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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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Aug 29, 2016

 

Carolyn:
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. In just a moment, we will be discussing the very topical subject of wearable cardioverter defibrillators in patients at high risk of sudden cardiac death. Yes, this is the topic of our feature paper which really builds on prior US data using these devices and extends it, now, to a healthcare system outside the United States. First, here's the summary of this week's journal.

 
 
The first paper describes a novel class of mediators that may revolutionize the nonsurgical treatment of limb ischemia. This paper from first author Doctor Jung from University of Louisville School of Medicine and corresponding author Doctor Spite from Harvard Institute of Medicine and colleagues looked at resolvents. Resolvents are a family of lipid mediators synthesized from Omega-3 polyunsaturated fatty acids that promote the resolution of inflammation and have been shown to regulate the transition from inflammation to repair. Now, this is very relevant to limb ischemia because most other mediators that promote revascularization also exacerbate inflammation, thus potentially limiting their therapeutic use in chronic inflammatory diseases such as diabetes.

 
 
To assess the role of resolvents in revascularization and resolution of inflammation, the authors using a Murine model of hindlimb ischemia coupled with Laser Doppler profusion imaging, micro-computed tomography and targeted mass spectrometry. They identified that resolvent D2 is produced in the skeletal muscles of their Murine model of limb ischemia as well as in skeletal muscle biopsies of patients with peripheral artery disease. They showed that resolvent D2 increases tissue profusion by promoting arterial genesis that is collateral artery growth and, importantly, that it rescues defective revascularization in diabetic mice. These findings are important because they could inform the development of novel strategies for the clinical management of limb ischemia.

 
 
The next paper addresses food fortification with folic acid, which we all know prevents neural tube defects but may now even prevent congenital heart defects. This paper is from Doctor [Mule 00:02:53] and colleagues from The Center for Chronic Disease Prevention, Public Health Agency of Canada who studied approximately six million Canadian births from 1990 to 2011 and compared the prevalence rates and temporal trends in congenital heart disease sub-types before and after 1998 when folic acid fortification was mandated in Canada. They quantified the effects of folic acid fortification on the birth prevalence of specific non-chromosomal congenital heart disease sub-types, after controlling for concomitant changes in maternal age, pre-pregnancy diabetes, preterm pre-eclampsia, multiple birth and pregnancy termination. They found that there was an eleven percent reduction in non-chromosomal congenital heart defects following folic acid fortification. Specifically, folic acid fortification was associated with a twenty-seven percent reduction in conotruncal defects, a twenty-three percent reduction in coarctation of the aorta, a fifteen percent reduction in ventricular septal defects and an eighteen percent reduction in atrial septal defects. This large ecological study, therefore, provides evidence of a modest protective effect of folic acid fortification on congenital heart defects.

 
 
The last study suggests that in patients with ischemic cardiomyopathy and right ventricular systolic dysfunction, we should perhaps be taking a look at the mitral valve. This is work from first author Doctor Seib from the Beth Israel Deaconess Hospital and Harvard Medical School, corresponding author Doctor Kwon from the Heart and Vascular Institute of Cleveland Clinic Foundation and colleagues, who looked at over five hundred and fifty patients with ischemic cardiomyopathy, all of whom underwent cardiac MRI. They found that mitral regurgitation, as measured by effective orifice area, was a significant independent predictor of right ventricular ejection fraction. They further found that the relationship between right ventricular ejection fraction and mortality may be affected by mitral valve surgery in that a reduction in right ventricular ejection fraction was associated with increased mortality in non-repaired patients but not in patients who had undergone mitral valve repair.

 
 
The clinical take-home messages are that right ventricular function should be carefully assessed in patients with ischemic cardiomyopathy and if systolic dysfunction is found, patients should be assessed carefully for significant mitral regurgitation as well as other known risk factors such as right bundle branch block, right ventricular scar or a decreased left ventricular ejection fraction. The study suggests that mitral valve surgery may mitigate the relationship between right ventricular rejection fraction and mortality, however further studies are clearly needed.

 
 
Those were the summaries. Now, for our feature paper discussion.

 
 
I am thrilled to be joined by three guests today to discuss the feature paper on wearable cardio defibrillators in patients at high risk of sudden cardiac death. This is a real world experience all the way from Germany. Joining us today we have two authors of the paper, the first and corresponding author Doctor Nadine Visnic as well as author Doctor Ruth Strasser, both from the University of Dresden and Heart Center Dresden in Germany. Welcome, ladies.

 
Ruth:
Hello, how are you?

 
Carolyn:
Very good, thank you.

 
 
We have Doctor Mark Link, Associate Editor from UT Southwestern. Thank you for joining us, Mark.

 
Mark:
You're very welcome.

 
Carolyn:
Mark, let's start with a behind the scenes look. We have data from the United States describing the wearable cardio defibrillator. We have ample data on the implantable cardio defibrillators. What made the editorial board decide that this particular paper from Germany was so important?

