The Annals of Thoracic Surgery, Vol 58, 135-138, Copyright © 1994 by The Society of Thoracic Surgeons
Ultrasonic assessment of internal thoracic artery graft flow in the revascularized heart
CC Canver and NA Dame
Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine, Madison 53792.
We investigated the clinical applicability of the transit-time 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.