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Circulation on the Run

Each monthly episode will discuss recent publications in the fields of genomics and precision medicine of cardiovascular disease.
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Nov 11, 2019

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.

Dr Greg Hundley: And I'm Greg Hundley, associate editor, director of the Pauley Heart Center at VCU Health in Richmond, Virginia.

Dr Carolyn Lam: Greg, we are going to have a great discussion coming right up regarding intensive versus standard ambulatory blood pressure control and its effects on cerebrovascular outcomes in older people. It's the INFINITY trial, but that's all I'm going to tell you for now because I want to hear all about your picks for this week's journal first.

Dr Greg Hundley: Absolutely Carolyn and I can't wait to hear about that discussion regarding hypertension. My first paper though is about titin and it comes from Dr Charles Murry from the University of Washington. The giant sarcomere protein titin is important in both heart health and disease as mutations in the gene encoding for titin are the leading cause of familial dilated cardiomyopathy. The uneven distribution of these mutations within titin motivated the authors of this article to seek a more complete understanding of this gene and the isoform it encodes in cardiomyocyte sarcomere formation and function.

Dr Carolyn Lam: Cool. What did these investigators find?

Dr Greg Hundley: Using genetically engineered human induced pluripotent stem cell derived cardiomyocytes, the authors experimentally confirmed that the gene encoding for the giant sarcomere protein titin includes an internal promoter and start site. This internal start site encodes for the isoform Cronos, which the authors demonstrate support some sarcomere formation in these human induced pluripotent stem cell derived cardiomyocytes.

Dr Carolyn Lam: Oh, nicely summarized. What are the clinical implications Greg?

Dr Greg Hundley: Well, Carolyn identification that Cronos titin, a previously unstudied form of titin is necessary for normal human cardiomyocyte function could be contributing to some of these titinopathies that are relevant for some patients with dilated cardiomyopathy.

Dr Carolyn Lam: Cool. Mine has to do with heart failure as well and presents new results regarding heart failure and heart failure related outcomes from the EXSCEL trial.

Dr Greg Hundley: Carolyn, what was the EXSCEL trial? What did it find?

Dr Carolyn Lam: Ah, so as a reminder, EXSCEL was the largest glucagon-like peptide-1 receptor agonist or GLP-1 receptor agonist trial reported to date where once weekly, exenatide had a neutral effect on hospitalization for heart failure with no differential treatment effect on major adverse cardiovascular events or MACE, by baseline heart failure status. However, the question remains, what about exenatide's effects on secondary endpoints based on the heart failure status? This is from Dr Rob Mentz and colleagues from Duke Clinical Research Institute who aim to explore the effects of exenatide on secondary outcomes in patients with and without baseline heart failure and test the effects of exenatide on recurrent heart failure hospitalization events.

Now they found that out of more than 14,750 EXSCEL participants, 16% had heart failure at baseline and when stratified by the presence or absence of baseline heart failure, there was no observed reduction in all cause death with exenatide in patients with baseline heart failure. While the risk of mortality was reduced with exenatide in the no heart failure group. And that was a significant interaction P value of 0.031. Similar results were observed for the combined outcome of all cause death or heart failure hospitalizations.

Now regarding recurrent heart failure hospitalizations, 450 patients experienced at least one hospitalization for heart failure, but there were 713 hospitalization heart failure events in total. The effect estimate that included the recurrent events was separately, statistically significant while the primary analysis based on just first events was not.

In conclusion in EXSCEL, the use of exenatide in patients with or without heart failure was well tolerated, but the benefits of exenatide on reduction in all cause death and first heart failure hospitalization were attenuated in patients with baseline heart failure. Now this is accompanied by a great editorial by Bruce Neil and Claire Arnett who caution against using post talk subgroup analysis, but the interaction of exenatide tout with baseline heart failure, it's interesting, although should be treated with caution until confirmed by findings from another trial.

Dr Greg Hundley: Very nice Carolyn, especially a nice issue regarding heart failure and I'm going to steer a little bit away from that and talk about atrial fibrillation duration and CHA2DS2-VASc scores. Putting those two together and this article comes from Rod Passman from Northwestern University. Studies of patients with cardiovascular implantable electronic devices show a relationship between atrial fibrillation duration and stroke risk though the interaction with a CHA2DS2-VASc score is poorly defined. The objective of their study was to evaluate rates of stroke and systemic embolism in those patients with cardiovascular implantable electronic devices as a function of both the CHA2DS2-VASc2 score and A-fib duration.

