S‐ICD in Hypertrophic Cardiomyopathy: Fewer Complications Without Increased Inappropriate Shocks Versus Transvenous Systems

BACKGROUND: The subcutaneous implantable cardioverter defibrillators (S-ICD) in hypertrophic cardiomyopathy (HCM) remains controversial. HCM patients are often younger and exposed to longer-term risks: complications and inappropriate therapy (IT). The S-ICD avoids vascular risks associated with transvenous ICDs (TV-ICD), but the rate of IT remains a concern. We conducted a retrospective observational study in HCM patients who received ICDs: assessing outcomes and utilizing a multi-event statistical model, we provide a novel assessment of the cumulative complication risk. METHODS: A retrospective study of all HCM patients who received an ICD at a tertiary center from 2006 to 2022 was conducted, utilizing electronic pacing and health records. Cox-proportion hazard models were applied for comparative outcome analysis and a multi-event statistical model was used to assess the cumulative burden of complications. Propensity score matching was used to adjust for baseline differences. RESULTS: We analysed data from 611 patients, with 141 receiving S-ICDs (26.7%). S-ICD patients had significantly fewer complications over a maximal follow-up of 137 months (HR 0.309, 95% CI 0.103-0.923, p = 0.035). Multi-event analysis demonstrated a cumulative increase in complications over time for TV-ICD patients (HR 0.258, 95% CI 0.109-0.644, p = 0.004), conversely no S-ICD patients experienced multiple complications. There was no difference in therapy rates or mortality between matched groups. CONCLUSION: The S-ICD is associated with fewer complications than TV-ICD, this is amplified by multi-event analysis, but without differences in IT. This should be discussed with HCM patients, as the S-ICD could provide a better benefit/risk ratio.