Incidence of appropriate shock in implantable cardioverter-defibrillator patients with improved ejection fraction

Background: Heart failure with recovered ejection fraction (EF) is a recently described clinical entity. There is insufficient information on the management of implantable-cardioverter defibrillator (ICD) patients with improved EF at generator replacement. Methods and Results: We examined the incidence of appropriate shocks in 91 consecutive patients with ICDs for primary prevention of sudden death who underwent generator replacement. Improved EF was defined as both EF >35% at generator replacement and increase in EF by ≥10% since original implantation. Patients were 70 ± 11 years old, and 76% had ischemic cardiomyopathy. At generator replacement, 25 patients (27%) had improved EF (0.49 ± 0.08 vs 0.31 ± 0.07 at baseline; P <.0001). Over 6.2 ± 2.2 years of follow-up after original implantation, 9 patients (36%) with improved EF versus 19 (29%) with unchanged EF had appropriate ICD shocks (P =.51). Incidence of appropriate ICD shocks was similar between the two groups before (P =.90) and after (P =.97) generator replacement. Of the 9 improved EF patients with appropriate shock, 4 had shocks before generator replacement, 2 had shocks before and after generator replacement, and 3 patients, who never had shocks before, had their first shock after generator replacement. Conclusions: Some ICD patients whose EF improves to >35% at generator replacement remain at risk for appropriate ICD shocks.