Pathophysiology of cardiac inflammation: Molecular mechanisms

Background: Inflammatory processes induced by viral infection are believed to be one of the major pathogenetic mechanisms in inflammatory dilated cardiomyopathy. Although the reason for progression to myocardial failure is not fully understood, postulated mechanisms include persistent viral infection alone or in combination with autoimmune processes. Pathophysiology: Murine models of myocarditis have provided insight into the mechanisms by which autoimmune responses to cardiac antigens, probably in response to viral infection of the myocardium, arise and cause tissue pathology. Organ-specificity, cross-reactivity between microbial agents and cardiac tissue, and induction of tolerance to self-antigen are issues still at stake. In addition, cytokines mediate activation and effector phase of innate and specific immunity, which are both important in controlling viral infection. The innate immune response not only has an important protective function but also serves to initiate and regulate subsequent specific immune responses. In man, on the one hand specific T cells and antibodies against different cardiac tissue components have been demonstrated in myocardium and sera of patients with inflammatory cardiomyopathy, and on the other hand viral genome has been identified in endomyocardial biopsies due to the rapid development of new molecular biological techniques such as polymerase chain reaction (PCR), southern blot analysis and in-situ hybridization. But it is still a matter of debate whether virus infection itself, the ensuing immune response, or both, contribute to the deterioration of left ventricular function. Conclusion: Taking these mechanisms into account, screening for viral genome by PCR and detection of inflammatory infiltrates by immunohistochemistry are considered crucial for the establishment of a definite diagnosis thereby allowing for the initiation of specific therapeutic strategies.