Noninvasive evaluation of aortocoronary bypass graft patency by contrast-enhanced computed tomography. Incrementation mode and dynamic mode.

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Abstract
Coronary bypass graft patients (43) were examined with contrast-enhanced computed tomography (CT) to evaluate bypass graft patency. Six 4.8-s sequential scans with 1.4-s interscan intervals were obtained during the injection of a bolus of a contrast medium into a peripheral vein. The sequential dynamic mode and the rapid incrementation mode were used for scanning with contrast enhancement. CT diagnosis correlated with angiographic assessment of graft patency in 36 out of 36 grafts to the left anterior descending artery, in 4 out of 4 grafts to the diagonal branch, in 19 out of 20 grafts to the left circumflex artery and 6 out of 7 grafts to the right coronary artery. Overall, CT correctly identified 62 out of the 64 patent grafts (sensitivity 96.9%); and 3 out of the 3 occluded grafts (specificity 100%). The sensitivity of the incrementation mode alone to detect the bypass graft was 93.0% and that of the dynamic mode was 88.6%. The sensitivity of CT with both modes was 100%. Although CT does not have sufficient resolution to define graft stenosis, it is a noninvasive and clinically useful technique to evaluate bypass graft patency with high accuracy.