Iliac Artery Torsion and Calcification Predicts Endovascular Device Rotation and Poor Patient Outcomes in Advanced EVAR

Crawford, Sean 1, 3 ;  Sanford, Ryan 2 ;  Doyle, Matthew 2, 3 ;  Eisenberg, Naomi 3 ;  Wheatcroft, Mark 4 ;  Forbes, Thomas 3 ;  Amon, Cristina 1, 2

1. Institute of Biomaterials and Biomedical Engineering, University of Toronto; 2. Department of Mechanical and Industrial Engineering, University of Toronto; 3. Division of Vascular Surgery, University Health Network, University of Toronto; 4. Division of Vascular Surgery, St. Michael's Hospital, University of Toronto

Objective: Advanced endovascular aneurysm repair (EVAR) with fenestrated and branched stent grafts are increasingly being used to repair complex aortic aneurysms; however, these devices can rotate unpredictably during deployment, leading to device misalignment. The objectives of the current study are A) to identify anatomical markers that can predict stent graft rotation and B) to quantify the short-term clinical outcomes in patients with intra-operative stent graft rotation.

Methods: A prospective study evaluating all patients undergoing advanced endovascular aneurysm repair was conducted at two university affiliated hospitals between November, 2015 and December, 2016. Stent graft rotation was defined as any rotation = 10° as measured on intraoperative fluoroscopic video of the deployment sequence. Standard pre-operative CTA imaging was used to segment the arterial anatomy and calculate the local geometric properties of the arterial tree (i.e. vessel radius, curvature, and torsion). Any post-operative in-hospital/30-day complications were prospectively documented and a composite outcome of any end-organ ischemia and/or death was used as the primary endpoint.

Results: Thirty-seven patients undergoing advanced EVAR were enrolled in the study with a mean age of 75 [64-89] and a mean aneurysm diameter of 63 mm [42-90mm].  The primary indication for surgical repair was aneurysm size (n=36) and rapid aneurysm growth (n=1). One patient was excluded from the analysis following an aborted procedure. The incidence of stent graft rotation was 39% (n=14) with a mean rotation of 25.4° [10.2-51°].  The total net torsion of the iliac arteries was significantly higher in patients with stent graft rotation, 8.9±0.84 mm-1 vs 4.1±0.53 mm-1 (P<0.0001).   The total volume of calcific plaque in the iliac arteries was also significantly higher in patients with stent graft rotation, 1054±143 mm3 vs 537±89 mm3 (P<0.01). There was no significant difference in iliac artery radius or iliac artery curvature.  The composite outcome of end-organ ischemia and/or death was significantly higher in patients with stent graft rotation, 43% vs 4.5% in the control group (P<0.01). Additionally, patients with stent graft rotation had significantly higher rates of type 1 and type 3 endoleaks 36% vs 9% (p<0.05).

Conclusions: Iliac artery torsion and calcification are strongly associated with stent graft rotation, and patients who experience intraoperative stent graft rotation have significantly higher rates of severe post-operative complications. These findings also suggest that pre-operative quantitative analysis of iliac artery torsion and calcification is important for patient risk stratification prior to advanced EVAR.