Histopathologic findings in explanted heart tissue from patients with end-stage idiopathic dilated cardiomyopathy

Explanted hearts were examined to determine whether specific histopathologi c features are present in the myocardium of patients with end-stage idiopat hic dilated cardiomyopathy (IDC). Extensive histopathologic examination by light microscopy, electron microscopy and immunohistochemistry revealed mar ked fibrosis in the hearts of 21 of 37 IDC patients and in 26 of 35 patient s with heart diseases of known causes. Reactive (interstitial and perivascu lar) fibrosis predominated in the IDC hearts, whereas both reparative (repl acement) fibrosis and reactive fibrosis were found in the comparison group. Endocardial fibroelastosis was found in nine patients with IDC and in 14 p atients from the comparison group. Distinct patterns of fibrosis were the s ole significant histopathologic difference between myocardial samples from patients with IDC and from those with heart diseases of known causes. The d iffuse presence of reactive fibrosis in IDC patients suggests a more genera lised dysfunction that affects the composition of the myocardial extracellu lar matrix.