Background: Progressive damage of cardiomyocytes with interstitial and replacement fibrosis accompanied by less inflammatory cell infiltration is observed in patients with dilated cardiomyopathy (DCM), suggesting some other mechanisms rather than necrotic cell death.
Hypothesis: The aim of this study was to assess the possible involvement of apoptotic process in the pathogenesis of DCM and myocarditis.
Methods: Endomyocardial biopsy was performed in patients with DCM (n = 9), myocarditis (n = 4), or atypical chest pain syndrome (as controls; n = 5). The TUNEL method was used for in situ detection of oligonucleosomal DNA strand breaks.
Results: The TUNEL-positive cells were observed in three of nine patients with DCM and in all four with myocarditis, but in none of the controls. The TUNEL-positive nuclei were observed exclusively in cardiomyocytes in DCM, whereas in myocarditis they were detected mainly in interstitial cells and in a few myocytes. In DCM, interstitial fibrosis was greater in the TUNEL-positive than in TUNEL-negative patients (p < 0.05). In either DCM or myocarditis, electron microscopic examination could not reveal morphologic features of apoptosis of cardiomyocytes.
Conclusion: The DNA strand breaks were detected in cardiomyocytes in patients with DCM and mainly in interstitial cells in myocarditis. It is possible that the DNA strand breaks can be involved in mechanisms of progressive loss of functional cardiac units in these myocardial diseases.