Diagnostic approach to the patient with cardiomyopathy: whom to biopsy.

The prevalence of congestive heart failure is increasing and the prognosis remains poor. Cardiomyopathy is one of the most frequent causes of congestive heart failure and is the most common etiology of patients submitted to heart transplant. Determination of the etiology of cardiomyopathy has both prognostic and therapeutic implications. History, physical examination, transthoracic echocardiogram, selected laboratory studies, and coronary angiography can often define the cause of cardiomyopathy, however, the etiology occasionally remains unknown despite this initial evaluation. The indications for endomyocardial biopsy (EMBx) in patients with cardiomyopathy and a negative initial evaluation remains uncertain. The search for Dallas histological criteria proven myocarditis prompted the performance of EMBx in patients with unexplained cardiomyopathy in hopes of identifying an etiology for which treatment would result in improvement in left ventricular function. The "negative" results of the Myocarditis Treatment Trial, with treated and controlled patients improving equally, dampened enthusiasm for this diagnostic procedure. However, our experience and recent evidence suggests that EMBx may be a valuable diagnostic modality and should be included in the evaluation of patients with initially unexplained cardiomyopathy.