Evaluating Potential Autologous Bypass Grafts Using 3d Tomographic Ultrasound (tUS)

Introduction - Vein mapping using duplex ultrasound is helpful in selecting appropriate autologous grafts for bypass, correlates well with surgical utility [1-3], but is time-consuming, operator-dependent and requires that the surgeon trusts the ultrasonographer or vascular scientist. We compared tomographic 3D ultrasound (tUS) with standard duplex for vein mapping. Methods - Vein mapping using standard duplex and tUS on the morning of coronary or peripheral artery bypass were compared. The time taken to acquire each imaging modality was recorded. Post-operatively the operating surgeon scored the agreement for each imaging modality with his score for the graft harvested. A score of 5 was complete agreement, with scores of 4 or 5 counting as good. Results - Standard Duplex and tUS were compared in the assessment of 81 potential grafts in 41 patients: Duplex imaging took a mean (+/-sd) of 11.7±6.8mins compared with 1.1±0.5mins for tUS (p<0.001). tUS was scored as equal or more valuable than duplex at determining the most optimal vessel for bypass in 31 grafts with surgeons scoring that tUS gave them the same or better information than duplex in 32. Surgeons felt that tUS matched the duplex when compared to the graft used for bypass in 19 grafts but that tUS correlated more highly than duplex in a further 11. Surgeons reported that tUS would have changed their decision on which vessel to harvest if they had seen the images pre-operatively in 14 grafts. For a further 14 grafts, surgeons concluded that tUS could replace duplex mapping altogether. Compared to the actual vein graft used, most surgeons agreed tUS could replace duplex. (Figure 1. tUS vein map of the LSV showing associated branches and perforators) Conclusion - Surgeons preferred to see the potential autologous graft to be used for bypass themselves through the use of tUS images. tUS was significantly quicker than duplex and requires less operator skill, making tUS more cost effective. References1.Head, H.D. and M.F. Brown, Preoperative vein mapping for coronary artery bypass operations. The Annals of Thoracic Surgery. 59(1): p. 144-148.2.Cohn, J.D. and K.F. Korver, Optimizing saphenous vein site selection using intraoperative venous duplex ultrasound scanning. The Annals of thoracic surgery, 2005. 79(6): p. 2013-2017.3.Luckraz, H., et al., Pre-operative long saphenous vein mapping predicts vein anatomy and quality leading to improved post-operative leg morbidity. Interactive CardioVascular and Thoracic Surgery, 2008. 7(2): p. 188-191.