Inflammation in dilated cardiomyopathy

Inflammation is an important component in the pathogenesis of many common cardiovascular diseases. In most cases, the role of inflammation is a natural response to injury, and an important mechanism for healing and tissue repair. However, the inflammatory response can be either inadequate or overwhelming, leading to direct injury or severe host disease. Accumulating data has revealed an important inflammatory component in the pathogenesis of dilated cardiomyopathy (DCM), and there is growing evidence, that myocarditis and DCM are closely related. Many faces of DCM coexist, while different phases of the disease progress simultaneously: phase 1 is dominated by viral infection itself, phase 2 by the onset of (probably) multiple autoimmune reactions, and phase 3 by the progression to cardiac dilatation without an infectious agent and cardiac inflammation. Separation between the phases is not always distinct, they may overlap one another and phase 1 and 2 may recur after progression of DCM. Appropriate treatment during phase 1 includes eradication of virus and amelioration of injury caused by the virus. During phase 2, which is characterized by autoimmune processes, immunosuppression is the most appropriate therapy and warrants sophisticated diagnostic strategies including molecular biological and immunohistochemical techniques. Phase 3, DCM, although a result of viral and autoimmune injury, may then progress independently. The more attention given to serologic, molecular and immunologic factors to characterize and diagnose DCM lead to several changes in the terminology. The term cardiomyopathy is no longer reserved for the idiopathic forms but can be used interchangeably with the term heart muscle diseases including specific, secondary forms. Right ventricular cardiomyopathy (RVCM), valvular, hypertensive, ischemic, and inflammatory cardiomyopathy have been introduced. Idiopathic, autoimmune, and infectious forms of inflammatory cardiomyopathy were recognized. Viral cardiomyopathy is defined as viral persistence in a dilated heart. It may be accompanied by myocardial inflammation and is then termed inflammatory viral cardiomyopathy. Because of the overlap of pathophysiological stages in DCM, design of the appropriate therapy is important. It requires the immunohistochemical and molecular biological investigation of endomyocardial biopsies in parallel. In the modern molecular era the infective agent-immune system-host interaction has to be clarified leading to a better knowledge of the etiology of DCM. This may change the management of the disease in the future. One of the hopes is to discern the underlying dominant mechanism in a given patient to make a decision for the most promising therapy.