Dr Carolyn Lam: Interesting. What did the authors do?

Dr Greg Hundley: They had 21,768 non-anticoagulated cardiovascular implanted electronic device patients from the Optum electronic health record, de-identified database from 2007 to 2017 and they link those to the Medtronic CareLink TM database of CIEDs capable of continuous AF monitoring. Now the age averaged about 69 years and 63% were men and they found that increasing a fib duration, and of course increasing CHA2DS2-VASc2 score were both significantly associated with annualized risk of stroke and systemic embolism. These rates were low however, in those individuals with CHA2DS2-VASc2 scores of zero to one, regardless of the device detected a fib duration.

Dr Carolyn Lam: Ah. Were there any particular threshold values that seemed important?

Dr Greg Hundley: Great question, Carolyn. Yes, the stroke risk crossed an actionable threshold defined as greater than 1% per year in those with CHA2DS2-VASc2 score patients of two or more with greater than 23 and a half hours of a fib or those patients with CHA2DS2-VASc2 scores of three or four with greater than six minutes of a fib duration or finally in those individuals with CHA2DS2-VASc2 scores greater than five even if they had no atrial fibrillation.

Dr Carolyn Lam: Wow. Very nice clinically relevant conclusions here. Thanks Greg. I'm going to tell you what else is in this issue. There's also a research letter by Dr Rosenmeier entitled, “Aerobic Exercise Induces Cardiac Fat Loss and Alters Cardiac Muscle Mass Through an Interleukin 6 Receptor Dependent Mechanism.” And this is a cardiac analysis of a double blind randomized controlled trial in abdominal obese humans. We have an on my mind paper by Dr Delbridge entitled “HFpEF, It's Time to Explore the Role of Genetic Heterogeneity in Conferring Phenotypic Variability.” And this discusses among other things, the role of induced pluripotent stem cells and functional studies of bioengineered HFpEF patient derived cardiac micro tissues that could potentially enable several important questions to be answered for the first time. There's an ECG challenge as well by Dr Naru Kanya, and it's really interesting. It's a hiccup artifact. If you haven't heard about that, you should take a look. And finally cardiology news by Dr Kuhn and it's entitled, “Nourishing Native American Communities by Increasing Access to Traditional Food.” A very interesting paper right there.

Dr Greg Hundley: Carolyn, I have a few papers. Robert Gerszten provides a perspective piece regarding emerging affinity reagents for high throughput proteomics, sort of an emerging field, everyone doing proteomic studies, we have to pay a special attention to the reagents that are being used. And then Andrew DeFilippis from University of Louisville as well as Johns Hopkins reviews important concepts related to the definition of MI.

Dr Carolyn Lam: Is this pertaining to that fourth universal definition of MI?

Dr Greg Hundley: Yes, Carolyn. Absolutely. And basically in this white paper, the authors review the epidemiology, risk factor associations and diagnostic tools that may assist in differentiating between non-ischemic myocardial injury, type 1 MI and type 2 MI. And then finally from Suowen Xu from the University of Rochester, there's a letter discussing the CCN family of matricellular proteins CCN 1, CCN 2 and CCN 3, that are mechano-sensitive proteins that are differentially regulated by sheer stress, the frictional force exerted by blood flow in our vessels. Well Carolyn, that's a great issue. How about we move on to our feature article?

Dr Carolyn Lam: Let's go Greg.

For our feature discussion today we are talking about intensive versus standard ambulatory blood pressure control and that effect on cerebral vascular outcomes in older people or the INFINITY trial. Very, very important stuff and I'm so pleased to be with the corresponding author, Dr William White from Calhoun Cardiology Center in University of Connecticut School of Medicine. Dr White, thank you so much for being here. Could you maybe set up already the background of what you were thinking when you started this trial? Especially given the results that we know from SPRINT and SPRINT mind. Could you perhaps comment on how this INFINITY trial is different?

Dr William White: We started work in this area about 15 years ago and we initially were interested in interactions among vascular risk factors including ambulatory blood pressure, lipids and other sort of thrombotic factors and so forth with the development of small vessel disease in the brain that led to these fairly classic images on MRI called white matter hyperintensity lesions. And we learned from a prospective cohort study that we started about 15 years ago, that there was a very strong relationship between ambulatory blood pressure and the development and progression of these white matter hyperintensity lesions on MRI, but not very nice relationship with the clinical blood pressures measured in the standard office practice.

