Flow Evaluation of a Compliant Coronary Artery Anastomosis Model

Coronary artery bypass grafting (CABG) is a common surgical procedure for coronary artery diseases or severe stenosis of the coronary arteries. It makes use of a peripheral vein (usually the saphenous vein of the leg) to form a conduit between the aorta and the coronary artery distal to the obstructive lesion. It is rapidly becoming the treatment of choice in cases where the vessel is more than 70% occluded or when angioplasty is not possible. However, a significant number of grafts subsequently fail due to acute thrombosis in the early post-operative period or to restenosis within months or years. Intimal thickening in the CABG anastomosis has been implicated as the major cause of restenosis and long-term graft failure. Several studies point to the interplay between non-uniform hemodynamics (including disturbed flows and recirculation zones), wall shear stress, and long particle residence time as possible etiologies. An important feature of the anastomosis geometry, is a bulge that forms at the veno-arterial junction. This sinus forms as a result of the stretching of the thin venous wall when the graft is exposed to aortic pressure conditions. The resultant sinus, and the impedance mismatch of the vein-artery connection, contribute to a complicated region of highly disturbed flow at the divider and may have a primary role in restenosis and final failure of the graft.