Evaluation of Residual Myocardial Ischemia in the Infarct Zone by Dipyridamole Stress SPECT 99mTc-MIBI Myocardial Scan

ABSTRACT

In the recovery phase of acute myocardial infarction, residual ischemia is an important predictor of future cardiac event. To quantitatively evaluate the residual ischemia in the infarct zone and to see whether it can be predicted by particular coronary angiographic characteristics, dipyridamole stress SPECT 99mTc-MIBI myocardial scan was used in 31 patients with uncomplicated acute myocardial infarction. Quantitative assessment of residual ischemia in the infarct zone was made by the ratio of reversible defect in the polar display of SPECT MIBI scan to the total polar map area. Residual ischemia in the infarct zone in these patients does not correlate with patency, collateral circulation or jeopardy score of the infarct related artery. PTCA was performed in 7 patients with significant reversible defect and suitable anatomical lesion to evaluate the reversibility by revascularization. Following the PTCA mean reversible defect decreased significantly from 10.1+/-2.2% to 1.3+/-1.3%(P<0.05). In 10 patients with multivessel disease, 7(54%) out of 13 remote sites showed significant reversible defect showing limited usefulness in the detection of concomitant remote lesion in multivessel disease. Thus dipyridamole stress 99m Tc-MIBI myocardial scan is useful in the evaluation of residual ischemia in the infarct zone, and helpful in the decision making and assessing the result of revascularization.