Intraoperative graft verification in coronary surgery: increased diagnostic accuracy adding high-resolution epicardial ultrasonography to transit-time flow measurement.

Objectives: Transit-time flow measurement (TTFM) allows intraoperative functional assessment of grafts in coronary artery bypass grafting (CABG). The major limitation of this technique is a low positive predictive value (PPV) that could lead to unnecessary graft revisions. A combined approach with high-resolution epicardial ultrasonography (HR-ECUS) and TTFM was evaluated for the first time in terms of diagnostic accuracy. The aim of this study is to evaluate the added value of intraoperative HR-ECUS for an improved graft patency verification.
Methods: From November 2009 to September 2012, 333 patients underwent isolated CABG. A total number of 717 grafts were performed; all grafts were intraoperatively verified by means of both TTFM and HR-ECUS.
Results: Among 678 grafts considered functioning at TTFM, 3 (0.4%) were failing at HR-ECUS and promptly redone (2 bilateral internal mammary artery-Y-grafts and 1 left internal mammary artery to left anterior descending (LIMA-LAD)). These were confirmed as true positive at graft revision due to technical error. HR-ECUS confirmed the good functioning of the remaining 675 grafts already demonstrated by TTFM; among them, 8 showed high troponin I release (clinical false negative), whereas the remaining 667 had no high TnI release (clinical true negative). In 2 of 39 grafts malfunctioning at TTFM, HR-ECUS confirmed the graft failure; surgical inspection of the anastomosis during redo procedure (in both cases LIMA-to-LAD graft) showed a technical error leading to define those 2 grafts as 'true positive' on the basis of either direct vision and improved post-redo TTFM parameters. Finally, in 35 cases, HR-ECUS did not confirm TTFM diagnosis demonstrating a full patency of the anastomosis; these grafts had an uneventful clinical course (true negative). The main result of this study is the increase of PPV from 10% with TTFM to almost 100% of TTFM + HR-ECUS, avoiding many unnecessary graft revisions.
Conclusions: HR-ECUS should be considered complimentary to TTFM. Simultaneous use of the two methods during CABG provides morphological and functional information improving considerably diagnostic accuracy of intraoperative graft verification procedure close to 100%.