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VEST: Wearable cardioverter defibrillator cuts total mortality, but not sudden death post-MI
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ORLANDO, Fla. — Use of a lightweight wearable vest equipped with a cardioverter defibrillator, in addition to guideline-directed medical therapy, reduced total mortality, but not sudden death mortality, compared with medical therapy alone in the first 90 days after MI in patients with reduced ejection fraction.
At 90 days, the rate of sudden death or death due to ventricular arrhythmias — the primary endpoint of the VEST trial — was 1.6% among patients in the wearable cardioverter defibrillator group vs. 2.4% among patients who received medical therapy only (P = .18). The rate of death from any cause — a secondary endpoint — was lower in the defibrillator group (3.2% vs. 4.9%; P = .04), with a relative risk reduction of 35.5% and an absolute risk reduction of 1.7% with the vest vs. medical therapy alone.
This is the first randomized controlled trial of the LifeVest Wearable Cardioverter Defibrillator (Zoll Medical).
“We did not find that the wearable cardioverter defibrillator statistically significantly reduced sudden death mortality, but it was associated with reduced total mortality,” Jeffrey Olgin, MD, professor and chief of cardiology at the University of California, San Francisco, said during the late-breaking clinical trial presentation. “Despite the negative result, based on the associated lower total mortality, it is reasonable to prescribe the wearable cardioverter defibrillator in patients who are post-MI with a low LVEF until evaluation for an ICD, which is recommended by guidelines to occur at 40 to 90 days.”
Post-MI comparison
The multicenter, randomized, open-label trial enrolled 2,302 patients (mean age, 61 years; mostly men) who had an acute MI and left ventricular ejection fraction of 35% or less within 7 days of hospital discharge. Patients were randomly assigned in a 2:1 fashion to the wearable cardioverter defibrillator in addition to guideline-directed medical therapy (n = 1,524) or guideline-directed medical therapy alone (n = 778). Enrollment occurred from 2008 to 2017 at 108 sites in the United States, Germany, Poland and Hungary. During the study period, the wearable cardioverter defibrillator was commercially available in the United States and Germany, but was only available through the study in Poland and Hungary.
Participants and sites were not blinded to treatment, but they were blinded to any arrhythmia detections during follow-up. Crossovers and ICDs were prohibited by study protocol, although ICDs were allowed for secondary prevention during the follow-up period.
The primary outcome was a composite of sudden cardiac death and death due to ventricular arrhythmias. Secondary outcomes included total mortality, cause-specific death and nonfatal outcomes, such as CV hospitalizations, wearable cardioverter defibrillator compliance and adverse events.
Initially, the primary outcome was total mortality. However, slower-than-expected enrollment made the preferred sample size of 4,500 unfeasible and the trial steering committee approved a change in the primary outcome, Olgin said.
The primary analysis was intention to treat, with participants of unknown vital status or indeterminate cause of death being treated as not having the primary outcome. A weighted sensitivity analysis was also performed by excluding these deaths from the denominator.
In other secondary endpoint findings, the rate of stroke death was higher among patients who received medical therapy only (0.5% vs. 0%; P = .01), but no significant differences emerged in rates of death from congestive HF, recurrent MI, and other or indeterminate causes.
Rehospitalization rates for CV causes or any cause were also comparable between the two groups, according to data presented.
Twenty participants in the wearable cardioverter defibrillator group received at least one appropriate shock. Of those, six died and 14 survived. Ten participants received inappropriate shocks, and 70 participants aborted shocks by pressing the response button on the vest.
There were no differences in prespecified symptoms associated with the treatment, but, as expected, more participants in the wearable cardioverter defibrillator group, as compared with the control group, reported rashes or itching, Olgin said. However, the proportion of participants who reported shortness of breath was higher in the control group (45.4% vs. 38.7%; P = .003).
Notably, 20 participants in the control group crossed over to the wearable cardioverter defibrillator group, which was against protocol.
