Jun 12, 2017
Dr. Carolyn Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. I'm Dr. Carolyn Lam, Associate Editor from the National Heart Center, and Duke National University of Singapore.
In our feature discussion today, we will be talking about insights from the PROMISE Trial regarding the prognostic value of non-invasive cardiovascular testing in patients with stable chest pain. First, here's your summary of this week's journal.
The first paper reports novel findings on gene smoking interactions in coronary heart disease. Co-corresponding authors Dr. Salahin from the University of Pennsylvania and Dr. Riley from Columbia University and colleagues used data on almost 61,000 coronary heart disease cases and more than 80,000 controls to investigate effect modification by smoking behavior at established coronary heart disease and smoking-related genetic loci.
They found that the cardio-protective effects associated with allelic variation at the A-D-A-M-T-S seven, or ADAMTS7 locus, were attenuated by 60% in patients who smoked tobacco, compared to those who did not smoke. Allelic variation in ADAMTS7 associated with reduced coronary heart disease risk, was associated with reduced ADAMTS7 expression in human aortic endothelial cells and lymphoblastoid cell lines.
Furthermore, exposure of human coronary artery smooth muscle cells to cigarette smoke extract led to induction of ADAMTS7. These human genomic data therefore provide new insights into potential mechanisms of coronary heart disease in cigarette smokers and suggests that inhibition of ADAMTS7 may be a novel potential therapeutic strategy for coronary heart disease that may have particular benefits in individuals who smoke cigarettes. This is discussed in an editorial entitled Holy Smokes, an Interaction, by Dr. Braxton Mitchell.
The next paper provides first evidence that genetic over-expression of CD39 may offer ischemic cerebral protection. CD39 is an ectoenzyme with a PYRase activity, which cleaves ATP and ADP. CD39 is expressed on the surface of myeloid and vascular endothelial cells where it dissipates the high local concentrations of ATP and ADP, which would otherwise serve as potent pro-inflammatory and pro-thrombotic signals.
In the current study from first author Dr. Bick, corresponding author Dr. Pinsky from University of Michigan Medical Center and colleagues, authors used a model of permanent middle cerebral artery occlusion to show that CD39 expression reduced edema, infarct volume, and inflammation with corresponding improvements in neurological outcomes, compared to control mice. Over-expression of CD39 in only the myeloid cells also reduced cerebral infarct volume. Thus, amplification of endogenous CD39 expression, or even administration of exogenous circulating CD39, may be of future interest as a therapeutic target to minimize ischemic injury caused by cerebral ischemia.
The next paper provides pre-clinical data to show that MicroRNA93 may have a therapeutic role in peripheral artery disease. First author Dr. Ganta, corresponding author Dr. Annicks and colleagues from University of Virginia, used MicroRNA-106b-93-25 cluster knockout mice and showed that MicroRNA93 over-expression alone was sufficient to enhance angiogenesis, arteriogenesis, and perfusion in ischemic muscle via increased M2-like macrophages.
MicroRNA93 targeted interferon regulatory factor 9 to inhibit immune response gene 1, and itaconic acid generation in macrophages to induce M2-like macrophage polarization. Furthermore, MicroRNA93 over-expression produced a paracrine effect on macrophages that induced angiogenesis and skeletal muscle recovery under hypoxic conditions in vitro.
Thus, these data demonstrate that MicroRNA93 induces beneficial effects in multiple cells that can enhance perfusion in ischemic limb and thus identifies MicroRNA93 as a putative therapeutic target in clinical peripheral artery disease.
The next study is a large scale genetic analysis that represents the most comprehensive causal assessment of adiposity with cardiometabolic diseases to date. Co-corresponding authors Dr. Cassis and Dale from University College London used 97 snips for BMI, and 49 snips for waist-hip ratio adjusted for BMI, to conduct mendelian randomization analysis in 14 prospective studies supplemented with coronary heart disease data from CADRIoGRAM+C4D, stroke data from METASTROKE, Type II Diabetes data from DIAGRAM and lipids data from GLGC Consortium.
They found that both waist-hip ratio adjusted for BMI, and BMI had causal effects on coronary heart disease and Type II Diabetes, and were associated with higher left ventricular hypertrophy, glycemic traits, interleukin 6 and circulating lipids. However, only waist-hip ratio adjusted for BMI increased the risk of ischemic stroke. Thus, both the amount of adiposity and its distribution play important roles in influencing multiple cardiometabolic traits and the development of cardiometabolic disease.
Furthermore, the findings indicate that body fat distribution has multiple roles in disease that are independent of general adiposity. This suggests that physicians should pay attention to measures of adiposity beyond BMI.
