IMA-graft patency control by thermal coronary angiography during coronary bypass surgery

Thermal coronary angiography (TCA) was evaluated for the intraoperative assessment of graft patency and flow in internal mammary artery (IMA) bypass grafts. TCA was performed in 210 patients undergoing 460 vein and 153 IMA bypass grafts after completion of the distal anastomoses. The IMA grafts and the recipient coronary arteries were delineated by the temperature differential between a cold epimyocardium and the perfusing warm blood after bulldog clamp release. TCA provided information about graft and anastomosis patency, initial flow patterns, and native coronary stenoses. TCA was performed in all studied IMA bypass grafts: 142 grafts were patent. Low flow but patency was observed in 24 IMA grafts and 11 IMA grafts showed no flow. Subsequently, 8 anastomotic failures and 3 proximal IMA graft occlusions were encountered. Based on these findings, 8 anastomoses were successfully revised and 7 additional vein grafts were added. One low flow IMA graft was not revised leading to postoperative ST elevation. Thirty-one distal native coronary stenoses were detected in the recipient LADs, 3 of which were not seen in the preoperative cineangiogram. In 20 instances, TCAs were obscured by an excess of fat or myocardium impeding image analysis. In 8 cases, TCA results were confirmed by conventional angiography postoperatively showing an excellent correlation in all cases. We conclude that intraoperative TCA demonstrates early IMA graft function and initial flow patterns. During our study, TCA documented a 7.2% IMA graft early failure rate. Intraoperative decision making was aided by TCA in 9.2% of all IMA grafts; this confirmed the clinical relevance of TCA.