The objectives of this study were to analyze the incidence of chronic
myocarditis in
dilated cardiomyopathy and to evaluate the diagnostic value of
tenascin C for assessing inflammatory activity in the resected myocardium.
Dilated cardiomyopathy patients with chronic
myocarditis have a poor clinical outcome despite recent advances in medical treatments. Therefore, a precise diagnosis of inflammatory activity is critical to ensuring appropriate
therapy.
Tenascin C is an extracellular matrix
glycoprotein that plays an important role in tissue remodeling in various
heart diseases. Myocardial samples obtained during left ventriculoplasty from 64 patients (50 +/- 13 years, 56 men and 8 women) with
dilated cardiomyopathy were examined by immunostaining for
tenascin C. Histologic diagnosis was based on the Dallas criteria modified by the International Society and Federation of Cardiology task force. Nine cases (14%) had active
myocarditis, 21 (33%) had borderline
myocarditis, and 34 (53%) had no
myocarditis. Intense
tenascin C expression was observed at the site of active
inflammation, with abundant cell accumulation, and in organized granulation tissue during the resolving phase but not in
scar tissue during the healing phase. The ratio of
tenascin C-positive area to the whole myocardium in the active and borderline
myocarditis groups was significantly greater than that in the noninflammatory group. These findings suggest a high prevalence of chronic
myocarditis in
dilated cardiomyopathy patients and that
tenascin C may prove to be a useful marker for distinguishing inflammatory
cardiomyopathy from other types of
dilated cardiomyopathy.