The next study addresses the conundrum that clinical trials show benefit of lowering systolic blood pressure in people aged 80 years and above, but yet, non-randomized epidemiologic studies suggest lower systolic blood pressure is associated with higher mortality. In the current study by Dr. Ravindrarajah and colleagues of King's College London, a population based cohort study was conducted using electronic health records of 144,403 participants aged 80 years and older, registered with family practices in the United Kingdom, and followed for five years.
Mortality rates increased with frailty level, and were highest at a systolic blood pressure of less than 110 millimeters mercury. Furthermore, systolic blood pressure trajectories showed an accelerated decline in the last two years of life, without evidence of intensification of anti-hypertensive therapy.
Thus, a terminal decline of systolic blood pressure in the final two years of life suggests that non-randomized epidemiological associations of systolic blood pressure with higher mortality may be accounted for by reverse causation. That is, participants with lower blood pressure values were closer on average to the end of life. This is discussed in an accompanying editorial by Dr. Naveed Sattar.
Well, that wraps it up for our summaries. Now for our feature discussion.
The evaluation of stable patients presenting with suspected coronary artery disease is by far one of the most common diagnostic evaluation strategies that we need to undertake in cardiovascular medicine. There's a whole host of evidence supporting prognostication based on various non-invasive tests, such as anatomic imaging with coronary computed tomography angiography, but also with stress testing, or functional testing, such as stress nuclear or echocardiography, or exercise electrocardiography.
However, our paper today really sheds light on the comparison of these two strategies. And I'm just delighted to have starts with me. First, the primary author of the paper, from the PROMISE Trial, Dr. Udo Hoffmann, from Massachusetts General Hospital, Harvard Medical School, and the editorialist of a beautiful accompanying editorial, Dr. Leslee Shaw from Emory University School of Medicine, Atlanta, Georgia.
Dr. Udo Hoffmann: Hi, Carolyn. Hi, Leslee.
Dr. Leslee Shaw: Hi, Udo, how are you?
Dr. Carolyn Lam: So, Udo, could you start by just sharing what you did in this PROMISE Trial?
Dr. Udo Hoffmann: The Promise Trial is a large comparative effectiveness trial that was done between 2009 and 2012, with follow-up ending 2013, at [inaudible 00:10:13] sites across the U.S. and Canada. And what it did was compare two strategies for testing patients with suspicion of coronary disease, symptomatic patients. These patients were randomized to either receive a functional test first, or an atomic test first, and the idea was to see whether providing the functional information or the anatomic information leads to differences in outcomes of these patients.
As you know, the primary paper showed that the health outcomes of these two strategies were similar and not different. Now in this paper here, we took the slightly different approach and we really wanted to see how the results of the tests as they were seen by the [inside 00:11:02] so it was all based on the sight interpretations of these tests. How the results of these tests actually were associated, or were associated with the health outcomes. And so we directly compared categories of CT results, and categories of functional testing results, and how they are related to outcomes. The good news I think is that sight interpretations in real life do actually have prognostic value for both the anatomic or the CT, and also the functional testing, and so findings as significant disease [inaudible 00:11:36] ischemia have in fact similar prognostic value. And we also saw that on the lower end of the findings, so mildly abnormal findings for example, that the ability to see nonobstructive CAD, perhaps if you're a difference maker and identify from additional patients or group of patients that is at risk for [inaudible 00:12:01].
Dr. Leslee Shaw: I think that often times we struggle with negative trial results, if I can put PROMISE in that negative trial results. And here we have a paper that I think really applies clinically. I think it's going to have far-reaching clinical implications. I think if you look at the CTA findings, this is a real world practice. I think there's a simplicity to CTA interpretations that really is amplified in the nice ability to risk stratify. Whereas the functional interpretation, as you both know, is complex. It integrates a lot of factors, wall motion, perfusion imaging, ST segment changes, exertional symptoms, all of that, and I think we see a lot of sight variability in that image interpretation on the ischemia-side of the functional testing arm.
But there's and important finding from this paper, which I think we have seen in bits and pieces prior to this report, and that is that on the CTA side, you had about a third of the patients having pure normal coronaries. So you see that very low risk in that population. But what you see on the functional testing arm is that the event rate in patients with normal studies and in patients with a mildly abnormal study, the event rates were identical, which is fascinating.
And importantly, two thirds of the population on the functional testing arm were in those normal and mildly abnormal subgroups, something like that. And that has important implications for what is in that one third on a CTA side with normal findings versus three quarters? Well I think from this randomized trial, I think we can infer that you're going to have some non-obstructive disease in that population, but you're also going to have non-ischemic obstructive disease.
