Patency of internal mammary-coronary grafts

Patency of internal mammary artery (IMA) coronary grafts was evaluated in 150 patients having an early (20 days) and late (13 months) postoperative angiogram. Early and late failure for 76 right IMA grafts was 3 and 5 respectively and for 139 left IMA grafts 7 and 7 an overall IMA patency of 95% and 90%. The IMA and coronary internal diameter did not relate to graft closure. Right IMA free flow did not correlate with graft closure. Free flow for thrombosed left IMA grafts (91 ml/min) was significantly (P less than 0.05) lower than for patent grafts (118 ml/min). Right IMA anastomotic flow of 55 ml/min was significantly (P less than 0.001) higher than occluded graft flow of 26 ml/min as was true for patent left IMA grafts (55 ml/min) and occluded grafts (43 ml/min) (P less than 0.025). Five of 215 IMA grafts had diffuse stenosis (greater than 50%). Saphenous vein coronary bypass was performed in 88 instances with an early patency of 89% (79/88) and a late patency of 88% (78/88). Only one of 38 vein grafts to the right coronary artery failed whereas eight of 44 grafts to the circumflex artery occluded. Experience was associated with increased late IMA patency from 81% (57/70), to 89% (;8/76), to 99% (68/69) in each successive group of 50 patients. Currently, the left IMA is routinely used for the left anterior descending artery and the right IMA is rarely used.