Thoracic Endovascular Aortic Repair (TEVAR) 

Updated: Jan 12, 2021
Author: Thomas M Beaver, MD, MPH; Chief Editor: Dale K Mueller, MD 

Overview

Background

In 1994, Dake et al first reported the use of thoracic "stent-grafts" for the treatment of descending thoracic aortic aneurysms (TAAs) in patients who were believed to be at excessive risk with conventional open surgery.[1]  They showed that placement of thoracic stent grafts, otherwise known as thoracic endovascular aortic repair (TEVAR), could be performed from a technical standpoint with relatively low morbidity; however, they noted that long-term follow-up would be required. The initial stent grafts were actually constructed by the implanting physicians themselves; later, the devices were restricted to those under investigational study.

In 2005, the US Food and Drug Administration (FDA) approved the first commercially available thoracic stent graft, the W. L. Gore TAG endograft system (Flagstaff, AZ); in 2008, the FDA approved the Cook Zenith TX2 (Bloomington, IN)[2]  and the Medtronic Talent (Santa Rosa, CA) thoracic endograft systems. All three of these devices were approved for use in the treatment of TAAs.

The randomized clinical trial that led to the approval of the TAG device demonstrated that in patients with appropriate anatomy, TEVAR could be performed with lower operative mortality than open surgical repair (2.1% vs 11.7%) and with less spinal cord ischemia (3% vs 14%), respiratory insufficiency (4% vs 20%), and renal failure (1% vs 13%).[3]  However, TEVAR yielded more vascular access–related complications. Importantly, a small percentage of patients who were undergoing TEVAR did not have their aneurysms entirely excluded from the aortic circulation at 1- and 2-year follow-up. As in the 1994 study by Dake et al, the authors maintained that all patients undergoing TEVAR required close long-term follow-up.

Dake et al and investigators in Europe later showed that TEVAR was technically feasible in patients with descending thoracic aortic dissections (patients with tears in the wall of their aortas).[4]  Nonetheless, ongoing studies are still trying to identify which patients with thoracic aortic dissection can benefit from TEVAR. Patients with complicated dissections, including those involving malperfusion (where a blood supply is impeded by flaps of aortic tissue caused by the dissection), appear to benefit from TEVAR to seal the site of dissection and reappose aortic wall layers.[4]

It should be noted that historically, open surgical approaches in patients with dissection-related malperfusion have had a high mortality.[5] Accordingly, a US clinical trial examined TEVAR for patients with complicated dissection (STABLE trial, Cook Inc, Bloomington, IN). This multicenter study included patients with complicated type B aortic dissection (cTBAD) who were treated with an endovascular system consisting of proximal TX2 thoracic stent grafts and distal bare-metal dissection stents (Zenith Dissection Endovascular System; Cook Medical, Bloomington, IN). Indications for enrollment included the following:

  • Branch-vessel malperfusion
  • Impending rupture
  • Aortic diameter ≥40 mm
  • Rapid aortic expansion
  • Persistent pain or hypertension despite maximum medical therapy

In this trial, the 30-day mortality was 5% (2/40); two more deaths occurred after 30 days, leading to a 1-year survival rate of 90%. The investigators noted aortic remodeling with a decrease in false lumen diameter and an increase in true lumen diameter, with complete thrombosis of the false lumen in 31% at 1 year.

It would seem logical that TEVAR could also be used in patients with uncomplicated dissections. To address this question, a prospective randomized clinical trial was completed in Europe, the INSTEAD XL trial (INvestigation of STEnt grafts in patients with type B Aortic Dissection).[6] Initially, at 1 year, this trial did not show a mortality benefit[6] ; however, 5-year follow-up revealed an aorta-specific survival benefit in patients treated with TEVAR vs medical therapy (6.9% vs 19.3% risk of aorta-specific mortality), as well as less disease progression risk (27.0% vs 46.1%).[7]

Since the 2005 FDA approval of the TAG device for thoracic aneurysms, the use of endovascular stent grafts for thoracic aortic disease has increased dramatically. Surgeons have subsequently devised novel techniques to facilitate the use of TEVAR in higher-risk patients with more complex anatomy. Branch vessels that would have been occluded by the stent grafts can often be bypassed, and the landing zone can be moved more proximally to allow an adequate seal.[5, 8, 9]  

Additionally, trials are currently under way that are aimed at addressing thoracic aortic pathology encroaching on or involving the arch branch vessels, such as the Gore Thoracic Branch Endoprosthesis (Gore TBE) trial (see the first image below), the Medtronic MonaLSA trial (see the second image below), and the Bolton Dual Arch branch graft trial.

