728-5 Value of Magnetic Resonance Imaging in Assessment of Coronary Artery Bypass Graft Patency and Function: An Angiographically Controlled Study

Abstract

Magnetic resonance (MR) imaging offers the potential to assess coronary artery bypass graft (graft) patency and flow. The purposes of this study were firstly, to assess the graft function by measuring the flow pattern and flow rate with use of MR cine gradient-echo (GE) phase velocity imaging. Secondly, to investigate whether this technique has additional value over spin-echo (SE) imaging for the assessment of graft patency. Forty-seven patients with a previous history of CABG underwent angiography and MR SE and cine GE phase velocity imaging. SE and GE images were evaluated by 3 independent observers who were blinded forthe angiographic results. The spatial mean velocity was measured at consecutive 50 ms intervals throughout the cardiac cycle. Volume flow was calculated by integrating average velocity × graft-area. The 47 patients had 98 proximal aortotomies. Eighty-four grafts (19 occluded) were eligible for comparison of the results of SE and GE images. The comparison of the results of contrast angiography and SE and GE MR imaging techniques showed that both techniques had a high sensitivity (both 98%) and somewhat lower specificity (85% and 88%, respectively) for graft patency. The strength of the interobserver agreement on GE images was good (Kappa: 0.66), whereas on SE images it was moderate (Kappa: 0.51). Graft flow was characterized by a balanced biphasic forward flow pattern. The volume flow of sequential grafts to 3 regions (136 ± 106 ml/min) was significantly higher than in single grafts (63 ± 41 ml/min, p < 0.01). It is concluded that cine GE phase velocity mapping is a promising clinical tool in the non-invasive assessment of graft patency and function.