The Past, Present, Future, and Obvious: Standout Posters on Day 1 of HRS 2017

John Mandrola, MD


May 10, 2017

Heart Rhythm Society meeting organizers usually begin the scientific part of the sessions with a "featured" poster session on the evening of the first day.

This year, at the Heart Rhythm Society (HRS) 2017 Scientific Sessions, I found seven posters that stood out in six somewhat-contrived categories.

Futuristic Category

Pacers without onboard batteries. One of many problems with wireless pacemakers is the need for an onboard battery. (Another issue is dyssynchronous pacing—but that's a topic for a different column.) The onboard battery makes the device larger and limits placement to certain geographies (eg, RV septum).

Researchers from Houston Texas demonstrated feasibility of a micropacemaker that receives RF signals with an antenna and converts the signal from AC to DC power. The end result was epicardial capture in an ovine model without the need for an onboard battery. This technology is coming soon.

Dogma-Smashing Category

MRI safety in patients with cardiac devices. Two posters share this category. Both demonstrate safety of MRI scans in patients with abandoned leads.

The concern here is that the abandoned lead can act as an antenna for energy that may result in tissue heating and induction of arrhythmia. The first study included 57 patients with 63 abandoned leads who underwent 70 MRI exams (1.5 T). About half the patients had troponin levels measured before and after the scan. The Mayo-Clinic–led authors observed no clinical problems, no CIED malfunction, and no significant troponin rises. Of course, all these scans were done with careful monitoring and under an institutional protocol.

University of Pennsylvania researchers reported similar results in a series of 24 patients who underwent 34 MRI exams with a mean number of 1.45 abandoned leads. Most of these exams were of the brain, but five patients had cardiac MRI. (Pause there for a moment: abandoned leads and cardiac MRI.) The researchers observed no acute adverse effects on the device; no patient reported discomfort, and of 16 patients who had long-term device data available, no device issues were noted.

HRS will release a consensus document at this meeting on MRI scans in patients with cardiac devices. I was one of the authors. One of my assignments was the evidence review for nonconditional devices. I found a literature replete with studies like these two. After reviewing the published data, I can conclude that if we define "safe" in reasonable terms, essentially all cardiac devices are MRI-safe if done with careful monitoring and under the guise of institutional protocol.

Parsimonious-Care Category

Cost-effectiveness of VT ablation. The main results of VANISH,[1] a multicenter randomized controlled trial comparing ablation vs escalation of therapy in patients with ischemic cardiomyopathy and monomorphic VT, slightly favored ablation.

At the HRS 2017 meeting, VANISH authors reported a cost-efficiency analysis that found ablation was cost-effective compared with escalation of drug therapy for patients with VT despite amiodarone at baseline but not for those with VT despite taking another antiarrhythmic drug.

This is an important point, because the difference in the composite primary outcome in the main trial was less than 10%, barely meeting statistical difference (P=0.04). There were no mortality differences. Also, the subgroup analysis in the main trial showed clear superiority of ablation in the group of patients with VT on amiodarone vs the group with VT on another drug. (P<0.01).

These data argue for consideration of a trial of amiodarone before ablation if the patient is not on amiodarone when presenting with VT. The recurrence rate of VT on drug therapy was 33%, higher than that for ablation at 24%. But this means two-thirds of patients treated with drugs did not have a recurrence.

I am not against VT ablation; I do VT ablation. But I have seen VT ablation extended to patients who have not been offered drug therapy in a fair and balanced way. Increasingly, patients with VT have multiple comorbidities, which increase the risk of the procedure. (Some day I will write a column explaining that amiodarone toxicity concerns—especially in older patients with VT—are overblown.)

Help-for-a-Tough-Condition Category

Inappropriate sinus tachycardia (IST).[2] IST is a vexing problem, affecting young women in the prime of their life. Beta-blockers work some of the time, but many patients do not tolerate the drugs. Ablation of the sinus node is fraught with problems—inefficacy, phrenic-nerve injury, and need for pacemaker. I can almost use the modifier always before the phrase avoid IST ablation in a young woman.

A group of Polish and German researchers tested the value of structured exercise in patients with IST who were taking beta-blocker.

This was a randomized comparison of 26 patients. After 6 months, the authors reported that patients in the formal exercise group had statistically significant lowering of resting rate, lower average heart rates on 24-hour monitors, and improved exercise capacity. Patients in the exercise group also reported significant and stable improvement in their own perception of exercise tolerance as well as in total quality of life.

Imagine the benefits to humankind if trials with exercise were encouraged. I could envision this sort of study for many diseases and conditions. Also, don't knock the authors for the small numbers. IST is not rare, but it's not common either.

See-the-Patient-Not-the-Ejection-Fraction Category

Diabetes and the ICD. It took more than a decade, but cardiologists seem to be showing interest in honing the use of the primary-prevention ICD. All practicing doctors know this: we don't put ICDs in the "average" patient enrolled in randomized clinical trials; rather, our patients have unique characteristics that may either increase or decrease their odds of gaining a net benefit from an ICD.

The DANISH trial, for instance, showed that benefit of ICDs in nonischemic patients may turn on age.[3] The concept of heterogeneous treatment effects[4] of the ICD need more study.

That's why I was drawn to a meta-analysis that asked whether or not diabetes affects ICD efficacy. The study included over 2300 patients with heart failure from four major randomized controlled trials. Compared with medical therapy alone, the ICD reduced the risk of all-cause death among patients without diabetes (hazard ratio [HR] 0.56, 95% CI 0.46–0.67); however, in patients with diabetes, ICDs did not significantly reduce the risk of all-cause mortality (HR 0.88, 95% CI 0.7–1.12; P interaction between ICD and diabetes 0.015).
 The Kaplan Meier curves show a compelling picture.

Similar studies have been done, but mostly ignored. One of my favorites is from Fishbein et al,[5] who showed ICD benefit in the SCD-HeFT[6] trial was greatest in patients with good walking ability. Like the patients with diabetes in this HRS poster, poor walkers garnered no mortality advantage from the ICD.

The point here is not to exclude patients but rather to think about the way the ICD may help or harm the patient who sits before us in the exam room.

Jumping-to-Conclusion Category

Apple Watch ECG. The award for jumping to conclusions on this first day of the HRS meeting goes to the group from University of Oklahoma. They reported the first validation of an Apple Watch ECG event recorder. This group showed that a lead 1 recording from a watch matched readings from regular limb leads in 23 volunteers and 18 patients. This a nice finding.

But then they concluded "a watch-based event recorder is likely more cost-effective than an implantable loop recorder; however further studies are needed. This technology has the potential to create a paradigm shift in arrhythmia monitoring."

I like the AliveCor device. Recording a symptomatic rhythm is often helpful. Once. Twice, maybe. Then, after you know a patient has SVT or AF, I'm not convinced the information is that valuable.

We don't understand the importance of short-lived AF episodes as a surrogate marker for stroke. And we surely don't know whether or not anticoagulation will improve outcomes in these patients. That's why it's a leap of faith to conclude this technology may be cost-effective or paradigm-changing.

And . . . at the risk of sounding old-fashioned, can you allow me to worry a little about the rush to connect our bodies to devices? One need not cite Thoreau to understand the concept that incessantly looking at devices may cause us to miss both the forest and the trees.


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