Dual-beam ultrasound versus transit-time flow meter for intraoperative graft flow measurement during coronary artery bypass grafting

: Assessment of graft flow during coronary artery bypass grafting (CABG) is increasingly practiced as a quality measure, particularly in patients undergoing minimally invasive or "off-pump" revascularization. Transit-time flow meters such as Transonic system (TS) are currently the most frequently used technology. The QuantixOR flow probe (QOR) is a novel technology comprised of dual-beam ultrasound transducer and a digital pulse-wave Doppler, allowing immediate, quantitative blood flow measurements. Excellent correlation between QOR and TS was observed in phantom and animal models. This study evaluated the QOR in patients undergoing CABG.

: Graft flow was measured in 75 patients undergoing CABG (203 grafts). Intraobserver (n = 169) and interobserver (n = 33) variability was assessed and the QOR was compared with the TS (n = 155).

: An average of 2 probe sizes per case and "skeletonization" of a short segment of the vessel were required to measure flow in arterial conduits using TS. In contrast, measurements of flow with the QOR were achieved using a single probe without special vessel preparation for all types of conduits. Average intraobserver and interobserver variability using the QOR were 5 ± 41% and 4 ± 40%, respectively. Correlation was observed between 2 sets of measurements by the same observer (R = 0.746, P < 0.0001) and between 2 different observers (R = 0.667, P < 0.0001). Correlation was also observed between the QOR and TS (R = 0.542, P < 0.0001) with a variance of 12 ± 21%.

: The QOR technology provides a reliable quantitative graft flow assessment that is simpler to obtain compared with TS. Correlation between the QOR and TS is excellent.