Jul 1, 2019
Dr Greg Hundley Welcome back everyone from our week hiatus for this July 2nd issue of Circulation On the Run. I'm Dr Greg Hundley, from the Pauley Heart Center at VCU health in Richmond, Virginia.
Dr Carolyn Lam: And I'm Carolyn Lam, associate editor from the National Heart Center and Duke National University of Singapore. So good to be back, Greg.
Dr Greg Hundley Absolutely. So Carolyn, our featured articles going to focus on amyloid and transthyretin amyloid is recognized in middle age and older individuals with increases in LV mass and heart failure. And in our featured article from the United Kingdom, Dr Gilmore and colleagues are going to discuss the natural history of this disease and compare outcomes of those with acquired versus hereditary forms of the disease. But before we get to that interview, how about we discuss several other original articles?
Dr Carolyn Lam: For sure, Greg. Thanks. I want to pick two genetic papers in this issue. They're really exciting. The first one is actually the first study to consider the association between rare genetic variance in a large set of cardiomyopathy genes and the occurrence of cancer therapy induced cardiomyopathy. So this paper is from co-corresponding authors, Dr Garcia-Pavia from hospital Universitario Puerta de Hierro from Madrid, and Dr Christine Seidman from Harvard Medical School in Boston, Massachusetts. The authors studied 213 patients with cancer therapy induced cardiomyopathy from three cohorts. The first retrospectively recruited adults with diverse cancers, the second prospectively phenotyped breast cancer patients. And then the third prospectively phenotyped children with acute myeloid leukemia. They showed an increased prevalence of rare variants in cardiomyopathy genes, particularly the truncating variants of the TTN gene in both adults and pediatric cancer patients with cancer therapy induced cardiomyopathy. They confirmed the human genetic data with experimental analyses showing that anthracyclines induced protracted left ventricular dysfunction in mice with truncating variants of TTN genes but not in the wild type mice.
Dr Greg Hundley Aha. So what are the clinical implications of this study, Carolyn?
Dr Carolyn Lam: Well, the findings show that variance in cardiomyopathy genes contribute to cancer therapy induced cardiomyopathy susceptibility among adult and pediatric cancer patients. And thus the identification of genetic risk factors really opens the door to new opportunities to define patients at high risk of cancer therapy induced cardiomyopathy and associated adverse outcomes.
I want to go onto the next paper because it's so related. It's another genetic paper. This time looking further at the truncating variants of the TTN genes and a very novel approach, they aim to assess a genomics first approach to assess the consequences of these TTN variants. So, this was from corresponding author Dr Zoltan Arany from Perelman School of Medicine in University of Pennsylvania where he and his colleagues reviewed whole exome sequence data for more than 71,000 individuals to identify anyone with truncating variants of TTN genes. They further selected individuals with these variants in exons highly expressed in the heart and using a linked electronic health record, they evaluated the associations of these truncating variants of TTN genes with the diagnosis and quantitative echocardiographic measures. They also reviewed data from the Jackson Heart study to validate specific analyses for individuals of African ancestry.
Dr Greg Hundley Interesting. So we're hearing a little bit about different ancestry and TTN genes. What did they find?
Dr Carolyn Lam: So, I should have first clarified that that first look was in individuals of European ancestry. And they found there that the individuals of European ancestry identified through this genomics VERSE approach had a much greater odds of developing dilated cardiomyopathy and had lower left ventricular function than their peers, whether or not a clinical diagnosis of dilated cardiomyopathy was present. They also found that the association of the TTN variants and dilated cardiomyopathy was much weaker in individuals of African ancestry. So in summary, truncating genetic variants of TTN had a measurable effect in large clinical populations with respect to both strong associations with cardiomyopathy and with associations with quantitative differences in cardiac structure and function. Given the caveat though, that these association appeared strongest in individuals of European ancestry. So Greg, what did you have?
