New research in the Journal of the American College of Cardiology showed that survival rates with a wearable cardioverter-defibrillator (WCD) vest were comparable to that of an implantable cardioverter defibrillator (ICD).[1] In this interview we learn more about the study from lead author Mina K. Chung, MD from the Cleveland Clinic.

What was the purpose of this study? What prompted this study?
The reason we wanted to look at this was to see if the WCD really worked. Unlike implantable ICDs that don't require patient input to function, the WCD requires a patient to actually wear the vest for it to work. We were also interested in looking at how effective it was for terminating arrhythmias, and whether it could be as effective as an implantable ICD, since we use it for patients we consider at potential high risk for sudden death.

How many patients participated in the study? Which type of wearable cardioverter-defibrillator was utilized?
A total of 3,569 patients were included in the registry. The WCD used in the study was the LifeVest (ZOLL Lifecor, Pittsburgh, PA).

Tell us about the nationwide registry of post-market release WCDs.
All patients issued a WCD after market release in the U.S. are entered into a database maintained by ZOLL Cardiac Management Solutions for regulatory, reimbursement, and tracking purposes. The database contains indications, baseline demographics (age and gender), compliance, and events.[1] All patients signed consent to use their data for quality monitoring, health care operation activities, and/or research.[1]

Describe the patients' willingness to wear the device and percentage of patient compliance. How often did patients wear the WCD on average?
In terms of compliance, one reassuring finding of the study was that we showed that the WCD was worn with good compliance by most patients. Patients did wear the vest. Daily use was >90% in over half of patients. Mean daily use was about 20 hours.

Compliance was defined as the time during a day that a WCD user had the device on, the belt connected, and at least one electrocardiogram lead contacting the skin.[1]

Tell us about the results.
The WCD proved to be quite effective in terminating life-threatening cardiac arrest due to ventricular tachycardia or fibrillation, with first shock success in 99% of these events and an overall survival of 99.2% over the duration of its use. Survival was similar to that of patients with implantable defibrillators. We did also see that not all cardiac arrests were due to arrhythmias that could be saved by a shock. Asystole (no heart rhythm) or pulseless electrical activity accounted for a quarter of sudden cardiac arrests and had very high mortality rates. The current WCD does not have pacing capabilities, but future forms will likely incorporate the ability to pace and treat life-threatening slow heart rates as well.