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Published on: November 24, 2014
An evaluation of the intraoperative transit time measurements of coronary bypass flow
T Hirotani1, T Kameda, S Shirota
1Department of Cardiovascular Surgery, Tokyo Saiseikai Central Hospital, 1-4-17 Mita, Minato-ku, 108-0073, Tokyo, Japan. hero.takashi@nifty.ne.jp
Insights
Intraoperative coronary bypass flow measurement is crucial for identifying errors. Graft flow is influenced by factors like perfusion area and artery diameter, but flow rate alone cannot predict graft issues.
Area of Science:
- Cardiovascular Surgery
- Vascular Surgery
- Surgical Technology
Background:
- Intraoperative measurement of coronary bypass flow aids in detecting technical errors before sternal closure.
- The transit-time flow method is effective for assessing internal thoracic artery (ITA) graft flow.
Purpose of the Study:
- To analyze the factors influencing bypass graft flow rate during coronary artery bypass grafting (CABG).
Main Methods:
- Blood flow was measured in 291 in situ ITA and 190 saphenous vein (SV) grafts from 171 patients using transit-time flow during surgery.
- Postoperative coronary angiography was performed, and graft flow rates were assessed after weaning from cardiopulmonary bypass.
Main Results:
- Mean flow rates were 65.1 ml/min for ITA grafts and 56.4 ml/min for SV grafts.
- Graft flow significantly correlated with grafted perfusion areas and bypassed coronary artery diameter.
- Occluded SV grafts had significantly lower flow rates (29.2 ml/min) than non-occluded grafts (56.4 ml/min).
Conclusions:
- Bypass flow is multifactorial, and flow rate alone is insufficient to predict graft stenosis or narrowing.
- ITA grafts to coronary arteries with less stenosis were more prone to narrowing.
Objective:
The intraoperative measurement of the coronary bypass flow enables the identification of technical errors while the sternum is still open. The transit-time flow method is able to effectively measure the internal thoracic artery graft flow. The aim of the present study was to analyze the factors which affected the bypass flow rate.
Methods:
We measured the blood flow of 291 in situ internal thoracic artery (ITA) and 190 saphenous vein (SV) grafts constructed in 171 patients undergoing coronary artery bypass grafting from December 1996 to March 2000 using this method during the surgery. All patients underwent postoperative coronary angiography before the patients were discharged. The blood flow rate of all bypass grafts constructed was assessed after the patients were weaned from cardiopulmonary bypass.
Results:
The mean flow rate of all ITA grafts was 65.1+/-36.7 ml/min and that of all SV grafts was 56.4+/-29.9 ml/min. According to analyses using correlation tests, the graft flow was found to significantly correlate with the grafted perfusion areas and the diameter of the bypassed coronary arteries. However, no significant difference was observed between the flow rates of the ITA grafts with and without stenosis or string phenomenon, but significant (P<0.0001) correlation was observed between the occurrence of a string sign and the degree of proximal stenosis of the recipient coronary artery. Regarding SV grafts, the mean flow rate of occluded grafts (29.2+/-20.5 ml/min) was significantly (P<0.0001) less than non-occluded grafts (56.4+/-29.9 ml/min).
Conclusions:
The bypass flow was affected by such a large number of factors that only measuring the bypass flow rate could not sufficiently predict either stenosed or narrowed grafts. However, ITA grafts bypassed to the coronary arteries with less stenosis were shown to more easily become narrowed.
