JACC: 'Wearable' ICDs prevent sudden death
Although compliance is slightly more than 50 perecent, patients who wear the cardioverter-defibrillator vest have a high survival rate, similar to that of ICD patients, according to a study in the July 13 edition of the Journal of the American College of Cardiology.

Effectiveness of the wearable cardioverter-defibrillator for prevention of sudden death is dependent on event type, patient compliance and appropriate management of ventricular tachycardia/ventricular fibrillation (VT/VF).

Mina K. Chung, MD, and colleagues from the Cleveland Clinic sought to determine patient compliance and effectiveness of antiarrhythmic treatment of those wearing the device.

Of more than 3,500 patients evaluated, daily use of the wearable cardioverter-defibrillator was nearly 20 hours per day in 52 percent of the patients over a span of an average of 52 days. Researchers found that the more days patients wore the wearable cardioverter-defibrillator, the higher the daily use.

Eighty sustained VT/VF events occurred in 59 patients (1.7 percent). First-shock success was 76 of 76 for unconscious VT/VF and 79 of 80 for all VT/VF.

Eight patients died after successful conversion of unconscious VT/VF. Asystole occurred in 23 patients (17 of whom died), pulseless electrical activity in two and respiratory arrest in one, representing 24 percent of sudden cardiac arrests.

During wearable cardioverter-defibrillator use, 3,541 of 3,569 patients survived overall. Survival occurred in 72 of 80 VT/VF events and 78 of 106 for all events. Long-term mortality was not significantly different from first ICD implant patients but highest among patients with traditional ICD indications.

Researchers concluded that compliance was satisfactory with 90 percent wear time in more than 50 percent of patients and low sudden death mortality during use. However, asystole was an important cause of mortality in sudden cardiac arrest events.

"There are few reported data on actual arrhythmic causes of sudden cardiac death. This study documented that asystole or pulseless electrical activity accounted for 24 percent of sudden cardiac arrest events with high associated mortality rates," they wrote.

"These data indicate the need to incorporate pacing therapies into future wearable cardioverter-defibrillator systems, although it is unclear whether pacing would prevent deaths in these patients," they concluded.