Intraoperative flow measurement of coronary bypass grafts using the ultrasound transit time flowmeter

The aim of the study was to compare the mean and maximum flow and the flow pattern of coronary vein grafts (SVG) supplying target vessels of The infer ior and lateral wall with internal mammary (IMA) grafts to the left anterio r descending artery (LAD). In 21 patients 25 bypass grafts (13/25 SVG, 12/2 5 IMA) were investigated. Using the transit time ultrasound method, flow wa s measured every 5 ms and the flow data of 60 s were acquired. The flow pat tern showed significant differences between both graft types during their c ycle. IMA grafts showed only one peak occuring after completing 45.4 +/- 18 .6% of their cycle. The investigated vein grafts showed 2 peaks, one occurr ing after 22.1 +/- 12.3% and the second after 63.4 +/- 15.5% of their cycle . The mean flow was not different in both graft types (IMA: 45.3 +/- 27.0 m l/min and SVG: 41.8 +/- 26.7 ml/min, p = n. s.) as it was the case for the maximum flow (IMA: 98.4 +/- 45.2 ml/min and SVC: 75.7 +/- 55.4 ml/min, p = n. s.). In conclusion, there is a different flow pattern for both graft typ es concerning the number and the occurrence of flow-peaks in the bypass cyc le. The mean and peak flow showed no significant difference.