We know from FFR and all of the angiographic literature that not every obstructive lesion is ischemic. And so on the stress testing side, we have a lot of obstructive disease that potentially is missed. And I think this study really clearly illustrates that limitation of stress testing and it reflects sight variability in imaging and the interpretation. It reflects the patient populations and the struggles with doing stress testing, but also just flat out reflects the ischemic cascade, and what we can expect from an obstructive lesion, or a non-obstructive lesion, that may not elicit ischemia.
So to that extent, I think Udo's paper is just, just far-reaching and really clearly one of the most advanced papers that we have seen in such a long time. From really providing an important message for those imagers and for folks doing stress testing in this country.
Dr. Carolyn Lam: should we then always do anatomic testing first before selective stress testing?
Dr. Udo Hoffmann: The choice of testing is very much I think tied to the population of the patient you're talking about. I think when you follow the literature, 30 years ago when all the classic studies out of [experienced centers 00:18:53] such as Cedar Sinai, were published, the ischemia burden was much higher in the tested population. Back then you had probably a third or 40% of patients who in fact had some abnormality or ischemia on stress testing. One of the findings here in this study, and that is true for both tests, is that the prevalence of severe findings, severe abnormalities, whether ischemia or obstructive disease, is what I found testing is pretty similar, so it's both around 12%, but it is relatively infrequent. And I think that has changed.
And you cannot expect, as Leslee pointed out nicely, it is not expected from a stress test to detect non-obstructive disease that has prognostic value, but doesn't necessarily explain these symptoms that the patient is presenting. So we should not forget that these patients do not come for primarily for prognostic assessment, they come because they're symptomatic. And the primary question is do we find an equivalent that could explain the symptoms of the patient? And only once we are convinced that there's no such equivalent that would for example lead us to further assess the patient for potential reverse [inaudible 00:20:19] therapy, then the second question that can be answered is for the prognostic implication of the test. And I think in this relatively low risk population, this prognostic aspect gains more importance irrelative to the diagnostic aspect.
Dr. Carolyn Lam: I think Leslee made it very clear in her editorial as well, not to forget in essence at the extremes of disease, that both tests, both strategies conveyed similar prognostic information, and it was more for the fine grain teasing apart that perhaps we need to consider very, very carefully what your paper is saying. But at the end of the day, it's about treating the patients for their cardiovascular risk management, isn't it? Recognizing that even if you don't have ischemia, if you've got the risk factors, like you nicely showed, that we should be treating them for the risk factors.
Leslee, want to share some of your thoughts there? You covered that so nicely in your editorial.
Dr. Leslee Shaw: Well I think that's one thing we've seen from PROMISE, SCOT-HEART, and many, many other recent trials as of late, over the last three or four years, is that the stress test is an opportunity not only to assess ischemic burden, or that CTA's not only a test to assess the extent and severity of coronary disease as well as plaque, but it's an opportunity to identify clear, preventive strategies for the patients.
And this is really something that I don't think at least historically within the stress testing community, that we have taken upon ourselves in order to say, "Okay, here we have a symptomatic patient. We not only are going to assess ischemia, but we're going to look at what else they need to do in order for us to guide prevention." I think this is a clear reminder that this is a great opportunity for us to have a bit of a paradigm shift on the diagnostic testing, to take that whole picture if you will of the patient, and really to focus in on prevention because that is a great opportunity, as Udo talked about just a few minutes ago, it's a great opportunity for us to set the patient on the correct course.
The guidelines, as both of you know, focus in on having that diagnostic evaluation and to implement guideline directed medical therapy as a front line examination. This is a great opportunity for us to just use that diagnostic evaluation ad the initiation of appropriate care for the patient, and then to look at symptom burden, recurrent symptoms, the need for additional interventions. But that first step is guideline directed medical therapy for the patient.
Dr. Udo Hoffmann: Continuing on Leslee's excellent point, I think the paper I think is hopefully a starting point to think about randomized trial, because we assume some maybe come to the conclusion, okay, if you have non-obstructive disease, you should be treated with [inaudible 00:23:13] and aspirin. But we don't know that. I think this is really a call for randomized trial. PROMISE was the one, and it was a good trial. It looked at the association of strategy with an outcome. I think one trial that is needed is to look what specific therapeutic decisions based on imaging or based on test diagnostic test findings, would be justified and would potentially lead to improved outcomes. And that is true for both the stress testing and the CT side. So I think this paper shows the opportunities, but I don't think we have the randomized data to exactly define what are the management options for each of these details of the information that these test results deliver us.
Dr. Carolyn Lam: