CABG Guidebook 1

9. OPTIMAL PROBE PLACEMENT Place the probe approximately 1.5 cm proximal to the anastomosis you want to examine, as turbulence is more easily detected when the probe is positioned near any narrowing in the vessel. PROBE PLACEMENT In some cases, the probe needs to be placed more proximally to avoid displacement of the heart. Note that the mean flow may remain the same, but the flow curve and PI may differ with a more proximal placement of the probe. A case published by Jelenc et al. in 2013, illustrates how placement of the probe affects TTFM parameters.21 The mean flow is approximately the same for both measurements, but the PI and backflow are different.