MYOCARDIAL SCINTIGRAPHY WITH TECHNETIUM-99M STANNOUS PYROPHOSPHATE - INSENSITIVE TEST FOR NONTRANSMURAL MYOCARDIAL-INFARCTION

Myocardial scintigraphy with technetium-99m pyrophosphate has proved to be a sensitive technique for diagnosing acute transmural myocardial infarction and has also been considered reliable in the recognition of nontransmural or subendocardial infarction. To assess the accuracy of pyrophosphate scintigraphy in diagnosing this latter entity, this procedure was studied in 31 patients with a confirmed nontransmural infarct, 43 with a transmural Infarct and 40 with stable angina pectoris. Radionuclide uptake was graded on a scale of 0 to 4+ and classified as discrete or diffuse. Diffuse uptake appeared to be nonspecific, occurring in 19 percent of patients with a subendocardial infarct and in 10 percent of those with stable angina pectoris; neither rate was significantly different from the 14 percent prevalence rate reported among patients without heart disease undergoing routine bone scan. Discrete uptake was highly specific for acute infarction but occurred in only 32 percent of patients with a nontransmural infarct compared with 84 percent of patients with a transmural infarct (P < 0.001). In both patient groups, scintigrams showing discrete uptake occurred in those with higher levels of creatine kinase MB level (P < 0.025), whereas scintigrams showing diffuse uptake occurred in patients whose enzyme level was similar to that of patients with negative scintigrams. It is concluded that discrete radionuclide uptake is a specific indicator of acute necrosis in patients with either transmural or nontransmural infarction, whereas diffuse uptake is nonspecific. However, discrete uptake occurs in only a minority of patients with subendocardial infarction, and therefore pyrophosphate scintigraphy is an insensitive technique in these patients. © 1979.