Gore Thoracic Branch Endoprosthesis (Gore TBE). Co Gore Thoracic Branch Endoprosthesis (Gore TBE). Courtesy of WL Gore & Associates, Inc (Investigational use only. Limited by US law to investigational use.).
Medtronic Thoracic Branch Stent Graft. Courtesy of Medtronic Thoracic Branch Stent Graft. Courtesy of Medtronic (Investigational device; use is limited by law to clinical investigational use only. It is not approved for sale in the US or OUS.).

A landmark paper from 2013 by Patterson et al, using prospectively collected data on over 1000 TEVARs from the Medtronic Thoracic Endovascular Registry (MOTHER), performed a subgroup analysis of patients undergoing TEVAR for TAA, chronic type B aortic dissection (CTBAD), and acute type B aortic dissection (ATBAD).[10]  TEVAR was protective from aortic-related mortality, with aortic-related deaths less than 1 per 100 patient-years (equivalent to 1%/y). Freedom from all-cause mortality by life-table analysis over the whole follow-up period was 56% in the TAA group, 64% in the CTBAD group, and 42% in the ATBAD group. Freedom from aortic death was 93%, 96%, and 85%, respectively.

At present, there are four thoracic aortic stent grafts available for commercial use in the United States, each with unique characteristics that should be considered in operative planning and device choice:

  • Valiant Navion thoracic stent graft (Medtronic)
  • TAG conformable thoracic endoprosthesis (W. L. Gore & Associates)
  • Zenith Alpha thoracic device (Cook Medical)
  • RelayPlus system (Terumo Aortic, previously Bolton Medical)

All four devices have FDA indications for use in treating aneurysmal disease; the TAG conformable thoracic endoprosthesis and the Valiant thoracic stent graft have indications for the treatment of all descending thoracic aortic lesions.

Over the course of time, smaller-profile TEVAR devices have been investigated through trials. Currently, the Cook Alpha and the Medtronic Navion are the smallest-profile devices that are commercially available and may be considered in patients with small iliac arteries. Terumo’s Relay Pro low-profile device is currently in the trial phase. Improved device designs result in better conformability with a significant reduction in endoleaks (to as low as 1-2%).[11, 12, 13]

TEVAR has been around for two decades and has been established as the first line of treatment for most descending thoracic aortic pathology (including aneurysms, dissections, and penetrating aortic ulcers), yielding significant reductions in morbidity and mortality as compared with open surgical repair. Improved materials, reduced delivery sheath sizes, enhanced conformability, tapered grafts, and a wider range of sizes have improved TEVAR applicability and outcomes over this initial decade of widespread use. 

Indications

Descending thoracic aortic aneurysm

The official FDA-approved "on-label" indication for the stent grafts currently available commercially in the United States (W. L. Gore C-TAG, Cook Alpha, Medtronic Valiant and low-profile, Navion, and Bolton Relay) is for treatment of descending TAAs with a diameter at least two times greater than that of the adjacent aorta. Furthermore, there must be sufficient aorta (typically 2 cm) of normal dimensions on either side of the aneurysm (the so-called proximal and distal landing zones) to allow the stent graft to adhere (seal) to the aortic walls and achieve exclusion of the aneurysm.

Complicated descending thoracic aortic dissection

TEVAR is increasingly being used as the optimal treatment for patients complicated descending thoracic aortic dissections in preference to open surgery.[4, 5] Clinical experience over time, the ongoing evolution of endovascular devices, and several multicenter trials have led to FDA approval of Medtronic and Gore thoracic stent graft devices for use in patients with acute and chronic dissection. The Zenith Dissection Endovascular Stent is now FDA-approved for patients with chronic dissections and intended to be used as a distal component to support delaminated segments of nonaneurysmal aorta with dissection distal to a Zenith TX2 Dissection Endovascular Graft with Pro-Form.

