Arrhythmic and Mortality Outcomes Among Ischemic Versus Nonischemic Cardiomyopathy Patients Receiving Primary ICD Therapy

Objectives: This study sought to determine the association of cardiomyopathy etiology with the likelihood of ventricular arrhythmias, appropriate implantable cardioverter-defibrillator (ICD) therapy, and mortality. Background: There are conflicting data on the benefit of primary prevention ICD therapy in patients with ischemic versus nonischemic cardiomyopathy (ICM/NICM). Methods: The study population comprised 4803 patients with ICM (n = 3,106) or NICM (n = 1,697) with a primary prevention ICD enrolled in 5 randomized trials conducted between 1997 and 2017. The primary end point was sustained ventricular tachycardia (VT) ≥200 beats/min or ventricular fibrillation (VF). Secondary end points included appropriate ICD therapy and all-cause mortality. Differences in cause-specific mortality, including noncardiac, sudden cardiac, and non-sudden cardiac death, were also examined. Results: Patients with ICM were significantly older and had more comorbid conditions, whereas those with NICM had a more advanced heart failure class at enrollment and were more often prescribed medical or cardiac resynchronization therapy for heart failure. Multivariate analysis showed that ICM versus NICM had a similar risk of VT/VF events (HR: 0.98 [95% CI: 0.79-1.20]) and appropriate ICD therapy (HR: 1.03 [95% CI: 0.87-1.22]), whereas the risk of all-cause mortality was 1.8-fold higher among ICM versus NICM patients (HR: 1.84 [95% CI: 1.42-2.38]), dominated by non-sudden cardiac mortality. Conclusions: Combined data from 5 landmark ICD clinical trials show that ICM patients experience a similar risk of life-threatening ventricular arrhythmic events but have an increased risk of all-cause mortality, dominated by non-sudden cardiac death, compared with NICM patients.