What to do about primary-prevention implantable cardiac defibrillators in patients with improved ejection fraction

Approximately 20-40% of heart failure patients with reduced ejection fraction (EF) demonstrate substantial improvements in their EF during follow-up. A subset of these patients who had originally received implantable cardioverter defibrillators (ICD) for the primary prevention of sudden cardiac death (i.e., patients with EF < 35%) pose a challenge to cardiologists when they present with improvements in EF to above 35% at the time of their battery depletion. Little is known about the risk of sudden cardiac death in these patients. Is the risk high enough to warrant the replacement of the ICD generator? In the following article, we review the available data on the risk of sudden cardiac death in these patients, and aim to assist the clinician and the patient in making informed decisions about whether the ICD therapy should be continued.