Intraoperative Assessment of Internal Mammary Artery Bypass Graft Patency by Thermal Coronary Angiography

Abstract

Following early graft failure in some patients during routine use of the internal mammary artery In coronary bypass surgery, a thermal coronary angiography technique was used for direct intraoperative control of internal mammary artery graft patency. This non-invasive method allows the evaluation of graft patency, anastomotic integrity and initial flow patterns without compromising the conduct of the surgical procedure. Internal mammary artery graft patency was controlled by thermal coronary angiography in 348 patients undergoing coronary bypass surgery. Graft anatomy, perfusion and distal run-off in the recipient native coronary artery was delineated by thermal coronary angiography using the temperature gradient of the warm perfusing blood and the cold myocardium. Thermal coronary angiograms were evaluated for graft and anastomotic patency as well as for direction and magnitude of internal mammary artery flow in the native coronarles. Some 348 internal mammary artery grafts, including 13 sequential grafts, were evaluated. Thermal coronary angiography failed for technical or logistical reasons in seven of 348 cases (2.0%). Thermal coronary angiography documented optimal anterograde flow in 282 of 341 cases (82.7%). reduced anterograde flow in 38 of 341 (11.1%) and no anterograde flow in 21 of 341 (6.2%). Using this approach 21 internal mammary artery graft occlusions were discovered, 18 at the anastomotic site and three at the site of the previously placed bulldog clamp. In addition, six unexpected distal native coronary stenoses and three Internal mammary artery graft spasms were detected by thermal coronary angiography and found to be responsible for impaired anterograde flow. Based on these findings, 16 anastomotic revisions, nine additional vein grafts and two additional vein patches were performed. Following revision, the patency of internal mammary artery anastomoses and of additional vein grafts was well documented by thermal coronary angiography in all but two cases; in these an additional vein graft was performed when revision of the internal mammary artery graft anastomosis proved ineffective. Thermal coronary angiography revealed an early internal mammary artery graft failure rate of 6.2%, caused by technical error in most cases. Thermal coronary angiography findings led to immediate, low-risk revision and affected intraoperative decision making in 7.9% of patients. Analysis of internal mammary artery graft failures demonstrated a lower incidence of technical errors among experienced surgeons. In conclusion thermal coronary angiography is an easy-to-use. intraoperative, non-invasive method of assessing internal mammary artery graft patency.