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 concerns and doubts about the quality of the coronary anastomoses performed. Intraoperative graft patency verification methods are not commonly used after coronary surgery and, most of the cardiac surgeons, rely on the simple clinical 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 during beating-heart and traditional bypass grafting. Although the results are very encouraging, correct interpretation of the flow findings may prove difficult if specific rules are not properly followed. Flow curves, pulsatility index, and flow values should always be considered simultaneously before revising a coronary graft. Measurements should also be always performed with 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 transit time method.