Comparison of the waveforms of transit-time flowmetry and intraoperative fluorescence imaging for assessing coronary artery bypass graft patency

Abstract

An intraoperative fluorescence imaging (IFI) system, which can provide visual images, could be the common method for assessing graft patency intraoperatively. We conducted a prospective comparison of the diagnostic accuracy of both the fast Fourier transformation (FFT) analysis of transit-time flowmetry (TTFM) waveform and the IFI system to determine graft failure. The study included 10 saphenous vein grafts (SVGs), all of which were aortocoronary grafts. Each patient underwent isolated coronary artery bypass grafting (CABG), including conventional CABG or off-pump CABG, and then underwent X-ray angiography after CABG. When intraoperative hemodynamics had stabilized, the grafts were evaluated with both the IFI system and TTFM. Based on the obtained flow profile of TTFM, certain variables were calculated. The waveforms of TTFM were analyzed with the FFT series. Harmonic distortion (HD) was calculated from the amplitudes, and the fundamental frequency was thus determined using the FFT series. The IFI system demonstrated a satisfactory flow of all grafts. X-ray angiography demonstrated that one SVG was 75% stenosed, and the others were patent. The mean graft flow (MGF) and the pulsatility index (PI) of the patent SVGs were not significantly different from those of the stenosed SVG. The HD of the patent SVGs was significantly different from that of the stenosed SVG. The HD of the TTFM waveform can provide better diagnostic accuracy for detecting clinically significant grafts than MGF and PI of TTFM and the IFI system.