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 Centre and Duke National University of Singapore. Our featured paper this week is an in-depth paper on the cardiovascular and metabolic heterogeneity of obesity, and we will have a discussion with the authors on the clinical challenges, implications for management, and much more coming right up after these summaries.
How does MRI quantification compare with standard Doppler echo approach to identify organic mitral regurgitation and predict adverse outcomes? Well, our first paper this week addresses this question, led by first and corresponding author, Dr. Penicka from the Cardiovascular Center OLV Clinic in Belgium. These authors studied 258 asymptomatic patients with preserved left ventricular ejection fraction and chronic moderate and severe organic mitral regurgitation by echo. All patients underwent MRI to quantify regurgitant volume of this organic mitral regurgitation by subtracting aortic flow volume from the total left ventricular stroke volume. Severe organic mitral regurgitation was defined as a regurgitant volume of greater or equal to 60 milliliters.
The authors found that mean echo-derived regurgitant volume was an average 17 milliliters larger than the MRI-derived regurgitant volume. Concordant grading of organic mitral regurgitation severity with both techniques was observed in 76% of individuals. In the remaining 24% of individuals with discordant findings between the two techniques, this was mainly observed in patients with late systolic, eccentric, or multiple jets.
The MRI-derived regurgitant volume showed the highest discriminative power among all the imaging parameters to predict all cause mortality or its combination with development of indication for mitral valve surgery. Thus, this study demonstrates that MRI-derived assessments of organic mitral regurgitation are clinically accurate to identify asymptomatic patients with severe organic mitral regurgitation and at first outcomes. This may be particularly so when the mitral regurgitation is late systolic, eccentric, or multiple in jets where misclassification may occur with echo-derived approach.
The next study is the first large population-based study to analyze the association between low-dose ionizing radiation from cardiac procedures and incident cancer in adults with congenital heart disease. First author Dr. Cohen, corresponding author Dr. Marelli from McGill University, studied the population from the Quebec Congenital Heart Disease Database and performed a nested case control study comparing cancer cases with controls matched on sex, congenital heart disease severity, birth year, and age. They found that the cumulative incidence of cancer in adults with congenital heart disease between the ages of 18 and 64 years was 15%. The cumulative low-dose ionizing radiation exposure from cardiac procedures was independently associated with incident cancer after adjusting for age, sex, year of birth, congenital heart disease severity and comorbidities.
Results were similar using either the number of procedures or estimates of the effective doses with a possible dose-related response relationship between the low-dose ionizing radiation exposure level and cancer risk. Thus, increasing exposure to low-dose ionizing radiation from cardiac imaging in adults with congenital heart disease raises concerns about life-long risk of malignancy. Confirmation of these findings by prospective studies is needed to reinforce policy recommendations for radiation surveillance in patients with congenital heart disease.
The next study characterizes the long-term dynamics of potassium in heart failure and its associated risk of mortality. First and corresponding author, Dr. Nunez from Hospital Clinic University of Valencia in Spain, evaluated the prognostic implications of long-term longitudinal monitoring and dynamics of serum potassium in a prospective and consecutive cohort of patients following a hospitalization for acute heart failure. In these patients, serum potassium was measured at every physician-patient encounter, including hospital admissions and ambulatory settings.
The authors found that on a continuous scale, the followup trajectory of serum potassium levels independently predicted mortality through a U-shaped association with higher risk at both ends of the distribution, and the same was true using potassium categories. Furthermore, dynamic changes in potassium were independently associated with substantial differences in mortality risk. Persistence of normal potassium levels was linked to a higher risk of death compared to patients who maintained or returned to normal values. Conversely, potassium normalization was independently associated with a lower mortality risk.
These findings support the need for close monitoring of serum potassium after an episode of acute decompensated heart failure and suggest that maintaining serum potassium levels within normal range may be considered a therapeutic target.
The next study gives us an example of how functional metabolomics can translate into metabolomics derived biomarkers of disease mechanisms. Co-first authors, Dr. Zhang, Wei, and Li; co-corresponding authors, Dr. Zhu, Li, and Qi from Nanjing, China, studied a cohort of 2324 patients who underwent coronary angiography from four independent centers. They used a combination of ultra-performance liquid chromatography and quadrupole time-of-flight mass spectrometry in the negative ion mode for untargeted analysis of metabolites in the plasma.
The authors identified a total of 36 differential metabolites related to coronary artery disease progression. In particular, N-Acetyl-neuraminic acid, a metabolic marker highly elevated during coronary artery disease progression, acted as a signaling molecule to trigger RhoA and Cdc42 dependent myocardial injury via activation of the Rho-RACK signaling pathway.
Silencing neuraminidase-1, which is the enzyme that regulates N-Acetyl-neuraminic acid generation, ameliorated myocardial injury in vitro and in vivo. Pharmacologic inhibition of neuraminidase by anti-influenza drugs protected cardiomyocytes and the heart from myocardial injury.
Thus, in summary, functional metabolomics identified a key role for N-Acetyl-neuraminic acid in acute myocardial injury, and targeting neuraminidase-1 may represent an unrecognized therapeutic intervention for coronary artery disease.
The final study addresses the controversy of whether high density lipoprotein, or HDL cholesterol, plays a causal role in cardioprotection. First and corresponding author, Dr. Jensen from Harvard T.H. Chan School of Public Health and colleagues, hypothesized that subspecies of HDL defined by apolipoprotein C3, a key regulator of lipoprotein metabolism, may contribute new information to prediction of cardiovascular risk.
They used immunoaffinity chromatography to measure the apo A1 concentrations of HDL that contained or lacked apolipoprotein C3, or apo C3, in two prospective studies of adults free of coronary heart disease, the Multiethnic Study of Atherosclerosis and the Danish Diet, Cancer and Health Study. They then conducted a meta-analysis that combined these results with the previously published findings from two cohort studies that used similar laboratory methodology to measure lipoproteins.
The authors identified a subspecies of HDL that contained apo C3. HDL that contained apo C3 comprised 5 to 6% of apo A1 or 10 to 15% of HDL cholesterol. In the four prospective studies, HDL containing apo C3 was associated with a greater risk of coronary heart disease, whereas HDL that lacked apo C3 was inversely associated with risk more strongly than the total HDL.
These findings support the hypothesis that apo C3 may mark a subfraction of HDL cholesterol that is associated with higher risk of coronary heart disease. These findings therefore provide novel insights for cardiovascular risk that extend beyond traditional plasma HDL cholesterol concentrations. And that brings us to a close for the summaries. Now for our feature discussion.
For today's featured discussion, we are talking about obesity, a universal issue, or is it? And when we talk about obesity, are we talking about one thing or many things? Today's in-depth review is just such a great paper. I highly recommend it to everyone. So pleased to be discussing it with Dr. Ian Neeland today from UT Southwestern Medical Center.
Ian, first of all, congratulations. A beautiful paper. I learned so much reading it, and I've got so many questions. You started off pointing out that we talk about obesity. We've always defined it by body mass index, but that may not be the ideal biomarker. I love the way you said that. So, tell us a bit more about the reason for this review.
Dr Ian Neeland: Obesity, like you said, we define it by body mass index, but body mass index is such a crude marker. It's great to use for the clinic. It's easy to implement, but it doesn't really tell us a lot of information about the person. And so you can just look at a third of the population in the US right now is thought to be obese. And if you take a third of the population, clearly not everyone has diabetes and heart disease.