Dr Greg Hundley Well, Carolyn, the overlap of inflammatory processes operating in atherosclerosis and the rich presence of macrophages within plaques make macrophages a strong candidate for therapeutic targeting in atherosclerosis. And so this study comes from Levent Akyürek at the Institute of Biomedicine and involves targeting filament A to reduce macrophage activity in atherosclerosis. So filament A is a large actin binding protein that has been implicated in atherosclerosis and this study tested the hypothesis that targeting filament A in macrophages would impair atherosclerosis in vivo in mice and the investigators evaluated the expression of filament A in human atherosclerotic plaques.
Dr Carolyn Lam: Huh, interesting. So what did it show?
Dr Greg Hundley: Well, in humans, expression of filament A is increased in macrophages and advanced atherosclerotic plaques of human carotid arteries. In mice, in the absence of filament A, macrophages displayed impaired migration, proliferation and lipid uptake and secreted lower levels of inflammatory IL 6, also lack of filament A and macrophages in vivo reduced aortic plaque size and atherogenic mice.
There were additional mechanistic findings and that the C terminal fragment of Filament A produced by calpain cleavage regulated IL 6 secretion in macrophages and treatment with calpeptin, which inhibits calpain cleavage, reduced aortic plaque size and atherogenic mice. And so therefore, filament A might serve as a prognostic biomarker and atherogenesis and perhaps targeting the C terminal proteolytic fragment of filament A could be a strategy to reduce inflammation and atherosclerotic plaque development. Carolyn, I've got another paper, but guess what? This one has our first quiz of the academic new year. This is a paper about Nexclin, and it discusses a new component of junctional membrane complexes required for cardiac T-tubule formation. The corresponding authors are led by professor Zhou Shen from the University of California, San Diego. So, Carolyn in this quiz, what is a T-tubule?
Dr Carolyn Lam: Greg, that is mean! T-Tubules, something inside the cell. Something to do with membranes folding over.
Dr Greg Hundley Yeah, you know this is one of those, it's not multiple choice. It's an open ended question. You need your little blue book. You've got to write the answer. So T, or transverse, tubules are extensions of the cell membrane that penetrate into the center of cardiac muscle cells and interact with the sarcoplasmic reticulum to facilitate calcium release and thus help modulate myocardial contraction. T-tubule uncoupling and remodeling are known features of heart failure.
Dr Carolyn Lam: Alright, so that's T-tubules. Guess what Greg, I'm going to ask you before you ask me. So, what's Nexilin?
Dr Greg Hundley I read the paper like a good student of the American Heart Association. This was answered by the investigative team of Chen and his associates. Nexilin has been identified as an actin binding protein and multiple mutations in the nexin gene are associated with cardiac diseases. In this study, Nexilin was required for initiation of T-tubule invagination and overall T-tubule formation, with a loss of next sullen leading to impaired calcium handling. Clinically, these results identified Nexilin as a new possible target for T-tubule remodeling and provide mechanistic insight into molecular pathways leading to cardiomyopathy in patients with mutations in Nexilin. So Carolyn, great job on our first quiz of the academic new year. And how about we move on to that featured discussion?
Dr Carolyn Lam: Absolutely.
Dr Greg Hundley Welcome everyone to our featured article discussion on this July 2nd and we are going to discuss with Dr Julian Gilmore from London, and our editor Dr Justin Grodin from Dallas, regarding amyloid. And Julian, I understand this particular study you have investigated a natural history of transthyretin amyloidosis cardiomyopathy. Can you tell us a little bit about transthyretin amyloid as opposed to light chain amyloid? And then also I think there's two types of transthyretin amyloid, both a hereditary and then a wild type.
