Quantitative estimation of infarct size by simultaneous dual radionuclide single photon emission computed tomography: Comparison with peak serum creatine kinase activity

Abstract

To test the hypothesis that simultaneous dual energy single photon emission computed tomography (SPECT) with technetium-99m ( 99mTc) pyrophosphate and thallium-201 ( 201Tl) can provide an accurate estimate of the size of myocardial infarction and to assess the correlation between infarct size and peak serum creatine kinase activity, 165 patients with acute myocardial infarction underwent SPECT 3.2 ± 1.3 (SD) days after the onset of acute myocardial infarction. In the present study, the difference in the intensity of 99mTc-pyrophosphate accumulation was assumed to be attributable to difference in the volume of infarcted myocardium, and the infarct volume was corrected by the ratio of the myocardial activity to the osseous activity to quantify the intensity of 99mTc-pyrophosphate accumulation. The correlation of measured infarct volume with peak serum creatine kinase activity was significant ( r = 0.60, p < 0.01). There was also a significant linear correlation between the corrected infarct volume and peak serum creatine kinase activity ( r = 0.71, p < 0.01). Subgroup analysis showed a high correlation between corrected volume and peak creatine kinase activity in patients with anterior infarctions ( r = 0.75, p < 0.01) but a poor correlation in patients with inferior or posterior infarctions ( r = 0.50, p < 0.01). In both the early reperfusion and the no reperfusion groups, a good correlation was found between corrected infarct volume and peak serum creatine kinase activity ( r = 0.76 and r = 0.76, respectively; p < 0.01). Thus the infarct volume, as determined by SPECT, correlated well with peak serum creatine kinase activity, and the correlation became closer when infarct volume was corrected by the heart/bone ratio. Simultaneous dual energy SPECT was useful in accurate quantification of acute myocardial infarction, and the quantification improved further when infarct size was corrected by the ratio of myocardial to osseous 99mTc-pyrophosphate accumulation.