Transit time flow measurement and high frequency ultrasound epicardial imaging to guide coronary artery bypass surgery

BACKGROUND: Transit-time flow measurement (TTFM) should be routinely used in CABG surgery to verify graft function. Most recently, a 2D high-frequency-ultrasound (HF-US) epicardial imaging probe has been released (MiraQ (TM), Medistim, Oslo, Norway), which allows to evaluate the cannulation/clamping site of the aorta morphologically and to evaluate the completed anastomosis. We aimed to evaluate the use of TTFM and HF-US on surgical strategy during CABG surgery. METHODS: A total of 65 consecutive patients undergoing CABG surgery were evaluated. The target vessels, the clamping/cannulation site and the anastomosis were evaluated by HF-US. TTFM was performed on all grafts and the mean flow (mL/min) and pulsatility indices (PI) were recorded. Troponin-I levels (ng/L) were obtained within the first 4 postoperative days. RESULTS: A total of 3.3 +/- 0.9 grafts were performed, with 98.5% LIMA use and a sequential graft was performed in 55.4%. The mean PI and flow (mL/min) were 2.3 +/- 2.7 and 70.8 +/- 50.6 for the right coronary artery system, 2.4 +/- 2.2 and 82.0 +/- 47.6 for the circumflex system, and 2.1 +/- 1.2 and 78.0 +/- 35.0 for the LAD system, respectively. Postoperative troponin-I levels showed a maximum on postoperative day 1. A surgical strategy change, based on imaging, was done in 15%. Moreover, we observed a correlation of PI and flow with maximum postoperative troponin-I levels. CONCLUSIONS: The present study evaluated the combination of TTFM and HF-US in CABG surgery. Epicardial scanning was helpful to evaluate the potential opening site of the vessel, to evaluate the completed anastomosis or to evaluate the clamping or cannulation site. Troponin-I levels were directly correlated to mean graft flow and PI levels.