So, obesity in and of itself, defined by the body mass index really is very heterogeneous, and it's not possible to use that alone to tell an individual if they're really at risk for disease. And so this review is really about getting deeper under the skin, no pun intended, to really get a sense of what it means to be obese, how the body fat plays a role in disease, and really getting to the different aspects of obesity and how we can understand it a little bit better.
Dr Carolyn Lam: Yeah. You know, Ian, you had me at hello if I could say when I read your paper because I'm from Asia, and here, the World Health Organization actually even suggests that we use lower body mass index cutoffs to define obesity, simply because there's a different relationship as well with cardiometabolic disease. So, so true, but before we get there, to maybe ethnic differences, I want to ask you something. I heard the term, obesity paradox, thrown around a lot, and sometimes I think we don't really know what we're talking about when we say obesity paradox.
I love the way, in your paper, you broke it down into four types. There are four paradoxes. Do you want to just clarify this for the audience? I think it's important.
Dr Ian Neeland: So, the obesity paradox, what we mean by that is we think that obesity causes disease and gives someone an increased risk for disease and mortality and death, but the obesity paradox means that some people who are obese we see actually have better outcomes than those who are not obese. And how to describe that paradox and why that exists is really the subject of lots and lots of research and discussion.
And so when we talk about the obesity paradox, really it's important to understand that most of the time we're talking about people who already have established disease. Let's say, for example, heart disease. So people with heart disease who are obese tend to have better outcomes than those who are not, and there are a few ways to understand that.
So people who have obesity with established disease who may have better outcomes; that's the classic obesity paradox. Then there's a paradox really about fitness and being fat and fit, and that concept that you can be fat, but if you're fit, if you're able to do exercise and you have good cardiorespiratory fitness, that you actually may be protected from disease as well. And then there's also the obesity paradox of basically the pre-obesity paradox, so that overweight, right, where you haven't yet met the threshold for obesity can also be protective in people who don't have disease. And so being a little bit plump may be protective for different diseases down the road. And then the final one is that the metabolically health obesity. When we say that, it means that the person who is obese by body mass index but doesn't really have any hypertension or diabetes or lipid abnormalities. So, that's the metabolically healthy obese person.
Those are the four types of individuals we see who may be obese but actually have better outcomes long term, and the question is why that exists. So there's a lot of thinking about it. Maybe it has to do with the fact that being normal weight nowadays, often we have older folks that are normal weight. Well, they tend to be more deconditioned. They may be frail. They may have undiagnosed disease like cancer. And that might be why those people are the worst. And there are the naysayers out there who think that it's all just about what we call confounding, so things we can't account for when we look at that. People who smoke tend to be lower weight, and obviously they have worse outcomes, and then also people who are older. So it's kind of a conundrum, this obesity paradox, but there's lots and lots of data out there coming out all the time that we keep seeing it again and again and again.
One of the areas in the paper that I wanted to address was this concept of obesity heterogeneity in the obesity paradox, meaning to say is it potentially where the body fat is that may be playing a role in which obese person gets disease, and which obese person may be protected from disease. So it could be that it's not how much fat you have but where that fat is that is really telling about what someone's risk is, and that might help to describe the obesity paradox and get us a little bit more understanding.
Dr Carolyn Lam: Yeah, now, I thought that bit was just so key and important. Not how much fat, not weight per se, but where that fat is. Do you want to elaborate on that a bit?
Dr Ian Neeland: Sure. For, I don't know, 50, 60 years we've had this concept of the apple and the pear. Right? Fat in the belly being the apple shape and fat in the pear being fat in the hips and buttocks and that being two different body types of body fat. So we have a lot of technology nowadays, and we can actually directly image body fat and where it is in the body. So we can do MRI, we can do CT, and we can actually see where the body fat is distributed and how much body fat in one area may be related to disease compared with another area.
So we've gone away from the apple and pear and really getting down to what we call body fat depots or adipose tissue depots where we deposit fat. And the area that we deposit fat that has the most risk for cardiometabolic diseases is this visceral adipose tissue or VAT. VAT is fat that's around the intra-abdominal organs, also near the kidneys, and you can't actually tell how much visceral fat someone has just by BMI or waist circumference or just looking at them. You really have to do this dedicated imaging to find out. And the reason for that is that in the belly there's two types of fat. There's the visceral fat, and there's the subcutaneous, which is the fat under the skin. Both those fat areas make up the belly fat, but they're very different. And part of the review is really going into depth about why these are different and how they're different.
They have completely different metabolic profiles, so if you would take blood, lipids, inflammatory markers, they would look completely different even in a single individual. And then if you look at the genetics of where the fat is, they're different. If you look at what these fat areas secrete, they're completely different. So it's really important to know where the fat is, and that's why I think this concept of sick fat versus healthy fat comes into play.
So, sick fat is fat that's usually in this visceral fat depot, and that is really the three central tenets we talk about are visceral fat or ectopic fat. Ectopic means fat where it doesn't belong. Then inflammation and cytokines, so secretion of abnormal factors in the blood from this fat, and then insulin resistance. So those are the three kind of tenets of this sick fat. So that's why we think that the sick fat plays a role in disease, and then there's a concept of less sick fat or healthy fat, which is maybe a sink. It actually buffers some of these cytokines and inflammation from causing disease in the body.
Dr Carolyn Lam: Yeah. I found that concept so fascinating, and just to bring it back to the obesity paradox. So, some larger people may enjoy better outcomes because they actually have a predisposition to put the fat subcutaneously perhaps, rather than viscerally. Would that be correct? You worded it so eloquently in your paper. There are some ethnicities or some genetic predispositions that could make one lose that inability to put it peripherally, and therefore it all goes viscerally, is what I got from it. And that's the stuff that puts people at risk.
Dr Ian Neeland: Yeah. We find that fat in the lower body, the hips and the buttocks, is actually in epidemiology, protective against heart disease, protective against cancer. And the problem is we don't know why some people put fat in the belly and some people put it in the hips and buttocks. There's very interesting twin-twin studies that show if someone has a predisposition for obesity, so twins may be both obese, but there is some difference in where they actually put the fat. So I think genetics certainly plays a role, but environment also plays a role. And environments, things like appropriate nutrition and physical activity can really alter genetics and help someone to put fat where it should be and prevent disease.
So this obesity paradox, this concept of putting fat where it should be, is really the next frontier for this type of research. How can we modulate it? How can we fix it?
Dr Carolyn Lam: Exactly, and I love the way you ended your review when you said, "Therefore, maybe in all our complaints and so on, saying that we want weight loss, we should actually be focusing on waist loss. You could redistribute the fat to healthy areas, not change your weight, and still become healthier." That was the concept, right?
Dr Ian Neeland: That's right. Yeah. It really is amazing, and it's been shown again and again that people can stay the same weight, but their body fat really is very plastic. It can change, and it's modifiable. And that really makes a difference with health outcomes. So whether we can do that with lifestyle changes, so there's some data to support that. There's also some data to support pharmacology, so medications may be able to move fat from one area to another. And then certainly surgery, which is now getting a lot of popularity for people who are really high risk for cardiometabolic disease. Bariatric surgery has been shown to decrease visceral fat significantly, and that may be one of the reasons why it works so well.
Dr Carolyn Lam: Exactly, Ian. Fascinating, fascinating. I tell you what. Could I just ask you to give us some take-home messages?
