Occlusion of internal mammary grafts: a review of the potential causative factors.

The outcome of patient undergoing CABG is largely dependant on the long-term patency of the conduit used. Internal mammary artery (IMA) is considered whenever possible due to its improved long-term functionality over saphenous vein graft. However, a 10% rate of late arterial closure is described without well-known predictors. Chronic competition induced by a moderate coronary lesion on the bypassed native vessel is thought to be a major factor of arterial graft shrinkage even if conflicting data are reported in the available literature. Therefore, the decision to use an IMA to bypass a moderate native coronary lesion should be carefully weighted. When angiography is doubtful, more accurate functional investigations should be considered. Among them, pressure-derived fractional flow reserve could give an immediate answer of whether an intermediate lesion should be bypassed.