Should coronary arteries with less than fifty percent stenosis be bypassed?

Abstract

The unpredictability of progressive coronary atherosclerosis has caused a trend toward grafting arteries with less than 50% stenosis. To evaluate the patency of these grafts and the effect on the native circulation, we reviewed 92 patients (80 men and 12 women) with 302 potentially graftable coronary arteries. Of 226 bypassed arteries, 100 had less than 50% stenosis. The mean interval between operation and catheterization was 16 months. Forty-five patients underwent routine postoperative studies; 47 had symptoms or had had a cardiac event. Patency rates were similar for grafts placed to arteries with less than 50% stenosis (79%) and to arteries with greater than 50% stenosis (81%). Forty internal mammary artery grafts had a 95% patency rate, 96.3% for those grafted to vessels with greater than 50% stenosis and 92.3% for those grafted to vessels with less than 50% stenosis. One hundred eighty-six vein grafts had a 77.4% patency rate, 76.8% for those grafted to arteries with less than 50% stenosis and 78.2% for those grafted to arteries with greater than 50% stenosis. No difference in patency rates occurred for vein grafts to the right, circumflex, or anterior descending coronary arteries. Progressive atherosclerosis in coronary arteries was defined as an increase of at least 20% in estimated stenosis or progression to total occlusion. Progressive atherosclerosis was demonstrated in 20% of 40 nongrafted arteries with less than 50% stenosis, 63% of 100 grafted vessels with less than 50% stenosis, and 51.6% of 93 vessels with greater than 50% stenosis. Thirty-nine percent of arteries grafted with the internal mammary artery had progressive atherosclerosis and 67% of those grafted with saphenous vein (p < 0.05). No difference in progressive atherosclerosis was noted whether grafts were occluded (45%) or patent (57.5%). We conclude that (1) grafts to arteries with less than 50% stenosis have patency rates similar to those with greater than 50% stenosis; (2) internal mammary artery grafts have a higher patency rate and less progressive atherosclerosis than vein grafts to arteries with less than 50% stenosis; (3) in arteries with less than 50% stenosis, progressive atherosclerosis is greater in grafted than nongrafted vessels.