Dr Ian Neeland: Sure. So one take-home message I think is that we can move beyond the BMI, beyond the body mass index. Obesity is no longer just a number. It's really about the entire individual, biologic systems, what's going on, and there's just remarkable heterogeneity in the structure of obesity, where body fat is, the activity of body fat, the physiology of it, and also how it relates to diseases, either causing disease and potentially being protective for harmful outcomes.
I think it's also a key message to understand that there's sick fat and there is healthy fat and they're very different. And we can get to the bottom of those using specialized tools like imaging and special testing, but they're really very different, and not all body fat is created equal.
And then lastly, I think it's important to consider, like you mentioned earlier, that really public health and lifestyle going forward is going to be so important, and focusing on those areas that will have the biggest impact for people such as trying to promote waist loss, like you said, as opposed to weight loss. Really focusing and using our knowledge of body fat and obesity and how it's so different across individuals and populations, that it's really important to use that knowledge for our future goals and to have that mind when we recommend weight-modifying therapies for our patients.
It's really going to be a new frontier in weight. We're really moving beyond this concept of just check your weight and your height, and we can tell you what your risk is. No, it's really much more complex and complicated and much more interesting than that.
Dr Carolyn Lam: Oh, Ian, that's just so wonderful. I cannot help this last question. Who knows whether we'll put it in, but I just have to ask you. So how do you monitor your own status or your patients' status? Do you really get them DEXAs, all of them? Or PETs, FDGs? Or do you take your own weight?
Dr Ian Neeland: Yeah. I do. One thing I have noticed, I actually started an exercise and diet program for myself to improve my health about a year and a half ago. I took the research, and I said, "Okay, I'm really going to use this and apply this to my life." So, what's interesting is what I found and actually what other colleagues of mine in research are finding is that you can actually melt away visceral fat just with exercise alone, even if you don't actually go on a diet. And they've done studies like this where they do DEXA scans, and they give people high-intensity interval training. They don't give them a special diet. They just say maintain your current diet, and the visceral fat goes away.
It's really remarkable how lifestyle can be so important and make such a change. And you can see people who have diabetes who can cure their diabetes with a lifestyle program by really decreasing the visceral fat. Even if their weight doesn't change or only changes by a small amount, but their weight may change by, I don't know, five, 10 pounds, but their visceral fat may go away by 50%. And that really makes the difference.
It's obviously hard to monitor. We don't really have these tools clinically every day. Not everyone can do a DEXA and has the software to measure the visceral fat. Certainly could be coming in the future, but right now we should use the tools we do have and use the biomarkers we have and the clinical use, the waist circumference, triglycerides. These things are all surrogates for visceral fat but can be very useful to monitor for change. And it's not just about the scale. It's really about more than that with a person's metabolic status.
Dr Carolyn Lam: That is so helpful. Thank you so much, and I'm so glad you said that it was exercise, and you don't jump into a ice pool or something to try and convert the fat to brown fat or something. That's really, really encouraging to me. Thank you, Ian. This was so enjoyable. I'm sure all our listeners are thanking you as well.
Listeners, you've been listening to Circulation on the Run. Please tune in again next week.
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 Centre and Duke National University of Singapore. How common is perioperative myocardial injury after non-cardiac surgery, and what is its significance? A very important question and a very important feature discussion coming right up after these summaries.
Our first original paper this week tells us that risk assessment using only non-laboratory based risk factors may be a useful alternative in the absence of informational lipids, in predicting adolescents at risk of developing pre-clinical atherosclerosis.
First and corresponding author, Dr. Koskinen from University of Turku Finland and colleagues, studied almost 2,900 participants, age 12-18 years, from four longitudinal cohort studies from the United States, Australia, and Finland, and followed these adolescents into adulthood. When carotid intima media thickness was measured, a mean followup of 23 years later. Non-laboratory based risk factors such as age, blood pressure, body mass index, and lipids measured in adolescence, independently predicted high carotid intima media thickness in young adulthood. The addition of lipid measurements to these traditional clinic based risk factor assessments provided a statistically significant but clinically modest improvement on adolescent prediction of high carotid intima media thickness in adulthood.
The next study demonstrates the feasibility of large scale aptamer multiplexing at a level that has not previously been reported and with sample proof that greatly exceeds other existing proteomic methods.
Now, like antibodies, DNA aptamers can be generated as affinity reagents for proteins. Emerging data suggests that they can be used to measure blood protein levels in clinical cohorts. However, the technology has, to date, remained in its infancy. In today's study, co-first authors, Dr. Jacob and Dr. Ngo, co-corresponding authors, Dr. Jennings and Gerszten, from Beth Israel Deaconess Medical Center in Boston, tested the scalability of a highly multiplexed expended proteomic technique that uses single stranded DNA aptamers to assay human proteins with a markedly expended platform containing approximately 5,000 aptamers targeting a far broader range of analytes than previously examined using this technology. They applied the platform to a cohort of individuals undergoing septal alcohol ablation for hypertrophic cardiomyopathy, using this as a human model of planned myocardial injury.
Now, in addition to confirming findings from prior studies, they identified nearly 150 additional putative markers of myocardial injury. Thus, these findings suggest that the expanded aptamer based proteomic platform may provide a unique opportunity for biomarker and pathway discovery following myocardial injury.
The next study addresses the potential long-term effects of low LDL cholesterol on neurocognitive impairment and decline. This has been a concern with pharmacologic PCSK9 inhibition. The first author, Dr. Mefford, corresponding author, Dr. Levitan from University of Alabama at Birmingham, investigated the association between PCSK9 loss of function variants and neurocognitive impairment and decline in the regards study.
In this general population sample of African American adults, they found no association between PCSK9 loss of function variants and neurocognitive impairment or longitudinal neurocognitive decline. There was also no association between lower LDL cholesterol levels and neurocognitive impairment or decline during follow-up.
The study, therefore, provides evidence in a contemporary population that PCSK9 loss of function variants and resulting lifelong exposure to low LDL cholesterol levels are not associated neurocognitive impairment or decline.
The final study explores long-term outcomes in patients with Type 2 myocardial infarction and injury. First and corresponding author, Dr. Chapman from University of Edinburgh and his colleagues identified more than 2,000 consecutive patients with elevated cardiac troponin I concentrations at a tertiary cardiac center. All diagnoses were adjudicated as per the universal definition of myocardial infarction. They found that at five years, all cause death rates were higher in those with type 2 myocardial infarction or injury compared with type 1.
Although the majority of excess deaths with type 2 myocardial infarction or injury were due to non-cardiovascular causes, the observed crude major at-risk cardiovascular events are MACE rates were similar between groups. Coronary heart disease wan an independent predictor of MACE in those with type 2 myocardial infarction or injury. Thus, despite an excess in non-cardiovascular death, patients with type 2 myocardial infarction or injury have a similar crude rate of major at-risk cardiovascular events to those with type 1 myocardial infarction. Identifying underlying coronary heart disease in this vulnerable population may help target therapies that could modify future risks.
That wraps it up for our summaries. Now, for our feature discussion.
So, I'm gonna go back to my first question on this podcast. How common is perioperative myocardial injury after non-cardiac surgery and what is its significance? Well, to give us an answer, I am delighted to have the first and corresponding author of today's feature paper, Dr. Christian Mueller from University of Basel in Switzerland, and we also have Dr. Torbjorn Omland, and he is associate editor form University of Oslo in Norway. Now, in case you're having deja vu, you are right. I have had these gentlemen on this podcast before and they were so successful, I had to call them back. So, welcome, welcome Torbjorn and Christian. Thank you for coming back again. Christian, congratulations on another beautiful paper. Could you tell us the highlights of what you did and what you found, but this time in particular tell us the novel aspects in view of the previously published vision study that was just published last year. Maybe you could just point out some of the differences.
