[Quantification of myocardial infarct size by technetium-99m pyrophosphate single photon emission computed...

Myocardial infarct size in 41 patients with the first attack of acute transmural myocardial infarction (MI) was assessed by technetium-99m pyrophosphate single photon emission computed tomography (99mTcPYP-SPECT). A ratio of the number of voxels of 99mTcPYP uptake into the infarct area to that into the thorax was calculated as a parameter of MI size. The ratio was positively correlated with both peak CPK activity (r = 0.53, p less than 0.005, n = 24) and extent score in 201TI-SPECT (r = 0.70, p less than 0.005, n = 14) significantly in patients with anterior MI but not in patients with inferior MI. There was also significant negative correlation between the ratio and the left ventricular ejection fraction (LVEF) measured by RI angiography in both acute (r = -0.67, p less than 0.005, n = 18) and chronic (r = -0.75, p less than 0.005, n = 25) phases in patients with anterior MI. Recovery in LVEF at chronic phase was noted in patients with small anterior MI but not with large anterior MI. 8 of 14 patients with inferior MI had right ventricular MI, that might have affected evaluation of MI size and resulted in no correlation between variables. It was suggested that 99mTcPYP-SPECT was a useful method to evaluate MI size and to predict prognosis of cardiac function in patients with anterior MI but not in patients with inferior MI.