Ultrasonic assessment of internal thoracic artery graft flow in the revascularized heart

Abstract

We investigated the clinical applicability of the transittime ultrasound technique for quantitation of internal thoracic artery (ITA) graft flow in coronary artery bypass grafting. Intraoperative measurements of arterial and venous coronary graft flow were performed in 63 patients using an ultrasonic flowmeter. Native ITA blood flow was determined using a skeletonized segment of the ITA and a flexible perivascular flow probe. Simultaneous measures of ultrasonic blood flow from the proximal part of the ITA and free flow from the distal cut end of the ITA validated reliability. After coronary grafting, separate perivascular flow probes over the saphenous vein and ITA grafts were positioned to measure flows during cardiopulmonary bypass and immediately before the sternal closure. Mean native ITA flow was 7 ± 0.8 mL/min and ITA graft flow was 35 ± 4 mL/min, a fivefold increase after grafting to the coronary artery ( p < 0.001). Mean saphenous vein graft blood flow of 38 ± 4 mL/min was not significantly different from the mean ITA graft flow ( p = 0.37). Coronary blood flow via saphenous vein and ITA conduits was unaffected by the Cardiopulmonary bypass ( p = 0.73). No complications were directly caused by the flow measurements. Flow impedance resulting from pedicle twist at the distal anastomosis was easily detected in 2 patients using the ultrasonic flowmeter. We conclude that ITA graft flow can be quantitated intraoperatively by the transit-time ultrasound technique. Ultrasonic assessment of ITA graft flow in the revascularized heart may be a useful means of detecting immediate coronary graft failure caused by technical errors.