Determinants of coronary artery bypass graft patency: 64 multidetector computed tomography versus coronary angiography

Abstract

Background: To evaluate the usefulness of 64-slice multidetector computed tomography (MDCT) in assessing the patency of CABG and to compare MDCT with conventional selective bypass graft angiography (SGA), the gold standard for such assessment. Methods: A total of 131 bypass graft (80 left internal mammary artery grafts, 42 great saphenous vein grafts, two right internal mammary artery grafts, and seven radials artery grafts) in 47 patients (41 men, six women; mean age, 64.1 years; range, 39–85 years; mean heart rate, 67.3 bpm, range 46–98 bpm) were studied with MDCT and SGA, 5 days to 20.3 years (average 364.1 days, median 15.0 days) after CABG procedures. In these grafts, 172 sites of graft anastomosis were evaluated by both MDCT and SGA. Electrocardiogram-gated MDCT was performed with a Somatom Sensation 64 scanner (Siemiens) with a slices of 0.6-mm width at a pitch of 0.2 and gantry rotation of 330 ms. Based on volume-rendered 3D and multiplanar reformation images, anastomoses or bypass grafts were evaluated for patency, high-grade stenosis (≥50% diameter reduction), and occlusion. Results of MDCT and SGA were compared. Results: Of 172 anastomoses, SGA showed that 161 were patent, three were high-grade stenotic, and eight were occluded. Of these, MDCT demonstrated correctly 136 of 161 patent, two of three high-grade stenotic, and eight of eight occluded anastomoses. MDCT demonstrated one stenotic anastomosis to be occluded. According to these results, the overall sensitivity, specificity, and accuracy of the patency of graft anastomoses were 84.5% (136/161), 100% (11/11), and 85.5% (147/172), respectively. Of the 161 patent anastomoses, MCDT was unable to identify 13 because of metallic clip and misdiagnosed one as high-grade stenosis and eleven as occlusion. The major causes of the misdiagnosis on MDCTwere competing flow from and the small diameter of the native coronary arteries at the sites of anastomosis. Conclusions: Sixty four-slice MDCT is useful in assessing the patency of CABG and its use can obviate the use of conventional angiography if the technique demonstrates patency of graft anastomosis.