Mar 22, 2021
For this week's Feature Discussion, join author author Hannah Valantine and Senior Associate Editor Biykem Bozkurt as they discuss the Original Research Article "Cell-Free DNA to Detect Heart Allograft Acute Rejection."
TRANSCRIPT BELOW
Dr. Carolyn Lam:
Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal 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 Dr. Greg Hundley associate editor, director of the Pauley Heart Center at VCU Health in Richmond, Virginia. Well, Carolyn, I think we've got an interesting feature this week.
Dr. Carolyn Lam:
Oh boy, we sure do. This one is one of those potentially practice changing landmark papers. I'll give you a clue. It's about using cell-free DNA to detect heart allograft acute rejection in transplantation. Huge, huge, but you got to wait. Listen to the summaries of this week's exciting issue first. Greg, you want to go first?
Dr. Greg Hundley:
Yes. And I can't wait for that feature discussion. I think that's going to be one of our top papers this year, but first onto some of the summaries. So my first article comes to us from Dr. Pilar Alcaide from Tufts University School of Medicine. So Carolyn, despite the well-established association between T-cell mediated inflammation and non ischemic heart failure, the specific mechanisms triggering T-cell activation during the progression of heart failure and the antigens involved are poorly understood. So Carolyn, these authors hypothesize that myocardial oxidative stress induces the formation of isolevuglandin modified proteins that function as cardiac neoantigens to elicit CD4 positive T-cell receptor activation, and then promote heart failure.
Dr. Carolyn Lam:
Oh, that's really interesting. Inflammation in heart failure is a hot topic. Tell me more.
Dr. Greg Hundley:
So Carolyn, these authors discovered that TCR antigen recognition increases in the left ventricle as cardiac dysfunction progresses, and they identified a limited repertoire of activated CD4 positive T-cell chronotypes in the left ventricle. Mechanistically, cardiac pressure overload resulted in reactive oxygen species dependent dendritic cell accumulation of isolevuglandin protein adducts, which induced robust CD4 positive T-cell proliferation.
Dr. Greg Hundley:
So collectively, Carolyn, these results demonstrate an important role of reactive oxygen species induced formation of isolevuglandin modify cardiac neoantigens that lead to TCR dependent CD4 positive T-cell activation within the heart. And therefore, these results help understand the relationship between T-cell mediated inflammation and heart failure.
Dr. Carolyn Lam:
Wow. Super. Thanks, Greg. I'm moving all the way from basic science now to talk about intensive lifestyle interventions, which we know are first line approaches to effectively treat obesity and manage the associated cardio-metabolic risk factors. However, to date, whether effective lifestyle based obesity treatment in primary care works, we need more data. And this is what this paper provides.
Dr. Carolyn Lam:
This comes from Dr. Katzmarzyk and colleagues from Pennington Biomedical Research Center in Los Angeles. And what they report is the PROPEL Trial, which randomly allocated 18 clinics equally to usual care or an intensive lifestyle intervention, and subsequently enrolled 803 adults with obesity from participating clinics. The usual care group continued to receive their normal primary care, while the intensive lifestyle intervention group received 24 months of high intensity lifestyle-based obesity treatment in a program, embedded in the clinic setting and delivered by health coaches in weekly sessions initially and monthly sessions from months seven through 24.
Dr. Greg Hundley:
Well, Carolyn, sounds like a really practical study here. So what were these results?
Dr. Carolyn Lam:
Yes, Greg, this was a pragmatic trial. And although pragmatic, this lifestyle intervention was consistent with national guidelines, and participants receiving the PROPEL intensive lifestyle intervention lost significantly more weight over 24 months than those receiving usual care. Results also demonstrated clinically relevant improvements in high density lipoprotein cholesterol, total to HDL cholesterol ratio, metabolic syndrome severity, and fasting glucose. The PROPEL model may therefore be a viable option to deliver effective obesity and cardio-metabolic risk factor treatment in primary care.
