VALIDATION OF A NEW TRANSIT-TIME ULTRASOUND FLOWMETER IN MAN

Objectives: To validate the new CardioMed CM 4000 transit time ultraso und apparatus for intraoperative measurement of volume blood flow in v ivo in man. Design: Open, prospective series. Materials: Thirteen pati ents undergoing in situ saphenous vein grafting for chronic critical l eg ischaemia and 12 patients subjected to myocardial revascularisation with the internal thoracic artery as coronary bypass. Methods: During operations, volume blood flows were measured simultaneously by exsang uination from the cut distal end of the in situ saphenous vein graft o r the internal thoracic artery and by the transit time flowmeter equip ment. In addition, the feasibility to detect arteriovenous fistula dur ing in situ saphenous vein grafting was examined. Results: Within the examined blood flow range, the volume blood flow determined by the tra nsit time method corresponded to the directly measured bloodflow. For in situ saphenous vein grafts: y = -2.4 + 0.95 x (r = 0.99; 35 measure ments in 13 patients), and for internal thoracic artery grafts: y = -9 .6 + 1.1 . x (r = 0.99; 21 measurements in 22 patients), where y is bl ood flow determined by transit time and x is directly measured blood f low by exsanguination (r = correlation coefficient) as calculated by t he least squares regression method. Fistula detection was easy and swi ft. Conclusions: The transit time apparatus was simple to use during i ntraoperative settings and gave fast, precise measurements of volume b lood flow.