Risk stratification for ventricular tachyarrhythmia in patients with nonischemic cardiomyopathy

Introduction: The implantable cardioverter defibrillator reduces mortality among patients with heart failure (HF) due to ischemic heart disease. Clinical trial data have called into question the benefit of an ICD in patients with HF due to nonischemic cardiomyopathy (NICM). We developed a risk stratification score for ventricular tachyarrhythmia (VTA) among patients with NICM receiving a primary prevention ICD. Methods: The study population comprised 1515 patients with NICM who were enrolled in the landmark MADIT trials. Fine and Gray analysis was used to develop a model to predict the occurrence of VTAs and ICD therapies while accounting for the competing risk of non-arrhythmic mortality. External validation was carried out in the RAID Trial population. Results: Four risk factors associated with increased risk for VTA were identified: male sex, left ventricular ejection fraction <= 25%, no indication for cardiac resynchronization therapy with a defibrillator (CRT-D), and Black race. A score was generated based on this model, and patients were stratified into low (N=390), intermediate (N=728), and high-risk (N=387) groups. The 5-year cumulative incidences of VTA were 15%, 24%, and 42%, respectively. Application of score groups for the secondary endpoints of Fast VT or VF and Appropriate ICD Shock revealed similar findings. Recurrent event analysis yielded consistent results. The AUC in the validation cohort for the endpoint of Appropriate ICD Shock was 69.3. Conclusions: Our study shows that patients with NICM can be risk stratified using demographic and clinical variables and may be used when evaluating such patients for a primary prevention ICD.