Long-term follow-up in patients with hypertrophic cardiomyopathy after defibrillator implantation: analysis of appropriate and inappropriate therapy

Abstract

Abstract Background Treatment with implantable cardioverter-defibrillators (ICD) is effective for prevention of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM). Assessment of SCD risk and identification of patients most likely to benefit from primary prevention ICD is challenging. Purpose To investigate the long-term incidence of appropriate and inappropriate ICD therapy in patients with HCM. Methods This was a retrospective cohort study including all patients with HCM and ICDs implanted between 1995 to 2022 in our region (population 2.6 million). Both patients treated with primary and secondary prevention ICD were included. Data was retrieved from medical records. Patients with an ICD implanted for primary prevention were stratified into risk groups according to European Society of Cardiology HCM Risk-SCD score. Results We included 187 patients (65% male) with HCM and ICDs implanted for primary (80%) or secondary (20%) prevention. The median age at ICD implantation was 50 years (IQR: 40 to 61 years). During a mean follow-up of 9 years (IQR: 4 to 12 years), 53 patients (28%) experienced appropriate ICD therapy (antitachycardia pacing and/or shock), while 17 (9%) patients received inappropriate therapy. Patients with an ICD as secondary prevention were almost twice as likely to receive appropriate ICD therapy compared to patients with a primary prevention ICD (42% vs. 25%, p=0.04). The proportion of patients receiving appropriate shocks was 7 times higher in patients with an HCM Risk-SCD score ≥6% compared to patients with a risk score <4% (29% vs. 4%, p<0.001). There was no significant difference in the proportion of appropriate shocks between patients with a HCM Risk-SCD score ≥6% and patients with a risk score of 4%-6% (29% vs. 21%, p=0.49). (Figure 1). Conclusion One in four patients with HCM treated with an ICD experienced appropriate device intervention during 9 years of follow up. Patients with an HCM Risk-SCD score ≥6% had a 7-fold higher risk of appropriate ICD therapy compared to patients with an HCM Risk-SCD score <4%. There was no significant difference in the risk of appropriate shock therapy between patients with a risk score ≥6% and patients with a risk score of 4%-6%. The findings indicate the need for improved selection of patient with HCM for implantation of ICD’s.