End stage of arrhythmogenic cardiomyopathy with severe involvement of the interventricular septum

Detailed histopathologic, immunohistochemical, and ultrastructural analysis of the heart of a 56-year-old woman with end-stage arrhythmogenic cardiomyopathy with a pathogenic plakophilin-2 mutation is described. The explanted heart revealed severe fibrofatty replacement of nearly the entire right ventricular free wall. The left ventricle was severely affected, and, most remarkable, there was massive involvement of the interventricular septum. Immunohistochemical and electron microscopic findings of intercalated disks revealed areas with a heterogeneous distribution of connexin43 and focal electron microscopic abnormalities among these regions. This case illustrates that arrhythmogenic cardiomyopathy is not limited to the right ventricle but involves the entire myocardium, including the interventricular septum.