Spectral analysis of graft flow for anastomotic error detection in off-pump CABG

Objective: Flow probes have been introduced as a non-invasive means of anas tomotic quality assessment in off-pump coronary artery bypass graft (CABG). Flow waveform morphology cannot reliably be assessed visually unless sever e anastomotic stenosis is present (>90%). We applied spectral analysis tech niques to determine whether the frequency content of graft flow can improve the surgeon's ability to detect anastomotic errors. Methods: Forty-six mam mary to left anterior descending artery (LAD) anastomoses were created in m ongrel dogs during off-pump CABG surgery. Graft flow was measured using tra nsit-time flow probes with the LAD closed, and the mammary graft patent and with varying degrees of stenosis. The degree of anastomotic stenosis was c reated by an artificial stitch and verified by random postoperative angiogr aphy. Spectral analysis of the graft flow waveforms was performed. Differen ces in the magnitude and phase components of the graft flow for the first f ive harmonics were determined for the varying anastomosis test conditions. Differences were determined using analysis of variance and least square mea ns techniques. Results: The magnitude of the fundamental (zeroth) harmonic was statistically different in the internal mammary artery (IMA) with 0-25% stenosis compared to IMA with 50-75% stenosis (P < 0.01). Further, the mag nitude of the first, second, and fourth harmonics were statistically differ ent in IMA with 0-25% compared to IMA with 75% (P < 0.01). The phase of the first harmonic was statistically different in IMA with 25% stenosis than I MA with 50% stenosis (P < 0.01). No differences in interaction between the LAD and IMA for all ranges of stenosis were detected (P > 0.50). Conclusion : Spectral analysis of graft flow waveforms may be beneficial in detecting lesser degrees of anastomotic stenosis (i.e. < 90%) compared to traditional visual assessment of mean graft flow and/or graft flow waveform morphology . (C) 1999 Elsevier Science B.V. All rights reserved.