who are receiving doxorubicin or trastuzumab or a combination of the two therapies. And we're performing very careful cardiovascular phenotyping, from the time at which they initiate chemotherapy through their chemotherapy and then annually once a year we have them come back, for a total follow up time of 10 years.

                                                We took a subcohort, 277 patients, and from their echocardiograms, we analyze them very carefully for various measures of left ventricular size, function, not only systolic function but also diastolic function. We also looked at measures of contractility such as strain in multiple dimensions, and then also measures of ventricular arterial coupling, as well as arterial loads, so how the ventricle interacts with the arterial system. And what we found was that over a 3.2 period time period, on population average, these modest declines in left ventricular ejection fraction, and even across all three treatment groups, and even at three years there were persistent LVF declines.

Dr Gregory Hundley:      So, I understand, Bonnie, that you also collected some information as to whether or not these patients were experiencing symptoms associated with heart failure. How did the imaging markers relate to the symptomatology associated with heart failure?

Dr Bonnie Ky:                     What we found was that early changes in arterial stiffness or total arterial load, as well as early changes in EF were associated with worse heart failure symptoms at one year. A lot of our other analysis was focused on defining what echo parameters of remodeling, size, function are driving or associated most strongly with LVF decline, as well as LVF recovery.

Dr Gregory Hundley:      And then at two years, what happened? Did the echo parameters, were they still associated with heart failure or was there a little discrepancy there?

Dr Bonnie Ky:                     Interestingly, at two years ... no, there was no significant association with changes in arterial load and heart failure symptoms at two years.

Dr Gregory Hundley:      So there might be something transient that's occurring that is associated with heart failure early, and then the patients still had heart failure late, so maybe something else is operative. What do you think we need to do next? What's the next step in your research and then other investigators around the world; what do we need to do to design studies to look at these issues further?

Dr Bonnie Ky:                     Yeah. What does the field need, the field of cardio-oncology that's really growing and developing at rapid paces. Some of the major findings from the study was that changes in total arterial load were very strongly associated with both LVF decline and LVF recovery. So total arterial load is the measure of blood pressure or total arterial stiffness, it's derived from blood pressure. And to me, that begs the question, or begs the next step is that changes in blood pressure are associated with decline as well as recovery. I think, oh, as cardiologists we've also always recognized the importance of afterload reduction. And to me, this study suggests that we need a study, a randomized clinical trial, looking at blood pressure lowering in this population to help mitigate LVF declines.

Dr Carolyn Lam:                I'd actually like to turn it back to you. You are world-renowned for your work in cardio-oncology. Where do you think this fits in, and where do you think we need to address most urgently?

Dr Gregory Hundley:      I think where this fits in wonderfully is a lot of individuals around the world are collecting echocardiographic measures, and all different types. And what Bonnie has helped do is clarify what we would expect to see in this particular patient population. How those measures change over time and that feeds into another block of data, when the measurements head south, do we change therapy, do we add protective agents, and things of that nature. So I think Bonnie's work really contributes on that front. What she has also pointed out is that more research needs to be performed, not necessarily because the patients had heart failure symptomatology at two years, but not necessarily associated with the decline in EF; are there other systems in the cardiovascular realm that are being affected? The vascular system-

Dr Carolyn Lam:                Yeah.

Dr Gregory Hundley:      Skeletal muscle, many other areas. So as cardiologists start to work more with oncologists in this space, and we're all working together to make sure that not only patients survive their cancer, but they have an excellent quality of life, I think we'll see, as we have in other heart failure syndromes, a look toward other aspects of the cardiovascular system, body in general, to reduce the overall morbidity associated with the disease.

                                                I think what we need to recognize as cardiovascular medicine specialists is that now for many forms of cancer, cardiovascular events, and certainly morbidity are becoming the primary issue that folks have to deal with with survivors. It's not necessarily the cancer recurrence, it's not necessarily a new cancer, it's cardiovascular. So we've got to integrate cardiology earlier in working with oncologists to improve overall survival and create an excellent quality of life from our different perspectives.

Dr Carolyn Lam:                So, Maggie, let's move on to your paper now. You looked at radiotherapy's effect, whereas Bonnie looked at chemotherapy's effect. Could you tell us what you did and what you found?

Dr Margaret Redfield:    The rationale for doing this study was, of course, seeing a lot of patients with HFpEF who had had radiation therapy for breast cancer, and I always just sort of assumed that that was because 12% of women over the age of 40 get breast cancer and 20% of women over the age of 40 get heart failure, but it seemed to be somehow more common than that. The other rationale was that radiation therapy does not actually affect the cardiomyocytes; they are very radiation resistant. And what radiation does is cause microvascular endothelial cells damage and inflammation, and that is felt to be fundamental in the pathophysiology for HFpEF.

