Graft patency verification in coronary artery bypass grafting: Principles and clinical applications of transit time flow measurement

The increasing popularity of beating-heart coronary surgery has raised conc erns and doubts about the quality of the coronary anastomoses performed. In traoperative graft patency verification methods are not commonly used after coronary surgery and, most of the cardiac surgeons, rely on the simple cli nical signs (electrocardiogram tracings and hemodynamic stability) to make a diagnosis of coronary graft occlusion. New transit time ultrasound based methods for graft-patency verification have been adopted in many centers du ring beating-heart and traditional bypass grafting. Although the results ar e very encouraging, correct interpretation of the flow findings may prove d ifficult if specific rules are not properly followed. Flow curves, pulsatil ity index, and flow values should always be considered simultaneously befor e revising a coronary graft. Measurements should also be always performed w ith and without a proximal coronary snare. This article summarizes the main features of flowmetry and provides some technical pitfalls and suggestions to achieve an adequate intraoperative flow measurement adopting the transi t time method.