San Francisco Chronicle - (Sunday)
Defibrillator vests do save lives — but only if worn
UCSF study tracks use of device after heart attacks
A removable vest that delivers an electric shock when it detects a dangerously irregular heartbeat can be lifesaving for people who already have suffered a major heart attack — but a new study led by UCSF researchers found that, perhaps not surprisingly, it only works when patients wear it.
The study published last week in the New England Journal of Medicine found no statistically significant difference in the rate of death from abnormal heart rhythm, or arrhythmia, between patients who were given the wearable defibrillator device and those who were not.
But people prescribed the vests had a 35
percent lower rate of death from any cause compared to those who were not given the vest. And when scientists compared people who actually wore the device to those who did not, they found a 75 percent reduction in the death rate.
“If you are trying to apply this clinical trial result across the board — where you say any patient should be given a wearable defibrillator — I think that’s an overreach,” said Dr. Jeffrey Olgin, chief of the Division of Cardiology at UCSF and lead author of the new paper. “But if you have a patient who is likely to wear it, and if they do wear it, they are very likely to receive benefit and have reduced mortality.”
The study results had been highly anticipated by cardiologists who say the need is great for a way to prevent deaths among people who cannot get a battery-powered defibrillator surgically implanted in their chest. Earlier studies had produced mixed results on whether the vests would work — and the new study, frustratingly, doesn’t quite answer that question.
But the results hint at enough potential benefit that doctors should keep the vests in consideration when talking to patients who have just had a major heart attack and may need a defibrillator.
“In the context of a particularly motivated patient who is at high risk, we would still offer the wearable cardioverter-defibrillator,” wrote two physicians in a commentary in the New England Journal of Medicine that accompanied the paper.
Dr. Nora Goldschlager, a UCSF cardiologist who works out of San Francisco General Hospital, said the study results support use of the vests, but only among patients who are clearly interested in wearing them. And even with those patients, she’d be sure to tell them that the vests do not reduce the risk of sudden death to zero.
The UCSF-led study looked at 2,300 men and women who had suffered a serious heart attack that impacted their heart’s ability to pump blood. Patients with that kind of heart failure are very susceptible to sudden death from an irregular heart rhythm. They often will have pacemakers implanted in their chests to shock their hearts back into a normal rhythm as needed.
But for reasons that aren’t entirely clear, patients don’t do well if they get a pacemaker immediately after the heart attack. So they generally wait up to three months to get the implant, leaving them vulnerable for that time.
The external defibrillator — called a LifeVest, and made by Zoll Medical Corp. — can be worn around the clock, except when the patient is bathing. It’s a snug-fitting cotton vest with two pads, over the back and side, that deliver a shock, plus a system for monitoring the patient’s heart rhythm. When a patient’s heart goes into an abnormal rhythm, the vest emits an alarm, and if the wearer doesn’t turn off the alarm within a minute he or she is shocked.
In the study, twothirds of participants were given the LifeVest to wear during the window between their heart attack and surgery to get a pacemaker implanted. The remaining participants did not get a LifeVest. The participants were signed up between July 2008 and April 2017, and each person was followed for three months.
In the LifeVest group, 43 people never wore the device at all. And use dropped dramatically over time: More than 80 percent of the group was wearing the vest at least a few hours a day at the start of the trial, compared to just 41 percent by the end.
But notably, people who wore the vest tended to wear it around the clock — on average, more than 20 hours a day.
Although 48 of 86 people who died during the study had been given a LifeVest, only 12 were actually wearing it when they died, including nine people who suffered a fatal arrhythmia. Twenty people in the LifeVest group were given a shock at least once for a detected abnormal heartbeat, and 14 of them survived the arrhythmia.
Those are encouraging numbers — the vest seems to have worked for most people wearing it, Olgin said. But part of the reason the study didn’t show an advantage for patients given the LifeVest is that the numbers are too small. The scientists needed more people in the study — and more people actually wearing the vests — to reach statistical significance one way or the other, Olgin said.
In the meantime, he’s working on a follow-up study looking at reasons people may not wear the vests. Anecdotally, some people find them uncomfortable. Others have told Olgin that worrying about an accidental shock makes them anxious; in the study, nine people were shocked when they didn’t need to be. And patients sometimes reported their vests emitting alarms when they felt fine — another potential source of stress.
William Ochmann Sr., 60, was not part of the recent study, but he has worn the LifeVest. This month, he needed to have his implanted pacemaker removed due to an infection. His surgeons in Hawaii, where he lives, couldn’t remove all of the old pacemaker parts, so they sent him to UCSF to complete the procedure.
Between travel to and from airports and flight times, that meant almost a full day without a pacemaker, so doctors outfitted him with a vest.
“At first, I had a lot of anxiety wearing that thing. I didn’t want it to go off prematurely,” Ochmann said. “It made me feel like I had a bomb strapped to my chest.”
He also wasn’t convinced he needed it. He felt fine. Surely he’d be OK for a few hours.
“But after talking to the doctor, he said, ‘You never know.’ They assured me it was there to save my life,” Ochmann said. He got his new pacemaker implanted two weeks ago and was hoping to be back home in Hawaii this week.
The UCSF study received funding from the National Institutes of Health and Zoll, the company that makes the vests. Zoll was not involved in the study design or supervision, or in analyzing the results.
Erin Allday is a San Francisco Chronicle staff writer. Email: eallday@ sfchronicle.com