Myocardial Inflammatory Cell Infiltrates in Cases of Dilated Cardiomyopathy: Light Microscopic, Immunohisto‐chemical, and Virological Analyses of Myocardium Specimens obtained by Partial Left Ventriculectomy

Objective: Partial left ventriculectomy was introduced for the treatment of refractory dilated cardiomyopathy (DCM). To determine the presence and degree of inflammatory cell infiltrates in DCM and the correlation between the underlying myocardial injury and early clinical outcomes after the operation, we performed histopathological, immunohistochemical, and virological studies of the resected myocardium. Methods: Posterolateral walls of the left ventricle from 13 idio‐pathic DCM patients (9 males and 4 females; mean age = 53 ± 14 years) were examined. Qualitative and quantitative analyses of the interstitial fibrosis and of the infiltrating inflammatory cells were conducted. For the immunohistochemistry, leukocyte surface markers and antibodies to adhesion molecules and cytokines were used. The histopathological findings were compared with the clinical results, including outcome within 1 year, and pre‐ and postoperative hemodynamic data. Genomic analysis of the myocardium with polymerase chain reaction was performed for en‐terovirus, mumps, influenza A, cytomegalovirus, and hepatitis C virus. Results: (1) The three patients who died of cardiac insufficiency after surgery had a higher count of infiltrating inflammatory cells than the eight survivors (32.1 ± 10.4 vs 16.3 ± 11.9 cells/mm 2 , p = 0.07). The severity of interstitial fibrosis (percent fibrosis) did not differ significantly between these two groups (28.3 f 15.0 vs 24.0 ± 11.7%). (2) In patients who died of myocardial dysfunction, focal accumulations of lymphocytes were common, in which cytotoxic/suppressor T cells and helper/inducer T cells were observed. (3) Enterovirus genome was detected in the myocardium of two patients, both of them died after surgery. Conclusions: Inflammatory cell infiltrates or active myocarditis appear in some cases to play an important role in the etiology and pathophysiology of clinically diagnosed DCM. There is a possibility that those patients with a more severe or ongoing inflammatory process might have poor outcomes after partial left ventriculectomy.