A Novel Method to Determine the Cause of Left Internal Mammary Artery Instant Non-Patency Based on Transit Time Flow Measurement

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

As the current guidelines on myocardial revascularization recommend, transit-time flow measurement (TTFM) is increasingly used for intraoperative graft flow analysis during coronary artery bypass grafting (CABG) as a less invasive, more highly reproducible, and less time-consuming method. In addition to the morphological assessment using color Doppler, mean graft flow (Qm) > 15 ml/min, pulsatility index (PI) < 5.0, diastolic filling (DF) > 50%, and systolic reverse flow (SRF) < 4% have been reported to predict patent CABG grafts. However, it is difficult to determine the clear-cut cut-off value of these parameters, because they varies with the hemodynamic characters, including fractional flow reserve (FFR) of the target coronary artery. In addition to these parameters, we focused on fast Fourier transform (FFT) analysis, because the TTFM waveform morphology may be more important than Qm itself. FFT analysis is based on the principle that any periodic waveforms can be broken down into a series of pure sine waves or harmonics. Herein we review FFT analysis of the intraoperative TTFM waveforms for quality assessment of CABG grafts.

Flow characteristics of in-situ internal thoracic artery graft with competitive flow

We report flow characteristics of an in-situ internal thoracic artery (LITA) graft with angiographically competitive flow to the left anterior descending artery (LAD), based upon intraoperative transit-time flow measurement (TTFM) during coronary artery bypass grafting with aortic valve replacement (AVR) and during re-AVR seven years later. Although intraoperative TTFM of the graft showed lower mean flow and higher pulsatility index, suggesting inadequate anastomosis, fast Fourier transform (FFT) analysis of TTFM waveforms presented gradual waning of the amplitude, as shown in patent grafts. FFT analysis of the TTFM waveforms is helpful to judge the patency of LITA to LAD, even with competitive flow.

Learning objective

The internal thoracic artery (LITA) graft to left anterior descending artery (LAD) with angiographically competitive flow shows gradual waning of the amplitude on fast Fourier transform (FFT) analysis of the transit-time flow measurement (TTFM) waveforms, although lower mean graft flow, higher pulsatility index, and higher systolic reversal flow may suggest inadequate anastomosis. FFT analysis of the TTFM waveforms is useful to judge the patency of LITA to LAD, even with competitive flow.