Dr Julian Gilmore: Amyloidosis is a disorder of protein misfolding, and there are in fact many different proteins that can misfold and form amyloid fibrils. When they form fibrils they become insoluble and tend to build up and cause damage to whichever organ they're depositing in. Two of the proteins that form amyloid fibrils in humans in vivo are transthyretin, known as TTR for short, or immunoglobulin light chains, known as immunoglobulin light chains, and those two proteins cause transthyretin amyloidosis and AL amyloidosis or immunoglobulin light chain amyloidosis respectively. Those are the main two types of amyloid that affect the heart or cause a cardiomyopathy and they behave very differently in terms of their natural history in that AL amyloidosis is a very aggressive, rapidly fatal cardiomyopathy if untreated. Whereas cardiac transthyretin amyloidosis tends to be a more gradual albeit progressive cardiomyopathy.
Transthyretin amyloidosis, as you alluded to, can either be acquired, known as wild type or hereditary and in the hereditary version it's associated with mutations in the transthyretin gene of which there are more than 130 now that are recognized to cause disease. The wild type version of the disease, the non-hereditary version of the disease, is now an increasingly recognized cause of heart failure, mainly in older individuals and particularly older males. And the hereditary version essentially remains a rather rarer disease, although the mutation that is associated or it is associated with a risk of developing this disease occurs in certain populations and in particular occurs in 4% of people of African descent, as a particular genetic mutation that occurs in 4% of individuals of African descent. So and that is associated with risk of developing this hereditary transthyretin cardiomyopathy.
Dr Greg Hundley: And so, there's the UK National Amyloidosis Center. Tell us a little bit from that center, what did you do with this particular study in terms of its design and what were your results?
Dr Julian Gilmore: Essentially the UK National Amyloidosis Center is the single center in the UK, which is commissioned centrally to diagnose and type, stage, and provide treatment FYS for patients with amyloidosis. And that includes all parts of amyloidosis. We studied a large number of patients with cardiac transthyretin amyloidosis, so cardiac ATTR amyloidosis, who referred to our center and studied them longitudinally, if you like, over the course of many years. So this was a natural history study for a condition for which at the time of the onset of the study and until the end of the study there was no disease modifying treatment and essentially what we found is that there was a great delay in diagnosis amongst most patients diagnosed with the disease and in fact the median number of attendances in hospital for patients diagnosed with the disease before they were actually diagnosed with 17 which is quite amazing and unsurprisingly in a gradually progressive disease, by the time they were diagnosed, their quality of life was very poor.
We found that their quality of life symptoms gradually progressed and that they became more and more functionally impaired and had relatively poor survival with a median survival of somewhere in the region of five years. What we did find is that patients with a particular type of hereditary, ATTR amyloidosis, the type that I alluded to earlier, the mutation for which is present in 4% of people of African ancestry, he planted the V122I mutation. Patients carrying that particular mutation actually have more aggressive disease and survive for shorter than patients with the wild type disease.
So, 17 hospitalizations before diagnosis and the proceeding three years. Were there factors in your study that you could identify that we should now be looking for to try and make this diagnosis earlier?
Absolutely. So one of the reasons for not diagnosing the condition is basically the poor sensitivity and specificity of echocardiography, which is generally the first investigation that a cardiologist will request when a patient presents with symptoms of heart failure. There are some particular features on echocardiography that can provide clues such as strain measurement on tissue doppler imaging, where one can get a bullseye pattern, that's been reported in the literature. So there are particular features on echocardiography that one can look at to increase the chance of picking up this disease. And in particular the big increase in the number of diagnoses over recent years has been because of cardiac MRI scanning, which has become an increasingly used tool for the investigation of heart failure in which one gets a very characteristic picture of late gadolinium enhancement when it's performed in a patient with cardiac amyloidosis, which immediately triggers people to think, ah, here it is, we've got amyloid.
And the other sort of novel diagnostic technique as being bone scintigraphy. In the UK we use a bone tracer called DPD and in the US a bone tracer called PYP, and those bone tracers have exquisite sensitivity for cardiac amyloidosis. So if one injects these tracers in a patient with cardiac amyloidosis one gets cardiac uptake into the heart, which can't really be missed on a planar scan. So those two techniques basically, the increasing needs of cardiac MRI and the increasing use of bone scintigraphy to investigate patients with heart failure have resulted in a great increase in the number of diagnoses.
