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OBJECTIVE: Graft flow is the important predictor of patency of arterial and vein graft, and is determined by balance against native coronary flow and flow demand. Although evaluation of native coronary stenosis has been improved, impact of flow demand has not been fully discussed yet. We examined the impact of flow demand in the grafted region on the graft flow and patency.
METHODS: We examined 692 bypass grafts in 376 patients, who underwent off-pump coronary artery bypass graft and postoperative angiography between 2007 and September 2014. They consisted of 310 in-situ internal thoracic artery(ITA) to left anterior descending(LAD), 121 in-situ ITA and 63 aorto-coronary saphenous vein graft(SVG) to left circumflex(LCX), and 135 in-situ gastroepiploic artery(GEA) and 63 aorto-coronary SVG to right coronary artery(RCA). Only bypass grafts, which were individual, and created as the sole bypass graft for each vascular region were selected. Flow insufficiency(FI) was defined as 20ml/min or less in intraoperative flowmetry and graft failure was defined as occlusion or string sign in postoperative angiography. MLD was measured at the narrowest portion of the target vessel. Proximal lesion was defined as stenosis at #1~3,5,6 and11, while distal lesion was defined as stenosis at #4,7,and 12~14.
RESULTS: There were 120/692(17.3%) “FI” and 46/692(6.6%) “Failure”. FI significantly correlated with graft failure of ITA(x3.1), GEA(x2.8) and SVG(x5.8), respectively (p<.001). By multivariate logistic regression analysis, distal lesion(OR=3.45, p<.001), RCA(OR=13.3, p<.001) and LCX(OR=2.23, p=.01) region, previous myocardial infarction in the grafted region(OR=3.72, p=.02), and large MLD(OR=3.72, p<.001) were identified as significant predictors of FI.
For RCA, there were 52/198 (26.3%) “FI” and 26/198 (13.1%) “failure”. The causes of FI were competitive flow; 23.1%(11/52), small revascularized area due to hypoplastic RCA or stenosis at midportion of posterior descending branch; 34.7%(17/52), history of myocardial infarction; 34.7%(17/52) and LCX ectasia providing abundant collaterals; 5.8% (3/52).
CONCLUSIONS: Since graft selection based on severity of native coronary stenosis has been introduced, the incidence of competitive flow decreased, whereas influence of flow demand and collateral circulation became evident. The size and viability of revascularized area should be taken into account for surgical decision-making to achieve sufficient graft flow and patency.