Intraoperative evaluation of coronary anastomosis by transit-time ultrasonic flow measurement

Background. Intraoperative assessment of the anastomosis is important during coronary bypass on a beating heart. The purpose of this study is to predict the quality of anastomosis using transit-time flow measurement and to find out the most accurate indicator. Methods. Eight swine underwent internal thoracic-anterior descending coronary artery bypass grafting on a beating heart. Flow measurement and angiography were performed at various degrees of stenosis created on the graft. As flow parameters, total flow, systolic flow, diastolic flow, diastolic/total flow ratio, systolic peak flow, diastolic peak flow, systolic/diastolic peak flow index, and pulsatility index were used. Mixed procedure and probability test (negative means successful anastomosis) were used to analyze the diagnostic ability. Results. Diastolic flow, diastolic/total flow ratio, diastolic peak flow, systolic/diastolic peak flow index, and pulsatility index showed significant variance with increased stenosis. Among these measures, diastolic/total flow ratio showed the highest value of area under the curve (0.91) and the highest specificity (82%) at 90% sensitivity with actual value of 42%. Conclusions. Diastolic/total flow ratio was the most reliable indicator to predict critical stenosis in coronary artery bypass grafting.