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Eliminating Redundancy in the Pre-Operative Vascular Surgical Patient Workup: Computed Tomography Angiography for Greater Saphenous Vein Mapping as an Alternative to Traditional Ultrasonography
William F. Johnston, MD, Damien J. Lapar, MD, Kenneth J. Cherry, MD, John A. Kern, MD, Margaret C. Tracci, MD, Gorav Ailawadi, MD, Gilbert R. Upchurch, Jr., MD.
University of Virginia, Charlottesville, VA, USA.
OBJECTIVES: Autologous greater saphenous vein (GSV) graft is frequently used as a conduit during infrainguinal arterial bypass. Pre-operative vein mapping is used to define GSV anatomy, thereby decreasing operative time and reducing wound complications. The purpose of this study was to determine whether GSV mapping using computed tomography angiography (CTA) closely correlated with that of traditional duplex ultrasonography (US).
METHODS: From August 2009 through June 2011, 51 patients underwent CTA of the lower extremities primarily to determine arterial anatomy and US for pre-operative vein mapping. Most of the studies (84%) were performed within one month of each other. GSV diameters measured on CTA [both antero-posterior (AP) and lateral] and US were evaluated at levels of the proximal thigh, mid thigh, knee, mid calf, and ankle. The relationship between CTA and US measurements were compared at each anatomic level using linear regression. Cost savings were calculated to include technical and professional fees.
RESULTS: Average patient age was 61.6 years old with the majority of patients male (70.6%). GSV diameter sequentially decreased from the proximal thigh to the mid calf and then increased to the ankle as measured by CTA and US (both p<0.005). Overall, a high degree of correlation existed between CTA and US GSV diameters. The strongest degree of correlation occurred in measurements at the proximal thigh (CTA-lateral vs. US: R=0.92; CTA-AP vs. US: R=0.93), followed by the mid thigh (CTA-lateral vs. US: R=0.87; CTA-AP vs. US: R=0.86), mid calf (CTA-lateral vs. US: R=0.80; CTA-AP vs. US: R=0.78), knee (CTA-lateral vs. US: R=0.80; CTA-AP vs. US: R=0.76), and ankle (CTA-lateral vs. US: R=0.75; CTA-AP vs. US: R=0.74). All GSV measurements as measured by CTA and US were statistically equivalent (p<0.001 for all correlation coefficients). By eliminating US for the study patients, the potential cost savings at our hospital over the study period was $49,316.
CONCLUSIONS: Indirect venography by CTA correlates well to US for GSV mapping in the lower extremity and provides significant cost savings. CTA allows AP and lateral evaluation of the GSV throughout its anatomic course. As CTA is often performed prior to lower extremity arterial bypass, these results suggest that the use of indirect venography from the preoperative CTA should be considered an acceptable alternative to the use of ultrasonography.
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