Sixteen-slice multidetector computed tomography for graft patency evaluation after coronary artery bypass surgery.

Objective: To investigate the ability of 16-slice multidetector computed tomography (MDCT) to assess coronary artery bypass graft patency and to detect bypass stenosis by comparison with coronary angiography.

Methods: Thirty patients underwent both conventional coronary bypass angiography and retrospective ECG gated 16-slice multidetector computed tomography after surgery using 0.4 seconds rotation time and 1.25 mm slice thickness.

Results: Among a total of 107 bypass grafts, 101 grafts (94.4%) were evaluable by MDCT. Thirteen patients were taking oral beta blockers. Mean heart rate was 73.6 (52-105). Of the 40 internal mammary arteries and two radial arteries examined, only one was occluded by coronary bypass angiography and MDCT, resulting in a sensitivity of 100% and a specificity of 100%. MDCT correctly diagnosed all patent venous grafts and missed two of the 14 venous grafts shown occluded by conventional angiography resulting in a sensitivity of 85.7% and specificity of 100%. When occluded grafts were excluded, MDCT did not detect two out of two anastomotic arterial graft stenosis >50% and resulted in one false positive result for a sensitivity and specificity of 0% and 97.4%, respectively. MDCT correctly diagnosed one out of three venous stenosis >50% and falsely diagnosed one venous graft stenosis >50% yielding a 33.3% and 97.6% sensitivity and specificity, respectively.

Conclusion: Sixteen-slice MDCT allows for noninvasive evaluation of coronary bypass grafts patency with high diagnostic accuracy. Assessment of distal anastomotic stenosis was deficient, particularly for arterial grafts, still limited by low resolution or artifacts. Improved accuracy may be obtained by more aggressive heart rate reduction.