Enhanced detection of viable myocardium by technetium-99m-MIBI imaging after nitrate administration in chronic coronary artery disease

The aim of this study was to assess whether nitrate administration improves the imaging capabilities of ^99mTc-MIBI tomography in detecting viable myocardium in coronary artery disease (CAD). Methods: Thirty-one patients with angiographically proven CAD and chronic LV dysfunction (ejection fraction 39% ± 9%) underwent two ^99mTc-MIBI studies on separate days: one under rest conditions and the other after nitroglycerine (0.005 mg/kg per os) administration. Within 1 wk, all patients also underwent rest- redistribution ²⁰¹Tl imaging. Eight patients were also studied by echocardiography before and 5 ± 3 mo after coronary revascularization. Results: On resting ^99mTc-MIBI images, 302 segments had normal uptake, 183 segments had moderately reduced uptake and 197 had severely reduced uptake. Of the segments with severely reduced uptake, 54 (27%) had increased uptake after nitroglycerine and were viable on ²⁰¹Tl images. Of the 143 (73%) segments with severely reduced ^99mTc-MIBI uptake and no change after nitroglycerine, 81% were nonviable on ²⁰¹Tl images. In the eight patients studied before and after revascularization, 87% of segments with reversible ^99mTc-MIBI defects and abnormal LV function demonstrated functional recovery after revascularization, whereas 89% of segments with irreversible ^99mTc-MIBI defects did not. Conclusion: In patients with chronic ischemic LV dysfunction, nitrate administration improved the detection of severely hypoperfused but still viable myocardium on ^99mTc-MIBI images.