 
Mark:
There are a number of aspects that we looked at for this paper. This is exciting new technology that is beginning to impact the daily lives of all the physicians in the states, the wearable defibrillator. This is a very nice prospective study from Germany that looked at a very large group of patients with this wearable defibrillator, gave us real world experience and it also fits in with the circulation mission of becoming a world wide cardiac journal, not just United States journal. We were very interested in the topic. We're very interested in the international collaboration and we're very excited to publish this paper.

 
Carolyn:
I love that. Practicing in a non US system, as well, I found this particularly special about this paper.

 
 
Nadiene, we're all wondering, could you describe the patient population, just so we know the kind of patients that your results are applicable to.

 
Nadine:
The patients included in the register were regular patients we meet in clinic in every day life. No specific selection was made. For legal reason, of course, to analyze the data, they signed informed consent for the register. From April 2010 through October 2013, in total six thousand forty-three patients were using the wearable cardioverter defibrillator in Germany. All of these patients were registered into the life vest network, the registry to record demographic such as gender and age. Also, the cardiovascular indications and defibrillation treatments and daily wear time. The German population consisted of seventy-eight male and twenty-two female patients with median age of fifty-seven years.

 
Carolyn:
Great. What were the indications for the wearable defibrillators?

 
Nadine:
Most of the patients had to reduce the ejection faction by below thirty-five percent or even had experienced ventricular tachycardia as an indication. The largest group we had in our analysis was thirty-seven percent where those with newly diagnosed dilatative cardiomyopathy and ischemic cardiomyopathy accounted for twenty-seven of patients, especially forty days after myocardial infarction or after a high risk PCI or cabbage. Also, in total, we had twelve percent of patients that had an ICD explantation mostly due to infection situation. What is very special on that paper is that ten percent of all our patients had myocardidas as a diagnosis and was reason to use the WCD.

 
Carolyn:
Wow. That does sound very representative of the real world patients that we would put wearable defibrillators on, as well.

 
 
Ruth, could you tell us, what were the main results? Were there any differences by sub-groups?

 
Ruth:
Perhaps, we should first go on the compliance because this is very important to the daily wear time. This was more than twenty-two hours in ninety-four percent of the patients. Many patients who complained about the inconvenience but understanding that this life vest is a potentially life saving and only temporary treatment strategy made it acceptable to ninety-eight percent of the patients. As to the [inaudible 10:52] there is a difference, the younger patients, patients younger than forty-eight years of age or younger, they wear the life vest longer, sixty-six days. While the older patients, older than sixty-eight patients, this was statistically significant, wore it only forty-nine days. This difference was not used to compliance, because you do the description based on the cardiac diagnosis.

 
 
We also observed that the longer the cumulative wear of the life vest was, the longer day hours the patient had the life vest on. They were somewhat accustomed to it. One thing which is very, very important is, that in more than twenty-five percent of the patients, we could save the implantation of a permanent ICD due to the recovery of the ejection fraction. This was especially important for those patients who had the life vest, for example after myocardidas or after myocardial infarction, which is a very large population.

 
 
Also, which is important is that [full 12:06] shock treatment for reasons other then VT occurred only in point four percent, of less than one percent. Whereas those patients were successfully treated, this was one point six percent. They were treated in response to VT and VF. This means the incidence rate was eight point four per hundred patient years. This was even higher in those patients who had the life vest for the explantation. The life vest is very effective. It's a very effective strategy for general patient population with above indications. It can save the implantation, as I said already, in more than twenty-five percent in the population in Dresden itself. We could observe even a reduction of the need of implantation of permanent ICD more than thirty-five percent due to the recovery of the ejection. This is a very important treatment, especially for those patients who have an acute illness.

 
 
The German cohort is the first large cohort outside the US healthcare system. It confirms the overall value of the life vest and treatment pathways in Germany. Also, the cohorts analysis uncovered over two hundred forty-two sustained but self-terminated episodes of VT among seventy life vest patients, so that you have safely not treated because they were still conscious and could still press the response button. We found out that some of the self terminated VT episodes were even longer than eight minutes in duration time. All in all, we could see that the life vest is a device which is safe and which can prohibit shocks, as well.

 
Carolyn:
Thanks, Nadine. [Ruth 14:12]

 
 
Mark, though, for the readers, I'm sure we need to put in perspective, as well, because there are still patients where perhaps an implantable cardio defibrillator is still more important. Could you share some thoughts about that?

 
Mark:
Yeah. I think this is a very interesting, important study, for a number of regards.

 
 
One, is that there was a very high rate of compliance with using the life vest. To leave it on for twenty-three hours a day, for a mean of sixty days, is really quite impressive patient compliance. The data showed that it did recognize and treat VF in a small percentage, but in a important percentage, of people. This data does need to be put in perspective and the randomized trial is currently ongoing. The vest trial, which will randomize people, probably similar population to what the German study did, and look at the life vest performs in that population.

 
 
We look forward to further data from the vest trial and from other trials, that are looking at what the place of the wearable defibrillator will be in the future.

 
Carolyn:
Thank you, Mark and that's perfect take home message for all us out there.

 
 
Thank you, once again, Nadine, Ruth, Mark. It has been wonderful chatting with you.

 
 
To all of you out there, you've been listening to Circulation on the Run.

 
 
Thank you for joining us.

 
 

 

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