Stabilization of a steerable sheath during retrograde access to antegrade-oriented branches in complex endovascular aortic aneurysm repair

During branched endovascular aneurysm repair, cannulation of the visceral target vessels through antegrade branches and insertion of bridging stents are frequently done from an upper extremity access. A retrograde femoral approach is a challenging alternative when an antegrade approach is not preferred. Herein, we describe a technique to increase stability of a steerable sheath, using a single suture, for bridging antegrade-facing branches from a retrograde access. This technique secures the sheath's deflected tip and provides more pushability to the steerable sheath.

Femoral access during endovascular treatment of thoracoabdominal aortic aneurysms is often combined with an upper extremity (UE) access to cannulate and to insert bridging stents into the visceral target vessels. Particularly for stent grafts with antegrade branches, a UE access may be beneficial for antegrade catheterization. 1 However, UE access is associated with occurrence of complications, such as stroke, pseudoaneurysm, hematoma, nerve compression, thrombosis, and distal embolization. 1-3 A retrograde femoral access, using steerable sheaths or curved delivery sheaths, can be used as an alternative when a UE access is contraindicated. 2,3 However, the insertion of stiff guidewires or bridging stents through a curved sheath tip may be challenging because of their rigidity. This report describes a new technique to increase the stability and pushability of a steerable sheath through a retrograde femoral approach during branched endovascular aneurysm repair (BEVAR). The patient has consented to publication of the details and images pertaining to the case.  (Fig 1). After the steerable sheath was deflected toward the preferred angle, the end of the suture was pulled (Fig 1, A and B) and wrapped around the sheath's handle for a firm grip (Fig 1, C). The tip of the sheath was hooked into the respective branches for more stability. Subsequently, four branches and corresponding vessels were cannulated (

DISCUSSION
During BEVAR, a UE access has always been the preferred approach for catheterization of antegrade branches and their target vessels. However, there may be anatomic limitations to a UE access, such as a debranched aortic arch, frozen elephant trunk, severe tortuosity, shaggy arch, or thrombus in supra-aortic branches or in the aortic arch. 2 Furthermore, a UE access is associated with stroke, 1,4 particularly with a right or bilateral UE approach. 5 To refrain from using a UE access, a retrograde femoral access has been described for target vessel cannulation and stenting during BEVAR. To adjust for the angulation from a retrograde approach, a steerable sheath can be used. This is a difficult technique because of lack of pushability and angle stability. Advanced iliac angulation can increase these difficulties. Therefore, we describe a new technique for stabilization of a retrograde steerable sheath for antegrade-oriented branches during BEVAR. A braided suture from the sheath's tip along the outside of the sheath can be pulled downward to secure the tip's angle. It prevents the tip from straightening out when stiff guidewires or rigid stents are advanced through the sheath (Figs 1  and 3). The range of angulation can even be increased as the external force of the supporting wire pulls the sheath tip farther downward. In theory, for our technique, any suture can be used. However, we propose the use of a braided suture as this does not stretch, as opposed to monofilament sutures like Prolene, resulting in a stable curve while a sheath or covered stent is being advanced into the branch.
Branched endografts usually have a relatively small diameter, so retrograde branch cannulation may benefit from a small curve for a better range of motion inside the endograft. A small curve can be provided by a steerable sheath, 2 with the possibility of stabilizing and increasing its curve with a suture, as described in this paper.
Different techniques for retrograde cannulation of downward-facing target vessels or branches have been described previously. 2,3,6,7 A steerable sheath for retrograde use can be created by looping a 0.014-inch guidewire or a suture through a flexible nonsteerable sheath. 6,7 Despite the advantage to creation of a steerable sheath using cheap off-the-shelf materials, this technique is limited by the reduction of the inner diameter. The looped 0.014-inch guidewire or suture decreases the inner lumen of the 10F Fustar sheath, making the passage of a 7F or 8F sheath impossible.
With our technique, the full luminal diameter of the steerable sheath is preserved. Furthermore, because the suture is attached to the Fustar 5 mm from the tip, the free part of the tip can be hooked into the branch, providing for more stability. This is not possible with a looped guidewire or suture through the lumen of the sheath, as described by Mallios et al 6 and Panuccio et al. 7 Thus, the main advantages of our technique are increased stability and pushability, a small curve diameter, and an increased range of deflection. A retrograde approach is associated with prolonged use of large access sheaths in the femoral arteries. As opposed to a UE access approach, the large femoral sheaths cannot be removed for early reperfusion. This may lead to lower extremity ischemia and subsequently even compartment syndrome, or it may increase paraplegia rate. 8,9 Therefore, in our technique, we downgraded to a 14F access sheath to guide our steerable sheath, resulting in better distal perfusion.
Thus far, we have used this technique in 12 cases, in which an additional UE access has not been necessary because of failure of the retrograde approach. This technique has become our preferred approach for treating all BEVARs.

CONCLUSIONS
This technique for retrograde cannulation of antegrade branches during complex endovascular aortic repair, using a steerable sheath and a braided suture, provides stability and pushability and facilitates retrograde insertion of bridging stents while securing the sheath's curved tip. This technique provides a stable alternative when a UE access is not preferred.