Evaluating subcutaneous implantable cardioverter defibrillators in hypertrophic cardiomyopathy: fewer complications without increased therapies

Abstract Introduction The use of Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) in Hypertrophic cardiomyopathy (HCM) remains controversial. HCM patients are commonly younger, exposing them to longer-term risks, such as complications and inappropriate therapy (IT). The S-ICD avoids vascular risks associated with transvenous ICDs (TV-ICD), but the rate of IT and lack of antitachycardia pacing (ATP) remain a concern. Purpose We investigated outcomes of HCM patients who received S-ICD and TV-ICD, assessing ICD therapy outcomes, and, utilising a multi-event statistical model to provide a novel, complete assessment of cumulative complication risk. Methods A retrospective audit of all HCM patients who received an ICD at a large tertiary centre from 2006 to 2022 was conducted, using electronic pacing and health records. A multi event statistical model (Lin Wei Yang Yin) was used to assess the cumulative burden of complications. Propensity score matching was used to adjust for baseline differences and Cox-proportion hazard models were applied for comparative outcome analysis that were conducted independently (e.g. first IT for IT analysis and first complication for complication analysis). Results We reviewed 611 patients, (mean age of 48.7 ± 14.5 years) with 470 receiving TV-ICDs (73.3%) and 141 S-ICD patients. TV-ICD patients had a significantly longer follow up than S-ICD patients; 83.46 ± 68.43 months vs 41.80 ± 30.40 months (p<0.001). TV-ICD patients had significantly more complications than S-ICD patients (21.7% vs 2.8%, p<0.001), mostly due to lead-related complications, that were more common in the TV-ICD group (Table 1). Multi-event analysis demonstrated a cumulative increase in complications over time for TV-ICD patients. No S-ICD patients experienced multiple complications through follow up, although some had advisory shorter than expected battery life. This was primarily due to lead-related issues and device infections. Interestingly many of the multiple complications occured after 150 months time period. There was no difference in inappropriate and appropriate therapy rates between both groups. Conclusion The S-ICD is associated with less complications over 120-month follow-up compared to TV-ICD in HCM patients, without significant difference in IT. The multi-event statistical methods highlight the importance of cumulative risk over time, with the compound risk of complication increasing as leads begin to fail after 150 months. Longer-term follow-up is required for SICD comparisons; however, our data suggests the SICD to be a potentially safer device in the long term for HCM patients. This should be discussed with HCM patients at consultation for ICD therapy, as the S-ICD provided a better benefit / risk ratio over 10 years follow up.Figure 1