A new way to use transit-time flow measurement for coronary artery bypass grafting.

OBJECTIVES Transit-time flow measurement is a recognized method for graft evaluation in coronary surgery. However, single flow measurement has been associated with a low specificity for detecting graft dysfunction. The goal of this study was to assess the value of transit-time flow measurement for assessing in situ internal mammary artery grafts during non-existent native coronary circulation and the relevance of collateral blood flow in target vessels. METHODS Between 2014 and 2018, a total of 134 patients undergoing on-pump coronary artery bypass grafting were evaluated using transit-time flow measurement. We analysed 111 single left internal mammary artery and 57 single right internal mammary artery bypasses. Correlations between coronary relevant parameters were calculated using Spearman's ρ coefficient. Risk factors for decreased flow with an arrested heart (FAH) 3.0 as well as flow reduction >30% were calculated. RESULTS FAH correlated with the diameter of the target vessel (Spearman's ρ = 0.32; P  3) was mainly influenced by percentage of flow change [OR 0.99, CI 95% (0.98-1.00); P = 0.031]. CONCLUSIONS FAH and percentage of flow change are related to the dimensions of the target vessel and the degree of stenosis. The addition of flow measurements with the heart arrested provides additional information about the bypass graft, the quality of the anastomosis and the physiology of the coronary circulation.