ANTIMYOSIN SCINTIGRAPHY AND IMMUNOHISTOLOGIC ANALYSIS OF ENDOMYOCARDIAL BIOPSY IN PATIENTS WITH CLINICALLY SUSPECTED MYOCARDITIS - EVIDENCEOF MYOCARDIAL-CELL DAMAGE AND INFLAMMATION IN THE ABSENCE OF HISTOLOGIC SIGNS OF MYOCARDITIS

Objectives. This study compares the results of antimyosin scintigraphy in patients with clinically suspected myocarditis with histologic and immunohistologic findings in the endomyocardial biopsy. Background. I n patients with clinically suspected myocarditis, antimyosin scintigra phy often demonstrates myocardial cell damage but histologic evaluatio n of the endomyocardial biopsy often fails to show evidence of myocard itis, Recently developed immunohistologic techniques appear to be more sensitive for the detection of myocardial inflammation than histologi c analysis alone. Studies comparing antimyosin scintigraphy and immuno histologic analysis of the endomyocardial biopsy in patients with cli nically suspected myocarditis are not yet available. Methods. Sixty-fi ve patients with clinically suspected myocarditis underwent antimyosin scintigraphy. Antimyosin antibody uptake was correlated with histolog ic and immunohistologic findings in the endomyocardial biopsy. Results . Antimyosin scintigraphy showed evidence of myocardial cell damage in 36 (55%) of the 65 patients and was negative in 29 (45%) patients. Hi stologic analysis of the endomyocardial biopsy revealed myocarditis in nine patients: six had a positive and three had a negative antimyosin scan, respectively. Thirty (83%) of 36 patients with evidence of myoc ardial cell damage on antimyosin scintigraphy were histologically nega tive for myocarditis, Immunohistologic analysis showed evidence of myo carditis in 31 (86%) of 36 patients with a positive antimyosin scan an d also in 17 (59%) of 29 patients with a normal scan (p < 0.047). Conc lusions. Antimyosin scintigraphy often shows myocyte injury in patient s with clinically suspected myocarditis. Histologic analysis of the en domyocardial biopsy alone is often negative, but additional immunohist ologic analysis of the endomyocardial biopsy frequently provides evide nce of myocardial inflammation in these patients. With immunohistologi c analysis as the reference method, antimyosin scintigraphy has a high specificity but a lower sensitivity for the detection of myocarditis. (C) 1998 by the American College of Cardiology.