Thoracic Artery and Its Sub-Divisions

25 Objective: We compared the flow rates, reactivity and morphology of the distal Internal Thoracic Artery 26 (ITA) and its branches, the Superior Epigastric (SE) and Musculophrenic (MP) arteries to test their 27 applicability as possible conduits in coronary artery bypass grafting (CABG) surgeries. 28 Methods: Skeletonized ITA and sub-divisions of patients undergoing CABG were studied 29 intraoperatively (n=100) for flow and length measurements and in vitro in organ baths (n=58) for active 30 response to Norepinephrine (NE). Quantitative microscopic analysis of the muscle density and the degree 31 of intimal hyperplasia was performed. Results were analyzed according to age, gender, risk factors and 32 medications. 33 Results: ITA subdivisions contributed an average extra length of 2 cm. Free flow rates were 129±45, 34 114±41 and 93±36 ml/min in ITA, SE and MP, respectively. Sternum and ITA length and free flow rates 35 were significantly lower in women. The sub-divisions were significantly more reactive to NE than the 36 distal ITA (p~0.005), though sensitivity to NE was similar. Patients treated with β-blockers had 37 significantly decreased reactivity (p=0.009). Microscopic analysis suggests similar muscle content in ITA 38 and sub-divisions. Eccentric (28%) and concentric (62%) intimal hyperplasia was observed in 90% of 39 specimens, with no evidence for atherosclerotic plaques. There was no significant difference in the 40 degree of intimal hyperplasia between the distal ITA and its subdivisions, and there was no correlation to 41 risk factors. 42 Conclusion: Our results confirm the previous studies on the higher contractility in ITA sub-divisions, 43 suggesting caution in the use of the bifurcation for revascularization. However, the extra length, 44 sufficient flow, and favorable histological properties suggest that the bifurcation may be appropriate for 45 coronary revascularization in selected cases. 46 47