AHA Issues Statement on Wearable Defibrillators, Cautions That Effectiveness Data Are Limited

The American Heart Association (AHA) has issued a new scientific statement on the use of wearable cardioverter-defibrillators for the prevention of sudden cardiac death, acknowledging such therapy may be “reasonable” or “considered” in certain clinical situations but cautioning that it has been studied in very limited populations and lacks solid evidence to date.  

Wearable cardioverter-defibrillators are being used increasingly in clinical practice, according to the AHA, but “only preliminary data exist on the actual effectiveness of this intervention in improving survival among patients who are at risk for sudden cardiac death.”

“Sudden cardiac death is a great concern for all of us,” Manesh Patel, MD (Duke University Medical Center, Durham, NC), one of the statement coauthors, told TCTMD. “Importantly, there are these data gaps in the use of implantable defibrillators in patients post-MI, post-CABG, postrevascularization, and other places, and even in certain conditions that haven’t been studied. People are always trying to figure out the best way to care for these patients.”

The wearable cardioverter defibrillator is a technology that holds “promise,” and physicians are increasingly wondering how it can or should be used in clinical practice, said Patel. Right now, though, the data supporting its use is based on expert opinion or limited cohort studies. “There is a need for more evidence,” he said. “There are many possible clinical indications in patients that would benefit, but there is a need for more clinical trial information, or even observational studies, to show us where those benefits lie.”  

Published March 28, 2016, in Circulation, the AHA statement is chaired by Jonathan Piccini, MD (Duke University Medical Center), and endorsed by the Heart Rhythm Society. It lists six different indications/recommendations for the therapy, including instances where use of the wearable defibrillator would be considered a reasonable treatment option.

These include situations in which there is a clear indication for an implantable cardioverter-defibrillator (ICD) but such treatment is temporarily stopped or contraindicated because of an infection (class IIa, level of evidence C). In addition, a wearable defibrillator is considered reasonable as a “bridge to more definitive therapy,” such as heart transplantation (class IIa, level of evidence C).

A wearable cardioverter defibrillator is also considered “reasonable” for patients who have an increased risk of sudden cardiac death that may resolve over time or with the treatment of left ventricular dysfunction (class IIb, level of evidence C). These include patients with ischemic heart disease undergoing coronary revascularization, those with newly diagnosed nonischemic dilated cardiomyopathy starting guideline-recommended medical therapy, or those with a secondary cardiomyopathy in which the underlying cause can be treated.

A wearable defibrillator might be considered an appropriate option as a bridging therapy in situations where an ICD has been shown to reduce sudden cardiac death but not improve overall survival, such as in the 40 days after an MI (class IIb, level of evidence C). Currently, the Centers for Medicare & Medicaid Services require a 90-day waiting period after coronary revascularization with CABG or PCI before the placement of an ICD for primary prevention. Although improved survival in the immediate post-CABG period has not been shown with an ICD, a wearable defibrillator might offer a “bridge of protection” in high-risk patients within 90 days of CABG or PCI, according to the AHA.

“This is one of the more common clinical scenarios,” said Patel. “After people have a heart attack, they have myocardial dysfunction that may improve. In an effort to demonstrate the value of an implantable [defibrillators], they were studied in patients some period after a heart attack so that there was an opportunity to get stable myocardial function. In that period where patients might have reversible myocardial dysfunction, there is a question as to whether things like a wearable would be beneficial, and who would they benefit? Certainly, that’s an area where more evidence is needed.”

The AHA says the wearable defibrillator should not be used in patients where the risk of nonarrhythmic events significantly exceeds the risk of arrhythmic events, particularly in patients not expected to live beyond six months.

The US Food and Drug Administration first approved the wearable cardioverter defibrillator in 2002 on the basis of the WEARIT/BIROAD study, small 289-patient study that included patients with heart failure and those awaiting an ICD for other indications.