Dr. Greg Hundley:
Well, Carolyn, what an interesting article. A lot that we can take home from that. Well, I'm going to switch and talk to you about blood flow restoration and its effect on venous thrombosis and vein wall injury. And this article comes to us from Dr. Farouc Jaffer from the Massachusetts General Hospital at Harvard Medical School. So Carolyn, up to 50% of patients with proximal DVT will develop the post-thrombotic syndrome, which is characterized by limb swelling and discomfort, hyperpigmentation, skin ulcers, and impaired quality of life. While catheter based interventions, enabling restoration of blood flow, have demonstrated little benefit on post-thrombotic syndrome, the impact on the acuity of the thrombus and mechanisms underlying this finding remain obscure. So here, these authors in experimental and studies, they examined whether restoration of blood flow has a restricted time window for improving DVT resolution.
Dr. Carolyn Lam:
Oh, very interesting, and potentially a significant clinical implications, huh? Tell us about it.
Dr. Greg Hundley:
Well, Carolyn, there were two types of studies performed in mice and those in human subjects in the ATTRACT pharmacomechanical Catheter-Directed Thrombosis trial. So in the series of experiments in mice, within a restricted therapeutic window, restoration of blood flow improved DVT resolution. And then in the human studies, the pharmacomechanical catheter directed thrombolysis did not improve the PTS scores for patients having a symptom onset to randomization or SOR time of less than four days or greater than eight days. So therefore, further studies are warranted to examine the value of time restricted restoration of blood flow strategies to reduce post-thrombotic syndrome in patients with deep venous thrombosis.
Dr. Carolyn Lam:
Interesting. Thanks. Greg. My next paper is related, also talking about anticoagulants. And this time, the authors led by Dr. Hijazi from Uppsala Clinical Research Center in Sweden evaluated the risk benefit balance of antithrombotic therapy according to kidney function in the AUGUSTUS Trial. As a reminder, in the AUGUSTUS Trial resulted in less bleeding and fewer hospitalizations than vitamin K antagonists, whereas aspirin caused more bleeding than placebo in patients with atrial fibrillation and acute coronary syndrome or PCI treated with a P2Y12 inhibitor.
Dr. Greg Hundley:
Carolyn, thanks for reviewing for us the AUGUSTUS Trial results. So what did they find in this study?
Dr. Carolyn Lam:
So what they did is they looked at patients with atrial fibrillation and ACS and/or a PCI, and found that apixaban, as compared to vitamin K antagonists, displayed a consistent safety and efficacy profile, irrespective of kidney function, without significant interaction and in accordance with the overall trial.
Dr. Carolyn Lam:
Next, they found that aspirin, relative to placebo, on top of oral anticoagulation and a P2Y12 inhibitor resulted in more bleeding, irrespective of kidney function again, and with an even greater increase among those with a GFR more than 80.
Dr. Carolyn Lam:
These findings can help clinicians perhaps make informed decisions on the antithrombotic therapy in patients with atrial fibrillation and kidney disfunction, with ACS and/or a PCI.
Dr. Greg Hundley:
Very nice.
Dr. Carolyn Lam:
All right, Greg. Well, tell you what, let's go onto the other papers in this issue. I would like to tell you about a letter to the editor from Dr. Saleh on carotid atherosclerosis thickness, a proxy for cardiovascular disease events. There's an ECG challenge by Dr. Liu entitled, intriguingly, A Noteworthy Electrocardiogram, and this really describes new SD segment elevation and its differential diagnosis. To refresh, look up the paper.
Dr. Greg Hundley:
Very nice, Carolyn. Well, I have a research letter to tell you about from Dr. Lanz entitled One Year Outcomes of a Randomized Trial, Comparing a Self-expanding to a Balloon Expandable Transcatheter Aortic Valve. And then finally, Dr. Maron has a very nice perspective piece entitled Exploring New and Old Therapies for Obstructive Hypertrophic Cardiomyopathy Mavacamten in Perspective. Well, Carolyn, I can't wait to get to this week's feature discussion. How about you lead us through that?
