A new study finds that a wearable cardioverter defibrillator can prevent sudden death in people with dangerous arrhythmias, helping them survive to hospital discharge.

Researchers at the University of Pittsburgh School of Medicine (PA, USA) gathered heart rhythm records and calls about shocks from a registry of 14,475 patients with wearable defibrillators listed from 2007 through 2009. Of those, 185 (1%) received an appropriate shock, and 91.6% survived one or more episodes of ventricular fibrillation or ventricular tachycardia (VT), the most common abnormal rhythms during cardiac arrest.

Wearable defibrillators also delivered 223 inappropriate shocks to 213 people who were not experiencing ventricular fibrillation or VT; however, no one died as a result. The researchers attributed the inappropriate shocks to signal noise, rapid non-VT rhythms, and rhythm misinterpretation. The study was presented at the American Heart Association (AHA) Scientific Sessions 2011, held during November 2011 in Orlando (FL, USA).

“These defibrillators provide patients the critical advantage of not having to wait for a bystander or emergency responder to recognize the cardiac arrest and use an automated external defibrillator or manual defibrillator, both of which can lead to delays in treatment and markedly worse survival rates,” said lead author Vincent Mosesso Jr., MD, a professor of emergency medicine. “In these patients, the wearable defibrillator is a noninvasive 'insurance policy' against sudden arrest during their vulnerable period.”

Wearable defibrillators are used by people who may be at higher risk for sudden cardiac arrest, including those with weakened heart function, those awaiting cardiac transplant, or those with a condition that prevents or delays them from receiving an implanted defibrillator (ICD). About 5,000 patients in the United States are using wearable defibrillators at any one time, usually for about 60 days. The device monitors heart rhythm, emits alarms if a serious arrhythmia occurs, delivers an electric shock to the heart if needed, and alerts bystanders to help if the heart's electrical activity has stopped.

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