Detecting residual ischemia and identifying coronary artery disease after myocardial infarction using dobutamine technetium-99m-MIBI SPECT

Objective To evaluate dobutamine technetium-99m methoxy isobutyl nitrile (s estamibi) single-photon emission computed tomography (Dobu-ECT) in detectin g residual ischemia and identifying coronary vessel disease after myocardia l infarction. Methods Sixty-two patients with confirmed myocardial infarction were studie d with Dobu-ECT at the time of coronary artery angiography. Dobutamine was administered intravenously in incremental rates from 5 to 40 mu g . kg(-1) . min(-1) at 5-minute intervals. At the highest infusion rate, 7.4 x 10(8) Bq (99)mTc-MIBI was injected intravenously, and tomographic imaging was per formed after one hour. Resting images were taken after 24 hours, with a sec ond dose of Tc-99m-MIBI. Results The sensitivity of Dobu-ECT in detecting residual ischemia of myoca rdial infarction was 76%, which was higher than dobutamine electrocardiogra phy (Dobu-ECG). Regardless of the single-, double- or triple-vessel disease s, Dobu-ECT was superior to Dobu-ECG in identifying residual ischemia (56% vs 4%, 86% vs 27%, 100% vs 47%, P < 0.01, respectively), The incidence of r esidual ischemia in patients receiving thrombolytic therapy was 67%, lower than patients without thrombolysis (72%) or those with an old myocardial in farction (94%). But the differences were not statistically significant. Dob u-ECT detected only 56% of ischemias in non-infarct related myocardium. Eig hty-two percent of all significantly stenosed vessels were detected with Do bu-ECT, and 84% of patients with multivessel disease could be accurately id entified. The sensitivity of Dobu-ECT was significantly greater for detecti ng severe stenosis over moderate stenosis. The sensitivity for detecting st enosis in the right coronary artery was greater than left anterior descendi ng or left circumflex, but its specificity was lower. Conclusion Dobu-ECT can identify residual ischemia, as well as its location and extent after myocardial infarction. Dobu-ECT can also accurately detec t significantly stenosed vessels.