We decided to pursue a clinical trial, a randomized clinical trial in which we would evaluate different levels of ambulatory blood pressure versus the development of the small vessel disease as imaged by MRI, but very importantly we also wanted to link it to functional outcomes because this was in older people, typically in their late seventies, eighties and even nineties in which cognitive impairment begins to develop. There's problem with mobility, bladder function and things of that nature. And since our funder was always the National Institute of Aging of the NIH, there's a great deal of interest in more than just the vascular risk factors and even the cerebral vascular disease that we would detect on the MRI. That was the background of why the study got developed the way it did.

Dr Carolyn Lam: That's so interesting. You've already pointed out ways that this was very different from SPRINT OR SPRINT MIND in looking at ambulatory instead of clinic blood pressure and I suppose in the population you selected, out of curiosity, you mentioned that your prior work showed a relationship between white matter hyperintensity on MRI and perhaps future dementia. In which direction? And is there any basis to suspect low, too low blood pressure may also be bad in these older people who already have microvascular brain disease?

Dr William White: Absolutely. Very important point. When we look at our prospective cohort which was about a 100 older people, we followed for four years without any intervention. This was just a mixture of normal tensive and hypertensive individuals. Some on meds, some not on meds. But we did show that when you got too low or if you stay too low during those four years with a systolic blood pressure of under 115 on a 24-hour blood pressure monitor, it seemed like there was an almost like U shaped relationship with progression of white matter disease. Below 115 there was more accrual of white matter disease. Above 150 there was a systolic blood pressure, there was also a greater accrual, but in between about 125 and 145 we weren't really sure if there was going to be a difference. And that there was the target is that everybody's talking about for clinical measurement, so we decided to pursue that in this study to determine if we could figure out whether or not there was a sweet spot for the desk blood pressure without getting into trouble with hypotensive symptoms.

Dr Carolyn Lam: Nice. Thank you for drawing that up so nicely. Now I get it that you chose the targets that you did, which just for everyone, just a reminder, it was a 24 hour mean systolic blood pressure by ambulatory blood pressure control and the two targets were 130 millimeters mercury and less versus 145 millimeters mercury and less. With that, could you please tell us the results?

Dr William White: Right. We called the 130 or less systolic group, the intensive treatment group and the 145, the standard group. We focused on the primary endpoint was changes in mobility parameters in conjunction with changes in white matter hyperintensity lesion growth. And after a period of about three to four months of randomization, post randomization, we achieved a 24-hour systolic blood pressure about 128 millimeters of mercury in the intensive treatment group and 144 in the standard group. And we maintained a pretty good separation in blood pressure, ambulatory blood pressure throughout the three years of treatment. Now the changes in gait speed, which was one of our primary parameters for mobility actually turned out not to be different between the treatment groups. That is intensive versus standard. However, the changes in the accrual of light matter hyperintensity volume was smaller in the intensive treatment group of a 0.29% versus a 0.48% in the standard treatment group. That was significant at a P value of 0.03.

We actually also had a pre-specified sensitivity analysis, sort of a per protocol analysis that allowed us to look at people who stayed in their sort of assigned treatment groups based on blood pressure throughout the three years of the trial. And in that circumstance, there was actually a stronger separation because these are people who stayed clearly at 130 or less than about 145 throughout the three years and now the differences were approximately 0.23% in the intensive group and 0.58% in the standard group. And now the P value is smaller, .0028.

I think we proved in the study that maintaining a systolic blood pressure on the ambulatory recorder over 24 hours of 130 or less benefited patients by reducing the accrual of white matter hyperintensity lesions by about 40% relatively speaking compared to a standard ambulatory blood pressure value of a 145. One of course caveat is that after that happened within three years, but we did not see the expected benefit on mobility or on most of the cognitive parameters either. And while we were a little bit surprised about that, when we went back and analyzed our situation with where people started from as far as this particular cohort of patients, they might've been a little on the healthy side compared to some other studies. A very educated group, very compliant with everything that they did. And probably three years was just not long enough to show the result of this white matter hyperintensity benefit on some of the functional outcomes.

Dr Carolyn Lam: That's really interesting and I'm glad you sort of tackled head on that sort of apparent dissociation between the clinical end points and the MRI end point. Could I also ask, wouldn't those findings also be consistent with SPRINT and SPRINT MIND?

