The Food and Drug Administration yesterday issued an update for health care providers treating patients at risk for sudden cardiac arrest using a Zoll LifeVest 4000 wearable cardioverter defibrillator. In January, FDA alerted patients and providers that the device may fail to deliver a life-saving shock if not replaced soon after displaying a particular “call for service” message code. The update provides additional information regarding the manufacturer’s efforts to remedy the potential hazard as well as recommendations for providers.