[Diagnosis of myocarditis: description and assessment of available methods]

Myocarditis is a common disease in all age groups. Correct diagnosis of myocarditis is difficult, but of clinical and scientific importance. It is the aim of this review to describe and evaluate diagnostic possibilities. It is not possible to make a definitive diagnosis of myocarditis by electrocardiography, laboratory tests or echocardiography. Nor can techniques of nuclear medicine or coronary angiography provide an unequivocal diagnosis of myocarditis. Myocarditis can be diagnosed with certainty only by endomyocardial biopsy, which must be examined by histological, immunohistological and molecular techniques to obtain maximal sensitivity. But optimal diagnosis of a biopsy is subject to the problem of sampling error. Furthermore, myocardial biopsy is in practice used only rarely, despite a low complication rate. Thus the diagnosis of myocarditis is often based merely on suspicion. The limitations of standard methods employed so far have made cardiac magnetic resonance imaging (CMR) a valuable new additional test when there is the clinical suspicion of myocarditis. A myocardial biopsy will often reveal myocarditis in patients with cardiac symptoms and CMRI findings typical of myocarditis, especially if the biopsy was obtained near the area of contrast enhancement in the CMRI. CMRI can also be used for noninvasive and low-risk follow-up of functional parameters and tissue damage.