November 26, 2014

Fenestrated and Branched Stent Grafts are Best for Arch Aneurysms

Aortic arch aneurysms present a significant clinical challenge. Despite improvements in operative techniques and peri-operative care, open repair of aortic arch aneurysms is still plagued by significant morbidity and mortality. Endovascular approaches have significantly altered our approach to aortic arch disease, with the hopes of diminishing complications and mortality. When considering endovascular repair, however, there are many notable obstacles that must be overcome in order to achieve successful exclusion of the aneurysm. Some of these mandates are not unique to endovascular repair of the arch, such as the need for adequate length and diameter of the proximal and distal seal zones. Some obstacles, however, are unique to the arch and include the potential difficulty of navigating through tight arches, maneuvering near the aortic valve, preventing stroke, and maintaining perfusion of the great vessels. Initial approaches to endovascular repair have relied upon extra-anatomic debranching of the arch, with inflow to the great vessels transitioned to a site away from the intended seal zones. These debranching techniques have included bypasses using the ascending aorta as an inflow source, or other extra-anatomic locations such as the carotid arteries.

Initial approaches to “pure” endovascular repair of the aortic arch involved the incorporation of a solitary branch – designed initially for the subclavian artery. These involved the placement of a fenestration (reinforced hole), or an actual branch, incorporated into a thoracic endograft. The fenestration or branch would be aligned with the subclavian artery and secured in place with a bridging stent. One of the original series for this approach was reported by Inoue et al. in 1999 (1). They described the placement of a branched aortic endograft within the aortic arch in 15 patients. Fourteen patients had a solitary branch, while 1 had two branches. Their initial technical success (complete exclusion of the aneurysm) was 60%, with 2 patients have access issues and 4 patients having an initial endoleak. In a mean follow up of 12 months, 73% of patients had complete exclusion of their arch aneurysm. Similar approaches have recently been employed by both Medtronic () and Gore () who have launched clinical trials to assess the outcomes of a single branched aortic arch branched endograft.

The incorporation of one branch, however, does not allow for the total endovascular repair of aortic arch pathologies without at least some hybrid approach to preserve flow to the left carotid and subclavian artery systems. To overcome this, and with the evolution of endovascular device designs, several different devices have been described for the complete repair of the aortic arch with fenestrated and branched endografts. One approach has been to apply in situ fenestrations to standard thoracic aortic endografts. This can be accomplished with the use of a retrograde puncture of the endograft with the use of either a stiff wire system or a laser. The fenestration is then reinforced with the placement of a bridging stent. Arch-specific grafts have also been described. The largest series comes from the mid-term results of Next-gen Fenestrated TEVAR trial in Japan (2). The trial employs a customized, precurved, fenestrated endograft (Najuta Stent-graft, Kawasumi Laboratories, Tokyo, Japan), which is comprised of expanded polytetrafluoroethylene membrane supported by self-expanding Z-stents. The device has 19 types of curved stent skeleton designs and 8 types of graft fenestrations. The system was used in 393 patients with aortic arch aneurysms at 35 medical centers between 2010 and 2011. Technical success (ability to deliver and deploy the graft) was achieved in 99% of patients, with an initial success without type 1 or 3 endoleaks was achieved in 95% of patients. Thirty-day mortality was only 1.5% and only 1.7% of patients had a neurologic event. Critics of the study, however, that durability of this system has yet to be demonstrated.

The use of a true branched endograft has been described by Haulon et al (3). They describe the outcomes of 38 patients (from 10 centers) that underwent complete arch replacement with a branched aortic endograft. The majority of the grafts had two branches that would allow for the incorporation of the innominate artery and the left carotid artery. Technical success (placement of the endograft with incorporation of the branches and no type 1 or 3 endoleak) was achieved in 84% of the patients. In this high-risk group, 30-day mortality was 13.5% with a similar 13.5% rate of neurologic events. Twenty-nine percent of the patients had evidence of an endoleak on pre-discharge imaging, with 5 proximal type 1 endoleaks, 3 type 2 endoleaks, 1 type 3 endoleak, and 2 of unknown etiology. Two of the endoleaks required an early intervention, and by 6 months of follow up the two indeterminate endoleaks and one of the type 1 endoleaks spontaneously resolved. At a median follow up of 12 months, 9% of the patients required a secondary intervention. In addition, there as a 12% late mortality, none were aortic arch related. The authors were able to demonstrate a significant learning curve with this technology. When compared with the first 10 global cases, the remainder of the cohort had significantly lower intraoperative complications, operative time, fluoroscopy time, endoleak rates and secondary procedure rates.

The evolution of endovascular therapy is significantly changing our approaches to treating aortic disease. This progress is clearly seen even in the complex setting of aortic arch pathology. With improvement of device design, and a growing global experience, improved technical performance and immediate clinical outcomes will continue to improve. Clearly, however, we will need larger volume analysis over a significant period of time to better assess the durability of these devices in the setting of the aortic arch.

References:

  1. Inoue K, Hosokawa H, Iwase T, Sato M, Yoshida Y, Ueno K, et al. Aortic arch reconstruction by transluminally placed endovascular branched stent graft. Circulation 1999; 100 (19 Suppl II): 316-21.
  2. Azuma T, Yokoi Y, Yamazaki K. The next generation of fenestrated endografts: results of a clinical trial to support an expanded indication for aortic arch aneurysm treatment. European J of Cardiothoracic Surg 2013; 44: e156-e163.
  3. Haulon S, Greenberg RK, Spear R, Eagleton M, Abraham C, Lioupis C, et al. Global experience with an inner branched arch endograft. J Thor Cardiovasc Surg 2014; 148: 1709-16.