Comparison of blood-flow velocity waveforms in different coronary artery bypass grafts. Sequential saphenous vein grafts and internal mammary artery grafts.

Abstract

Characteristics of blood-flow velocities were investigated at different sites in two types of coronary artery bypass grafts, sequential saphenous vein grafts (SSVG) and internal mammary artery grafts (IMAG). The latter appear to have the longest life span. The patency rate of the side-to-side anastomosis of the SSVG is better than that of the end-to-side anastomosis. The SSVG was anastomosed to the major diagonal branch by side-to-side anastomosis and to the left anterior descending coronary artery (LAD) by end-to-side anastomosis in 13 patients who had 75-100% and 75-90% stenoses in the LAD and major diagonal branch, respectively. IMAG anastomoses were performed to the LAD in 10 patients with 75-100% stenoses of the artery. The blood-flow velocities were measured by the 20-MHz, eighty-channel ultrasound pulsed Doppler method during surgery. In six patients in the SSVG group, we investigated the configuration of velocity profiles at the region just proximal to the side-to-side anastomosis and at the bridge portion between the side-to-side and end-to-side anastomosis. In the other seven patients, we measured the blood-flow velocity at several centimeters proximal to the side-to-side anastomosis and compared it with that in the IMAG. At the region just proximal to the side-to-side anastomosis, the velocity profile skewed toward the anastomosis side wall in all patients, and the flow velocity near the wall opposite to the side-to-side anastomosis was reversed in five of six patients. In the bridge portion, directional changes in skewing of the velocity profile were recognized, that is, a skewed pattern toward the wall opposite to the anastomosis (four patients) or a symmetric pattern (two patients). The peak diastolic velocity in the region was 25.4 + 5.8 cm/sec, significantly lower than that (46.6 ± 12.3 cm/sec) just proximal to the side-to-side anastomosis. The velocity profile across the IMAG several centimeters proximal to the graft-coronary anastomosis showed a parabolic configuration with a narrow spectrum. The velocity profile in eight of 10 patients was statistically parabolic. In the SSVG, however, only two of seven patients were parabolic at the region several centimeters proximal to the side-to-side anastomosis. The peak diastolic velocity in the IMAG (26.6 + 2.0 cm/sec) was almost the same as that in the SSVG (26.3 ± 5.5 cm/sec), but the estimated graft diameter of the IMAG (2.3 ± 0.2 mm) was significantly smaller than that of the SSVG (3.4 ± 0.5 mm), indicating a relatively high shear rate in the IMAG. These findings may provide insight into the underlying mechanisms of graft viability because the patterns of blood flow seem to be a contributory factor in determining the fate of the graft. (Circulation 1988;78:1210-1217 From the Departments of Thoracic Surgery and Medical oronary bypass grafting is frequently perEngineering, Kawasaki Medical School, Kurashiki, Japan. formed to provide adequate perfusion to an

Seminars in Thrombosis, Thrombolysis and Vascular Biology

“…Saphenous veins, both in their na tive form and following aortocoronary anas tomosis, express a weak vasodilatory re sponse to endothelium-dependent mediators such as acetylcholine, thrombin and adeno sine diphosphate [46], In contrast, endothe lium-dependent responses are normal in in ternal thoracic arteries [46]. Furthermore, the blood flow profile in internal thoracic arteries is parabolic with a narrow spectrum of velocity variation, while saphenous veins rarely exhibit parabolic flow and frequently contain complex, skewed velocity fields, par ticularly in the region of the distal arterial anastomosis [47], Beyond the marked differ ences in blood flow characteristics, surgically mediated endothelial damage within the in ternal thoracic artery is minimal, and there fore significant platelet deposition and hy perplastic responses to injury would not be anticipated.…”

Three-Dimensional Simulation of Coronary Artery Bypass Grafting with the Use of Computational Fluid Dynamics

“…CFD can demonstrate the rationality of the optimal flow in many complex problems, but has so far been only limitedly applied to designing cardiac surgery except for a few studies. 10,11 We attempted to simulate CABG using CFD. The preliminary results are reported herein and all clinical inferences based on this study are addressed while focusing on energy loss and the recirculating jet along with wall shear stress, which is thought to play a major role in intimal hyperplasia.…”

Functional Dilatation and Medial Remodeling of the Renal Artery in Response to Chronic Increased Blood Flow

“…Mean blood flow in the renal artery was double the baseline value immediately after creation of infrarenal AC fistula, as a result of increased aortic blood flow. The increased peak flow velocity on the ultrasonic flow tracing indicated the distensibility of blood vessel in order to accommodate for acute increase in blood flow [16,17] . However, both mean flow rate and peak flow velocity in the renal artery were restored to the baseline levels 8 weeks after the creation of AC fistula, while the regional aortic blood flow remained increased [11,12] .…”