Relation of intraoperative flow measurement with postoperative quantitative angiographic assessment of coronary artery bypass grafting

Background. It is critical to evaluate the anastomotic quality of coronary artery bypass grafting (CABG) in the operating room. The aim of this study is to determine the validity of intraoperative flow measurement for predicting the quality of CABG by comparison with the post-operative quantitative angiographic evaluation of the grafts. Methods. Eighty-two grafts, including 37 internal thoracic arteries, were examined intraoperatively with a transit-time flowmeter. Coronary angiograms were performed 14±5 days after CABG to quantify the diameters at the toe, heel, and anastomosis proper of the grafts. Results. There were significant differences between patent and nonpatent grafts in all intraoperative flow parameters. However, the only cut-off value to distinguish patent from nonpatent was a fast Fourier transformation (FFT) ratio of 1.0. FFT is the ratio of powers of the fundamental frequency and its first harmonic. Postoperative quantitative angiography indicated that the stenosis was greatest at the heel of the anastomosis. The degree of stenosis at the heel of the anastomosis alone correlated significantly with intraoperative mean flow values. Conclusions. Fast Fourier transformation analysis of flow measurement may be useful to differentiate patent grafts intraoperatively. Intraoperative flow measurement may predict the most stenotic part of the anastomosis.