Wearable Cardioverter Defibrillator Not Shown to Reduce Sudden Death Mortality

Jeffrey E. Olgin, MD

In the first randomized, controlled trial of a wearable cardioverter defibrillator (WCD), the device was unable to significantly reduce the risk of mortality due to sudden death in patients with acute myocardial infarction (MI) and ejection fraction (EF) at 35% or lower.

The VEST trial, presented by Jeffrey E. Olgin, MD, a cardiologist and electrophysiologist, co-director of the UCSF Heart and Vascular Center and the chief of Cardiology at the 67^th American College of Cardiology’s Scientific Sessions in Orlando, Florida, did, however, reveal an association between the WCD and a lower total mortality in the patient’s first 90 days post-MI, for those with left ventricular EF (LVEF) at ≤35%.

“Prescribing the WCD is reasonable to protect high-risk patients with a low LVEF post-MI until their evaluation for an implantable cardioverter defibrillator (ICD) at 40 to 90 days,” Olgin said.

The study, which randomized 2302 patients 2:1 to either the WCD and guideline-directed therapy or guideline-directed therapy alone, was limited in that the investigators, nor the participants, were blinded, as well as the crossover that occurred. In the control group (n = 778) 20 (2.6%) of the participants received a WCD—a protocol violation—while in the WCD group (n = 1524), 19% (n =289) did not utilize the device.

“This should show bias toward the null,” Olgin said, “but we still found a difference in total mortality.”

The all-cause mortality rate in the WCD group was 3.1% (n = 48) compared with 4.9% (n = 38) in the control group (P = .04). Most differences in cause-specific deaths were found not to be statistically significant, save for death due to stroke, which did not occur in any patients in the WCD group, but in 0.5% (n = 4) of the control group (P = .01).

While the composite outcome of the rate of sudden ventricular tachyarrhythmia death was revealed to be lower in the WCD group than the control group over the 90-day trial period, it was not statistically significant (P = .18). The originally planned primary outcome of sudden death was lower in the WCD group (1.6%; n = 25) than control group (2.4%; n = 19) but was also not found to be statistically significant (P = .18).

“There could possibly be a misclassification of sudden deaths, which reduced the trial’s power for the sudden death outcome, but not total mortality,” Olgin noted. “WCD may confer additional protection beyond sudden death, such as earlier care for bradycardia, non-sustained ventricular tachycardia, or aborted shocks.”

At least 1 appropriate shock was administered by the device to 13 patients (0.9%) and 2 or more were administered to 7 (0.5%) patients in the WCD group (P = .002). Inappropriate shocks were administered in 10 patients—1 shock in 8 (0.5%) patients, and 2 or more in 2 (0.1%) patients (P = .05). “In all, 14 of the 20 participants that received an appropriate shock survived to 90 days,” Olgin said.

The device sounded with an alarm prior to administering the shock, in which case patients could abort with the press of a button. There were 43 patients (2.8%) that aborted 1 shock, while 12 (0.8%) aborted 2 or more and 15 (1.0%) aborted more than 5 shocks (P <.001).

Overall, the WCD was received by 95.5% of the intervention group (n = 1455). The average hours the device was worn per day was found to be 14.1 ±9.3 in the WCD group compared to 0.8 ±3.9 when compared to the 20 patients in the control group that received the device (P <.001).

As expected, in pre-specified symptom measurements, the WCD group showed higher rates of rash in any location (15.2% vs. 7.1%; P <.0001), rash on torso (12.9% vs. 3.8%; P <.0001), itch in any location (17.2% vs. 6.4%; P <.0001) and itch on torso (14.5% vs. 3.1%; P <.0001).

“[The WCD] may, however, have reduced anxiety or increased medication compliance, as there was an observed higher rate of shortness of breath in the controls,” Olgin said. The WCD group experienced a 38.7% rate of shortness of breath compared to 45.4% in the control group (P = .0003).

During follow-up at month 1 and month 3, 5.7% (n = 44) of the patients in the control group received an ICD while 4.4% (n = 67) of the patients in the WCD group received one. The control group received ICD more quickly, with in a mean of 58 days post-randomization (range, 25—77) compared to 62 days (range, 24–81) in the WCD group.

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