Use of gallium 67 scintigraphy to differentiate acute myocarditis from acute myocardial infarction.

This study was designed to evaluate the role and effectiveness of gallium 67 imaging in the diagnosis of acute myocarditis that mimics acute myocardial infarction. Of 315 consecutive acute myocardial infarction patients admitted to our institution over a 4-year period, 5 (2 men, 3 women) were suspected of having acute myocarditis. These 5 patients ranged in age from 23 to 69 years (median, 32 yr). All had experienced diarrhea or flu-like symptoms within the preceding 4 weeks, and each presented with signs, symptoms, and electrocardiographic findings consistent with acute myocardial infarction. Echocardiography revealed decreased left ventricular systolic function. Gallium 67 myocardial scintigraphy was performed in 4 patients, 72 hours after intravenous injection of 9 mCi of gallium citrate Ga 67, and sooner than that in one. In all 5 patients, the results were positive, consistent with a diagnosis of acute myocarditis. One patient died of progressive heart failure 4 days after admission. Within 1 month of beginning medical therapy, the 4 surviving patients experienced resolution of abnormal ventricular function and symptoms. During a median follow-up period of 64 months, no cardiovascular events were observed, and the prognoses were deemed excellent. We suggest that gallium 67 scintigraphy is a useful method by which to identify acute myocarditis in patients in whom the condition is suspected. To our knowledge, this is the 1st report of the use of gallium 67 myocardial scanning to differentiate acute myocarditis from acute myocardial infarction.