Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

BACKGROUND: Guidelines advocate transit time flowmetry (TTFM) for intraoperative graft patency verification during coronary artery bypass graft surgery (CABG), but studies on accuracy and precision of the TTFM technique are few. In an observational study of CABG patients, we analyzed covariation of left internal mammary artery (LIMA) blood flow with TTFM and free flow measurements. METHODS: Covariation of TTFM and free blood flows was evaluated in 60 patients undergoing CABG using the LIMA as one of the conduits. With LIMA flow measurements routinely performed before and after vasodilation, results are based on 120 paired intraoperative measurements. RESULTS: As demonstrated by a combined approach of regression and Bland-Altman analysis for the two flow situations, TTFM was higher than free flow in 64% of measurements, with an overestimation by TTFM of 7.1% ± 16.3% in the overall cohort (prevasodilation), statistically carried by measurements with 4-mm probes (overestimation by 13.3% ± 15.4%, both p < 0.01). In a multiregression analysis, oversizing of the TTFM probe (odds ratio 9.56, 95% confidence interval: 2.03 to 45.10, p = 0.004) and high flows (odds ratio 1.02, 95% confidence interval: 1.01 to 1.04, p < 0.001) were independent determinants of flow overestimation by TTFM, although in the Bland-Altman analysis no systematic overestimation was seen in the postvasodilation situation. In a receiver-operating characteristics analysis, optimal cutoff value as determined from Youden's index for assuming flow overestimation was 68 mL/min. CONCLUSIONS: Overall, with slight overall overestimation of 7.1%, TTFM is an accurate indicator of LIMA blood flow during CABG, with a clinically acceptable precision. Overestimation may be expected with flows greater than 68 mL/min, but most importantly, in situations with oversized TTFM probes.

Original publication




Journal article


Ann Thorac Surg

Publication Date





532 - 538


Academic Medical Centers, Aged, Blood Flow Velocity, Cohort Studies, Coronary Angiography, Coronary Artery Bypass, Coronary Circulation, Coronary Stenosis, Female, Graft Occlusion, Vascular, Humans, Internal Mammary-Coronary Artery Anastomosis, Logistic Models, Male, Middle Aged, Monitoring, Intraoperative, Prognosis, Pulse Wave Analysis, ROC Curve, Retrospective Studies, Rheology, Treatment Outcome, Vascular Patency