Endovascular Repair of Thoracic Aortic Disease: Overview of Current Devices and Clinical Results

Peter H. Lin; * Hosam F. El Sayed; * Panagiotis Kougias; * Wei Zhou; * Scott A. LeMaire; † Joseph S. Coselli†

Disclosures

Vascular. 2007;15(4):179-190. 

In This Article

Gore TAG Endoprosthesis

The initial feasibility trial of the Gore TAG Endoprosthesis was completed in the United States in 1998, followed by the pivotal trial in 1999.[2] Following a voluntary withdrawal by the manufacturer in 2001 owing to the discovery of fractures involving the longitudinal deployment stent, a modified device was reintroduced after a confirmatory trial in late 2003. It became the first commercially approved thoracic device in the United States as the FDA granted its approval for clinical application in 2005.[1]

The Gore TAG Endoprosthesis is composed of a symmetric expanded polytetrafluoroethylene (ePTFE) tube externally reinforced with a layer of ePTFE and fluorinated ethylene propylene (FEP) (fig 1). An exoskeleton consisting of nitinol stents is attached to the entire external surface of the graft with ePTFE-FEP bonding tape. Both the proximal and distal segments of the endograft have scalloped flares, which are to facilitate endograft conformity in a tortuous thoracic aorta. Two radiopaque gold bands are attached to the base of the flares, serving as a guide during deployment and in graft surveillance. A polytetrafluoroethylene sealing cuff, which is affixed to the base of the flares, is attached on one end with FEP, whereas the other end is allowed to remain free. This is designed to enhance the device attachment to the aortic wall and potentially reduce type 1 endoleaks.

The Gore TAG endoprosthesis.

This device contains a unique deployment mechanism in which the endograft is constrained by an ePTFE-FEP sleeve connected to a deployment knob located at the control end of the delivery catheter (fig 2). Release of the endograft begins in the midgraft region to reduce distal displacement via a “windsock' effect. Following device deployment, a unique trilobed balloon, which permits continuous antegrade aortic blood flow during balloon inflation, is used to ensure full device attachment to the aortic wall (fig 3). The flexible catheter delivery system and the rapid deployment mechanism are potentially beneficial, particularly for deployment in curved segments of the aorta within or close to the aortic arch. The delivery system and compatible introducer sheaths vary according to the diameter of the device and scale over a range of 20F to 24F sheath. Grafts are available in diameters ranging between 26 and 40 mm, and lengths are available in 10, 15, or 20 cm.

Deployment of the Gore TAG endoprosthesis. A, Initial deployment involves turning and pulling the deployment knob. B, The endoprosthesis is fully constrained on the delivery catheter. C, The stent graft is deployed from the middle segment, expanding outward. D, Fully deployed thoracic device.

A trilobed balloon is used to inflate the aortic stent graft while allowing continuous antegrade blood flow during balloon inflation.

The feasibility study was conducted between 1998 and 1999 to establish preliminary device safety data and included 28 patients at two clinical sites. At 30 days, there was one mortality and no paraplegia or stroke. At the 1-year follow-up, the all-cause mortality rate was 21%, with no aneurysm-related mortality. There was an 8% rate of sac enlargement with stent fracture in 32%.

A phase II pivotal trial was conducted between September 1999 and May 2001 and was halted when the high rate of longitudinal wire fractures was detected. This study was a prospective, multicenter, nonrandomized study that evaluated the safety and efficacy of the Gore TAG Endoprosthesis in 17 institutions for the treatment of descending thoracic aortic aneurysm in 142 patients compared with an open surgical repair group of 94 patients.[2] The primary safety end point was the percentage of patients with more than one major adverse event (MAE) through 1 year post-treatment. The primary efficacy end point was the percentage of patients free from major device-related events through the 1-year follow-up for the TAG group. One hundred thirty-nine (98%) of 142 patients had successful implantation of the device. Inadequate arterial access was responsible for the three failures. A conduit was placed to facilitate access in 21 patients (15%). Operative mortality, defined as death within 30 days of the procedure or during the same hospitalization, occurred in 3 (2.1%) patients after a TAG repair and was significantly lower than in the surgical control group, with a mortality rate of 11.7%. Within 30 days of the operation, 45 (32%) patients had at least one MAE: 5 (4%) experienced a stroke, 4 (3%) demonstrated temporary or permanent paraplegia, 20 (14%) experienced vascular trauma or thrombosis, and 2 (1.5%) died. The mean follow-up was 24.0 months. The 2-year all-cause mortality rates were comparable between the TAG and open surgical groups, which were 24% and 26%, respectively. The incidence of MAEs at the 1-year follow-up was significantly lower in the TAG group compared with the surgical controls, which were 42% versus 77%, respectively. The majority (70%) of MAEs were noted to have occurred within 30 days of the original procedure. This advantage to the TAG group persisted through the 3-year follow-up. Kaplan-Meier estimates of the probability of freedom from MAEs at 3 years were 48% after TAG repair and 20% after open repair. During the 3-year follow-up, five patients underwent endovascular revisions and one patient underwent open surgical conversion. Twenty fractures were noted in 19 patients, 18 of which were in the longitudinal spine and 2 in the apical nitinol support tings. Clinical sequelae developed only in one patient, who manifested a type 3 endoleak that was successfully treated with an additional endograft. There were no device-related deaths noted through the 3-year follow-up. Based on the findings of this study, the authors concluded that the Gore TAG Endoprosthesis represents a safe alternative for the treatment of descending thoracic aneurysms, with remarkable 2-year freedom from aneurysm-related death.[1–3]