Focal penetrating ulcer

Patients with focal penetrating ulcers in the thoracic aorta constitute another group in which TEVAR may prove beneficial because these patients have defined, limited areas of the thoracic aorta where loss of endothelial integrity can lead to potentially life-threatening rupture. Coverage of the ulcer with a stent graft can be performed with minimal morbidity. However, patients with penetrating ulcers often have extensive peripheral vascular disease, which may limit their suitability for TEVAR.[6, 14]

Aortic trauma

TEVAR can be life-saving and has now become the standard of care for patients with thoracic aortic trauma resulting in intimal tears, pseudoaneurysms, or frank ruptures.[15]  

Contraindications

Patients undergoing TEVAR must have anatomy that is suitable for deployment of the endografts. The following would be contraindications for placement of TEVAR devices:

  • Proximal or distal landing-zone aortic diameter beyond the range of 18-42 mm (fusiform and saccular aneurysms/penetrating ulcers), 18-44 mm (blunt traumatic aortic injuries), or 20-44 mm (dissections)
  • Proximal and distal aortic neck lengths < 20 mm (fusiform and saccular aneurysms/penetrating ulcers, blunt traumatic aortic injuries); the proximal extent of the landing zone is dissected
  • Extensive circumferential thrombus or calcification of the aortic wall at the desired landing zones; this is a relative contraindication for TEVAR and leads to type I endoleaks
  • Iliac/femoral access vessel morphology that is not compatible with vascular access techniques, devices, or accessories; however, an iliofemoral or aortofemoral conduit may be created to facilitate the use of TEVAR for the thoracic aortic pathology
  • Involvement of branch vessels (including the celiac and subclavian or carotid arteries); however, these branch vessels can often be bypassed to create landing zones in so-called hybrid techniques, [16] or the use of branch graft trial devices may be considered

Patients with connective tissue disorders in whom a high likelihood exists of further tissue degeneration (eg, those with Marfan disease) were specifically excluded from the trials that led to FDA approval of the devices available in the United States (Cook Alpha, C-TAG, Medtronic Valiant, Bolton Relay).

 

Periprocedural Care

Equipment

Hybrid operating rooms (ORs) provide optimal imaging technology for endovascular procedures such as thoracic endovascular aortic repair (TEVAR) and also are sufficiently large to accommodate open surgery in cases where it is required. The authors use the Artis zee system (Siemens Medical Solutions USA, Malvern, PA) in their hybrid OR (see the image below). Ceiling-mounted monitors showing the patient’s vital signs and preoperative computed tomography (CT) scans are recommended.

The authors use the Artis zee system (Siemens Medi The authors use the Artis zee system (Siemens Medical Solutions USA, Inc) in their hybrid operating room. Courtesy of Mark Herboth Photography, LLC, for the University of Florida.

The operating table should allow free access to the imaging C-arm below and should be long enough to accommodate the long guide wires that are used via the femoral artery access points.

Intravascular ultrasonography (IVUS) using a Volcano catheter (Volcano, San Diego, CA) is recommended to optimize graft placement in patients with challenging anatomy and in all patients with aortic dissection. 

Patient Preparation

Anesthesia

Both general anesthesia and continuous spinal anesthesia have been used by the authors. Large-bore intravenous (IV) access for volume infusion is mandatory, along with continuous arterial pressure monitoring.

Spinal cord ischemia is a dreaded complication of TEVAR; therefore, spinal drains are used in patients undergoing this procedure. Drains are placed to drain at 10 mm Hg (15 cm H2O) for 24 hours and are then removed at 48 hours. One may reserve spinal drains for patients deemed to be at highest risk for spinal ischemia (eg, patients undergoing extensive coverage of the thoracic aorta and those with a history of prior abdominal aortic aneurysm [AAA] repair).

Vigilant monitoring for the development of neurologic deficits in the early postoperative period is essential. Delayed neurologic deficits can still be reversed with elevation of systemic arterial pressure and drainage of spinal fluid.[17]

Positioning

The patient remains in the supine position. When brachial artery access is required, the arms are placed at 90º angles and prepared and draped in the operating field.

Bilateral femoral artery access points are prepared along with the abdomen to the level of the nipples.

The entire field is covered with iodine-impregnated adhesive wrap.

