A comparative ultrastructural study on the nature of interstitial cell constituents in idiopathic myocarditis and myocardial infarction.

In order to observe the characteristics of interstitial cellular proliferation in cases with myocarditis of possible viral origin, a systematic ultrastructural analysis of the cell components in the interstitium was made employing endomyocardial biopsy at the acute (0-10 days after onset), subacute (11-25 days), and convalescent stages (26-167 days) of the disease in ten cases. For comparison, myocardial specimens from cases with myocardial infarction were taken from early autopsy cases or from tissue obtained during surgery. The dominant interstitial cells observed in the acute stage of myocarditis were fibroblasts (38.3% +/- 17.5%, mean +/- SD), macrophages (23.3% +/- 12.1%), and lymphocytes (18.0% +/- 18.1%); at the convalescent stage, fibrocytes (44.6% +/- 20.2%) and fibroblasts (22.5% +/- 8.0%) were commonly seen. In myocardial infarction, the dominant cells were macrophages (35.0% +/- 16.0%) and neutrophils (26.0% +/- 13.9%) at the acute stage, and lymphocytes (30.0% +/- 17.8%), plasma cells (27.1% +/- 20.0%), and macrophages (26.4% +/- 11.4%) at the late stage. Thus, some differences between the two diseases could be recognized.