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Using Transit-Time Flow Measurements (TTFM) during Total Coronary Arterial Revascularization Significantly Protects Against Major Adverse Cardiac Events (MACE) and Should Be Mandatory

By Susan Eymann, MS06 Jul 2023

Between January 2017 and February 2020, Sorbonne Université clinicians from the Department of Thoracic and Cardiovascular Surgery of the Institute of Cardiology, Paris, France, investigated the clinical impact of transit-time flow measurements (TTFM) on early postoperative outcomes during total arterial coronary revascularization. Their primary end point was to determine an occurrence of an in-hospital major cardiac adverse event (MACE) when TTFM was used during surgery to evaluate the quality of the anastomoses and compare the results to when TTFM was not used.

The retrospective analysis of cardiopulmonary (CPB-on pump) total arterial coronary artery bypass grafting was conducted on 910 patients. Revascularization included skeletonized bilateral internal thoracic arteries (ITAs) with a Y-configuration, or a single internal thoracic artery (ITA) in cases of isolated left anterior descending artery (LAD) disease. Patients were divided into two groups: one (430 patients) in which TTFM was used to assess the anastomoses, and a second (430 patients) where no TTFM measurements were performed. Measurements for each anastomosis were performed at the following points: after cross-clamp release on partial CPB, after total cross- clamp release, and after weaning off CPB. This was done to ensure that the lengths of the grafts and the geometry of the sequential anastomosis were correct, and to inform about competitive flow. Graft patency was assessed using diastolic flow diastolic filling (DF) (>70% for the left coronary bed and >50% for the right coronary bed); mean flow > 15 mL/min, and pulsatility index (PI) between 1 and 5.

Results are shown in the table below.




Time on CPB


Intraoperative Graft Revision

Post-op angiography


Immediate post-op revascularization

Cardiac Related Mortality


TTFM Measurement



0 pts

7 pts (1.4%)


4 pts


3 pts (0.7%)

14 pts (3.3%)

No TTFM Measurement



6 pts (1.4%)


12 pts (2.5%)


8 pts


9 pts (1.9%)

33 pts (6.9%)


Non-cardiac causes of death in the no-TTFM group were septic shock (3), hypoxic arrest (2), and cerebrovascular accident (1). Non-cardiac causes of death in the TTFM group were cerebrovascular accident (3) and mesenteric ischemia in one patient.

From their study, the clinicians concluded that, even though use of TTFM is associated with slightly longer on-pump times, intraoperative graft flow measurement with TTFM reduces MACE occurrence significantly, and TTFM graft evaluation should be mandatory in arterial coronary artery bypass grafting surgery. They state, “TTFM gives important and accurate intraoperative information about the status and patency of each individual graft. It enables technical problems such as kinked, twisted or stenotic grafts to be diagnosed accurately, thereby allowing prompt revision of the constructed grafts before the patient leaves the operating room. Thus, haemodynamic instability during the early postoperative period, which could be catastrophic, is possibly prevented, and the probability of early graft failure is minimized significantly, improving the outcome of CABG surgery.”


REFERENCE Laali M, Nardone N, Demondion P, D'Alessandro C, Guedeney P, Barreda E, Lebreton G, Leprince P. Impact of transit-time flow measurement on early postoperative outcomes in total arterial coronary revascularization with internal thoracic arteries: a propensity score analysis on 910 patients. Interact Cardiovasc Thorac Surg. 2022 Jul 9;35(2). (Transonic Reference # CV-2022-6-2 Laali)