Intraoperative Evaluation of Blood Velocity Waveforms in Different Coronary Artery Bypass Graft

We investigated the characteristics of blood velocities in different types of coronary bypass grafts, i.e., the saphenous vein graft (SVG; 6 cases) vs the internal mammary artery graft (IMAG; 6 cases) and for different positioning of the sequential saphenous vein bypass graft (SSVG), i.e., the side-to-side anastomosis (SSA) vs the end-to-side anastomosis (ESA), the life span of which are known to be different. The blood velocities were measured by the dual mode (zerocross and FFT), multichannel, high frequency ultrasound Doppler method during bypass graft surgery. Comparing the blood velocities in the SVG with those in the IMAG (longer life span), the velocity profile was much more parabolic and the velocity spectrum was narrower in the IMAG. Regarding the velocities in the SSVG (the SSA has longer life span), the skew of the velocity profile and the reverse flow at the position just proximal to the SSA were always recognized near the probe-side wall (the opposite side of the SSA), indicating the existence of flow separation and recirculation in this region. The direction of skew changed between the SSA and the ESA in almost all cases. These patterns of blood flow seem to be a contributory factor in determining the fate of the graft.