Role of graft flow measurement technique in anastomotic quality assessment in minimally invasive CABG

Background. Anastomotic quality is currently the critical issue in minimally invasive coronary surgery. Although little is known about its effectiveness, surgeons routinely assess grafts intraoperatively using flow probes. This study was designed to determine whether mean flow and the pattern of now tracing in internal mammary artery grafts obtained with a transit-time now probe are reliable indicators of anastomotic quality. Methods. Mongrel dogs (n = 14, 30 to 35 kg) underwent off-pump left, right, or left and right internal mammary artery to left anterior descending artery anastomosis (23 grafts). Moderate to severe degrees of stenosis were created at the anastomosis by an additional suture. Internal mammary artery graft flow was measured before and after the stenosis was created with the left anterior descending artery occluded. Angiography was performed at random postoperatively to validate the degree of stenosis. Mean now and flow tracing morphology were compared under various degrees of stenosis. Results. There were no significant differences in mean graft now or the morphology of the flow tracing between patent (<15%), mild (<25%), moderate (<50%), and moderately severe (<75%) stenosis. However, mean graft now decreased (p < 0.05) With severe stenosis (>75%). Conclusions. Although differences in mean graft flow and graft now morphology were detectable in anastomoses with severe stenosis (>75%), they were indistinguishable in anastomoses with mild (<25%) to moderately severe (<75%) stenosis. Flow measurement techniques are valuable tools intraoperatively, but surgeons should exercise caution in their interpretation.