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

Background. Assessment of viable myocardium in territories of hypoperf used myocardium is important for predicting functional recovery after revascularization. This study was designed to evaluate quantitative an alysis of Tc-99m-labeled 2-methoxyisobutyl isonitrile (MIBI) myocardia l perfusion imaging combined with isosorbide dinitrate (ISDN) infusion to detect myocardial viability in patients with chronic coronary arte ry disease before and after revascularization. Methods and Results. Tw enty-seven consecutive patients with previous myocardial infarction an d left ventricular dysfunction (left ventricular ejection fraction 35. 2% +/- 13.5%) referred for coronary artery bypass (CABG) were studied with Tc-99m-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 p rofiles, Left ventricular function (global and regional) was assessed by radionuclide ventriculography before and after CABG, Out of 212 abn ormal perfusion segments with resting Tc-99m-labeled MIBI SPECT, 99 se gments (47%) showed improved uptake of Tc-99m-labeled MIBI during ISDN infusion, The mean ratio of myocardial uptake was 0.58 +/- 0.25 (rest ing 0.53 +/- 0.23; p < 0.05), After CABG, of 212 segments with hypoper fusion, 108 segments (51%; p > 0.05 vs ISDN) showed improved uptake of Tc-99m-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 i mprovement of post-CABG wall motion and that of pre-CABG ISDN perfusio n imaging was 83%, between the improvement of wall motion and perfusio n imaging after CABG 94%, and between the improvement of pre-CABG ISDN and post-CABG perfusion imaging 83%, respectively. Conclusion. ISDN i nfusion can improve the uptake of Tc-99m-labeled MIBI in hypoperfused myocardium and increase the efficiency of Tc-99m-labeled MIBI in the d etection of viable myocardium in patients with previous myocardial inf arction and left ventricular dysfunction.