Dr Christian Mueller: The topic is about an interdisciplinary topic and something, I think that is so important for us as cardiologists to get involved in with much more detail in the future. So, we are aware of acute myocardial infarction, sustained myocardial infarction event that we have studied extensively for decades and for which I think we have a fuller understanding of its cardiophysiology and we have excellent treatments. Completely novel entity is perioperative myocardial injury, so cardiomyocytes that die in the context of non-cardiac surgery. It's something that we as cardiologists should be really focused on because its likely the most important contributor to death in the perioperative period. So, the death rate among non-cardiac surgery is despite improvements in anesthesia and surgery remains remarkably high, between 1 and 4% within 30 days, depending on patient characteristics and surgical directives. And, it seems from our current understanding that the heart really plays a major role, rather high percentage of these deaths.
So, what is new in our study? Overall, our study took advantage of insight gained in the first phase of the vision study in that its has been documented that this perioperative myocardial injury fairly commonly occur without the patient or we as physicians getting aware of it. Either because the patient is still having anesthesia or because he may have symptoms that are atypical. So, we can only reliably detect this event if we screen an appropriate population, and that's what we have done. So, I think the criteria where a patient that's at higher risk of cardiovascular complication is defined at an age of 65 or higher or having pre-existing cardiovascular disease. So, this is the first major difference in which also much younger patients were enrolled. That's the most important differentiate as we had an open label screening. So, the screening was part of clinical routine and it was fine tuned to patients of whom we thought may have a reasonable high risk of developing this complication.
Dr Carolyn Lam: And, your main findings, because they were striking.
Dr Christian Mueller: As our most important finding, we were able to report the incidence of how many patients actually have a relevant amount of cardiomyocytes dying during the operation, and it was one out of seven patients entering our study. So, an incredible high incidence of this complication and that this complication not only is a very good end point that you shouldn't care too much was highlighted again and in full agreement, the suspicious is that if patients develop this complication of perioperative myocardial injury, their risk factor of whether they have any symptoms or atypical ischemic symptoms, and again, only a small minority had the risk of dying both within 30 days as well as in one year, was substantially increased.
Dr Carolyn Lam: Christian, before you go on, could you just please clarify, how did you define perioperative myocardial injury in this case, and was it the same as the definition used in Vision?
Dr Christian Mueller: The perioperative myocardial injury concept initially in Vision it was defined as detecting an elevated troponin just after a non-cardiac surgery, and why this was a perhaps an appropriate definition at the time when we were still using very poorly sensitive troponin assays inevitably is no longer appropriate nowadays because its obvious that particularly elderly patients may have chronic elevations and high sensitive troponin usually. Mild elevations due to a variety of disorders and [inaudible 00:11:51] important studies for us to understand that it is mild elevations troponin is quite common in patients with heart failure, with coronary artery disease or hypertensive heart disease, whatever. So, if we could detect or start detecting likely elevated troponin only after operation, we would never know whether this is something related to the operation itself or whether it's perhaps had already been around for months and weeks and represents the chronic condition. So, the novel concept is that we have to identify an acute rise in troponin, a dynamic genetics or just like that requested for the universal definition of myocardial infarction also of course [inaudible 00:12:32] So, we requested in this study, an increase from the concentration prior to surgery of at least 14 ng/l of high sensitivity cardiac troponin.
Dr Carolyn Lam: Right. Wow. What a great study. So systematic. So, all patients, basically had readings before and after surgery. You know, I've got so many questions, but I really, since you mentioned Torbjorn, I would really like to ask his perspective on what you think was the most striking parts of it and any questions you may have on Christian.
Dr Torbjorn Omland: First, I would like to say that this is a very impressive study with some very important results in a neglected area of medicine, really. So, there are several very strong points with this study, and I think that if we're able to, in such a large population, both have pre-operative and post-operative and was able to calculate the delta, and the importance of that was a very strong part of the study, because it showed that, as Christian alluded to, the baseline level did carry some information but there was also important additional information from the serial measurements. So, that's maybe one of the most important findings, I think.
Then, we addressed the question, how should we use these data? So, my question to Christian is actually, how will screening for exceptional myocardial injury affect clinical practice? Will it lead to clinical deficiency interventions that will improve outcome or will it just result in unnecessary testing?
Dr Christian Mueller: Very good important point, Torbjorn. I think you are absolutely right in indicating that I think we are just beginning to understand all of the part of physiology behind the event that we can now capture, detect really, rather simple and precisely with troponin screening. So, I think it's important that we highlight that the part of physiology behind this event differs from patient to patient. So, there are some patients who clearly have a type 1 myocardial infarction as the cause of myocardial injury. Very likely, they are the minority in this setting. Likely, the majority to have a kind of a type 2 myocardial infarction have a physiology with imbalance between supply and demand, and again, in these patients, of course, the management needs to be to identify the trigger and to correct the trigger as rapidly as possible. And it can be that detecting myocardial injury by the rise in troponin, is the first indication that there is a problem ongoing. Now the patient can have a physiological rearrangement might have already been aware to the physicians if it's a type 1 myocardial infarction, then obviously very likely the same therapy will be beneficial to this patient as we would apply in spontaneous myocardial infarction.
A very important, and I'm glad you alluded to that the different ways of, a rather wide variety of patient settings that are summarized of the term perioperative myocardial injury. And the consequences, likely will have to be individualized to really ensure that we do something good for the patient.
And if I may, I would like to ask you and Carolyn for your thoughts about the most appropriate wording. So, the current wording that we used, of course, has to be in any scientific precaution, a very conservative one, perioperative myocardial injury. And it's important that, in fact, there are some entities where likely injury is derived from the patients who have the injury related to serious sepsis or related to a stroke, or pulmonary embolism. However, it's very likely that the vast majority of patients, the term perioperative myocardial infarction would be appropriate. And, I think it's so important to be aware of the implication that this, perhaps, on first slight small difference might have. As long as we keep using the term "injury", cardiologists will not really feel the same need to be involved, the same need to really take care of this patient as compared to the use of "myocardial infarction". So, I think it's a balance between scientific accuracy, but also the need to create awareness.
So, I feel that if cautiously applied, we'll do more good if would more liberally use "myocardial infarction" within this context. So, would you agree with this perchance?
Dr Carolyn Lam: I think "injury" is at least better than what we used to say, "a leak'. You know, we used to say, "Oh, it's just a troponin leak". So, at least we're saying injury, recognizing that there is damage done. I just wanna highlight that in your paper, something that really struck me was that these patients with perioperative myocardial injury or infarction, indeed did as badly as those who did or did not fulfill myocardial infarction criteria. So, that kind of supports what you are suggesting. I did get that right, right? In your paper?
Dr Christian Mueller: Absolutely. I think for spontaneous myocardial infarctions, so clearly that the criteria defined in the universal definition are mandatory. There's nothing to discuss about, but we cannot criticize a patient who is undergoing general anesthesia that he doesn't feel chest pain, and therefore, we deny him the appropriate word of the events. I think is just important that we clearly highlight that it really can be the same event in the chest without symptoms. But, not due to anything else but because he is undergoing anesthesia.
