Determination of the Best Parameter for Defining the Hemodynamic Significance of an Iliac Artery Stenosis Detected on Computed Tomography Angiography

Abstract

Purpose The purpose of this study was to determine the best parameter, derived from computed tomography angiography (CTA) for accurate prediction of a hemodynamically significant stenosis of the common or external iliac artery. Methods A retrospective keyword search was performed on the Radiology Information System at our tertiary academic medical centre. Reports from January 2008 to September 2013 were searched using the keywords iliac, stenosis, and pressure. Patients who had both and CTA and a pelvic angiogram with pressure measurements obtained across a potential stenosis were selected. Using 3D postprocessing software (TeraRecon, Foster City, CA), the CTAs were analysed for the following parameters of each lesion: minimum diameter of stenosis, minimum cross-sectional area of stenosis, percent narrowing of vessel diameter, and percent reduction in vessel area. The percent stenosis was calculated in reference to the outer diameter at the point of maximal narrowing and also in reference to a normal segment of vessel more distal to the stenosis. These parameters were then compared with the measured pressure gradient using receiver-operating characteristic analysis and the Mann-Whitney U test to determine which best predicted a significant stenosis, defined as a greater than 10% drop in systolic pressure across a lesion. Results One hundred and two stenoses in 83 patients (26 women, 57 men; 47-88 years old) were identified. Mean diameter of the stenosis was 2.8 mm for significant stenosis compared to 3.8 mm in nonsignificant stenoses ( P = .005). Mean minimum area for significant stenoses was 11.8 mm2 compared to 17.22 mm2 for nonsignificant stenoses ( P = .032) No other variables showed a significant difference between significant and nonsignificant stenoses. A minimum diameter of ≤4.0 mm at the level of a stenosis is 92% sensitive and 48% specific for predicting a hemodynamically significant iliac artery stenosis, with a positive predictive value of 88%. Conclusions A simple measurement of the minimum diameter of an iliac artery at the level of stenosis is the best predictor of the hemodynamic significance of a stenosis in the common or external iliac artery.