Limited clinical diagnostic specificity of technetium-99m stannous pyrophosphate myocardial imaging in acute myocardial infarction.

To test the sensitivity and specificity of technetium-99m stannous pyrophosphate myocardial imaging in the diagnosis of acute myocardial infarction, myocardial scintigrams were performed in 115 patients. Positive scintigrams were found in all 48 patients with acute myocardial infarction; uptake was localized in 29 patients with transmural infarction and diffuse in 2 patients with transmural infarction and in the remaining 17 patients with subendocardial myocardial infarction. Positive scintigrams were also found in 31 of 67 patients without clinical evidence of acute myocardial infarction. Diffusely positive scintigrams were found in 3 of 3 patients with unstable angina pectoris, 7 of 30 patients with stable angina pectoris, 4 of 13 patients who had undergone aortocoronary bypass surgery, 4 of 4 patients with congestive cardiomyopathy and 1 patient studied 1 day after direct current cardioversion. Localized uptake of 99mTc-pyrophosphate was found in 9 of 10 patients with left ventricular aneurysm and in 3 of 13 patients after aortocoronary bypass surgery. All four patients with atypical chest pain and two patients with pericarditis had normal scintigrams. Our data confirm the previously reported sensitivity of 99mTc-pyrophosphate imaging in detection of acute myocardial infarction but indicate that positive scintigrams are not specific for this entity.