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Intraoperative Bypass Graft Flow Measurement With Transit Time Flowmetry: A Clinical Assessment

Sanaz Amin1, Raphael S Werner2, Per Lav Madsen3

  • 1Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom; Department of Cardiovascular Surgery, Oxford University Hospitals Trust, Oxford, United Kingdom.

The Annals of Thoracic Surgery
|April 2, 2018
PubMed

Insights

Transit time flowmetry (TTFM) accurately measures left internal mammary artery (LIMA) blood flow during coronary artery bypass graft surgery (CABG), with clinically acceptable precision. However, oversized probes and high flows may lead to overestimation.

Area of Science:

  • Cardiovascular Surgery
  • Medical Device Technology
  • Hemodynamics

Background:

  • Transit time flowmetry (TTFM) is recommended for intraoperative graft patency assessment in coronary artery bypass graft surgery (CABG).
  • Limited studies exist on the accuracy and precision of TTFM for left internal mammary artery (LIMA) graft verification.

Purpose of the Study:

  • To analyze the covariation of LIMA blood flow with TTFM and free flow measurements.
  • To evaluate the accuracy and precision of TTFM in a real-world CABG setting.

Main Methods:

  • Observational study involving 60 patients undergoing CABG.
  • 120 paired intraoperative LIMA flow measurements using TTFM and free flow, before and after vasodilation.
  • Statistical analysis including regression and Bland-Altman methods.

Main Results:

  • TTFM showed a slight overall overestimation of 7.1% compared to free flow.
  • Overestimation was more pronounced with 4-mm probes (13.3%) and high flow rates.
  • Oversized TTFM probes and high flows were independent predictors of overestimation.

Conclusions:

  • TTFM is an accurate and precise indicator of LIMA blood flow during CABG.
  • Potential overestimation should be considered with flows > 68 mL/min and particularly with oversized probes.
  • TTFM remains a valuable tool for intraoperative graft assessment.
Abstract

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