Value and limitations of computed tomography in assessing aortocoronary bypass graft patency.

To determine the value of nondynamic computed tomography (CT) in assessing aortocoronary bypass graft patency, we studied 67 patients with 125 grafts by CT and by coronary angiography at close time intervals. CT scans were performed before and after one to three (average 1.98 +/- 0.65) 50-ml i.v. bolus injections of contrast material. Eighty-four of 92 grafts patent at angiography were also visualized by CT (sensitivity 91.3%); 29 of 33 grafts closed at angiography were considered to be occluded by CT (specificity 87.9%). Eleven of 13 grafts demonstrating one or more severe obstructions at angiography were considered to be patent by CT. Interobserver disagreement existed in four of 125 grafts (3.2%) and intraobserver variability was 1.6%. Although nondynamic CT allows a correct assessment of graft patency in many cases, it does not provide sufficient information on graft stenosis and function to replace angiography in patients who are symptomatic after surgery.