Diagnostic performance of two types of low radiation exposure protocol for prospective ECG-triggering multidetector computed tomography angiography in assessment of coronary artery bypass graft

Background: Multidetector computed tomography (MDCT) is useful in evaluation of coronary artery bypass graft (CABG). However, radiation exposure is a reason for concern. We compared diagnostic performance and effective dose of a new dedicated post-processing reconstruction algorithm with BMI-adapted scanning protocol (MDCT-XTe) vs. standard prospective ECG-triggering protocol (MDCT-XT) and retrospective ECG-triggering (MDCT-Helical), compared to invasive coronary angiography (ICA), in the assessment of grafts and nongrafted or distal runoff coronary arteries.

Methods: One hundred and nineteen patients with 277 grafts were randomized to Group 1 based on BMI-adapted scanning protocol with prospective ECG-triggering (40 patients), Group 2 with prospective ECG-triggering (39 patients) and Group 3 (40 patients) with retrospective ECG-triggering. Data were acquired using 64-slice MDCT.

Results: MDCT correctly assessed the patency of all CABG in 3 groups. After comparison with ICA, MDCT was able to correctly detect the occlusion or stenosis of CABG in all groups, with the exception of one case of Group 3. In Group 3 sensitivity, specificity, positive predictive value, negative predictive value and accuracy of CABG evaluation were 100%, 98.4%, 96.7%, 100% and 98.9%, respectively. In Groups 1 and 2 the diagnostic accuracy of CABG evaluation was 100%. Effective radiation dose was 3.5±1.4mSv in Group 1 vs. 7.4±2.6mSv in Group 2 vs. 27.8±9.4mSv in Group 3.

Conclusions: Our results indicated that MDCT-XTe and MDCT-XT have a diagnostic performance in the evaluation of CABG similar to MDCT-Helical, with a significant reduction of radiation exposure, specially for MDCT-XTe.