Clinicopathological manifestations of myocarditis in a heart failure population.

Myocarditis continues to present challenges in diagnosis and management. The goal of this study is to determine the occurrence and manifestations of myocarditis in a heart failure (HF) population. The analyzed patients had acute or persistent HF and were referred over a 6-year period to a quaternary HF center for advanced HF therapies including mechanical circulatory support, left ventricular assist device (LVAD) implantation, and/or heart transplantation. The histopathological diagnosis of myocarditis was made based on the presence of an inflammatory infiltrate of the myocardium, typically with associated cardiomyocyte (CMC) damage, combined as indicated with immunohistochemical and molecular biology characterization. The pathological findings were correlated with a panel of clinical parameters and clinical course of the patients. Myocarditis was identified in 36 patients, with initial diagnoses made in 10 (40%) of 25 by endomyocardial biopsy (EMB), 1 by atrial biopsy (maze procedure), 7 (2.1%) of 331 at LVAD implantation, and 18 (7.8%) of 229 in the explanted heart. There were 20 cases of lymphocytic myocarditis, 4 cases of giant cell myocarditis, 3 cases of eosinophilic myocarditis, and 9 cases of lymphohistocytic with granulomas myocarditis - cardiac sarcoidosis. EMB was performed in 25 patients and was positive in 10 (40%) of cases. Myocarditis was found in 23 explanted hearts including 18 cases de novo and 5 cases with a previously positive specimen. Of the 23 explanted hearts, 21 were nonischemic cardiomyopathy and 2 were ischemic cardiomyopathy. Our findings show that, in patients presenting to a quaternary medical center, myocarditis can be manifest as acute HF as well as a complicating factor in chronic HF.