Additionally, 19% of participants assigned to the wearable cardioverter defibrillator group did not wear the vest. Those who did wore the vest for an average of 22 hours per day, and the researchers observed a decrease in time spent wearing the vest over 90 days.
During a discussion of the findings, Olgin told Cardiology Today that one potential reason for the discrepant findings in terms of mortality may be related to misclassification of deaths.
“It’s difficult to adjudicate sudden death in these participants with minimal documentation or if the deaths are not witnessed. In the way our analysis was designed, the protocol was that we dropped anyone with death from an indeterminate cause from the analysis of the primary outcome but not from the total mortality,” he said.
“Because we had, by design, few outcomes, any misclassification or dropping of participants from the primary outcome reduces our power to see a difference. Although the Kaplan-Meier curves for sudden death are in the right direction, they didn’t reach statistical significance, largely because we did not have the power to detect a difference due to misclassification of sudden death,” Olgin added.
Implications and future study
Although the VEST trial did not meet its primary endpoint, the results indicate that the wearable cardioverter defibrillator still has benefit for patients in the early post-MI period, Olgin said.
At present, further analyses are planned, he noted.
“The priority right now is going to be to look at the effects of the intervention in people who actually wore the vest. We’re also going to have to do a deep dive into all of the deaths and, in the wearable cardioverter defibrillator arm, figure out how many deaths occurred in people who were wearing the vest vs. not wearing the vest,” Olgin told Cardiology Today. – by Melissa Foster
Reference:
Olgin JE. Joint ACC/JACC Late-Breaking Clinical Trials. Presented at: American College of Cardiology Scientific Session; March 10-12, 2018; Orlando, Fla.
Disclosures: The study was partially funded by the Zoll Medical Corporation. Olgin reports he has received consultant fees/honoraria from VivaLink.
Perspective
Back to TopDhanunjaya Lakkireddy, MD, FACC
This is a very important study because it highlights the concept of the risk for death in the post-MI period. So, the fundamental question is whether the wearable cardioverter defibrillator really made a difference, and the study partially answered this question.
The authors should be congratulated on such an arduous process because any time findings may be affected by patient compliance, our ability to evaluate efficacy decreases significantly. As is highlighted in the study, 19% of people assigned to the wearable cardioverter defibrillator group did not wear it, which could have contributed to the diminished value, as pertains to sudden cardiac death events in these patients. That is something for us to reckon with. Subgroup analyses will also be important to see which patients actually have the best chance of benefiting from the device. The WCD should not be used indiscriminately in everyone with low EF and recent MI. Because this study clearly showed that it is not going to be of much value from sudden cardiac death prevention.
Can we write off the external defibrillator completely? I don’t think so. What we need is a study with a higher level of compliance and identify higher risk groups that are more vulnerable for sudden death and see if a WCD helps to save lives.
Perspective
Back to Top
B. Hadley Wilson, MD, FACC
The most important takeaway from VEST is that total mortality was reduced with the wearable cardioverter defibrillator device. However, the disappointment is that, in the actual group of patients whom the researchers hoped would benefit the most — those with sudden cardiac death — there was no change.
Interestingly, when the audience was polled after the presentation, there was no change in their response to how they would conduct their practice in terms of using these wearable cardioverter defibrillators post-MI. It’s a class IIa recommendation to use the device, but most practicing health care providers in this area are not going to prescribe it for everyone and instead target the higher-risk population. I would say that the investigators may have wondered if the outcomes would be that all post-MI patients should have these wearable cardioverter defibrillators, and the study clearly shows that is not the case.
Looking ahead, every study begets other studies that we learn from. It helps us know the best way to treat patients and affects guidelines. Therefore, after the post-hoc analyses are conducted, we can see if there are certain subgroups who might benefit more from these wearable cardioverter defibrillators. Additionally, the researchers had a significant problem with enrollment and had to make some changes to the study. Consequently, we may have had an unfair result in that the higher-risk patients were actually not included in the study. If we could target the highest-risk patients first rather than a broad group of post-MI patients, then maybe we will see the true benefit of these wearable defibrillators post-MI.
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