Normalization of Left Ventricular Ejection Fraction and Incidence of Appropriate Antitachycardia Therapy in Patients With Implantable Cardioverter Defibrillator for Primary Prevention of Sudden Death

• Fifty-five (44%) of the 125 patients who received ICDs or CRT-Ds for primary prevention of sudden death and never received appropriate antitachycardia therapy had partially improved (36%–49%) or normalized (≥50%) LVEF at the time of generator replacement.
• During an overall follow-up of 25 ± 18 months after replacement, none of the 30 patients with normalized LVEF experienced a major ventricular tachyarrhythmic event, whereas 20% of the patients with partially improved LVEF required appropriate antitachycardia therapy.
• Although generator replacement is necessary in patients with partially improved LVEF, these data suggest that patients whose LVEF normalizes over time may be at a lower risk for appropriate antitachycardia therapy.

BackgroundPatients with severely depressed left ventricular ejection fractions (LVEFs) receive implantable cardioverter-defibrillators (ICDs) for the primary prevention of sudden death. In some patients, however, LVEF may improve or even normalize over time. Limited data are available on the incidence of appropriate antitachycardia therapy, including pacing and shock, in these patients.Methods and ResultsWe retrospectively identified consecutive patients at our institution with an ICD for primary prevention who had LVEF measurement available at initial implantation and at the time of generator replacement. None of these patients had ever received appropriate antitachycardia therapy before generator replacement. The incidence of appropriate antitachycardia therapy after generator replacement was assessed. Of the 125 patients who received generator replacement, 53 (42%) received an ICD and 72 (58%) a cardiac resynchronization therapy–defibrillator (CRT-D). Among them, 30 (21%) had LVEF normalized to ≥50%, 25 (17%) had LVEF partially improved to 36%–49%, and 70 (63%) had LVEF that remained depressed at ≤35%. During an overall follow-up period of 25 ± 18 months, none of the individuals with normalized LVEF experienced appropriate antitachycardia therapy regardless of ICD or CRT-D. Meanwhile, 20% of patients with LVEF at 36%–49% and 14% of patients with LVEF at ≤35% received appropriate ICD therapy. The omnibus P value for any differences among the 3 LVEF groups was 0.046 for the entire cohort, 0.01 for ICD, and 0.15 for CRT-D patients.ConclusionsThese preliminary data suggest that patients with reduced LVEF and primary-prevention ICDs who normalize their LVEF over time may be at lower risk of appropriate antitachycardia therapy.