Clinicopathologic study of persistently positive technetium-99m stannous pyrophosphate myocardial scintigrams and myocytolytic degeneration after myocardial infarction.

In a select series of 46 patients studied by serial myo- cardial scintigraphy, 19 (41%) retained persistent, usually low grade (2+) positive technetium-99m stannous pyrophosphate ('9mTc-PYP) myocardial scintigrams for at least 3 months after acute myocardial infarction. The one major difference between patients with positive and negative postinfarct 59mTc-PYP myocardial scintigrams was a more symptomatic postinfarct course in the former group, characterized by severe angina pectoris in 16 of the 19 patients and by severe congestive heart failure with angina in three patients. In a separate clinicopathologic series of seven patients, persistently positive 'mTc-PYP myocardial activity was associated with promi-IN OUR EXPERIENCE, MYOCARDIAL SCINTIG- RAPHY with technetium-99m stannous pyrophosphate (SSmTc-PYP) has proven to be an effective and sensitive method for detection of acute myocardial infarction in patients and experimental animals."'2 The test also has been positive in approximately one third of patients with unstable angina pectoris."13 Review of the literature reveals a generally similar experience."4 Myocardial scintigraphy with 99mTc-PYP also detects muscle necrosis due to etiologies other than coronary heart disease, including trauma, repeated cardioversion, and metastatic tumor. 4-17 In addi- tion, positive 99mTc-PYP scintigrams with uptake in heart and other soft tissues may occur in patients with metastatic calcification."' 18,1 , Autoradiographic studies in experimen- tal acute myocardial infarcts have shown that radiopharmaceutical concentration occurs predominantly in frankly necrotic myocardium as well as in a small population of damaged border zone muscle cells admixed with necrotic muscle cells.'0 Experimental studies also have shown that approximately 3 g of necrotic myocardium is needed for the test to maintain a high degree of sensitivity;" however, a similar determination has not been made in humans.