The last thing to say is that a huge proportion of patients with amyloid or transthyretin amyloid cardiomyopathy have actually had carpal tunnel syndrome previously. The median time from carpal tunnel syndrome to presentation with heart failure is about seven years, but that is another red flag, if you like, that ought to at least trigger a doctor to think could be amyloid. A thick walled heart in the context of someone whose had previous carpal tunnel syndrome. So there are a few clues there as to how one might make an earlier diagnosis, which is absolutely necessary given the nature of our data, sharing the delays that I outlined down here.
Dr Greg Hundley And Julian, last quick question before we get with Justin here. In your data, can you describe for us the importance of that earlier diagnosis related to long-term outcomes as opposed to the group that was diagnosed much later, you know, beyond your median. What was the difference in prognosis in those two groups?
Dr Julian Gilmore: There is no doubt that if patients are diagnosed earlier, they survived for longer, reflecting the natural history of the disease. So these patients, as I mentioned earlier, did not receive any disease modifying therapy and we did divide the patients into pre 2012, when patients were essentially diagnosed by endomyocardial biopsy, or the vast majority of them were diagnosed by endomyocardial biopsy, and post 2012 by which time most patients were diagnosed via an imaging, if you like, algorithm that we published in 2016 in the same journal in circulation. And the patients who were diagnosed earlier had significantly improved survival. Just corroborating really the fact that they were actually diagnosed earlier. What's particularly relevant there, is that the treatments that have been developed for this condition, and there are some recent new potential disease modifying treatments that have been developed, they find that things seem to slow progression of the disease rather than stop it or reverse it, so that if one can diagnose a patient early when their quality of life is still good and then slow progression, there's a high chance of improving quality of life quite substantially and obviously prolonging life.
Dr Greg Hundley Thank you so much, Julian. And Justin as the managing editor of this article, what struck you most in terms of its results and conclusions, and how we should manage patients today suspected of transthyretin amyloid?
Dr Justin Grodin: Well, I would say that really there are four things that in my opinion that were quite striking. The first at least as highlighted by Professor Gilmore is that the UK National Amyloid Center, they get the national case load. So this is unlike other cohorts and other centers across the world in that this is subject to less referral bias than others. So I think that's the first thing that's quite impressive. And I think Professor Gilmore really hit the nail on the head when he highlighted that this paper, that this analysis really underscores the importance of an early efficient diagnosis. And a lot of this is really through his seminal work in achieving a non-biopsy diagnosis of ATTR amyloidosis and his findings have been replicated in other cohorts as well. So I think those, I would like to say are really one and two.
And then number three, which is one that I don't think Dr Gillmor mentioned, I think he mentioned indirectly, but we were also struck by the prognostic importance or I should say the prognostic meaning of having the V122I mutation. So these are individuals like hereditary amyloidosis and they have a single mutation. This is the one that is prevalent, at least we think from population studies, in approximately 4% of the African or Afro-Caribbean population. And we really see unequivocally that the time from symptom onset to diagnosis was shorter and the prognosis was actually worse in comparison to other mutations or in individuals with wild-type amyloid. And this is an important finding really for two reasons. Number one, it is largely confirmatory from other studies, but it's important to note that those studies were subject to referral bias. And we could never ever successfully incorporate whether or not socioeconomic status had actually influenced the bad outcomes of these individuals.
And I would say that Professor Gilmore's findings are quite compelling in that regard. And then the second thing for this point is really this underscores I think the importance of genetic testing. I mean I think all the readers can take that message away. And then the fourth thing, which as Professor Gilmore alluded was the striking amounts of healthcare utilization, although it was in a minority, certainly quite compelling and really what it speaks to is multiple missed opportunities. Even in the UK where they have a centralized center of excellence, just like Professor Gilmore's, that there were delays in diagnosis and then when delayed these patients are quite ill. And I think I'm making all these points because at least in 2019, the regulatory environment about amyloidosis, specifically ATTR therapies. In The United States, it's actually changed. So a disease where we had therapies that might be off label or our therapies were largely symptomatic, where we managed the patient's signs and symptoms, we now actually have disease modifying therapies.