The confirmatory trial was performed after the reintroduction of the modified device in 2003 to compare the safety and early results of the modified device with the original device. This was a prospective nonrandomized trial performed on 51 patients at 11 test sites, who were compared with the 94 control subjects used in the pivotal study.[3] At the 30-day follow-up, the incidence of MAEs was noted to be 12% in the TAG group and 70% in the control group. This was a statistically significant difference corresponding to an 83% risk reduction for those with TAG repair, although risk classification according to the American Society of Anesthesiologists (ASA) was very similar between both groups and the Society for Vascular Surgery risk score was slightly higher in the TAG group. There were no deaths. There were no major device-related events noted at the 30-day follow-up. This is in comparison with the 4% major device-related complication rate reported in the pivotal study (4%).[3] Based on the anatomic inclusion criteria with a 2 cm landing zone in the proximal and distal aortic neck, patients with descending thoracic aortic aneurysms enrolled in this confirmatory study and other multicenter trials uniformly had an excellent outcome when treated with the Gore TAG endograft devices.[1–3] The 2 cm landing zone in a normal thoracic aorta proximal and distal to an aneurysm is a critical anatomic consideration when placing a thoracic endograft device, and this serves as an important criterion in the device's instructions for use (IFU).

Since the TAG device was approved by the FDA in March 2005, the device has been increasingly used in practice for the treatment of different thoracic aortic pathologies. Experiences from various institutions using this device within the various clinical scenarios and indications are being continuously added to the literatures.[4–7] From our own institutional experience, 128 patients have undergone successful endovascular thoracic repair using the Gore TAG device since March 2005. Among them, 86 patients had a descending thoracic aortic aneurysm with anatomy suited for the device's IFU. The remaining 42 patients had an unsuitable landing zone, with thoracic aneurysms extending either proximally to the aortic arch (n ?=? 25) or distally to the celiac artery (n ?=? 17). These patients underwent aortic debranching procedures in which either the left carotid bypass was debranched to increase the proximal landing zone or the visceral arteries were relocated to increase the distal landing zone. The clinical outcome of these patients who underwent aortic debranching procedures to accommodate Gore TAG device implantation was previously reported.[8,9] The overall mean aortic aneurysm diameter was 6.7 ± 3.2 cm. Technical success was achieved in all patients. Among the 86 patients whose aortic anatomy was within the recommended IFU, one device was used in 43% of patients, whereas 57% required two or more endografts to cover the thoracic aneurysm. The mean intensive care unit (ICU) stay was 2.5 days, whereas the overall hospital stay was 6.4 days. Within 30 days, 14 (16%) patients had at least one MAE, which included 4 (4.7%) patients with renal insufficiency, 2 (2.3%) patients with transient paraplegia, 5 (5.8%) patients with stroke, and 3 (3.5%) patients with femoral artery trauma that necessitated iliofemoral bypass. Among the 42 patients who required either aortic arch vessel or visceral debranching operation to lengthen the device landing zone, significantly greater MAEs were noted, which occurred in 12 (29%) patients. Among them, four (9.5%) patients developed myocardial infarction, five (11.9%) patients developed renal insufficiency, three (7.1%) patients developed transient or permanent paraplegia, and two (4.8%) patients developed stroke. Based on our experience, an excellent clinical outcome can be achieved when using the Gore TAG Endoprosthesis in patients with a descending thoracic aortic aneurysm when endograft placement is based on the device's IFU, a finding that was confirmed by other series.[3,4,10,11] When treating patients with an inadequate proximal or distal landing zone, however, surgeons must be cautious as efforts to lengthen these landing zones by performing aortic arch or visceral debranching operations can still result in relatively high perioperative complication rates.

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