Dr Carolyn Lam: Very good point. You know, I would really like, though, to go back to Torbjorn’s point, because I think that skeptics are gonna say we've created a problem that we don't know how to solve, or that we don't know how to treat. Do you know what I mean? So we're detecting all these things, because now we have all these assays. Patients are asymptomatic, and then we really don't know whether it's modifiable. We don't know what to do to improve outcome. So, could I ask both your expert thoughts on what the future should hold? What is next step? Because, I see a gap.
Dr Torbjorn Omland: Yes, that's of course, a key question. So, I think we need to be innovative and patient, because what we really need is clinical trials, perhaps and more clinical trials looking into different strategies. But, of course, that's also challenging because as Christian told us, the path of physiology among this group of patients with perioperative myocardial injury differs. So, what's going to be appropriate for one patient, may not be the appropriate therapy for the next patient. So, I think his suggestion of an individualized approach is the best thing we can say at this moment, while we are awaiting data from future clinical trials.
Dr Christian Mueller: I fully agree with Torbjorn [inaudible 00:19:53] what you said, you will criticize some people will argue to that it's irrelevant. Why do you measure this and you don't want to hear it? You don't want to see it. But, I think it's important to remember the starting point for us as cardiologists is to get involved is death. If death is within 30 days after non-cardiac surgery in a patient who was fit, relatively fit otherwise, who underwent a surgery that was not a very high risk surgery from which he would expect a certain percentage of patients to die. So, that's the starting point. Again, of course perioperative myocardial infarction is not the only contributor to perioperative death. But, it seems, in addition to severe sepsis, to be the second commonest and most important. So, I think it's really, really important to first, as a really as a first important thing to increase the awareness of this problem and to encourage our colleagues to start bringing their research efforts, so that we get smarter in identifying the underlying part of physiology in these infarcts or injuries.
Because, only once we understand, or have a reasonable understanding what is the mechanism, we will be smart enough to select the most important priority for any intervention study.
Dr Carolyn Lam: Wow. What a wonderful note to end this podcast on. Words of wisdom, as always from both of you, Christian and Torjorn.
See, listeners. Didn't I tell you this was gonna be a great podcast? Don't forget to tune in again next week.
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 Centre and Duke National University of Singapore.
Have you ever wondered, which is better for heart health, low calorie vegetarian or a Mediterranean diet? Well, this week's feature paper provides some answers with a very intriguing discussion coming right up after these summaries.
The first original paper this week suggests that human fat pools are not the same and in fact are highly diverse in their response to lifestyle interventions during weight reduction first author Dr. Gepner, co-corresponding authors Dr. Shai from Israel and Dr. Stampfer from Boston aim to assess whether distinct lifestyle strategies could differentially affect specific body adipose depos. They performed at 18-month randomized control trial among 278 sedentary adults with abdominal obesity or dyslipidemia in an isolated work place with a monitored, provided lunch.
Participants were randomized to an isocaloric low fat or a Mediterranean low carbohydrate diet with or without added moderate physical activity. The overall primary outcome was body fat redistribution and the main specific endpoint was visceral adipose tissue. The authors further followed the dynamics of different fat depos by magnetic resonance imaging. They found that Mediterranean diet was superior to the low fat diet in mobilizing specific ectopic fat depos such as visceral, hepatic, cardiac and pancreatic fats. Exercise had an additional independent contribution to visceral fat loss. Long term persistent moderate weight loss inadequately reflected the significant beneficial effects of diet and exercise on the fat depos. Independent of weight loss, visceral and hepatic fat reduction was mainly associated with improved lipids profile whereas deep subcutaneous fat loss was associated with improved insulin resistance and superficial fat loss was neutral.
In other words, two distinct patterns were identified, a differentially responsive depo that was sensitive to the type of intervention, and those recites mostly directly related cardiometabolic health and a uniformly responsive depo, which corresponded only to weight loss per se irrespective of the intervention. Overall, these results suggest that more specific strategies for weight loss may be considered to treat distinct organ specific fat depos in the management of cardiometabolic risk.
Current guidelines recommend nonvitamin K antagonist oral anticoagulants or NOACs in patients with nonvalvular atrial fibrillation as these drugs have several benefits over the vitamin K antagonists but do these benefits remain when NOACs have to be combined with aspirin therapy? Well co-first authors Dr. Bennaghmouch and de Veer, corresponding author Dr. ten Berg and colleagues from the Netherlands provided a meta analysis comparing NOACs and Vitamin K antagonists in more than 21700 patients with atrial fibrillation who are treated with concomitant aspirin therapy. NOACs were found to be more effective in terms of stroke or systemic embolism reduction as well as vascular death reduction and as safe as vitamin K antagonist with respect to major bleeding. NOACs were in fact safer with respect to the reduction of intracranial hemorrhage. Thus, these authors found that NOACs were an effective and safe alternative as compared to vitamin K antagonists in atrial fibrillation patients treated with concomitant aspirin therapy.
The next study shows that an integrative approach using genomics and proteomics has the potential to identifying new biological pathways for biomarker discovery and pharmacologic targeting in early cardiovascular disease. Co-first authors Dr. Benson and Yang, co-corresponding authors Dr. Wang and Gerszten from Beth Israel Deaconess Medical Center in Boston had recently identified 156 proteins in the human plasma that were each associated with a net Framingham cardiovascular disease risk score using an aptamer-based proteomic platform in the Framingham Heart Study Offspring participants.
Now, in the current student these authors hypothesized that performing a genome-wide association study and exome array analyses on the levels of each these 156 proteins may identify genetic determinants of risk associated circulating factors and provide insights into early cardiovascular pathophysiology. Indeed, they discovered dozens of novel genetic variants that were each strongly associated with circulating levels of the Framingham Risk Score associated proteins. They highlighted numerous examples of how these novel gene locus protein associations provided new insights into cardiovascular disease risk pathophysiology including a novel pathway by which the gene phosphatase 1G modulated circulating levels of apolipoprotein E, a key regulator of cholesterol handling.
The final study suggests that bariatric surgery represents an effective strategy for reducing antihypertensive drugs in patients with obesity and hypertension. First and corresponding author Dr. Schiavon from Heart Hospital in Sao Paulo, studied 100 patients with obesity and hypertension who were randomized to gastric bypass or medical therapy alone. The patients randomized the gastric bypass were six times more likely to reduce by 30% or more the total number of antihypertensive medications while maintaining controlled blood pressure levels. In addition, 51% of the patients undergoing gastric bypass showed remission of hypertension. Now, the authors are quick to alert that given the morbidity of surgery these results do not imply that all patients with obesity and hypertension should be submitted for bariatric surgery. Rather, these results suggest that gastric bypass surgery represents one extra option to consider in achieving blood pressure control in these patients.
That wraps it up for our summaries now for our feature discussion.
So, which is better for heart health the vegetarian or the Mediterranean diet? Oh, what an awesome topic and to be able to discuss it from Asia to the United States to Italy, I'm so please to have the first and corresponding author of our feature paper this week Dr. Francesco Sofi from University of Florence in Italy and our dear associate editor Dr. Wendy Post from Johns Hopkins. Francesco, could you please start by telling us what inspired you to do this trial?