So, in the United States in 2018, there were two biological agents that actually silence the livers production of transthyretin or TTR and they were approved for hereditary ATTR polyneuropathy. But there is some suggestion from sub-studies that those will have the efficacy in cardiac amyloid. And then number two in the United States, we recently gained approval in May of a drug that actually stabilizes the transthyretin protein or tetramer. So in other words, just as Professor Gilmore had highlighted at the beginning of this call, it stabilizes the breaking up, if you will, of this protein, which is the rate limiting step of amyloid formation. So you take this pill and then the transthyretin molecule does not then deposit amyloid. So this is really exciting because professor Gilmore's cohort study really captures now at least the impact that these therapies might have, and in the United States and across the world and in the UK, these therapies are being studied for all types of ATTR amyloid and really they're on the horizon. So it's given us very deep insights into how these might impact our patient's lives with ATTR.
Dr Greg Hundley Julian, Justin, that was just such an impressive discussion of a very important topic and something that again, with echocardiography, we really need to start thinking about when perhaps we appreciate some LVH, diastolic dysfunction. We have apical sparing of systolic function, but abnormal basal systolic function. Could you just summarize one point, each of you, that we should be thinking about as we move forward and we're seeing patients in our clinic that might have this disorder.
Dr Justin Grodin: The first thing to say is that awareness is all important. You know, 25% of male individuals in autopsy studies over the age of 80 have ATTR amyloid deposits in their heart, and when one sees a thick walled heart in any situation, and particularly in an elderly individual, one needs to think, could this be, amyloid, that's the first thing. And the second thing I'd like to say is that if that thought occurs, which it should occur at a much earlier stage than it does probably in most cardiologists minds, then one should think about either a bone scan, which is a cheap, simple tests. The PYP scan in the US or DPD scan in the UK and or an MRI scan, which has a very characteristic picture in a patient with cardiac amyloidosis. So those would be my take home messages to try and improve early diagnosis.
You know, I'd like to dovetail what Professor Gilmore had said cause he just about took the words out of my mouth and I would like to emphasize the first point in that the diagnosis of AL, we mentioned earlier, or an ATTR amyloidosis, really necessitates a very, very high index of suspicion. What do I mean by that? When somebody has a thick heart muscle and it's not explained by something else, in other words, they don't have a lifetime history of high blood pressure and they don't have high blood pressure seeing you, or maybe they don't respond adequately to standard heart failure therapies when something is not fitting, it's always incumbent to the treating clinician to think amyloid.
I would also like to highlight some of the clues that Professor Gilmore had mentioned, that any individual with carpal tunnel syndrome or who might be hospitalized with heart failure, in other words, they have shortness of breath and swelling, and the squeeze of their heart is normal, or the ejection fraction is normal, that should increase your index of suspicion for amyloidosis. And then individuals that might've had lumbar canal surgery or really any issue impacting their tendons. And then they're now presenting with a thick heart muscle. That should be a clue. It doesn't necessarily mean it's diagnostic. In fact, the majority of those individuals might not have, or a large proportion, might not have ATTR amyloid, but it should certainly raise an eyebrow and then kind of allow the clinician to move forward with the evaluations that Professor Gilmore had mentioned.
Dr Greg Hundley Well, listeners, what a phenomenal discussion that we've had from Professor Julian Gilmore from London, and Dr Justin Grodin from Dallas, Texas, educating us on transthyretin amyloid and thinking about that early and being suspicious as we evaluate patients, particularly older individuals that are symptomatic with heart failure. Well, on behalf of Carolyn Lam, this is Greg Hundley. We look forward to seeing you next week. Have a great week.
Dr Carolyn Lam This program is copyright American Heart Association 2019