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 (sestamibi) single-photon emission computed tomography (Dobu-ECT) in detecting residual ischemia and identifying coronary vessel disease after myocardial infarction.

METHODS

Sixty-two patients with confirmed myocardial infarction were studied with Dobu-ECT at the time of coronary artery angiography. Dobutamine was administered intravenously in incremental rates from 5 to 40 micrograms.kg-1.min-1 at 3-minute intervals. At the highest infusion rate, 7.4 x 10(8) Bq 99mTc-MIBI was injected intravenously, and tomographic imaging was performed after one hour. Resting images were taken after 24 hours, with a second dose of 99mTc-MIBI.

RESULTS

The sensitivity of Dobu-ECT in detecting residual ischemia of myocardial infarction was 76%, which was higher than dobutamine electrocardiography (Dobu-ECG). Regardless of the single-, double- or triple-vessel diseases, 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 residual ischemia in patients receiving thrombolytic therapy was 67%, lower than patients without thrombolysis (72%) or those with an old myocardial infarction (94%). But the differences were not statistically significant. Dobu-ECT detected only 56% of ischemias in non-infarct related myocardium. Eighty-two percent of all significantly stenosed vessels were detected with Dobu-ECT, and 84% of patients with multivessel disease could be accurately identified. The sensitivity of Dobu-ECT was significantly greater for detecting severe stenosis over moderate stenosis. The sensitivity for detecting stenosis in the right coronary artery was greater than left anterior descending 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 detect significantly stenosed vessels.