MR IMAGING OF CORONARY ARTERY BYPASS GRAFT:A PRELIMINARY STUDY

Objective. To make a preliminary investigation of the patency and function of coronary artery bypass grafts(CABG) by magnetic resonance(MR) images and to establish a suitable method for followup study after CABG operation among Chinese. Methods. MR imaging was performed with a Toshiba 15T unit in 27 patients with 74 grafts. All patients were examined with a breathhold ECGgated twodimensional fast field echo (FFE) sequence to evaluate the patency of bypass grafts, among them 16 patients with 42 grafts were further examined with a phase shift magnetic resonance angiography flow (PSMRAflow) sequence to evaluate the grafts patency as well as the flow velocity and flow volume vs. time. Results. The results showed that 66 of the 74 grafts in the patients of the present series studied with FFE were patent with a patency rate of 892% The results evaluated both with FFE and PSMRAflow remained the same except that two grafts were patent with FFE and the results with PSMRAflow were uncertain. Diastolic perfusion pattern curves were found in 25 of the 32 grafts in patients of the present series. Comparing the flow curves of the grafted left internal mammary artery with those of the native right internal mammary artery in 7 patients, the systolic peak velocity value(SPV) of the grafted arteries was significantly lower than that of the ungrafted ones, whereas the diastolic peak velocity value(DPV) and the ratio of DPV to SPV were significantly greater than that of the ungrafed ones. Conclusion. The FFE and PSMRAflow sequences were efficient in evaluating patency and obtaining the curves of flow velocity and volume of the bypass grafts. Therefore, they may offer a noninvasive screening method for followup study in patients after CABG surgery, although its accuracy should be further evaluated in more patients and comparatively studied with other methods.