AUGMENTED MYOCARDIAL PERFUSION BY CORONARY BYPASS SURGICAL PROCEDURE: EMPHASIZING FLOW AND SHEAR STRESS ANALYSIS AT PROXIMAL AND DISTAL ANASTOMOTIC SITES PROVIDING THE BASIS OF BETTER GRAFT PATENCY RATES

Coronary artery bypass grafting (CABG) surgery is an effective treatment modality for patients with severe coronary artery disease. CABG is a routine surgical treatment for ischemic heart disease. A large number of CABG cases fail postoperatively due to intimal hyperplasia within months or years, due to deleterious blood-flow velocity and shear–stress distributions at the graft–artery junctions. The conduits used during the surgery include both the arterial and venous conduits. Long-term graft patency rate for the internal mammary arterial graft is superior, but the same is not true for the saphenous vein grafts. At 10 years, more than 50% of the vein grafts would have occluded, and many of them are diseased.

This chapter presents the fluid-dynamics of blood flow in (i) the aorto-right in-plane CABG model (the centerline of the aorta, graft, and the host artery all lie in a plane) and (ii) an out-of-plane CABG model (the centerline of the aorta, graft, and the host artery do not lie in a plane), wherein the left anterior descending artery is bypassed using the sapheneous vein. In our model, the dimensions of the aorta, saphenous vein, and the coronary artery simulate the actual dimensions at surgery, and we employ three-dimensional computational fluid-dynamics, to analyze the blood flow at both proximal and distal anastomoses.

Our results have revealed that (i) maximum perfusion of the occluded artery occurs during mid-diastole, (ii) the maximum wall shear–stress variation is observed around the distal anastomotic region, and (iii) there is a decrease in the magnitude of the peak wall shear–stress at the bed of the anastomosis in the non-planar CABG model as compared to the planar geometry, supporting the view that non-planarity of the blood vessel may lead to better graft patency.