Abstract
Background/Aims Randomized clinical trials demonstrate that implantable cardioverter defibrillators (ICDs) are effective for the primary prevention of sudden cardiac death in selected patients with left ventricular systolic dysfunction (LVSD). A recent study by Al-Khatib from the National Cardiovascular Data Registry’s (NCDR) ICD Registry reported that 22.5% of U.S. ICD patients with LVSD belong to clinical subgroups outside of trial-based evidence, which provides a meaningful comparison for our analysis. Among the aims of the Cardiovascular Research Network Longitudinal Study of ICDs (CVRN LSICD) is to evaluate the extent to which primary prevention ICD patients meet trial-based evidence criteria for implantation.
Methods Study subjects were ascertained from 14 implanting hospitals at 7 CVRN sites. We used NCDR data and the criteria from the published NCDR national study by Al-Khatib to calculate comparable inclusion and exclusion characteristics. Inclusion criteria included:
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first time primary prevention ICD, with no history of sustained ventricular tachyarrhythmia;
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ischemic or non-ischemic etiology; and
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past myocardial infarction (MI) with an ejection fraction <=30%, or, congestive heart failure (CHF) with an ejection fraction <=35%. Subjects were considered outside trial evidence with either recent MI (<40 days), recent CHF diagnosis (<90 days), or advanced CHF symptoms (New York Heart Association class IV). Patients receiving cardiac resynchronization therapy ICDs were not included in this analysis.
Results Among 1726 subjects meeting inclusion criteria, 301 (17%) had one or more exclusion criteria, mostly a recent MI or CHF diagnosis. Having one or more exclusion criteria was more common among men than among women (19% [254/1345] vs. 13% [47/375], p=0.009), but did not differ by race (17% [190/1106] among whites vs. 18% [110/610] among non-whites, p=0.75). Subjects outside of trial-based evidence for implant were slightly older than those with no exclusion criteria (median age 68 vs. 67 years, p=0.01).
Discussion About 1 in 6 primary prevention ICD patients in the CVRN LSICD fall outside of trial-based evidence for implantation, which is a smaller proportion than the 22% previously reported in the U.S. national population.
