Sudden death due to infiltration of left bundle branches by interventricular septal cardiac fibroma

Cardiac fibromas are benign conditions; however, their location and size may cause ventricular arrhythmias and sudden cardiac death. We report a case of a 68-year-old female who died suddenly. Postmortem investigation detected a huge cardiac fibroma in the pars muscularis of the interventricular septum, occupying almost the entire muscular septum, and restricting the volume of left ventricular chamber. Histological examination revealed numerous foci of calcification in the alternating complex interlacing or strictly parallel collagenous fiber mass. Tumor mass was mainly demarcated, but in some places, fibrous infiltration of surrounding working cardiac muscle was found. We present a case when direct tumor involvement in the descending left bundle branches was evidenced. Mainly, the branches of septal fascicle were disrupted, entrapped, and degenerated by the tumor mass. This case report emphasizes that postmortem histological examination of conduction system in all sudden cardiac death cases may substantially improve the accuracy of postmortem diagnosis.