Dual-Beam Ultrasound versus Transit-Time Flow Meter for Intraoperative Graft Flow Measurement during Coronary Artery Bypass Grafting

Abstract

Objective

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.

Methods

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).

Results

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 (R² = 0.746, P < 0.0001) and between 2 different observers (R² = 0.667, P < 0.0001). Correlation was also observed between the QOR and TS (R² = 0.542, P < 0.0001) with a variance of 12 ± 21%.

Conclusions

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.