Dr Francesco Sofi: The aim of the study was to compare two of the most beneficial diets we know from the literature in relation to the occurrence of many chronic degenerative diseases so the Mediterranean diet we have a lot of studies showing that Mediterranean diet is beneficial for many different diseases as well as we have some studies for the beneficial effect of a lacto-ovo vegetarian diet but no studies are available comparing these two diets' dietary profiles. Our hypothesis was to compare in the same population different times the two diets, which were the similar calories, the same isocaloric but just different in terms of composition especially for meat and fish.
Dr Carolyn Lam: Tell us the bottom line. I'm holding my breath because I think I've said it before, I'm vegetarian. Half my household is Mediterranean diet so what did you find?
Dr Francesco Sofi: We found that in the same group of patients, which were a low risk population because a low risk population here in Italy they were already following a Mediterranean diet but if you control their calories and their composition in terms of the Mediterranean, which included all the different food groups and the lacto-ovo vegetarian diet so all the different groups except for meat and meat-based and fish we noticed that after three months, the lacto-ovo vegetarian diet already determined a reduction of total cholesterol and LDL cholesterol and Mediterranean diet already determined reduction of triglycerides and both were effective for reduction of body weight and fat mass.
We noticed with great interest that after three months, all the study population were quite good in [inaudible 00:09:45] with this diet. I mean they didn't have any kind of problems. This is the one of the most important thing and most of the population or many of the patients after the end of the study they started or continued to follow a vegetarian diet. It means that they accepted very well. There was no problem at all. Also, in feasibility and acceptability of this diet and in relation to this also they have a beneficial effect in some parameters such as also oxidative stress parameters and the inflammatory parameters.
Dr Carolyn Lam: Right, so if I could summarize maybe crudely so the vegetarian diet, very effective for LDL, the Mediterranean very effective for triglycerides. I know that's a simplification but Wendy, I'd like to know do you think this is the dawn of maybe a more, "Oh, here we go again individualized diet planning"?
Dr Wendy Post: I think that this study is really important because there really have been few randomized trials about the vegetarian diet and we've learned a lot of the potential beneficial effects of a Mediterranean diet. I think what was really interesting about this study is seeing that they were both equally effective as a low calorie Mediterranean diet or vegetarian diet at reducing body weight, which is most often the biggest challenge for our patients who are either at risk for cardiovascular disease like these patients potentially were or who have cardiovascular disease.
I think the vegetarian diet is potentially an excellent option for some of our patients but it really is an individual choice and I have trouble getting some patients to just give up the red meat let alone any kind of animal meat. I think it really is potentially an individual choice and those who are interested in becoming vegetarian for either health reasons or other reasons these are additional data to suggest potential beneficial effects more to the Mediterranean diet.
Dr Francesco Sofi: I think one of the most important things to know from this study is that we have now two options. We need to individualize the diets to patients but if a person wants to follow a vegetarian diet for different reasons including also healthy reasons, we can say that it's beneficial. He or she can follow this diet without no problems so without having any health problems as well as if a person wants to follow also a Mediterranean diet, which included meat and fish with a regular and moderate consumption during the week.
Dr Wendy Post: Right but this is just a three month trial with intermediate outcomes so I'm not sure we can necessarily make definitive statements that this is potentially not leading to any adverse effects or some of the other statements that you made. I think we could just make the statements better relative to the outcomes that were seen here related to weight loss and traditional cardiovascular risk factors. Whereas, we have had long term clinical trials of the Mediterranean diet suggesting reduction in risk for events so I think this is definitely supportive of the vegetarian diet but I think we can't say that more studies aren't needed to potentially look at longer term outcomes and more definitive events as opposed to intermediate outcomes that this is a great first start and is really helpful in trying to understand some of the potential differences between the vegetarian diet and the Mediterranean diet.
Dr Francesco Sofi: Of course, I completely agree on that. We need more studies and larger studies and longer duration to establish some things but it was just a pilot study but the good thing is the first comparing two beneficial diets. In the literatures now, most of the studies were investigated either already a vegetarian person or vegetarian diet versus a westernized diet so probably there were some biases.
Dr Carolyn Lam: Indeed, I want to just echo in these words. Congratulations, Francesco. Beautifully done, very elegant, controlled in terms of caloric intact and I like that message that it's not saying that one is bad and the other is good. It's saying, "They're different but they both resulted in weight loss". I love that comment about getting a bigger study. I want to do it right here in Asia because the diets are just so different here and I'm just wondering how about in the US? Wendy, your perspective? How adoptable are these results?
Dr Wendy Post: Well, again I think it's a personal choice and if somebody is willing to become vegetarian then that's potentially wonderful especially if they have high LDL cholesterol and are trying to lose weight but we have to be careful about with the vegetarian diet is the carbohydrate intake, which might affect triglycerides. It might be an individualized approach based on the patient's individual risk factor profile and they're preferences but this is really impressive data suggesting that the vegetarian diet is very similar to the Mediterranean diet in many aspects especially as it relates to weight loss, which is really important.
Dr Carolyn Lam: You've hit the nail on the head. Let's remember that this is a low calorie vegetarian diet. I think that's the issue. Sometimes when I say vegetarian diet to some communities here in Asia that is actually a lot of calories and a lot of starch, which is not what we're talking about here.
Dr Wendy Post: Right, a low calorie diet so that's the key. That's the hard part isn't it?
Dr Carolyn Lam: Yeah, sadly.
Dr Francesco Sofi: We should say that most diets are similar background I mean in the backbone is similar so a dietary profile full of fruit and vegetables, complex carbohydrates, fiber, so the different things are meat and fish but with you can see in a regular consumption also Mediterranean diet of course, especially Mediterranean diet is beneficial for cardiovascular profile.
Dr. Wendy Post: Yeah, if we could get our patients in the United States to follow either the vegetarian or the Mediterranean diet that would be fabulous because they are obviously eating too much in the way of sugar sweetened beverages and deserts and fast food so just trying to follow either of these diets would be especially beneficial if it was a low fat vegetarian or Mediterranean diet. I think we need to get all our patients to be eating more fruits and vegetables, which is a key component of both of these diets and what they share in common, which often can lead to beneficial effects with weight loss due to the increased fiber and satiety and the healthful benefits of high fruit and vegetable diet.
Dr Carolyn Lam: Thank you so much.
Audience, thanks also for joining us. You've been listening to Circulation on the Run. Don't forget to tune in again next week.
Dr Carolyn Lam: Welcome to Circulation on the Run. Your weekly podcast summary and backstage pass to the Journal and its editors. I'm Doctor Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore. This week's journal features an international external validation study of the 2014 ESE Guidelines on Sudden Cardiac Death Prevention in Hypertrophic Cardiomyopathy. A very exciting discussion coming right up after these summaries.
The first original paper this week suggests that proteomics, a tool of precision medicine may prove useful in improving the safety and efficiency of drug development. First author, Doctor Williams, Corresponding Author, Doctor Ganz, from the Zuckerberg San Francisco General Hospital retrospectively applied large scale proteomics to blood samples from Illuminate, the trial of Torcetrapib, a cholesterol estrotransfer protein inhibitor, which raised HDL and lowered LDL cholesterol. Recall that this trial was terminated due to increases in cardiovascular events and mortality.
