Effectiveness of implantable cardioverter-defibrillators in survivors of inhospital cardiac arrest

Background: Although implantable cardioverter-defibrillators (ICDs) reduce mortality in patients with out-of-hospital cardiac arrest, their effectiveness in survivors of "inhospital" cardiac arrest-a population with different arrest etiologies and higher illness acuity than out-of-hospital cardiac arrest-is unknown. We therefore sought to conduct a comparative effectiveness study of ICD therapy in survivors of inhospital cardiac arrest.

Methods: We linked data from a national inpatient cardiac arrest registry with Medicare files and identified 1,200 adults from 267 hospitals between 2000 and 2008 who were discharged after surviving an inhospital cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia and who otherwise met traditional inclusion and exclusion criteria for secondary prevention ICD trials. The association between ICD treatment and long-term mortality was evaluated using an optimal match (≤4 controls for each ICD patient) propensity-score analysis.

Results: Of 1,200 survivors, 343 (28.6%) received an ICD during the index hospitalization. Overall, 3-year mortality was 44.2%, with higher unadjusted mortality in the non-ICD versus the ICD group (46.9% vs 37.3%; log-rank; P < .001). After successfully matching 343 patients treated with ICDs with 823 untreated patients by propensity score, ICD treatment was associated with a 24% lower mortality rate (adjusted hazard ratio [HR] 0.76; 95% CI 0.60-0.97; P = .025). This lower mortality was mediated by lower rates of out-of-hospital deaths among ICD-treated patients (22.1% vs 30.8%; adjusted HR 0.71 [0.52-0.96]; P = .019), whereas deaths occurring during a readmission were similar (15.2% vs 16.1%; adjusted HR 0.89 [95% CI 0.60-1.32]; P = .56).

Conclusions: Implantable cardioverter-defibrillator therapy in survivors of inhospital cardiac arrest due to a pulseless ventricular rhythm is used uncommonly but associated with lower long-term mortality. Given that fewer than 3 in 10 eligible survivors are treated with ICDs after surviving an inhospital cardiac arrest, our findings highlight a potentially modifiable process of care, which could improve long-term survival in this high-risk population.