Circulation March 20, 2018 Issue

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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.

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