Coronary artery grafting with the saphenous vein or internal mammary artery. Comparison of late results in two consecutive series of patients.

In two series of consecutive patients who underwent coronary artery grafting with the saphenous vein or the internal mammary artery (IMA), angiographic studies were conducted two weeks and one year after operation. The early patency rate was 91.8% in 184 vein grafts and 97.4% in 38 IMA grafts. Late patency was 93.1% in 143 vein grafts and 90.9% in 33 IMA grafts. Thus, the cumulative patency rate at one year was 84.9% for vein grafts and 88.3% for IMA grafts. The incidence of severe narrowing at the site of anastomosis was 2.2% in vein grafts and 7.9% in IMA grafts; the rate of occlusion of the distal limb of the recipient coronary artery was, respectively, 4.3 and 7.9%. Diffuse reduction in the caliber of grafts at one year was less frequent with IMA grafts (12.7 versus 6.6%). On the other hand, blood flow was significantly higher in vein grafts: 67.4 versus 45.2 ml per minute (p less than 0.001). Blood flow in IMA grafts whose caliber was larger than that of the recipient coronary artery was significantly higher than flow in IMA grafts with a caliber equal or inferior to that of the coronary artery: 63.1 versus 32.7 ml per minute (p less than 0.001). Although cumulative patency rates at one year were comparable in both series, because only one-third of the IMAs were larger than their recipient coronary arteries, flow was somewhat restricted in the other two-thirds. This suggests that the IMA does not constitute the better bypass conduit and, unless it is of large caliber, preferably should be used in the grafting of small coronary arteries or those with limited runoff.