Dr William White: In many ways our results were consistent with SPRINT MIND, a sub-study on the SPRINT MRI sub-study. Of course, just let me mention the differences between the two studies. Of course, SPRINT was very large but there are sub-studies were not as large as the parent study. The MRI study had about 300 plus patients randomized into it, but the measurement of blood pressure was done in the standard clinical fashion and used that digital device that was able to take measurements without somebody present in the exam room. Though they were a bit lower than what I would have seen on an ambulatory monitor during the day time. And their goals were 120 systolic versus 140, whereas ours were an ambulatory systolic of 135 and 145.

But the results were actually comparable because they showed a benefit with regards to lesser accrual of white matter hyperintensity volume in the intensive group versus this banner treatment group. But they also showed no differences after 3.4 years in the incidence of dementia. And they also showed in a separate study, no differences in gait speed in the population who are in intensive versus standard treatment. One would say that results were really actually comparable despite the age differences and the blood pressure measurement differences. And I think both studies really point to the fact that lower systolic blood pressures in older people should be our target because it's safer actually then than maintaining people in the 140s.

Dr Carolyn Lam: Maybe the follow-up period was not long enough. Could it be possible too that maybe blood pressure control should start earlier in life. Could that be it? And then also, could you give us an idea of the kinds of changes, the magnitude of the change on MRI that you see for those of us that don't think about this all the time, is this a big change considered for your cohort or is it a little change?

Dr William White: I think it's true that these people started out around 81 years old in this trial and so by the time they got to that age and had systolic hypertension for probably as many as 20 years, that some of the damage that was done was obviously permanent and we don't really know how long it took for that to accrue. What we did know is that with three years of intensive treatment, we benefited patients by reducing the continued growth or confluency of these small vessel lesions in the brain. Now the range in the amount of damage varies from about half a percent of the overall brain volume to about 5%, so a 10-fold magnitude difference in our cohort.

And as a result of that, certainly somebody who's got about two to 3% of their brain occupied by better hyperintensity lesions or damage is going to have a great deal more functional disability than somebody who's .5%. I think we have to look at the outliers as well as the mean and median changes that we saw. The mean changes are not huge. The difference between 0.2 and 0.6% for example, in our protocol analysis, 0.4% to me it's clinically relevant because I know that that means that there are some people who went up by a percent or two over the years versus the standard versus the intensive treatment group. That's a big difference in an individual over that period of time.

Dr Carolyn Lam: Yeah, I'd hate to think that I'm losing 1% of my brain.

Dr William White: Yeah. Plus it's also where it's located because the lesions are typically around the ventricles of the brain and it's exactly where neurons are going sort of posteriorly to anteriorly to transmit information. For example, from the visual center to the sort of spatial motor cortex. And when those are interrupted, even if it's in one or 2% of the tissue, it can cause substantial difficulties for people. And it's for both the flow of cognitive information as well as this flow of a mobility and balance. I think that it is very relevant, but the gray matter is affected much less by this compared to the white matter. But there are still studies that show that gray matter sort of follows in line with that so that of course also enhances thought processes and cognitive function as well.

Dr Carolyn Lam: Wow. I love the way you explained that. Very important question would of course be the safety and tolerability of this more intensive approach. Any comments there?

Dr William White: Our sponsor, the National Institute of Aging did recruit a data safety monitoring board that was independent from the study for all the years. Impressively over the course of this trial, even though there wasn't a large sample, it was a 199 people, we saw a significant benefit in the intensive group for cardiovascular events, so there were less admissions for heart failure. There were less myocardial infarctions, there was less strokes. All these kinds of things that we worry about in our patients as they get older with vascular disease was reduced by about 75% in the intensive treatment arm versus the standard arm. As far as the events that we were concerned about, such as falls and syncope and presyncope and things of that nature, they were virtually identical in the intensive treatment group and `the standard treatment group. When you take that into consideration, along with the fact that you're reducing the accrual of small vessel disease in the brain, it's clear that this population, even though they're older, would benefit from a lower systolic blood pressure.

Dr Carolyn Lam: Oh my goodness. Thank you so much, Dr White. That was a beautiful summary. That is the take home message right there.

Listeners, I'm sure you agree with me. Thank you so much for joining us this week, and don't forget to tune in again next week.

This program is copyright American Heart Association 2019.

 

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