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Wearable defibrillator study disappoints cardiac specialists

Doctors hoped device would prevent sudden death in heart attack patients

Dr. Michael Field
Dr. Michael Field specializes in diagnosing and treating electrical abnormalities of the heart. Photo by Son Nguyen
Mikie Hayes | | Sept. 27, 2018

Cardiac electrophysiologist Michael Field, associate professor of medicine at the Medical University of South Carolina, often wondered as a medical student what it would be like to have his ideas published in the New England Journal of Medicine. He no longer need wonder. The premier medical journal will publish an editorial he wrote on the outcome of an important cardiac study in the Sept. 27 issue. 

Field’s editorial, titled “Another Shock for Sudden Death Prevention after Myocardial Infarction,” accompanied a long-awaited trial known as the Vest Prevention of Early Sudden Death Trial or VEST.

VEST is the first randomized, controlled trial to assess whether the wearable cardioverter-defibrillator could reduce sudden death in patients who had recently suffered a heart attack and had reduced heart function. The wearable defibrillator, made by Zoll, has been available in the U.S. since 2001. It is a removable vest that when worn by an at-risk patient provides continuous rhythm monitoring and, if needed, rapid external defibrillation for rapid fatal heart rhythms known as ventricular fibrillation and ventricular tachycardia. The device is primarily used in clinical situations where a patient is perceived to be at high risk of sudden death but does not meet guideline indications for permanent implantable cardioverter-defibrillator (ICD) placement.  

The authors of VEST selected patients who suffered a recent heart attack and had reduced heart function. They were randomized to wearable cardioverter-defibrillator plus medication or just medications alone. In the final analysis, the trial didn’t produce the results many in the field anticipated. The primary study endpoint, reduction in sudden arrhythmic death, was inconclusive and failed to show the use of the wearable cardioverter-defibrillator significantly reduced sudden death in the first 90 days after a heart attack when added to standard medications. Many predicted the wearable cardioverter-defibrillator would reduce sudden death after heart attack in this population. This optimism made the ultimate findings of this study that much more surprising and disappointing.

Why is this important?

Field explained that sudden cardiac death is a serious complication of a heart attack that poses the greatest risk during the month following the event and especially for people with impaired heart function. But two earlier randomized trials showed no survival benefit when an ICD was implanted early after a heart attack in a similar population, resulting in guidelines that recommend waiting at least 40 days after a heart attack and 90 days after coronary revascularization to implant an ICD for primary prevention. This seemingly untenable paradox left patients with little way to prevent sudden death in this setting.

So the VEST investigators asked whether the wearable cardioverter defibrillator, a non-invasive approach, would be effective in the population where early ICD implantation fell short.

Field said earlier observational studies showed the wearable cardioverter-defibrillator was highly effective at stopping sustained ventricular tachyarrhythmias. If a patient experiences a life-threatening abnormal heart rhythm, the defibrillator’s alarm sounds, and it then delivers a shock to the heart to restore a normal heart rhythm. 

Field said the VEST study was incredibly important and ambitious and congratulated the authors for their tireless efforts to make it happen. 

Image of the wearable vest with defibrillator

The LifeVest is a lightweight vest worn under the clothing and is attached to a monitor worn in a holster at the waist. Photo provided

“We are sometimes faced with results that don’t fit our intuition or what we anticipate,” he said. “This study overall did not show a benefit in this population. So we have to move forward and reconcile, understanding that studies like this are time-consuming and expensive and likely will never be able to be repeated. Was this a study that failed to show a benefit because the therapy doesn’t work, or was there a flaw in the study design, such as poor enrollment or adherence to the treatment or lower than expected event rates?” 

Field is not giving up hope. “Efforts like these to identify ways to prevent sudden death are incredibly important, because the sudden and unexpected death of a loved one is a tragedy,” he said. 

“There has been a lot of anticipation for this trial to come out. We were eagerly awaiting the results. Ultimately, this is a population that when we take care of them in the hospital after their heart attack, we worry about them. There has been a lot of uncertainty about who’s the best candidate for this device. I wrote the editorial because I wanted to draw attention to the fact that this is an important population, and despite our best efforts in medicine to identify interventions that work, we can fall short but must not give up.”

So will Field continue to use the device for his patients? He wouldn’t rule it out in select patients. 

“The results speak to the fact there is reason to have an in-depth discussion with patients. No, I won’t uniformly use this device. It’s expensive. It can be problematic. The device is associated with frequent false alarms and inappropriate shocks that can lead to a great deal of stress and anxiety. Furthermore, the device is costly. Patients have to understand all this before it is prescribed. Also, since the evidence for benefit is less clear, we have to involve patients in the discussion. For a particularly well-informed and motivated patient, the wearable cardioverted-defibrillator may still be reasonable.”

Field also said there is a lot of fear associated with the subject of sudden death. He points out that many people misunderstand what cardiac arrest is and wants the public to be better educated about it. 

“People think cardiac arrest is the same thing as a heart attack and often use the terms interchangeably. A cardiac arrest occurs when the heart stops beating unexpectedly due to a dangerous rhythm disturbance, while a heart attack occurs when blood flow to the heart muscle itself is blocked and a portion of the heart muscle is damaged,” he explained.

While sometimes a heart attack can cause a cardiac arrest, he added, many cardiac arrests occur in patients without coronary blockages and can happen at a young age, on the athletic field, in the home or in public places. 

“It’s very important for people to be aware of this and know how to initiate CPR and use an automatic external defibrillator, or AED, and know what the steps are. There have been tragic examples where young athletes collapse, and people don’t know what to do. Time is of the essence. Bystanders need to recognize quickly that a cardiac arrest has occurred, and they should immediately call 911 and begin CPR, including using an AED if available. This is a public health concern and public education would go a long way.”

For more information about CPR, visit the American Heart Association.



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