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.