                                                So we thought we should look at this. I collaborated with a radiation oncologist and oncologists, and they were interested in looking at this because there's a lot of techniques now to reduce cardiac radiation exposure during radiation therapy, including proton beam therapy, and they're trying to prioritize who they use this new technology on. So what we did was start with a population-based study, all women who lived in Olmsted county who received radiation therapy for breast cancer in the contemporary era, where they're already using these dose reducing techniques. So we wanted to make it relevant to what's going on today. And so we started with a base cohort of all women. We matched patients' cases, it was a case-control study, so we matched cases and controls according to their age at the time of breast cancer, whether they had heart failure risk factors, like hypertension or diabetes, whether they got adjuvant chemotherapy, and tumor size, because we felt it was important that radiation could affect different parts of the heart, depending on whether it was right- or left-sided tumor.

                                                And what we found is that the risk of heart failure increased with the mean cardiac radiation dose. We measured the mean cardiac radiation dose in every case and every control from their CT scans and their radiation plants. And as the radiation dose went up, the risk of heart failure went up, even matching or controlling for chemotherapy, which wasn't used that often in this group, or heart failure risk factors. And the vast majority of these cases were indeed HFpEF.

                                                So we then looked at factors that happened in-between the radiotherapy and the onset of heart failure, making sure that this all wasn't just coronary artery disease, 'cause we know radiation can increase the risk of coronary artery disease. And indeed there were, only in about 18% of cases was there a new episode of coronary disease in the interim between the radiotherapy and the breast cancer. So, basically found that the mean cardiac radiation dose, even in today's era, does increase the risk of heart failure with preserved ejection fractions.

Dr Carolyn Lam:                The things that stuck out to me ... it's population based. You did such a comprehensive study to really answer very key questions: dose of radiation, is it really just mediated by age and age-related risk factors, is it just about MI or could it be more microvascular disease? Congratulations, I really appreciated this paper. Some of the take-home messages are directly related to the treatment of breast cancer, isn't it? And about the importance of minimizing radiation dose if possible. I suppose one of the take-homes is, as well, for screening and watching out for heart failure. One thing though: how were these woman diagnosed with HEpEF? I mean, this is always the questions I get. How do you get diagnosed with HEpEF?

Dr Margaret Redfield:    Right, well, first we started with looking to see if they had a ICD code for heart failure, and then we looked at each case of heart failure and determined if they either met Framingham criteria at the time of the diagnosis and the majority of them did. If they didn't actually meet the Framingham criteria, we looked to be sure there was a physician diagnosis of heart failure in the record and that they had supportive evidence of heart failure: echocardiographic findings, natriuretic peptide findings, and other clinical characteristics of heart failure.

                                                And importantly, in the large control group from where we, you know, got our controls, people, a very large group of patients who did not get heart failure, we'd use natural language processing to look at all those records to make sure we weren't missing anybody who didn't have an ICD diagnosis or code for heart failure to make sure we weren't missing any cases of heart failure. So, we really tried to use very stringent methods to make sure we had true cases and control groups.

Dr Carolyn Lam:                Indeed, and it actually goes back to Bonnie's paper as well, where we have to remind everyone that the diagnosis of HEpEF really starts with the symptomatology of heart failure in particular, that you so rigorously determined. I think just one last thing, Maggie: what do you think this implies now, for HEpEF? What do we do in general so the non-radiation-associated, do we believe more the Walter Paulus-Carsten Tschope hypothesis, and if so, what do we do?

Dr Margaret Redfield:    Yes, well I think it really does support that hypothesis. We know that radiation therapy, again, we know what it does to the coronary microvascular endothelial cells and that's been elegantly worked out both in patients and in animal models. I think this really supports the Paulus hypothesis because this microvascular damage was able to produce heart failure, so I think that really supports that hypothesis. And there's been some studies showing decreased coronary flow reserve in HEpEF patients; it's very common. So I think indeed it does support that hypothesis and that the coronary microvasculature is key in the pathophysiology of HEpEF.

                                                However it's a little scary to me because that sort of damage, once it's established, may be very hard to treat. You know, proangiogenic strategies in peripheral vascular disease have not yet yielded the benefits that we hoped for, so I think it's a tough therapeutic challenge that'll be very important to try to address in pre-clinical studies to try and figure out once the microvasculature is so damaged how do we treat that? How do we reverse that process?

Dr Carolyn Lam:                Yeah. Words of wisdom. Maggie, thanks so much for inspiring, just all of us in this field. I just had to say that. You know, you are the reason that I am totally in love with HEpEF. (laughter)

Dr Margaret Redfield:    (laughter)

Dr Carolyn Lam:                So thank you so much for joining me today on the show. In fact, thank you to all my three guests.

                                                You've been listening to Circulation on the Run. You must tell everyone about this episode, it is full of gems.

                                                Thank you, and tune in next week.

 

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