Assessment of coronary artery bypass grafts by magnetic resonance imaging

This study evaluated graft patency and flow at rest/stress in patients with coronary artery bypass grafts using MR flow measurements and MR angiography (MRA). 45 symptomatic patients with 86 grafts (46 arterial, 40 venous) were examined 5.5 years after surgery. MRA was used to assess bypass patency. Flow measurements were performed at rest and after stress induction with dipyridamole. All graft segments were evaluated at MRA for stenosis, and were additionally evaluated by the combination of flow measurements and MRA. Conventional coronary angiography or multidetector computed tomography was regarded as a reference standard. No significant stenosis was observed in 49 grafts (Group A), whereas significant stenosis was observed in 37 grafts (Group B). Sensitivity, specificity, and positive and negative predictive values for stenosis in arterial grafts were 95.2%, 96.8%, 80% and 99.4%, respectively, and in venous grafts were 100%, 97.8%, 87.5% and 100%, respectively. The mean blood flow rate at baseline/stress in Group B was significantly lower than that in Group A (p<0.002/p<0.001). With the combined MR method, 84 of 86 (97%) grafts could be correctly classified. In conclusion, MRI allows a combined assessment of graft status, including bypass patency and flow, in symptomatic patients after revascularization.