Suboptimal apposition of the iliac limb (arrow) in a tortuous artery (dotted lines) shown on angiography (A) and in a 3-dimensional reconstruction (B) of an abdominal aortic aneurysm treated endovascularly (arrow). (C) Possible mechanisms leading to limb occlusion involve either high grade stenosis due to reduction of the vessel lumen or vessel injury and intimal hyperplasia (red area) associated with the different directions of endograft and artery movement during the cardiac cycle. (D) Such suboptimal apposition may be addressed with placement of an additional self-expanding stent extending to the straight segment of the external iliac artery (arrow). The color version of this figure is available online at www.jevt.org. 

Contexts in source publication

Context 1

... and aortoiliac tortuosity (ie, the difference between the true iliac length and the shortest distance) have certain hemodynamic consequences on the magnitude and direction of displacement forces, as well as on the pressure Figure 2 illustrates the difference in stress distribu- tion and velocity profiles between the curved and straight renal stent configurations in 2 computational models of fenestrated endografts, as recently shown by our study group. 26 Accordingly, it would be logical to assume that devi- ation from the straight pattern and adaptation to tortuous or angled geometries can impose altered stress patterns to the endograft limbs ( Figure 2E and F). This assumption seems to be in accord with the recently proposed mechanism by Bisdas et al 27 to explain the relation between tortuous iliac geometry and limb occlusion. According to these authors, the excessive tortuosity of the iliac landing zone may lead to suboptimal apposition of the distal limb terminus ( Figure 3A and B). The resultant intimal injuries cause subintimal hyperplasia and local stenosis ( Figure 3C), which in the long run generate a shear stress gradient at the interface between the stent and intima and altered pressure distribution ( Figure 4A-H) dur- ing the cardiac cycle. These changes can predispose ulti- mately to limb occlusion. Notably, the hemodynamic effect of excessive oversizing of iliac limb diameters with respect to the native vessel can be described by the same model. Indeed, Chen et al 28 showed that the stent/vessel size mismatch can induce endothelial flow disturbances and intramural wall stress concentrations that correlate with the extent of neointimal hyperplasia and stenosis at the distal end of the iliac limbs. The gradual devel- opment of these phenomena seem to coincide with the fact that a certain percentage of limb occlusions do not occur within the first days or weeks but can rather appear up to 12 months after EVAR. Indeed, van Zeggeren et al 12 report that 35% of the iliac limb occlusions in their series of 496 patients treated with the Endurant device took place between 2 and 12 months after EVAR, with another 10% after 12 months. Similarly, Bisdas et al 27 identified limb occlusion as the lead- ing cause for reintervention in a series of 273 patients treated with the Endurant endograft in a median follow-up of 42 months; only half of the reinterventions were performed early (<1 year), while 15% of patients were subjected to late secondary procedures after 4 ...

Context 2

... and aortoiliac tortuosity (ie, the difference between the true iliac length and the shortest distance) have certain hemodynamic consequences on the magnitude and direction of displacement forces, as well as on the pressure Figure 2 illustrates the difference in stress distribu- tion and velocity profiles between the curved and straight renal stent configurations in 2 computational models of fenestrated endografts, as recently shown by our study group. 26 Accordingly, it would be logical to assume that devi- ation from the straight pattern and adaptation to tortuous or angled geometries can impose altered stress patterns to the endograft limbs ( Figure 2E and F). This assumption seems to be in accord with the recently proposed mechanism by Bisdas et al 27 to explain the relation between tortuous iliac geometry and limb occlusion. According to these authors, the excessive tortuosity of the iliac landing zone may lead to suboptimal apposition of the distal limb terminus ( Figure 3A and B). The resultant intimal injuries cause subintimal hyperplasia and local stenosis ( Figure 3C), which in the long run generate a shear stress gradient at the interface between the stent and intima and altered pressure distribution ( Figure 4A-H) dur- ing the cardiac cycle. These changes can predispose ulti- mately to limb occlusion. Notably, the hemodynamic effect of excessive oversizing of iliac limb diameters with respect to the native vessel can be described by the same model. Indeed, Chen et al 28 showed that the stent/vessel size mismatch can induce endothelial flow disturbances and intramural wall stress concentrations that correlate with the extent of neointimal hyperplasia and stenosis at the distal end of the iliac limbs. The gradual devel- opment of these phenomena seem to coincide with the fact that a certain percentage of limb occlusions do not occur within the first days or weeks but can rather appear up to 12 months after EVAR. Indeed, van Zeggeren et al 12 report that 35% of the iliac limb occlusions in their series of 496 patients treated with the Endurant device took place between 2 and 12 months after EVAR, with another 10% after 12 months. Similarly, Bisdas et al 27 identified limb occlusion as the lead- ing cause for reintervention in a series of 273 patients treated with the Endurant endograft in a median follow-up of 42 months; only half of the reinterventions were performed early (<1 year), while 15% of patients were subjected to late secondary procedures after 4 ...