Dilated cardiomyopathy: emerging role of endomyocardial biopsy

The development of safe techniques of endomyocardial biopsy has led to a significant increase in our understanding of the etiology and pathogenesis of dilated cardiomyopathy. The scope of patients for whom this technique is absolutely clinically indicated, however, remains quite narrow and should be restricted to those centers with active cardiac transplant programs, large oncology practices, or those involved with active research into the etiology and treatment of patients with heart muscle disease. The most exciting concept to emerge from the use of EMB is the role of myocarditis in the development of dilated cardiomyopathy. It can accurately be stated that a subset of patients with the clinical presentation of dilated cardiomyopathy may in fact have histologic evidence of myocarditis. Although there is a suspicion that immunosuppressive therapy may be helpful, a randomized trial of large numbers of patients is necessary before definitive conclusions may be drawn. If immunosuppressive therapy proves to be efficacious in active myocarditis, then one could argue that all patients with heart failure of unknown cause with no evidence of valvular or coronary artery disease should undergo endomyocardial biopsy as part of the routine diagnostic workup. However, this recommendation must be considered premature. Since routine histologic findings are nonspecific in dilated cardiomyopathy, biochemical, pharmacologic, and cell culture techniques may provide more definitive information regarding the functional state of the heart muscle. In conclusion, endomyocardial biopsy is rapidly emerging as a useful diagnostic tool in the evaluation of patients with heart failure of unknown cause.