Assessment of graft patency rate after coronary artery bypass surgery by exercise TL-201 single photon emission computed tomography

Noninvasive assessment of graft function requires detection of myocardial ischemia. Although T1-201 scintigraphy was primarily used to demonstrate improved perfusion soon after bypass surgery, it may be important in detecting graft stenosis late after surgery, identifying patients with symptoms due to graft occlusion. To investigate this, 38 symptomatic patients aged 58 ± 10 years who had undergone bypass surgery 3-7 years previously (mean 4.0 ± 1.2 years) in our center were studied by exercise T1-201 single photon emission computed tomography (SPECT) and coronary angiography. Patients with previous myocardial infarction were not included in the study. Of the 88 coronary bypass grafts examined 42 had significant luminal narrowing (>50%) T1-201 SPECT detected 36 of 42 (86%) stenosed grafts with perfusion defects corresponding to the proper vascular territory. T1-201 SPECT had a higher sensitivity (83% vs 50%, p < 0.01) and predictive accuracy (84% vs 58%, p < 0.02) compared with exercise stress testing in detecting graft stenosis. Sensitivity, specificity, and predictive accuracy of T1-201 SPECT for detection of stenosis were 87%, 93%, and 89% for the left anterior descending coronary artery; 90%, 89%, and 89% for the right coronary artery; and 78%, 76%, and 76% for the circumflex artery, respectively. These results indicate that T1-201 SPECT is a highly sensitive and specific noninvasive technique for detecting and localizing graft stenosis long after coronary bypass surgery.