Intraoperative fluorescence imaging after transit-time flow measurement during coronary artery bypass grafting

This report describes the complementary use of transit-time flow measurement (TTFM) and intraoperative fluorescence imaging (IFI) during off-pump coronary artery bypass grafting (OPCAB) and compares their results with those of subsequent coronary angiography.

The subjects were 159 OPCAB patients, with a total of 435 grafts at a single center between April 2009 and November 2011. During surgery, all grafts were assessed initially by both TTFM and IFI. Transit-time flow measurement was used for screening grafts for possible revision, then IFI was applied to check patency. For IFI, indocyanine green was injected into the superior vena cava, then the presence and timing of fluorescent enhancement were monitored in coronary and graft vessels.

Twelve grafts were revised after poor TTFM scores. Despite some poor TTFM scores even after revision, subsequent IFI showed that all grafts were enhanced. However, two grafts showed delayed enhancement. In one internal thoracic artery (ITA), delay was caused by competitive flow from a mildly stenotic native coronary artery. The other delayed-enhancement ITA was revised. Reanastomosis was constructed with shorter ITA at the larger lumen size. After about 1 week, all patients underwent coronary angiography (plain angiography for 31, computed tomography angiography for 128). These demonstrated that all 385 arterial grafts, and 48 out of 50 venous grafts, were patent.

Our OPCAB series using TTFM and IFI achieve extremely high graft patency in the early graft assessments. "Delayed enhancement" of one ITA in comparison with the other suggested either native competitive flow or a bypass graft problem.