In the current study, the authors found that plasma concentrations of 200 proteins changed significantly with Torcetrapib. Their pathway analysis revealed unexpected and widespread changes in immune and inflammatory functions, as well as changes in aldosterone function and glycemic control. A previously validated nine protein risk score was similar in the two treatment arms at baseline, but higher in participants with subsequent events. At three months, the absolute nine protein derived risk increased in the Torcetrapib plus Atorvastatin arm compared to the Atorvastatin only arm. Thus, this protein-based risk score predicted harm from Torcetrapib within just three months. A protein-based risk assessment embedded within a large proteomic survey may prove to be useful in the evaluation of therapies to prevent harm to patients. This is discussed in an accompanying editorial entitled "Harnessing the Power of Proteomics to Assess Drug Safety and Guide Clinical Trials" by Doctor Maggie Lam and Ying Ge.
The next study suggests that personalized monitoring of heart transplant outcomes may be achieved by profiling the genetic and phenotypic markers of the CD16-dependent natural killer cell activation pathway. First and corresponding author Dr. Paul from Vascular Research center in Marseilles in France and his colleagues collected blood samples from 103 patients undergoing routine coronary angiography for cardiac allograph vasculopathy diagnosis, a median of five years since their heart transplantation. They used a non-invasive natural killer cellular-humoral activation test to evaluate the association between genetic and phenotypic markers of the CD16 dependent natural killer cell activation pathway. They showed that the Fc-gamma receptor IIIAVV polymorphic variant, which encodes the highly responsive CD16-Fc receptor, was an independent baseline predictor of cardiac allograph vasculopathy, and may be useful for stratifying patients at higher risk of rejection. The implications of these findings also include the fact that individualized natural killer cell targeted therapies may limit vascular damage in responsive patients.
The next study suggests that estimation of polygenic atrial fibrillation risk is feasible, and together with clinical risk factor burden, can explain lifetime risk of atrial fibrillation. Co-first authors Dr. Weng and Preis, corresponding author Dr. Lubitz from Massachusetts General Hospital, and colleagues estimated the lifetime risk of atrial fibrillation in individuals from the community-based Framingham Heart Study. Polygenic risk for atrial fibrillation was derived using a score of approximately 1000 atrial fibrillation-associated SNPs. Clinical risk factor burden was calculated for each individual using a validated risk score for incident atrial fibrillation comprised of height, weight, systolic and diastolic blood pressure, current smoking, anti-hypertensive medication use, diabetes, history of myocardial infarction, and history of heart failure.
They found that the lifetime risk of atrial fibrillation after age 55 years was 37 percent was substantially influenced by both polygenic and clinical risk factor burden. Among individuals free of atrial fibrillation at the age of 55 years, those in the low polygenic and clinical risk tertiles, had a lifetime risk of 22 percent, whereas those in the high risk tertiles had a risk of 48 percent. Atrial fibrillation developed at an older age among individuals with a favorable clinical risk profile regardless of genetic predisposition. Nevertheless, the lifetime risk of atrial fibrillation in individuals with high genetic predisposition was substantial, even when the clinical risk factor burden was low. Thus, individualized projections of lifetime risk of atrial fibrillation may be refined by accounting for both genetic predisposition and clinical risk factor burden.
The final study tells us that in contrast to previous perceptions, Takotsubo cardiomyopathy has long-lasting clinical consequences. First and corresponding author Dr. Skally from University of Aberdeen in the UK and their colleagues did an observational case controlled study of 37 patients with prior Takotsubo cardiomyopathy and 37 age, sex, and co-morbidity matched controls. Although Takotsubo cardiomyopathy occurred 20 months before the study, the majority of patients had persisting symptoms compatible with heart failure and cardiac limitation on exercise testing. Despite a normal left ventricular ejection fraction in serum biomarkers, patients with prior Takotsubo cardiomyopathy had impaired cardiac deformation indices on echo cardiography, increased native T1 mapping values on cardio magnetic residence imaging and impaired cardiac energetic status on p31 spectroscopy. Taken together, these findings demonstrate that after Takotsubo cardiomyopathy, patients appear to develop a persistent long-term heart failure phenotype.
Well that wraps it up for our summaries. Now for our featured discussion.
Sudden cardiac death prevention and hypertrophic cardiomyopathy. Always such an important topic. I'm so pleased to have with us the author from our featured paper this week, Dr. Perry Elliot from University College London, nd our associate editor, Dr. Mark Link from UT Southwestern who also wrote a beautiful accompanying editorial with Tera Lynn Ho. So welcome both of you. Perry, I think to set us up, I'd really love if you could tell us a little bit more about the 2014 ESE guidelines for sudden cardiac death prevention and hypertrophic cardiomyopathy. And particularly pointing out how they may differ from the 2011 ACC AHA guidelines please.
Dr Perry Elliot: So, the 2014 guideline on sudden death prevention HCM, the aim of that guideline was to try to quantify the risk of sudden cardiac death. As you pointed out, sudden death is a significant complication of hypertrophic cardiomyopathy and one which we all as clinicians spend a lot of time trying to determine. If we look back over at, I don't know, a period of twenty, thirty years the approach we've developed is based upon the recognition of a number of clinical features of the disease that we know associate with a higher risk of sudden death. So things such as, you know, unexplained syncope or severity of hypertrophy. And it was that model of sort of taking those so called major risk factors which form the basis of the 2011 US guidelines and the essential model was the more of those things you have, the greater is your risk, and I suppose the higher indication for an ICD.
One of the problems with that approach was that it's not quantitative so you know, you could say, "Okay. Well I think you're at higher risk, but I can't say how much that risk is." And another problem with that way of doing things is when you start to think about some of the individual risk factors, it doesn't make a great deal of sense clinically.
And I suppose a good example of that is wall thickness. You know we have this magical number of 30 millimeters, above which we say you're at risk, but of course are we really saying that if your wall thickness is 29 millimeters you're at low risk? We know it doesn't really work that way in biology. So when we drew up the 2014 guideline we wanted to say, "Okay let's develop a model in exactly the same way that we do with atrial fibrillation or primary prevention in coronary disease so that we can say to the patient sitting in front of us, 'Based on your clinical assessment we think you've got a one, five, ten percent risk of something bad happening to you in the next five years.'" And then we can use that information to inform our decision about ICD implantation.
The model itself is not so revolutionary. I mean, it uses a lot of the conventional risk factors such as wall thickness, such as non-sustained VT on Holter monitoring, but what it did introduce was the factor of age, because we know that the age of the patient certainly determines their risk. We brought in [inaudible 00:10:12] obstruction because we've now got reasonable evidence showing that if you've got a big gradient, that certainly modulates your risk. And also probably for the first time, I suppose, left atrial size, which was one of those missing things I think in previous assessments. You know, it's a fantastic surrogate for restrictive physiology and certainly when we added it to the model it improved the predictive power of that model.
So I suppose in summary what we've done is to produce a tool which allows you to estimate risk and then use that to help you decide on whether an individual needs a defibrillator in the clinic.
Dr Carolyn Lam: You know Perry I believe you led those guidelines and I just want to congratulate you as well as that was such a beautiful explanation of what was going on behind those. Yup, but the proof is in the pudding isn't it? But you're providing that proof in today's paper. Tell us about it. So it's an external validation, a large international multi-centers study to actually validate these 2014 guidelines.
Dr Perry Elliot: That's right. I mean, I think when we generate these kind of models it's really important to test those models in different settings. The original model was based upon a relatively small number of European centers and I think what this paper does is it brings insights into different geographies and different health care systems. So we have participating centers from North America from the Middle East from the Far East and the idea here is to get as diverse a population as we can and just see if the model performs in the same way. And you know in a study just short of 4000 people, I think that we've shown that the model does indeed seem to behave in the same way. In fact, the numbers were remarkably similar. You know the ability of this model to discriminate between high and low risk patients was almost exactly the same as in the original paper, which I think gives us a level of reassurance that this model, this tool that we've developed, can be used in different health care settings.
