[Clinical picture and differential diagnosis of cardiomyopathy and myocarditis].

The main feature of idiopathic dilated cardiomyopathy is the dilation and impaired contractility of the left ventricle or both ventricles. The clinical picture with forward and backward failure is based on the pump impairment of the left ventricle. However, the clinical presentation of patients with dilated cardiomyopathy is indistinguishable from any other secondary form of heart failure. The symptoms of myocarditis are also often determined by the degree of left ventricular dysfunction and--apart from perimyocarditis-associated precordial discomfort--therefore also often indistinguishable from dilated cardiomyopathy. The differentiation of dilated cardiomyopathy from other myocardial diseases by noninvasive methods is insufficient. Without invasive tests about 1/3 of the patients will be diagnosed incorrectly. Therefore, invasive diagnostics including coronary angiography are necessary to differentiate dilated cardiomyopathy from other diseases, especially coronary artery disease. Standard laboratory findings and cytokine serum concentrations (e.g. TNF-alpha) are not suitable to differentiate dilated cardiomyopathy and myocarditis and endomyocardial biopsy is indicated. Endomyocardial biopsies have to undergo evaluation by standard histology and immunohistology, and should be tested for the persistence of infectious agents. According to cardiac catheterization and evaluation of the endomyocardial biopsy idiopathic left ventricular dysfunction can be further stratified using the criterion of a myocardial virus persistence and the presence/absence of inflammatory infiltrates. Idiopathic dilated cardiomyopathy (approximately 70 to 75%), virus-associated dilated cardiomyopathy (approximately 20 to 25%), myocarditis (approximately 7%) and autoimmune myocarditis (approximately 3%) are the 4 possible resulting forms of idiopathic left ventricular dysfunction. Beside conventional medical therapy there are new therapeutic concepts e.g. using interferon for enterovirus-positive patients and immunosuppression for autoimmune, virus-negative patients with a cellular infiltrate.