Progressive Anatomical Evolution Leading to Loss of S‐ICD Eligibility in Hypertrophic Cardiomyopathy: A Case Report

Subcutaneous implantable cardioverter defibrillators (S-ICDs) are designed to avoid complications from transvenous leads, but patient selection requires careful screening, especially in conditions like hypertrophic cardiomyopathy (HCM) with frequent conduction abnormalities. A 27-year-old male with HCM underwent S-ICD implantation in 2015 after successful screening. In 2020, inappropriate shocks due to T-wave oversensing led to vector adjustments. By 2022, further shocks and failed re-screening revealed ineligibility for S-ICD due to low R/T ratios in multiple vectors. Imaging and ECG comparisons from 2015 to 2022 showed disease progression, with increased fibrosis and conduction abnormalities. As a result, a transvenous ICD was implanted. This case underscores how HCM progression, associated with fibrosis and ECG changes, can render S-ICD unsuitable over time. It highlights the importance of periodic reassessment in high-risk patients, as disease progression can compromise S-ICD eligibility, necessitating alternative solutions for inappropriate shocks.