Dr. Carolyn Lam:
Me too. Let's go, let's go. I could not be more thrilled to be doing today's feature discussion. And I have to admit I'm feeling very star struck because I'm with two of the women I think are most at my own respect. And the first is Dr. Hannah Valantine, and she is professor from Stanford University now and also at NIH, and she's the corresponding author of today's incredible paper. And the next guest is of course, Dr. Biykem Bozkurt, senior associate editor of circulation from Baylor College of Medicine.
Dr. Carolyn Lam:
Welcome, ladies. On the topic today, it's really landmark. We could be talking about a new gold standard that may replace the endocardial myocardial biopsy. Wow. So if I could just start off, Dr. Valantine, could you please tell us about your study? What is cell-free DNA?
Dr. Hannah Valantine:
Yes. Thank you. It's a wonderful opportunity to be doing this podcast, and thank you for the interest on the technology. If you can imagine, when you put an organ transplant, essentially what you're doing is a genome transplant. You're transferring the genome of the donor into the recipient.
Dr. Hannah Valantine:
Now, we all have single nucleotide polymorphisms, otherwise known as SNPs, that are unique to the donor DNA, and that are unique to the recipient DNA. So that once we put that organ in and there is a teeny little bit of damage, little fragments of DNA come out of the donor organ into the recipient circulation, and we can pick that up, circulating in the plasma. And that's why we call it donor derived cell-free DNA.
Dr. Hannah Valantine:
So, you know the SNPs that belong to the donor, and you know the SNPs that belong to the recipient. You extract the DNA from the plasma of the recipient and you sequence it. And bingo, you can tell what the percentage of that cell-free DNA is coming from the donor, and that is the basis of the test.
Dr. Carolyn Lam:
Oh my goodness. I love that explanation. It's so lucid, and it's reminding me of what happened when I was pregnant. It's the same technology that's used, I think, in prenatal testing, in oncology in some cases, but this is the first time that you've shown it in a multicenter approach in cardiac transplantations. So could you please tell us about that?
Dr. Hannah Valantine:
Yes. Well, we first did this work in a single center when I was at Stanford, where we developed the technology, myself and a couple of colleagues in bio-engineering. But when you do a study, as you know, in one center, doesn't mean it's necessarily transferable or trans label into multicenter.
Dr. Hannah Valantine:
So when I went off to NIH, I transferred the technology there and did something else that was rather unique. I put together a consortium of the five local heart and lung transplant centers in the DC area. And we enrolled patients from each of those five centers into this study. And in the heart cohort, which is what is reported here, we were able to take blood samples on a serial basis. And there were 171 of them in the study. So, what happens is that we genotype the donor and the recipient of each of those 170 patients at the beginning, before the transplants, so that we could then know and monitor their cell-free DNA as they progress at serial time points after the transplant. And that's the way we were able to confirm the value of this test.
Dr. Hannah Valantine:
I can describe to you what the findings were. So what we found is that the cell-free DNA started to rise a lot earlier, before the heart biopsy showed a rejection. So it was just remarkable, because of the serial samples, we were able to look back and say, well, was there an elevation of the cell-free DNA before the positive biopsy? And that was definitively the case.
Dr. Hannah Valantine:
As you know, there are two types of rejection, antibody, mediated, rejection, and cellular driven rejection. And antibody mediator rejection, quite frankly, is the Achilles heel of organ transplantation because it's difficult to pick up and it occurs, that means it's diagnosed late, and it's really resistant to treat.
Dr. Hannah Valantine:
So what we found in this study is that the cell-free DNA was elevated for at least a couple of months before the heart biopsy actually showed the presence of antibody mediated rejection. And that has significant implications for the management of patients. And there are some other characteristics of the cell-free DNA that distinguish cellular and antibody mediated rejection. That is really important because the two types of rejection are treated differently. That's a great excitement of the results of this study.
Dr. Carolyn Lam:
Oh my gosh. I'm just tingling. My hairs are standing, just listening to you explain that. I really think we have a true liquid biopsy now for cardiac transplant rejection.