Dr Carolyn Lam: Mark. I really enjoyed your editorial. I love the way that you started out with a case that really shows why this is so important. And I also love that you discuss some other studies that tried to validate the 2014 ESE guidelines as well. Could you just give us some of your thoughts there.
Dr Mark Link: Yeah. I first want to congratulate Perry and his fellow authors for this paper. I think it was a very nice paper. I was a champion of this paper from the time it got sent into circulation. And, you know, the big change in the 2014 European guidelines compared to the American guidelines is really the linear risk of age, wall thickness, and I'll put tract gradient. And as Perry says, I agree, it's not a simple you have it or you don't, it's a linear risk and I applaud them for including that in their risk factor stratifier. And if you look at the current paper, I mean it was very good at picking out high risk patients. So if you have greater than a four percent, six percent risk over five years, you did. And so for picking out the high risk patients it was very good. And for picking out the medium risk patients, it didn't function as well. It was best for separating out the high risk and the low risk population.
And I will say, based on this paper, I've started using the European risk stratifier in my clinical practice. So I do want to applaud them, you know, for the risk stratifier tool and this paper. But I do want to say, and I'm sure Perry will agree, that we're not there yet. We need better tools, because not only in this data set but in other data sets, because more of these individuals reside in the low risk population, more of the sudden deaths are in that population. And we need better tools. And over time they will come. You know, they may be MRI tools. They may be scar tools. They may be other tools that we aren't even aware of that are coming on the horizon, but we do need better tools as we move forward to identify those at risk for sudden death in hypertrophic cardiomyopathy.
Dr Perry Elliot: Yeah. No. I agree. I mean I think what I would say is if you sort of take a step back and look at the overall perspective in this paper, despite the fact that, you know, we've got nearly 4000 people and they're followed in different health care settings, the overall sudden death rate in hypertrophic cardiomyopathy pretty low. You know, so that's good for patients 'cause I think it shows that at least in managed populations, the risk of sudden death which is real and we've got to assess it, but I think it's really important to get that message over to patients that for most people with HCM they're at low risk. It is of course the challenge because when you're dealing with rare events, it's really hard to predict them. And this model is far from perfect. I would argue it's probably the best we've got for the moment, but you know, it's not that bad. It's not that bad.
I mean agree with you absolutely Mark, 'cause you know, either end it performs pretty well. In the middle there it's not as predictive, although what it tends to do is overpredict, rather than underpredict. So you know, I think if you use this model in your every day practice just the greatest risk is that you'd end up putting in probably more ICDs then you really need to rather than missing a lot of patients. You know, we really want to prevent every sudden death if we possibly can, but that's always going to be really hard I think and I think the fight goes on. We got to look for new risk predictors. It may be that we can interchange some of these predictors. They might be easier to assess in some practices, but I'm not a born optimist, but I really think it's amazing just how well in such a complex heterogeneous disease that this relatively simple assessment works. You know?
Dr Mark Link: Going forward, what do you think the future of HCM [inaudible 00:15:47] stratification will include? We've got the risk stratifiers in your calculator ready. And more specifically where do you think gadolinium enhancement will play a role in the future? So MRI findings of scar or gadolinium enhancement.
Dr Perry Elliot: The base we have at the moment show that the more scar you have, the greater risk of sudden death. It sort of makes sense, doesn't it? It's part of that substrate for ventricular arrhythmia. My own reading of it just so far is that I'm not sure what it adds to the existing way of doing things. I mean I think this is true of any biomarker, you know. I've got a new biomarker, what does it tell me that I don't already know? And with scar, we know the greater amount of scar, it often tracks with wall thickness. You're likely to have a thicker heart, you're more likely to have non-sustained VT. But I'm openminded on that front. The beauty about this model, for me, is that it's a tool to into which you can plug other things and you know, if we can get big enough data sets and we can use gads and the amount of scar and put that into the model and if it improves the performance of the model that's great. Those studies are underway at the moment and I think we eagerly wait the results of those studies.
For me, one of the missing things is the genetics. This is a heterogeneous disease with quite a complex genetic architecture, and despite the fact that you know it's 20, 30 years now since we identified the first gene, we haven't really factored that in to our risk models and I think that for me is one of the big challenges and opportunities over the coming years is to put together really large international data sets so that we can answer once and for all whether your mutation determines your prognosis.
Dr Mark Link: Yeah. I agree with the genetics also I think getting more information on that. And it’s been 30 years it still is not helping us prognosticate the risk of sudden death, but it should. I mean it really should. And I do think hopefully we will find other tools also as time goes on because it really is imprecise and it's very difficult when you're sitting there in front of ... You know, I just had a 20 year old yesterday come in with his family and he's got a three centimeter septum and he's got 12 percent scar and he's saying, "Gee what would you do and what would you do if I were your son?" And it's easy when you're looking at it in the aggregate. It's much more difficult when you're sitting there one on one with a patient in front of you.
Dr Perry Elliot: Of course. Of course. And I think another factor I think which is changing the dynamic of that kind of discussion is the evolution of ICD technology. You know, I think when you're dealing with young people the fear is long-term complications with leads isn't it? And I think with the advent of the SICD I sense it's already tipping the balance into perhaps a slightly more liberal approach to ICD implantation exactly in the kind of scenario you've just described Mark, you know you've got guy who's 20. He's got a really severe hypertrophy. Well you know, if you and mess ICD you know your threshold for implantation might be a bit lower.
Dr Mark Link: Yeah and in fact, after a two hour discussion that's what we decided on is that subcu ICD was the right thing for him. And everyone's very happy with that choice.
Dr Perry Elliot: Yep. I think it also raises another thing which I often think about is that as medics we're also probably not good at considering what acceptable risk actually is. You know? We develop models in different settings and hyeprtrophic cardiomyopathy, coronary disease, heart failure, and actually if you go back and critically look at the thresholds that are used to put in defibrillators, the absolute risks vary enormously. So you know, here in [inaudible 00:19:02] we're talking about an approximate annual risk of sudden death of about one percent per annum is sufficient to put in an ICD, but in long-QT world it's quite a different threshold that's used and of course that's because there is no defined number. You know the number's we used in the ESE model of greater than six percent you should have an ICD, well yeah that's the consensus number, there's nothing magical about it. There's nothing biological about it. And I think we've probably had greater debates at what acceptable risks really are.
Dr Mark Link: And that's become a big shared decision now in the States and actually everywhere. It's become a big word because it sued to be that the physicians would decide on who gets an ICD and who doesn't. And it's no longer that way it's a discussion with the patient, with the family. How much risk are they willing to take, both with an ICD and without an ICD, because there are issues with ICD, even though I'm a big fan. There are issues and especially with transvenous ICDs, but also with subcutaneous ICDs.
Dr Perry Elliot: Absolutely. Absolutely.
Dr Mark Link: You know, it's a different world now than it was 15 20 years ago.
Dr Carolyn Lam: Perry and Mark, this has been one of the most wonderful conversations I've had on these podcasts. I just can't thank you enough. I'm sure all our listeners are thanking you too. You've been listening to Circulation on the Run. You must tune in again next week for more beautiful conversations.