TEVAR IN THE AORTIC ARCH

The aortic arch is a challenging environment for many anatomical and device attribute reasons such as tortuosity, the windsock effect, and others. As the indications for TEVAR expanded over the years to include patients with unfavorable anatomy, the limitations of some stent grafts became evident. Many patients have tortuous, calcified, or even small access vessels. Additionally, tortuosity of the descending thoracic aorta and angulation of the aortic arch makes trackability of most delivery systems difficult, increasing the risk of peripheral and cerebral embolization or vessel wall damage. Rupture of iliac vessels and retrograde dissection of the aortic arch have been described as possible complications of thoracic stent grafting.^7,8 The “gothic” arch configuration and the high-pressure environment in the aortic arch may lead to failure in trackability/delivery and deployment issues, thus contributing to type I endoleaks. The design of most thoracic stent grafts was derived from experience with devices for the infrarenal aorta. Furthermore, the currently available devices were intended to treat the straight tube segment of the descending aorta, and so deployment of a stent graft in the arch remains challenging. 

CURRENT LIMITATIONS OF PERFORMING TEVAR

In general, current device-related limitations while performing TEVAR are introduction profile (up to 24 F), accuracy and control during deployment, stent graft conformability, inner curve apposition, preservation of aortic branches, and long-term durability. Additionally, other limitations such as stroke, spinal cord injury, and endoleaks are well documented in the literature.

Use of a device in the distal aortic arch requires perfect conformability and good apposition to the inner curve of the aortic wall to avoid endoleaks, migration, or compression/collapse. Severe arch angulation resulting in lack of inner curve apposition remains a well-documented limitation of commercially available thoracic devices. Therefore, further product research and device development were necessary to produce devices specifically designed to meet the requirements of patients with different pathologies and treatment in different segments of the aortic arch and descending thoracic aorta. 

To better understand and address these clinical challenges and design issues, Gore & Associates created benchtop models to replicate real patient anatomies with severe arch angulation and challenging landing zones. This research supported the development of the next-generation device, which fulfills the need for a conformable thoracic stent graft to meet a broad range of anatomies, combined with an innovative deployment system that provides enhanced control, positioning, and wall apposition during deployment: the GORE^® TAG^® Conformable Thoracic Stent Graft with ACTIVE CONTROL System.*

STENT GRAFT DEVELOPMENT AND EVOLUTION OF THE NEXT-GENERATION SYSTEM

Since its first commercial use in 1998, more than 125,000 GORE^® TAG^® Devices have been distributed worldwide. The original GORE TAG Device was modified in 2003 to eliminate the clinically observed spine wire fracture failure mode. Innovation of stent graft design and improvement of device performance was continued with the Conformable GORE TAG Thoracic Endoprosthesis, which was engineered for endovascular repair of the descending thoracic aorta with special consideration given to the unique anatomic and physiologic characteristics of patients presenting with pathologies involving the aortic arch such as aneurysm, traumatic aortic transection, and aortic type B dissection. The new GORE TAG Conformable Thoracic Stent Graft with ACTIVE CONTROL System, which recently became commercially available in Europe, maintains all attributes of the Conformable GORE TAG Device and adds new tools (Figure 2).

The new delivery system enhances control during deployment and vessel wall apposition. Compared to the current one-step deployment that opens the stent graft from the center toward both ends, the new staged deployment first opens the stent graft to an intermediate diameter from leading to trailing end. This is then followed by a separate handle action that completes stent graft expansion to full diameter from trailing to leading end. 

Angulation along the inner curvature is possible at both intermediate- and full-diameter stages. It is optional and can be skipped at the discretion of the implanting physician. It is important to remember that angulation is irreversible; however, the auditory, visual, and tactile feedback during angulation allows for a slow and controlled adjustment of orthogonal positioning of the proximal end of the stent graft (Figure 3). 

The olive is now precurved and is designed to facilitate self-orientation of the stent graft to the outer curve in the aortic arch. A lock wire keeps the stent graft attached to the catheter throughout the procedure. In comparison to the current Conformable GORE TAG Device, the new-generation device comes with two constraining sleeves rather than one.

The two case reports that follow demonstrate our early experience with the new GORE TAG Conformable Thoracic Stent Graft with ACTIVE CONTROL System.

CASE REPORT 1

A 40-year-old man presented with an asymptomatic progressive postcoarctation aneurysm of 42 mm diameter after two previous open surgical repairs. He was treated with TEVAR in July 2017 at our institution to prevent rupture and aortic-related death. The left subclavian artery (LSA) was revascularized by a staged left carotid-subclavian bypass to create a sufficient proximal landing zone and to prevent endoleak from the LSA. After percutaneous right common femoral access was achieved, routine implantation steps for the GORE TAG Conformable Thoracic Stent Graft were followed using a double-curved stiff wire nested into the aortic valve, eliminating stored energy by first advancing past the target location and pulling the device back to the intended landing zone and by pushing the guidewire and device to the outer curvature during deployment. Upon deployment to intermediate diameter, the gold band demarking the edge of the graft material was clearly observed. At this intermediate-diameter stage, parallax correction was used to optimize device positioning before initiating full and final deployment (Figure 4). Pre- and postoperative images demonstrating successful exclusion of the aneurysm are shown in Figure 5.