In the one-quarter of heart failure patients who receive an implantable cardioverter defibrillator for primary prevention and whose left ventricular ejection fraction improves more than 35%, both mortality and appropriate ICD shocks are decreased, according to a report published online July 27 in Journal of the American College of Cardiology.
This raises the question of whether such patients’ risk for sudden cardiac death still warrants replacement of the ICD generator years later, especially among those whose devices have never needed to deliver a shock, said Yiyi Zhang, Ph.D., of the Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, and her associates.
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To examine this issue, the investigators analyzed data from PROSE-ICD (Prospective Observational Study of Implantable Cardioverter-Defibrillators), in which patients with systolic heart failure received primary-prevention ICDs at four U.S. cardiology centers after an initial LVEF assessment. For their study, Dr. Zhang and her associates focused on 538 of these study participants whose LVEF was reassessed at least once during roughly 5 years of follow-up.
About 57% of the study subjects were white and 70% were men. The average age at baseline was 59 years.
LVEF improved after ICD implantation in 215 (40%) of the participants, including 134 patients (25%) in whom it improved to greater than 35%. These patients were at significantly reduced risk of all-cause mortality and of requiring ICD shocks, compared with patients whose LVEF was either unchanged (47%) or decreased (13%) after ICD implantation, the investigators said. In a Cox regression model adjusted for age, sex, race, baseline LVEF, and stratified by enrollment center, the hazard ratio for all-cause mortality was 0.31, and that for an appropriate shock was 0.33 (J. Am. Coll. Cardiol. 2015 July 27 [doi:10.1016/j.jacc.2015.05.057]).
The mode of death could not be determined in many cases because records were unreliable for patients who died out of hospital, so the researchers couldn’t examine any association between LVEF changes and cardiac-specific mortality.
These study results are consistent with those of several previous studies, Dr. Zhang and her associates noted.
“Findings from our study indicate that repeated LVEF assessment after ICD implantation can provide additional prognostic information and may also allow for more informed decision making regarding ICD generator replacement, especially in patients whose LVEF improved significantly,” they said.
Further studies in larger populations that have more frequent LVEF reassessments are needed to establish whether ICD generator replacement has a positive or negative impact on this patient population, and to better guide clinicians in deciding whether ICD generator replacement should be deferred in individual patients, the investigators added.