Predicting Iliac Vein Compression With Computed Tomography Angiography and Venography: Correlation With Intravascular Ultrasound.

Background: Intravascular ultrasound (IVUS) is considered the gold standard in diagnosing common iliac vein (CIV) compression. The presence of >50% surface area reduction by IVUS is considered significant compression by most operators. Thus, we evaluated the role of computed tomography angiography (CTA) and venography in diagnosing CIV compression when compared to IVUS.
Methods: All patients who underwent CTA of the pelvis with venous filling phase, IVUS, and venography within a few weeks apart to evaluate for symptomatic CIV compression from one cardiovascular practice were retrospectively reviewed. Quantitative vascular analysis was performed on all images obtained to determine (1) percent stenosis (PS) by venogram; and (2) minimal lumen area (MLA) and PS by CTA and IVUS at the compression site (using ipsilateral distal CIV as reference area). Spearman's rank correlation, paired t-tests, or signed rank tests were performed as appropriate to compare between values of MLA and PS among the three different imaging modalities.
Results: A total of 96 patients were included (62.5% females; mean age, 62.3 ± 14.8 years). A significant correlation was found between MLA-CTA and MLA-IVUS (Spearman's rho, 0.27; P=.01) and PS-CTA and PS-IVUS (Spearman's rho, 0.327; P<.01). A significant correlation was also found between PS-venogram and PS-IVUS (Spearman's rho, 0.471; P<.001). MLA-CTA and MLA-IVUS had a median difference of +41 mm² (95% CI, 25.0-57.5; P<.001) whereas PS-CTA and PS-IVUS were not statistically different (median difference, -5.6 mm²; 95% CI, -12.2 to 0.7). Furthermore, PS-IVUS and PS-venogram had a median difference of +15.2% (95% CI, 10.4-20.1; P<.001).
Conclusion: PS-venogram correlates with PS-IVUS, but venogram underestimates the PS by an average of 15.2%. In contrast, PS-CTA and PS-IVUS are not statistically different despite an over-estimation of MLA by CTA when compared to IVUS. Therefore, we conclude that PS-CTA and not PS-venogram can be used to predict PS on IVUS.