Dr. Carolyn Lam:
But Dr. Bozkurt, you're such an expert in heart transplantation. Could you frame it for us, just how significant these findings are?
Dr. Biykem Bozkurt:
This is transformative. So first, I would like to congratulate Dr. Valantine and her team for pioneering and leading this concept for such a long time. And now with this validations study, for providing the framework for the future studies for alternative strategies, implementation of how we're going to do this, as the liquid biopsy in lieu of endomyocardial biopsy.
Dr. Biykem Bozkurt:
So the findings that I think are truly practice changing are, yes, this study validates the ability to detect rejection. The second very interesting finding is predict the rejection almost three months before that we're able to detect it by histopathology. Third, for the first time, being able to detect antibody mediated rejection, as well as cellular. Fourth, being able to eliminate the necessity in approximately 81% of the patients with a very high negative predictive value.
Dr. Biykem Bozkurt:
Now, but I'm going to pose this question to Hannah. What is the gold standard now? Because in the historical past, we used to rely on histopathology to be diagnosed myocardial infarction. Now, we know that Troponin-I is a driver or Troponin-T or cardiac troponin. The profile of this is so, I would say, impressive, both for its negative predictive value. And I do realize the sensitivity and specificity is over 80%. And in the positive predictive, when we use the biopsy as the gold standard, the numbers are not as high as a negative predictive value, but if we add the clinical, those who've had the LV dysfunction, those who developed rejection subsequently, three months later, it is performing quite well.
Dr. Biykem Bozkurt:
So what now is going to be the gold standard? I'm thinking, shall we start calling things allograft injury and go and embrace the injury drum now with this profiling, and then trying to determine whether we can intervene early and prevent rejection? And I guess my question is, what's the next step?
Dr. Hannah Valantine:
Thank you for that lovely summary. This clearly, at this point, I would say the gold standard should be the cell-free DNA because in the study we switched it on its head. And we said, if the cell-free DNA is the gold standard, then how sensitive is the heart biopsy? And it wasn't very sensitive. And this is something that we've known for many years.
Dr. Hannah Valantine:
And I'll tell you a little anecdote that has driven my passion over the last 35 years to come up with a better diagnostic tool. When I was first an assistant professor and using echocardiography to study whether or not we could replace the biopsy, I had a patient who in whom I noticed had diastolic dysfunction. And my protocol was if we saw diastolic dysfunction, we actually did a biopsy. And to cut a long story short, I ordered these biopsies, and the biopsy was negative. And in retrospect, I think he had antibody mediated rejection. But the sad part of it is that after a few weeks I got a call from his wife to inform me that she found him dead in bed.
Dr. Hannah Valantine:
And so this has really motivated me to really find something better. And to your question, the cell-free DNA should be the gold standard. The problem is that physicians are human, and there is often takes a lot of time for adoption. So even though the data speaks for itself, that adoption piece is a social, psychological factor that to be overcome. But actually, we've had a really interesting experience in the context of COVID-19 when we were not able to do elective procedures, many centers have reverted to the cell-free DNA technology, and guess what? The patients are doing very well, as we documented in this study. So I think we're going to see a huge paradigm shift in the management of patients with cell-free DNA being the gold standard.
Dr. Hannah Valantine:
But I think that's not all because you asked the very important question about what's next and what's next about this research is to figure out, using the same technologies, why it is that black patients reject their organs so much more than white patients. And in this study, I hope you noticed that 44% of the cohort are African-American. And so it opens the door now to study this area. And then the third implication is that we can use cell-free DNA to actually look at other mechanisms and develop the technology. For example, DNA methylation profiles will come on board very shortly that can teach us more about where the damage is happening and add to the diagnostic tools.
Dr. Biykem Bozkurt:
I have another burning question. The peripheral gene expression profiles that also are available clinically to be able to characterize these patients. How do you see the difference in the cell-free DNA versus gene expression? And in this study, both the donors and the recipients were genotyped. Do you see the necessity of having to do so? Whether the current, you know, snip analysis will allow us not having to genotype patients, which may have an implication on the cost, as well as the practicality of how to implement this on the clinician bedside.
