Normal post-race antimyosin myocardial scintigraphy in asymptomatic marathon runners with elevated serum creatine kinase MB isoenzyme and troponin T levels. Evidence against silent myocardial cell necrosis.

Abstract

Recent epidemiologic studies confirm that heavy physical exertion can trigger myocardial infarction. Diagnosis of acute myocardial injury in marathon runners is complicated by elevations of serum creatine kinase MB isoenzyme activity in asymptomatic finishers with normal post-race infarct-avid myocardial scintigraphy. Such isoenzyme elevations can arise from exertional rhabdomyolysis of skeletal muscle biochemically altered by training, from silent injury to the myocardium or from a combined tissue source. To assess silent myocardial cell necrosis in marathon runners, we performed quantitative anti-myosin myocardial scintigraphy after competition with serum immunoassays for creatine kinase MB isoenzyme and troponin T. Therefore, 8 male marathon runners with a mean age of 52 years underwent quantitative antimyosin myocardial scintigraphy immediately following the 1988 and 1993 Boston Marathons. Serum immunoassays for creatine kinase MB isoenzyme by a chemiluminescent method (CLIA) and troponin T by an enzyme-linked immunosorbent assay were performed in 4 runners after the 1993 race. Quantitative antimyosin myocardial scintigraphy was normal in all runners including 3 who participated after both races 5 years apart. Post-race serum creatine kinase MB isoenzyme and/or troponin T levels were in a range otherwise diagnostic of acute myocardial infarction in 3 of 4 subjects. Normal quantitative antimyosin myocardial imaging in asymptomatic marathon runners excludes silent myocardial cell necrosis as the source of elevated serum protein markers. Such imaging may be the optimal diagnostic modality for detection of myocardial cell necrosis in symptomatic athletes when results of conventional testing are inconclusive.