INTRODUCTION
Left ventricular ejection fraction (EF) is the cornerstone of the criteria for implementation of implantable cardioverter-defibrillator (ICD) therapy among patients without a prior cardiac arrest. Individuals with EF ≤ 35% and heart failure symptoms while on optimal medical therapy are eligible for ICD for primary prevention of sudden cardiac death (SCD).1 However, approximately 1/3rd of the patients with ICD experience an improvement in their EF to > 35% after implantation.2–6 These patients with “recovered EF” have a lower risk of appropriate ICD shocks and SCD than those whose EF remains ≤ 35%.2–6 However, despite the improvement in EF, some risk of SCD persists.
Previously, in a post-hoc analysis of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) we showed that among patients with recovered EF, where the mean EF increased from 25% to 45%, ICD therapy was associated with a reduction in all-cause mortality compared to placebo.7 To date, this is the only mortality data on the effect of ICD after EF recovery and corroborates the continuing risk of SCD due to ventricular tachyarrhythmias among these patients. One possible explanation for the continuing risk of SCD after the improvement of left ventricular function is the potential for fluctuations in EF that might not have been clinically evident. Indeed, the trajectory of EF among ICD-eligible patients has not been well defined. Thus, the objective of the present study was to examine the trajectory of EF among ICD-eligible patients who participated in the SCD-HeFT.