Multivessel grafting with internal thoracic artery (ITA) conduits may improve the long-term results of coronary surgery for patients with multivessel coronary disease. Sequential ITA grafting has been increasingly used as a means of allowing a single ITA to revascularize a greater amount of the myocardium (Izzat et al, 1994). In this procedure, the graft first supplies blood to a coronary artery via a side-to-side anastomoses and then delivers blood to a second site in the coronary vasculature through an end-to-side anastomosis. However, it is unclear if the complex geometry and hemodynamic patterns in the side-to-side anastomosis contribute to the development of intimal hyperplasia, as reported for end-to-side anastomoses (Bassiouny et al. 1992). In a previous study we studied the hemodynamics of side-to-side anastomosis when graft and host diameters are equal (Bonert et al., 1999). In this study, we examined the wall shear stress (WSS) characteristics in idealized models of a "parallel" and a "diamond" side-to-side anastomoses for the case in which the graft diameter is substantially larger than the host diameter (Lei et al., 1996). Regions of specific interest were those exhibiting low WSS and rapidly changing WSS (high spatial WSS gradient) both of which have been suggested to promote intimal hyperplasia.
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