Rate of Appropriate and Inappropriate Therapy in Patients with Non-Ischaemic Cardiomyopathy, A Comparison between Primary and Secondary Prevention Implantable Cardioverter-Defibrillator Patients

Abstract

Implantable cardioverter defibrillators (ICDs) have demonstrated favourable outcomes on survival in selected patients with cardiomyopathy. However, recent studies have questioned the protective role of ICD in Non-ischaemic Cardiomyopathy (NICM) for primary prevention. Aim: To investigate the differences in ICD therapy in primary and secondary prevention ICD patients. Between 2014–2017, 182 patients (male = 117; age = 63 ± 17 years, female = 65; age = 63 ± 17 years) had ICD for NICM. Patients were divided into primary prevention (n = 97) and secondary prevention groups (n = 85) based on implant indication. Patients’ Left Ventricular Ejection Fractions (LVEF) were determined by transthoracic echocardiogram. ICD stored data of ICM and NICM patients were utilised. Cumulative first shock rate, type and appropriateness of therapy were determined. There was no significant difference in clinical characteristics between the primary prevention group and secondary prevention group. Mean follow-up was 30 months after implantation. Overall ICD therapy rate was 19%. Cumulative probability of a first appropriate shock was higher in the secondary prevention group (p = 0.03). Overall, ICD therapy was significantly more frequent in the secondary prevention vs primary prevention group (25% vs 13%, p = 0.02). Inappropriate device therapy rate was insignificantly higher in primary prevention group (23% vs 19% p = NS). The rate of appropriate device therapy was significantly greater in secondary prevention group. Inappropriate device therapy was significantly high in both groups. Due to the inherent risks associated with ICD implantation, generator changes and inappropriate therapy, further risk stratification is required for risk of SCD.