Objectives: To investigate the generalizability of the reduction in mortality posed by implantable cardioverter-defibrillators, we examined the effectiveness of defibrillators as applied in routine medical practice.
Background: Implantable cardioverter-defibrillators have been shown to be efficacious in the primary and secondary prevention of overall and cardiovascular mortality in clinical trials.
Methods: Using the National Veterans Administration database, we identified a cohort of 6,996 patients from 1995 to 1999 with new-onset ventricular arrhythmia and pre-existing ischemic heart disease and congestive heart failure, of which 1,442 received a defibrillator, and followed them for three years to determine rates of mortality. With multivariate logistic regression analyses that adjusted for demographics, illness severity, and comorbidity, we assessed overall, cardiovascular, and noncardiovascular rates of mortality. To further address potential confounding, we also stratified the cohort by quintiles using a multivariable propensity score for each patient and determined mortality rates.
Results: For the overall cohort, multivariate regression showed that those who received defibrillators had significantly lower all-cause (odds ratio [OR] 0.52; 95% confidence interval [CI] 0.45 to 0.60) and cardiovascular (OR 0.56; 95% CI 0.49 to 0.65)] rates of mortality at three years. No significant differences were noted between groups in their rates of noncardiovascular mortality (OR 0.92; 95% CI 0.77 to 1.10). Propensity score analysis demonstrated similar mortality reduction benefits at three years: risk ratio (RR) 0.72 (95% CI 0.69 to 0.79) for all-cause; RR 0.70 (95% CI 0.63 to 0.78) for cardiovascular; and RR 0.95 (95% CI 0.83 to 1.08) for noncardiovascular rates of mortality. These results suggest that one death is prevented in this patient population for every four to five patients receiving a defibrillator for three years.
Conclusions: Implantable cardioverter-defibrillators in routine medical practice significantly reduce cardiovascular and all-cause rates of mortality at levels similar to secondary prevention trials.