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Iliac Artery Deformation During Abdominal EVAR has Consequences for Choice of Iliac Limbs, Optimal C-arm Angulation and Image Fusion Guidance.

      Introduction: The purpose of this study was to assess deformation of the common iliac artery by insertion of stiff guide wires and delivery systems during EVAR.
      Methods: Twenty-two patients treated with abdominal EVAR where included. Three sets of images; the preoperative computed tomography angiography (CTA), an intraoperative contrast enhanced Cone Beam CT (CBCT) acquired when the main trunk of the bifurcated stent graft had been released and both iliac limbs were engaged with stiff guide wires, and the first postoperative CTA, were merged and compared in an image analysis work station. Outcomes were the length and the tortuosity index of the common iliac artery, the Euclidian displacement of the aortic and the iliac bifurcations, and the optimal C-arm angulation for projection of the iliac bifurcation.
      Results: The common iliac artery was shorter in both the intraoperative, mean 6.4mm (95% CI 4.5-8.2 mm) (p<0.001) and the postoperative, mean 2.9 mm (95% CI 0.8 - 5 mm) (p=0.007) images compared to the preoperative CTA. The common iliac tortuosity index was higher in the preoperative CTA compared to the intraoperative CBCT (p=0.003). Intraoperative displacement of the aortic bifurcation was mostly in a cranial direction (100%) (median 5.9 mm) and displacement of iliac bifurcation was mostly in a ventral direction (93%) (median 5.5 mm). The intraoperative C-arm angulation for optimal projection of the iliac bifurcation was changed compared to the corresponding angle measured in the preoperative CTA. The optimal intraoperative anterior contralateral angle increased from median 42 degrees (IQR, 27 – 63) in the preoperative CTA to median 62 degrees (49 - 74) in the intraoperative CBCT.
      Conclusion: Stiff guide wires and delivery systems cause significant deformation of the common iliac arteries during abdominal EVAR. The aortic bifurcation is more cranial, the common iliac arteries are shorter, and the optimal C-arm angulation is more contralateral oblique when the iliac limbs are to be deployed compared to baseline measurements from preoperative CTA. This will also reduce the accuracy of image fusion overlay of the iliac arteries based on the preoperative imaging.

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