Quantitative analysis of technetium 99m 2-methoxyisobutyl isonitrile single-photon emission computed tomography and isosorbide dinitrate infusion in assessment of myocardial viability before and after revascularization

Abstract

Background. Assessment of viable myocardium in territories of hypoperfused myocardium is important for predicting functional recovery after revascularization. This study was designed to evaluate quantitative analysis of 99mTc-labeled 2-methoxyisobutyl isonitrile (MIBI) myocardial perfusion imaging combined with isosorbide dinitrate (ISDN) infusion to detect myocardial viability in patients with chronic coronary artery disease before and after revascularization. Methods and Results. Twenty-seven consecutive patients with previous myocardial infarction and left ventricular dysfunction (left ventricular ejection fraction 35.2% ± 13.5%) referred for coronary artery bypass (CABG) were studied with 99mTc-labeled MIBI single-photon emission computed tomograpy at rest and during ISDN infusion before CABG followed by resting imaging after CABG. Quantitative analysis was performed with circumferential profiles. Left ventricular function (global and regional) was assessed by radionuclide ventriculography before and after CABG. Out of 212 abnormal perfusion segments with resting 99mTc-labeled MIBI SPECT, 99 segments (47%) showed improved uptake of 99mTc-labeled MIBI during ISDN infusion. The mean ratio of myocardial uptake was 0.58 ± 0.25 (resting 0.53 ± 0.23; p < 0.05). After CABG, of 212 segments with hypoperfusion, 108 segments (51%; p > 0.05 vs ISDN) showed improved uptake of 99mTc-labeled MIBI. The mean ratio of myocardial uptake was 0.60 ± 0.26 (resting 0.53 ± 0.23; p < 0.05). The concordance between the improvement of post-CABG wall motion and that of pre-CABG ISDN perfusion imaging was 83%, between the improvement of wall motion and perfusion imaging after CABG 94%, and between the improvement of pre-CABG ISDN and post-CABG perfusion imaging 83%, respectively. Conclusion. ISDN infusion can improve the uptake of 99mTc-labeled MIBI in hypoperfused myocardium and increase the efficiency of 99mTc-labeled MIBI in the detection of viable myocardium in patients with previous myocardial infarction and left ventricular dysfunction.