[Acute viral myocarditis: new aspects of an old disease]

The causes of acute myocarditis include infections (viral, bacterial, protozoal), toxins, drugs, hypersensitivity, chemical and physical agents. One of the most interesting and not completely understood of these conditions is the viral myocarditis. This diagnosis is often invoked to explain non-specific chest pain in the absence of coronary artery disease, spontaneous onset of arhythmias associated or not to congestive heart failure of unidentified origin. In most instances, there is little evidence that myocarditis is the underlying pathology. The challenge for physicians is not only to recognize and treat myocarditis, but also to identify which patient might be at risk for progression to dilated cardiomyopathy. Although in most cases myocarditis is limited and does not progress to chronic left ventricular dysfunction, nevertheless a casual relationship exists between viral myocarditis and dilated cardiomyopathy. This association was initially supported by observation during epidemics of Coxsackie B infection since as many as 12% of infected patients manifested clinical sign of cardiac involvement and few of these developed subsequently a dilated cardiomyopathy. Experimentally, in animals affected by acute viral myocarditis, the T lymphocytes appear to mediate continued myocyte necrosis in the apparent absence of virus. In addition, cellular infiltration and myocardial necrosis are minimal in the athymic mouse where T lymphocytes are depleted: thus T lymphocytes may play some role in the subsequent development of chronic congestive cardiomyopathy. However, until the application of endomyocardial biopsy, arguments for and against this relationship were based primary on circumstantial evidence from clinical, serologic, epidemiologic findings. recent studies using endomyocardial biopsy have demonstrated that myocarditis is associated to dilated cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)