By including immunohistochemical parameters the WHF Task Force for the Definition of Acute and Chronic Myocarditis expanded the light microscopical Dallas criteria of myocarditis. The rapid development of new molecular biological techniques such as polymerase chain reaction (PCR) and in-situ hybridization has improved our understanding of the underlying etiological and pathophysiological mechanisms in inflammatory heart disease. Treatment of dilated cardiomyopathy with inflammation is still controversial, however. The American Myocarditis Treatment Trial could not demonstrate a significant difference in the improvement of ejection fraction between patients with active myocarditis in the cyclosporine/prednisolone treated group when compared to placebo. In the European Study of Epidemiology and Treatment of Inflammatory Heart Disease (ESETCID) patients with acute or chronic myocarditis are treated specifically according to the etiology of the disease. Patients are screened not only for infiltrating cells, but also for the presence of persisting viral genome (enterovirus, cytomegalovirus and adenovirus). By investigating endomyocardial biopsies of 3,055 patients ongoing inflammatory processes in the heart could be found in 17.2%. Only 182 showed a reduced ejection fraction below 45% fulfilling the entrance criteria for the ESETCID trial. These data imply that in symptomatic patients inflammatory heart muscle disease has to be considered regardless of left ventricular function and that endomyocardial biopsy can be an important tool for diagnosis. Virus could be detected in 11.8% (enterovirus 2.2%, cytomegalovirus 5.4%, adenovirus 4.2%). These first epidemiological results of this prospective randomized study demonstrate that viral persistence may contribute to the pathogenesis of inflammatory heart muscle disease, and that in chronic myocarditis viral persistence occurs in a smaller percentage of patients compared to previously published studies which were performed on highly selected patients.

Diagnosis of myocarditis has improved with the application of new techniques such as immunohistochemistry, polymerase chain reaction, in situ hybridization and Southern blot in endomyocardial biopsies. Treatment of inflammatory heart disease is still difficult and not yet validated by a study with patient numbers sufficient to allow statistical analysis. The European Study of Epidemiology and Treatment of Cardiac Inflammatory Disease (ESETCID) addresses problems of aetiology, pathogenesis and specific treatment of myocarditis. It is the first multicentre, double-blind placebo-controlled randomized study, apart from the Myocarditis Treatment Trial, to discriminate between different forms of myocarditis. Patients with cytomegalovirus-induced myocarditis are treated by hyperimmunoglobulin compared to placebo. Patients with enterovirus-positive myocarditis will receive interferon alpha vs placebo. Patients with virus-negative myocarditis, which is considered autoimmune, will be treated with immunosuppression compared to placebo. The primary endpoint of this study is an improvement in ejection fraction of more than 5%. This trial may give a better understanding of the course of myocarditis, leading to more specific treatment which may in turn reduce the number of patients with post-myocardial heart muscle disease who require heart transplantation as a final therapeutic remedy.

This overview examines the immunological rationale for immunosuppressive and immunomodulating therapy in man and experimental animals. The controversy of whether immunosuppressive treatment is beneficial in myocarditis will continue even after the Myocarditis Treatment Trials has been published. It is known that in viral heart disease immunosuppressive drugs should be avoided, but in autoreactive forms of myocarditis with proven humoral and cellular effector mechanisms they may be used in controlled randomized trials to validate or refute their benefit. Immunomodulating factors, e.g. immunostimulatory or antiviral substances such as ribaverin, the interleukins and interferons have demonstrated some effect in experimental animal myocarditis but proof of their benefit in man is still lacking. Hyperimmunoglobulin therapy appears to be of particular interest because it incurs few side effects and has positive results in cytomegalovirus-associated myopericarditis in man and suspected myocarditis in children.

Human cytomegalovirus (CMV) can persist in many organs after primary infection. Not only is it suspected to cause morbidity during reactivation in patients under immunosuppression, but it may also induce long-term latency by chronic disease, e.g. in the myocardium. Endomyocardial biopsies of 27 patients with active myocarditis, 35 patients with healing, 41 patients with healed and 25 patients with ongoing myocarditis according to the Dallas Criteria and 52 patients with dilated cardiomyopathy (DCM) and the biopsies of 25 healthy heart donors were studied for persisting CMV-DNA by polymerase chain reaction (PCR) and in-situ hybridization (ISH). CMV-DNA could be assessed in 5-14% of patients in the different stages of myocarditis and in 22% of patients with DCM. Although two biopsies of the control group showed a positive result, studies by in-situ hybridization demonstrated that in patients with heart muscle disease CMV persists in all cell types including myocytes, whereas in the controls it is only found in interstitial cells. CMV antigens could not be detected in the myocardium with our methods. It must be assumed that infection by CMV is more a persistent or latent than an active infection.

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