Novel and Evolving Aortic Endovascular Devices

Standard Thoracic Endografts

The Gore TAG device (W.L. Gore & Associates, Flagstaff, AZ) became the first commercially available thoracic endograft in the United States in 2005. The device has since been redesigned into a conformable version (CTAG), and most recently to CTAG with Active Control (CTAG-AC). Consistent with other Gore endografts, CTAG-AC is comprised of an expandable polytetrafluoroethylene (ePTFE) fabric with a nitinol exoskeleton and requires an external sheath for delivery. This newest iteration includes a mechanism that allows controlled deflection of the proximal portion of the graft in order to better conform to angulated anatomy. The graft is first partially deployed to 50% diameter, and the angulation mechanism is then used to the extent of the operator’s preference. A final deployment step then allows full expansion of the graft and release. Several single center experiences have been published, which have reported high accuracy and technical success in challenging anatomy. ^,

Medtronic (Santa Rosa, CA) recently updated their Valiant thoracic graft to the Navion platform. This newer generation TEVAR device has a lower profile delivery system than its predecessor (18–22 F outer diameter [OD]), and is offered both with a proximal bare metal stent (FreeFlo) and without (CoveredSeal). Valiant Navion is made of a woven polyester fabric with external nitinol stents. In the pivotal trial leading to FDA approval, there were zero access or deployment failures in 87 patients with high tortuosity of both access vessels and aorta. One patient (1.2%) had a type 1a endoleak at 30 days. One unique feature of this graft is that there are several sizes which are available in very short lengths, as short as 52 mm, expanding its potential clinical uses particularly in locations requiring large diameter, short length devices. Unfortunately, due to issues related to stent fractures leading to type III endoleak, this stent graft was recently subject to an FDA Class I recall and is no longer available. This unexpected problem reinforces the need for post-market surveillance of approved devices .

The current thoracic stent graft from Cook Medical (Bloomington, IN) is the Zenith Alpha device. This graft is very low profile (18 F OD for smaller sizes), and designed to be delivered without an external sheath. The Alpha device is also comprised of woven polyester material with self-expanding nitinol stents. One hundred and ten patients were treated with Zenith Alpha in their international, multicenter pivotal trial, with a technical success rate of 98.2%. At one-year follow-up, freedom from all-cause mortality was 95% and freedom from aortic-related mortality was 99%.

Terumo Aortic (Sunrise, FL) is currently in the process of updating the Relay Plus stent graft to a newer version as well (Relay Pro). While clinical results with the Relay Plus have been favorable, the current drawback has remained the relatively larger profile access required. Relay Pro maintains many of the positive aspects of the prior generation such as a flexible inner sheath for accurate deployment, while lowering the profile to better align with its competitors. Much like its predecessor, Relay Pro will also be available in both bare stent and non-bare stent configurations at the proximal edge. Relay Pro is currently in clinical trial for aneurysm, dissection, and traumatic aortic injury indications.

Finally, the E-Vita Thoracic 3G stent graft (Jotec GmBH, Hechingen, Germany) is an option currently available only outside the United States. This graft is available in both bare spring and covered spring stent options similar to several of the other grafts described here, and in a variety of lengths and tapered configurations as well. The E-Vita is deployed via a unique, stepwise release mechanism, which uncovers 4 mm of graft per click to enhance accuracy. Jotec was recently purchased by CryoLife (Kennesaw, GA), with plans to expand into the US market in the upcoming years.

Arch Branch Devices

Endovascular repair of the aortic arch remains a significant challenge in minimally invasive aortic surgery. The traditional approach to arch pathology has been open surgical arch replacement via either median sternotomy or thoracotomy, generally requiring cardiopulmonary bypass and deep hypothermic circulatory arrest. Hybrid techniques have become more common in recent years, in an attempt to mitigate some of the significant perioperative risk associated with open surgery. Hybrid options include open repair with placement of a thoracic endograft at the distal end of the surgical graft in a “frozen elephant trunk” configuration, ^, and approaches involving extra-anatomic debranching of the supra-aortic branch vessels in combination with standard TEVAR.

Total endovascular solutions for the aortic arch have also become increasingly prevalent, mostly involving off-the-shelf solutions such as parallel grafting ^, and in situ laser fenestration. These techniques have allowed for proximal extension of endovascular therapy into zones 0–2, but are limited by various issues related to the interfaces between components and are considered “off-label” uses of standard FDA-approved devices. Dedicated branched devices for the aortic arch are still in the early stages of development but should allow for more durable repair in the proximal arch once the technology is more mature. At the time this chapter was written, these devices are all still in various stages of investigational use both in and outside the US, therefore not yet commercially available.

Single-Branch Design

There are several single-branch devices currently in active US clinical trials ( Fig. 70.1 ). Because there is only one branch, these devices can be used either for zone 2 repair with branching into the left subclavian artery, or more proximally in combination with surgical supra-aortic debranching. The design of the Gore Thoracic Branch Endoprosthesis (TBE) is based on the CTAG platform, with an ePTFE graft material and nitinol stent frame. The side branch, located 20 to 40 mm from the proximal bare stent, is accessed through an internal portal that is oriented caudally to allow retrograde cannulation via femoral access. The dedicated branch component is tapered for a smooth transition from the portal to the target vessel.

Results from the TBE early feasibility trial were published in 2016, with 100% technical success in 22 patients treated into zone 2 for thoracic aortic aneurysms. Four type 1a endoleaks were seen (18.2%), all of which had resolved by 1-month follow-up without reintervention. Importantly, there were no cerebrovascular complications noted. Side branch patency was 100% at 1 month, and Kaplan–Meier overall survival was 94.7% at 6 months. Based on these encouraging results, TBE has now moved into the pivotal trial phase.

The Medtronic Valiant Navion LSA device (formerly Mona LSA) is based on its Valiant TEVAR counterpart, with a polyester fabric and a helical nitinol stent lattice. Rather than an internal portal, the opening for the side branch is a flexible, external, volcano-shaped cuff. This is cannulated via femoral access in order to deliver the bridging component.

Early feasibility results of the Mona LSA were favorable. Nine patients were treated for thoracic aortic aneurysm or penetrating ulcers, with main body placement into zone 2 and branch revascularization of the left subclavian artery. Technical success was 100%, with no perioperative or 30-day mortality. Four minor strokes were observed in three patients, but there were no major, disabling strokes. Four endoleaks were seen on initial postoperative imaging, two type II and two undefined; none required reintervention. There was also no loss of branch patency during the follow-up period. The Mona LSA recently underwent a redesign onto the newer Navion platform but was unfortunately shelved with the base Navion design following the FDA recall. Its future remains unclear at this time.