Late increase in luminal diameter of aortocoronary venous bypass grafts associated with an increase in the vascular region under supply

In a previous study, a significant inverse relation was found between the luminal size of aortocoronary venous bypass grafts and the vascular resistance of the coronary region that was perfused by the bypass graft in late stages after bypass surgery. This observation suggested that changes in the graft-dependent vascular area could influence the luminal size of the vein graft, even when they occurred several years after operation. Whereas it is well established today that aortocoronary vein grafts often decrease in luminal diameter after implantation, an increase in the bypass lumen has so far not been reported. Therefore, changes in luminal diameter of 27 vein grafts in 21 patients who underwent at least two postoperative angiographic studies (first study 8 +/- 5 months after surgery, second study 58 +/- 32 months after surgery) were compared with the size of the vascular region supplied by the bypass. The graft diameter was found to be unchanged between the two studies (3.3 +/- 0.6 versus 3.4 +/- 0.7 mm, p = NS) when the dependent vascular area was unchanged. A significant increase in graft diameter from 2.8 +/- 0.8 to 3.9 +/- 0.9 mm (p less than 0.001) was observed in nine patients in whom the area of perfusion had increased between the two studies because of the development of occlusion or obstruction of major coronary branches that were now perfused from the grafted vessel by way of collateral vessels. These data support the contention that the luminal size of aortocoronary vein grafts can adapt to the needs of the dependent myocardial vascular region even late after operation rather than being the result of a nonreversible degenerative process as commonly assumed.