IMMUNOHISTOLOGICAL EVIDENCE FOR A CHRONIC INTRAMYOCARDIAL INFLAMMATORY PROCESS IN DILATED CARDIOMYOPATHY

Objective-To determine whether immunohistochemical analysis of cardiac biopsies from patients presenting clinically as dilated cardiomyopath y (DCM) show a chronic inflammatory process. Design-Comparative case c ontrol study. Setting-Tertiary referral centre. Patients-Biopsies from 170 patients with DCM and 85 control patients with other cardiac dise ases. Results-Nine patients had sufficient interstitial inflammatory c ells to be called borderline myocarditis on conventional histology, le aving 161 patients with DCM. In 78 patients with DCM (48%) there were T lymphocytes in the myocardium. In 48 (62%) of these 78 T lymphocyte densities were in the range 2-14 per high power field (HPF), equivalen t to 7-50 per mm(2) of tissue. In 43 (89%) interstitial and endothelia l immune activation was demonstrated by MHC expression. In 30 patients with T cell counts in the range 1.5-2.0 per HPF, 80% also showed endo thelial activation. Lymphocyte density correlated with increased expre ssion of MHC class I and II antigens and the adhesion molecules ICAM, VCAM, ELAM, LFA-3, and GMP140. In all control biopsies the T lymphocyt e density was less than 1.0 per HPF (less than 2-5 per mm(2) of tissue ). Conclusions-Nearly half the patients with DCM had increased T lymph ocyte density and immune activation of endothelial and interstitial ce lls in their cardiac biopsies. A chronic autoimmune process is still a ctive within the myocardium in a significant percentage of patients wi th DCM. Immunohistochemical analysis of cardiac biopsies will enhance the sensitivity of cardiac biopsy and is essential for the diagnosis o f myocarditis.