Fast Fourier transform analysis of intraoperative transit-time flow measurement during coronary artery bypass grafting

Figures

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  Fig. 1. Parameters of intraoperative transit-time flow measurement (TTFM), mean graft flow (Qm); pulsatility index (PI); diastolic filling (DF); and systolic reverse flow (SRF)

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  Fig. 2. Distributions of the parameters of intraoperative transit-time flow measurement (TTFM), mean graft flow (Qm); pulsatility index (PI); and systolic reverse flow (SRF) [15]. Note that it is difficult to determine the definitive cut-off values of Qm, PI, and SFR to distinguish patent grafts (Pat) form non-patent grafts (Non)

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  Fig. 3. Fast Fourier transform (FFT) analysis of intraoperative transit-time flow measurement (TTFM) waveform [15]. As a parameter representing gradual decrease in power of the harmonics of the fundamental frequency, the FFT ratio is calculated as F0/H1, where F0 is a power of the fundamental frequency and H1 is a power of the first harmonic

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  Fig. 4. Four-quadrant matrix in relation between graft patency and the parameters of transit-time flow measurement (TTFM), mean graft flow (Qm) and fast Fourier transform (FFT) ratio

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  Fig. 5. Correlations of the preoperative fractional flow reserve (FFR) of the left anterior descending artery (LAD) and the parameters of intraoperative transit-time flow measurement (TTFM) of the in-situ left internal thoracic artery (LITA) graft and saphenous vein graft (SVG) to the LAD, including mean flow (Qm), pulsatility index (PI), and fast Fourier transform (FFT) ratio [26]. Note that the FFT ratio is not influenced by FFR

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  Fig. 6. Clinical application of fast Fourier transform (FFT) analysis. When the FFT ratio is ≥ 1.0, even if other transit-time flow measurement (TTFM) variables are suboptimal, the graft anastomosis can be considered satisfactory, and the surgical indication for revascularization is not adequate. Conversely, when the FFT ratio is < 1.0, there may be a potential issue with the anastomosis, and therefore graft revision should be considered. LITA: left internal thoracic artery, RCA: right coronary artery, LAD: left anterior descending artery