OBJECTIVETo investigate the histopathological features of primary restrictive cardiomyopathy (PRCM).

METHODSNine extransplanted hearts from heart transplantation recipients were examined. Gross and histopathological findings were observed, photographed and final pathological diagnosis was compared to clinical diagnosis. The myocardial ultrastructure changes were determined using transmission electron microscopy.

RESULTSThe hallmark pathologic feature of PRCM was distinguished by myocardial cell degeneration and hyperplastic collagen fibrils around the myocardial cells.Fibrosis was severer in left ventricle free wall than in ventricular septum and right ventricle. The degree of myocardial cell degeneration and poloidal disorder were severer in patients with reduced ejection fraction (EF) than in patients with preserved EF. Transmission electron microscope evidenced severe interstitial fibrosis, myofibrillar changes of sarcomere structure, abnormalities both on intercalated disc number and distribution.

CONCLUSIONSPRCM is characterized by hyperplastic collagen fibrils around the cardiomyocytes. Fibrosis is severer in left ventricle than in right ventricle. Sarcomere dysplasia is the main cause of PRCM, and ultrastructural examination is helpful for PRCM diagnosis.