Graft-Specific Issues for EVAR: The Aorfix Endograft

Introduction

Anatomical characteristics of infrarenal abdominal aortic aneurysms (AAA) are the most critical factors for successful endovascular repair (EVAR). The long-term durability of EVAR is highly dependent on the integrity of the proximal fixation site. Severe proximal aortic neck angulation (i.e., ≥60 degree angulation between the infrarenal aortic neck and the longitudinal axis of the aneurysm) and iliac angulation/tortuosity make it difficult to introduce the delivery system and deploy the Stent-Graft which tends to kink when encountering severe proximal neck angulation or compound curvatures of the iliac arteries. High proximal aortic neck angulation increases EVAR complexity and is associated with several postoperative complications including persistent Type Ia Endoleak, graft migration, aneurysm sac expansion with late rupture, and requirement for remedial procedures or delayed open conversion. Severe iliac artery tortuosity increases the risk of iliac limb occlusion and Type Ib endoleak.

Patients with these unfavorable anatomical features comprise a large proportion of those who eventually receive EVAR. Initial landmark clinical trials excluded up to 20% of patients with an infrarenal aortic neck angle >60 degrees from receiving EVAR since they did not meet the anatomic restrictions in the instructions for use (IFU) for the endografts available at the time of these trials. Newer generation devices have attempted to accommodate a wider range of aortoiliac anatomies. The Lombard Aorfix endograft (Lombard Medical Inc., Oxfordshire, United Kingdom) is a highly conformable nitinol/polyester device designed for transrenal fixation and accommodates highly angulated aortic necks of up to 90 degrees. Aorfix has been on the European market since late 2004 and was approved by the US Food and Drug Administration (FDA) in 2013 after initial early results of the Prospective Aneurysm Trial: High Angle Aorfix Bifurcated Stent-Graft (PYTHAGORAS) trial showed that outcomes associated with the use of the Aorfix were comparable to those of other endografts used in normal anatomy. The use of the Aorfix increased the number of patients eligible for EVAR, who were previously excluded from this type of treatment.

The Aorfix endograft remains the only on-label alternative to open repair for patients with highly angulated aortic necks. The device uses the ring stent concept and is designed to be flexible and conformable to the vessel, resistant to kinking and twisting, and able to shorten without kinking ( Fig. 9.1 ). These features make it particularly suitable when proximal and/or distal landing zones are considerably angulated, especially in larger aneurysms with elongated aorta and iliac arteries. When implanted, the Stent-Graft rings are reformed to have a saddle or “fish-mouth” shape hugging the renal artery orifice and allowing the endograft to be placed pararenally. The fish-mouth troughs are aligned with the renal arteries juxtarenally and the fish-mouth peak extends suprarenally. This provides optimum seal positioning, which might reduce endoleak risk ( Fig. 9.2 ). The Stent-Graft can also be used in patients with standard anatomy, which helps increase operator familiarity with the device. On certain occasions, namely in patients with tortuous iliac vessels and wide proximal aneurysm necks, main bodies made by other manufacturers in conjunction with the Aorfix iliac limbs have been used ( Box 9.1 ).

EVAR and Device-Specific Complications