Dr. Hannah Valantine:
Absolutely. As you know, there are now several ways to get around having to genotype the donor by using an array of 260 or so SNPs known that are common in the population. And you can use that. And when you use that technology, it's equally sensitive. So that is what is going to move this forward in terms of clinical utility, so that we don't have to do that. So it's an extension of the technology. I like to do the recipient and donor genotyping because there's so much more research. So from the research perspective, it's useful to continue this technology. But for the application, yes, we're going to be able to do it without the genotyping, and rapidly.
Dr. Hannah Valantine:
And even beyond that, there are now new technologies coming up that we could use. For example, DVPCR, that could be translated into more rapid, an even more rapid test. Right now, the test takes about a day and a half to come back. My goal ultimately would be to have a point of contact test that we could actually use right there to make the diagnosis on a sample of the patient's plasma. So lots of new things coming out. This is just the beginning.
Dr. Biykem Bozkurt:
We're also excited about the possibility of the cell-free DNA, being able to predict coronary artery vasculopathy and/or other clinical events. So I'm sure your team is going to come up with results in regards to the future prognostication regarding the clinical events. So any, perhaps, prediction as to what we shall see those who don't decay, especially after 28 days? I'm very intrigued by those patients, which I think was a subgroup in your study.
Dr. Hannah Valantine:
Yeah. So that's absolutely right. What we are seeing is that those in whom the cell-free DNA remains relatively elevated, because what we find is that immediately after transplant, in the first 24 hours, the cell-free DNA diminishes and to a baseline low level. And then when there is rejection, we see these spikes, but when it's remains elevated, this might be a predictor of ongoing injury, an injury to the vascular dithulium that then sets up the familio for allograft vascular disease. And so we're chasing that hypothesis. The trouble is that the end point takes a while to develop, which is good for the patients. And so look out for future studies that where we will look at the correlation of the cell-free DNA as a predictor of allograft vasculopathy.
Dr. Hannah Valantine:
The other really interesting thing goes back to mechanism. You mentioned the question of consistently elevated cell-free DNA. And so I'm asking myself the question, whether this three floating cell-free DNA can actually act as a trigger of the immune response and therefore lead to damage and rejection. And that again is research that's ongoing, which will have significant implications for patient care. And it might actually help us in understanding why it is that African-American patients reject their organs. Because even those that are doing well in this study, they had relatively higher levels of cell-free DNA throughout the course, and did not decay as in the same pattern as the white patients. So lots of exciting work to come.
Dr. Carolyn Lam:
Oh my goodness, this is just a mind blowing discussion. So might not just be a marker, but even a target for rejection or anti-rejection therapy. And as a trialist, I'm already thinking ahead. Might we see future trials with raised cell-free DNA, but no evidence of rejection on biopsy, and whether or not treating these patients would actually improve outcomes?
Dr. Carolyn Lam:
So this is incredible. I wish we had all day to chat, and I think I really cannot let this end without at least saying something about Dr. Valantine, your work in diversity, and to just thank you on behalf of everybody for really forging this, and especially as part of Circulation. As you know, we have an issue focused on disparities, and we're just incredibly privileged to have you on the podcast today. Biykem, please would you add some last words?
Dr. Biykem Bozkurt:
I second those sentiments. We're grateful to Dr. Valantine for being a trailblazer for our transplant patients, for our community, to enhance the diversity, and for scientific excellence in all fronts. So thank you, Dr. Valantine.
Dr. Hannah Valantine:
Thank you very much. I'm humbled by your comments and very appreciative, and thank you for the support of this work.
Dr. Carolyn Lam:
Thank you, audience, for listening today. You've been listening to Circulation on the Run. Thank you for joining us, and don't forget to join us again next week.
Dr. Greg Hundley:
This program is copyright of the American Heart Association 2021.