Device participants were fitted, trained and instructed to wear it continuously except while bathing. The WCD group wore the device an average of 14.1 hours daily over the study period, starting at 18 hours and decreasing to 12 hours by day 90, at which point only half of the WCD patients still chose to wear the device.

The study found no statistical difference in sudden cardiac deaths or rehospitalization between the two groups, in part due to the lower-than-expected wear time, said Olgin, the Gallo-Chatterjee Distinguished Professor of Medicine at UCSF. However, death rates dropped significantly during times the WCD was worn compared to times it was not. The study found a 35.5 percent lower risk of overall mortality in the WCD group, at 3.1 percent versus 4.9 percent in the control group.


Twenty (1.3 percent) of the device participants experienced at least one appropriate shock during the study, while nine (0.6 percent) received an inappropriate shock. About 70 percent of participants who had an appropriate shock survived to 90 days. Of the 48 participants who died, only 12 were wearing the WCD at time of death.

"Although this study result is subject to confounding, it suggests a benefit to wearing the device and implies that low adherence to wearing it may be a limiting factor in the potential benefit of a wearable cardioverter-defibrillator," said Mark J. Pletcher, MD, MPH, a UCSF professor of epidemiology and biostatistics who leads the VEST Data Coordinating Center.

The researchers are exploring new analyses for estimating the true causal effect of wearing the WCD, Pletcher said.


Co-Authors: Eric Vittinghoff, PhD, Trisha Hue, PhD, MPH, Carol Maguire, RN, Feng Lin, MS, Joel Simon, MD, MPH, and Stephen Hulley MD, MPH, from UCSF. Additional co-authors include researchers from the Medical University of Lodz, Poland; McLeod Regional Medical Center, Florence, S.C.; Ochsner Medical Center and Clinical School, New Orleans; Hartford Healthcare and University of Connecticut; Beth Israel Deaconess Medical Center and Harvard Medical School; University of Kentucky and Veterans Affairs Medical Center Lexington; University of Michigan; Stony Brook Medicine; University Medical Center Mannheim and German Center for Cardiovascular Research, Germany; and other VEST investigators.

Funding: The work was supported by the NIH (U01HL089458, U01HL089145) and Zoll Medical, which manufactures the LifeVest WCD used in the study. Zoll had no role in trial design, trial center selection or supervision, data analysis or interpretation, manuscript preparation, or decision to submit the manuscript for publication, but did participate in site monitoring.

Disclosures: Olgin received consulting fees from Novartis. Additional researchers' disclosures, including funding from Zoll Medical, Biotronik, Medtronic, Boston Scientific, Biosense Webster, AliveCor, Pfizer and Bristol-Myers Squibb, can be found in the NEJM paper.

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