A Rare Septal Hamartoma of Mature Cardiac Myocytes Manifesting With Cardiac Cachexia in a Teenager

Hamartomas of mature cardiac myocytes are a rare type of primary cardiac tumor, with only 5 cases of interventricular septal involvement reported to date. They are often challenging to diagnose, and there is currently no standardized approach to surgical resection. Here, we present a rare case of a large 6.0 × 4.4 × 3.8-cm interventricular septal hamartoma that manifested with cardiac cachexia in a teenage patient. Surgical biopsy was used after 4 attempts at endomyocardial biopsy were nondiagnostic, and partial debulking was performed as complete resection was not feasible.