VEST Evaluates Wearable Defibrillator for Patients After a Heart Attack

March 10, 2018—The Vest Prevention of Early Sudden Death Trial (VEST) findings were presented by Principal Investigator Jeffrey E. Olgin, MD, at the American College of Cardiology's (ACC) 67th annual scientific session held March 10–12 in Orlando, Florida.

VEST, the first multicenter randomized controlled trial of the wearable cardioverter defibrillator (WCD), demonstrated a reduction in the likelihood of dying during the first 90 days after a heart attack in patients whose heart function was impaired. Patients who wore the WCD during the study timeframe were 35% less likely to die for any reason compared with those who received medications alone. However, the study did not meet the primary endpoint of a significant benefit in terms of reducing sudden cardiac death.

The WCD (LifeVest, Zoll Medical Corporation, an Asahi Kasei Group Company) is a lightweight vest equipped with a cardioverter defibrillator that detects abnormal heart rhythms in addition to taking recommended medications. The device is worn under clothing, directly against the skin. It continuously monitors a patient's heart, sounding alarms and/or giving verbal commands to encourage people to seek medical care, if needed. If a life-threatening heart rhythm is detected, the device delivers a shock to restore a normal heart rhythm.

In the ACC announcement, Dr. Olgin commented, "It is possible that sudden deaths were misclassified as it's difficult to define sudden death with accuracy when a death is unwitnessed and there is little documentation. But the cause of death is irrelevant if we can prevent it. This study found that the device was associated with fewer deaths among people recovering from a heart attack with low ejection fraction. It's also the first therapy associated with a mortality benefit above and beyond standard medical therapy immediately after heart attack." Dr. Olgin, who is Professor and Chief of Cardiology, University of California San Francisco in San Francisco, California, is the study's lead author.

The VEST study was designed to test whether the WCD device could effectively reduce sudden death in patients who had recently experienced a heart attack and who had reduced heart function (defined as a low ejection fraction ≤ 35%).

Dr. Olgin noted that generally, the 3-month mortality rate is approximately 5% for patients recovering from a heart attack who also have reduced heart function, and that is with optimal medical management. Similarly, in VEST, 4.9% of participants in the control group died compared with only 3.2% of those wearing the WCD—an absolute difference of 1.7 %.

Dr. Olgin explained, "There is a very high risk of death immediately after a heart attack that tails off after about 3 months. The challenge is that we don't currently have a good way of preventing deaths during this very vulnerable period."

As outlined in the ACC announcement, the background of the study is that despite the high rate of sudden death in the months after a heart attack, implantable cardioverter defibrillators (ICDs) placed in the chest are not currently indicated for this patient population before 40-90 days, for several reasons. First, large studies have failed to show that implanting an ICD during this period results in long-term reductions in mortality. Second, in many cases, the patient's ejection fraction will improve in the ensuing months after a heart attack. For example, in VEST 60% of patients with low ejection fraction in the first 3 months after heart attack recovered and no longer met the criteria for an ICD at 90 days. Third, there is competing risk of death from other causes not preventable with a defibrillator (eg, another heart attack or cardiac rupture).

According to Olgin, the VEST findings suggest WCDs could fill the gap in cardiac therapy until patients can be evaluated for an ICD. Current guidelines recommend the WCD as a potential tool that practitioners can use, but the investigators believe this large randomized trial will add important data to further inform these guideline recommendations.

Dr. Olgin commented, "What's nice about the wearable defibrillator is that it's noninvasive and it's not permanent. Based on our results, I think we'll see more widespread use of this device in these patients."

As summarized in the ACC announcement, the trial enrolled 2,300 adult patients admitted to the hospital for heart attack with an ejection fraction of ≤ 35% across more than 100 trial sites in four countries. Upon discharge, patients were randomized 2:1 to either receive the WCD plus guideline-directed medical therapy or guideline-directed medical therapy alone for 90 days to determine the potential mortality benefit of the WCD.

Patients were advised and reminded to wear the WCD as much as possible and only take it off for bathing; participants who wore the WCD did so for an average of 21 hours a day.

The primary outcome was sudden death at 3 months and secondary outcomes were total and cause-specific mortality, nonfatal ventricular arrhythmias, and hospitalizations. Participants and sites were not blinded to the treatment arm, but they were blinded to any arrhythmia detections during the follow-up. Unblinding could be requested if a participant had a shock, cardiac arrest, or syncopal event. Outcomes were adjudicated by an independent, blinded panel.

The vast majority of patients in both groups (approximately 85%) received appropriate guideline-directed treatment for post–heart attack management, as well as heart failure management given patients' reduced ejection fraction. At the end of the study, the investigators searched the National Death Index for participants lost to follow-up. The rate of cardiovascular-related rehospitalizations was 25% and was similar in both groups.

Dr. Olgin advised that the study was originally designed with a primary outcome of total mortality. However, because of enrollment difficulties early in the study, the estimated sample size of 4,500 participants became infeasible. After the first 213 participants were enrolled in 2010, the primary outcome was changed to sudden death with a prespecified secondary outcome of total mortality.

The investigators are working on additional analyses from this study and plan on transitioning patients into a registry for longer-term follow up, noted the ACC press release.