Validation of a High-Resolution, Phase Contrast Cardiovascular Magnetic Resonance Sequence for Evaluation of Flow in Coronary Artery Bypass Grafts

Abstract

The aim was to validate a magnetic resonance high-resolution, phase-contrast sequence for quantifying flow in small and large vessels and to demonstrate its feasibility to measure flow in coronary artery bypass grafts. A breathhold, echo planar imaging (EPI) sequence was developed and validated in a flow phantom using a fast field echo (FFE) sequence as reference. In 17 volunteers aortic flow was measured using both sequences. In 5 patients flow in the left internal mammary artery (LIMA) and aorta was measured at rest and during adenosine stress, and coronary flow reserve (CFR) was calculated; in 7 patients, vein graft flow velocity was measured. In the flow phantom measurements, the EPI sequence yielded an excellent correlation with the FFE sequence (r = 0.99; p < 0.001 for all parameters). In healthy volunteers, aortic volume flow correlated well (r = 0.88; p < 0.01), with a minor overestimation. It was feasible to measure flow velocity in the LIMA and vein grafts of the 12 patients. The high-resolution, breathhold cardiovascular magnetic resonance velocity-encoded sequence correlated well with a free-breathing, FFE sequence in a flow phantom and in the aortae of healthy volunteers. Using the EPI sequence, it is feasible to measure flow velocity in both LIMA and vein grafts, and in the aorta.