Clinical study of Tc-99m pyrophosphate scintigraphy in exercise-induced ventricular ischemia: Validation of technetium pyrophosphate specificity in myocardial infarction

Abstract

Tc-99m pyrophosphate (PYP) localizes in acute myocardial infarctions; however, the critical question of whether ischemia (I) can cause abnormal PYP localization remains unanswered. Rest (R) and exercise PYP scintigraphy was performed in 15 patients (pts) with arteriography documented multivessel coronary disease (>75% stenoses). All 15 pts had exertional angina and treadmill ECG for I. In 11/15 R and exercise Rb-81 scintigraphy was also performed: all 11 had Rb-81 evidence of I with exercise. Multiple images were obtained 2 hours after intravenous injection of PYP using a scintillation camera with high resolution collimator. For exercise PYP studies, injection was made after exercise onset of chest pain and ECG evidence of I on treadmill. No evidence of + myocardial PYP activity after exercise compared to R was seen in 14/15. In contrast, definite + myocardial activity on the exercise PYP study occurred in one pt. In this pt particularly severe angina on exercise was associated with transient ST elevations on ECG. Although there was no serial ECG evidence of infarction, there was a rise in serum CPK and repeat resting PYP scintigraphy was positive 3 days after exercise, suggesting that small subendocardial infarction rather than transient ischemia had been produced. These results demonstrate that transient I is not sufficient to cause myocardial localization of PYP. Thus unlike exercise Rb-81 scintigraphy, exercise scintigraphy with PYP cannot be used in screening for coronary ischemia but, instead, is specific for recent myocardial necrosis.