BILATERAL VS SINGLE INTERNAL THORACIC ARTERY GRAFTING FOR LEFT MAIN CORONARY-ARTERY OCCLUSION

This study was conducted to compare the coronary flow distributed by s ingle and bilateral internal thoracic artery (ITA) grafts in the setti ng of the left main coronary occlusion. Ten dogs underwent coronary ar tery bypass grafting through a left thoracotomy, off pump, using a bri ef local occlusion to perform the anastomosis. Dogs were randomly assi gned to receive either a single left ITA (LITA) graft to the circumfle x coronary artery (CFX), or bilateral ITA grafts, with additional plac ement of the right ITA (RITA) to the left anterior descending artery ( LAD). After the grafts were placed, the left main coronary artery was ligated. Electromagnetic flows were obtained in the LAD and the CFX pr oximally and distally to ITA grafts in both groups before grafting and after grafting. ITA now in situ was also measured before rotation fro m the chest wall. Total left ventricular now requirements were satisfi ed equally well by either a single LITA graft (118.7 +/- 11.6 ml/min) or bilateral ITA grafts (total, 116.8 +/- 9.6 ml/min divided as LITA, 55.9 +/- 7.4 ml/min; RlTA, 60.9 +/- 12.0 ml/min). When two grafts were replaced, competitive now in the proximal regions of both native vess els was noted, although basal now requirements were maintained. When a n individual graft was occluded in the bilaterally grafted system, the remaining graft immediately recruited the additional flow, demonstrat ing that either right or left ITA can support now demands five to six times higher than in situ chest wall now (RITA, 21.9 +/- 3.1 ml/min; L ITA, 22.3 +/- 4.9 ml/min). These data suggest that in this canine mode l, a single ITA graft can support the entire now requirements of the l eft ventricle. Assuming no intervening stenosis is present in native c oronary systems, bilateral ITA grafting may provide a margin of safety , but under resting conditions, provides no perfusion advantages over a single ITA graft.