Evaluation of the flow characteristics of an internal thoracic artery graft after coronary artery bypass grafting by intercostal Duplex scanning ultrasonography.
We previously reported intercostal duplex scanning ultrasonography to be a reliable technique for the evaluation of the internal thoracic artery (ITA). The purpose of this study was to determine the flow characteristics of the ITA graft using this technique. We evaluated the flow characteristics of 69 ITA grafts who underwent coronary artery bypass grafting by this technique. The internal diameter, mean systolic and diastolic velocity, total flow volume and diastolic fraction were all thus obtained. One occluded graft was found during the follow-up. The mean systolic velocity significantly decreased after the operation (P=0.0001) and the mean diastolic velocity significantly increased both just after the operation (P=0.0002) and 1 year later (P=0.0283). The average diameter of the ITA graft after the operation (1.70+/-0.39), at 1 year (1.73+/-0.29) and at 2 years thereafter (1.66+/-0.27 mm) all significantly decreased in comparison to the preoperative value (2.30+/-0.35 mm) (P=0.0001). The average total flow volume after the operation (35.8+/-22.2), and at 1 year (29.4+/-16.5) and 2 years thereafter (23.4+/-12.7), respectively, were significantly decreased in comparison to the preoperative value (59.4+/-28.6 mL/min) (P=0.0001). However, the average diastolic fraction which was 25.1+/-10.5% before the operation significantly increased after the operation (54.5+/-12.0, 53.2+/-11.2 at 1 year and 50.4+/-9.3 at 2 years) (P=0.0001). This technique is thus considered to be a useful noninvasive for the postoperative follow-up of the graft function. A significant increase in the diastolic fraction is thought to be important for maintaining long term graft patency.