**2. Pathophysiology of coronary artery bypass graft failure**

The use of the SVG, arterial grafts or both during CABG is largely depending on the site of anatomic obstruction, the availability of good quality conduits, patient preferences, and the clinical condition of the patient. Adequate arterial conduits are not always available, in contrast SVG are usually of good quality and calibre and are easily harvested, and are thus commonly used as conduits. However, there is an increasing interest for the use of arterial conduits as coronary artery bypass grafts, especially for bypassing the left coronary artery. Although, the choice to use arterial conduits partly depends on the coronary run-off, the long-term patency of arterial grafts is superior for CABG compared to SVG. As more than half of SVG are occluded at 10 years post CABG and an additional 25% show significant stenosis at angiographic followup. [19] SVG failure is the main cause of repeat intervention either by redo CABG or PCI and is even more common than the progression of native coronary artery disease in patients whom underwent CABG. In spite the fact that SVG failure remains a significant clinical and economic burden, the majority of CABG procedures continue to use SVG. [21]

The concept of the 'failing graft' is one of a patent graft whose patency is threatened by a hemodynamically significant lesion in the inflow or outflow tracts or within the body of the graft. Salvage of the failing and failed bypass graft remains an important clinical and technical challenge. The high incidence of graft failure has led to the evolution of graft surveillance programs to detect 'failing' grafts and research has focussed on means to control the devel‐ opment of intimal hyperplasia. [22]