Monitoring & Follow-up

Over time, problems with stent grafts may arise (eg, kinking, migration, or leakage), and symptoms may or may not be experienced. Accordingly, lifelong routine surveillance with CT is warranted.[18] Most problems seen after repair can be managed with endovascular techniques.

At the time of discharge, follow-up appointments should be made for 1 month, 6 months, and 12 months from the date of repair, with a repeat CT scan obtained to evaluate the stent graft and the remodeling of the aorta around the graft. After the first 12 months, follow-up is typically done yearly. To ensure the most successful outcome after the procedure, it is crucial that patients comply with the follow-up plan provided.

 

Technique

Approach Considerations

The key to a successful thoracic endovascular aortic repair (TEVAR) procedure is to begin with meticulous preoperative planning to determine the precise size of the endograft, its length, and its relation to critical branch vessels. Several computer programs are available for this purpose; the authors prefer the use of TerraRecon Aquarius software to create a centerline and obtain precise measurements of the proximal and distal landing zones for preoperative planning.

Access sites are chosen on the basis of the anatomy as reconstructed with computed tomography (CT; see the image below). The femoral artery must be of sufficient diameter to allow passage of the endograft; otherwise, a conduit (10-mm Dacron tube graft) must be attached to the larger iliac artery via a retroperitoneal incision.[19]

Three-dimensional CT reconstruction of thoracic ao Three-dimensional CT reconstruction of thoracic aorta with aneurysm in the arch aorta.

Close collaboration with the anesthesia team is required. Place spinal drainage catheters prospectively in patients, especially in those at highest risk for spinal injury (patients who are undergoing complete thoracic aortic coverage or have previously undergone an abdominal aneurysm repair).

Endovascular Repair of Thoracic Aorta

Position and prepare the patient as outlined above (see Patient Preparation) in a sterile fashion.

Obtain percutaneous femoral arterial access on the side that will not be used for delivering the endograft. Insert a 5-French introducer sheath, and pass a pigtail catheter over a 0.035-in. guide wire. After meticulous removal of all air bubbles to avoid air emboli, connect the pigtail catheter to a mechanical contrast injection system (see the image below).

Automated contrast injection system attached to th Automated contrast injection system attached to the 5F pigtail catheter inserted via the left common femoral artery.

Perform an arch arteriogram, typically at 40º left anterior obliquity, to delineate the arch vessels (see the image below).

Baseline aortogram showing arch anatomy. Baseline aortogram showing arch anatomy.

Under ultrasonographic guidance, obtain percutaneous access to the common femoral artery bilaterally, and use two Perclose ProGlide devices (Abbott Vascular, Santa Clara, CA) on the side that will deliver the stent graft. If the access vessel (external iliac artery) is too small or diseased to allow passage of the delivery sheath, then sew a Dacron graft "conduit" to the side of the iliac artery via a retroperitoneal incision, and use this to pass the stent graft into position. (See the images below.) A 5-French sheath may be placed via the contralateral femoral access for placement of a pigtail/imaging catheter.

Retroperitoneal incision to access the right commo Retroperitoneal incision to access the right common iliac artery.
Dacron conduit attached to the right common iliac Dacron conduit attached to the right common iliac artery brought out below through a separate incision.

Directly cannulate this conduit with an 18-gauge needle, and pass a 0.035-in. guide wire into the ascending aorta under fluoroscopic guidance. Then exchange this flexible wire for a "superstiff" wire (eg, Lunderquist) that will be used to provide a rail to deliver the stent graft into position.

On the back table, prior to use, meticulously prepare the endograft delivery system according to the manufacturer's instructions to remove air bubbles and to ensure proper delivery of the endograft. (See the image below.)

The endograft delivery system. The endograft delivery system.

Use the radiographic markers on the endograft to position it exactly where it is to be deployed, and obtain confirmation angiographic images as necessary (see the image below). A sufficiently large landing zone (2 cm) is required to seat the endograft; occasionally, this requires deploying the endograft across the left subclavian artery. Deploy the thoracic endograft.

Predeployment angiogram showing the endograft in t Predeployment angiogram showing the endograft in the arch aorta.

Perform balloon dilation of the endograft when indicated according to instructions for use so as to ensure apposition of the endograft to the wall of the thoracic aorta and thereby minimize the potential for endoleaks around the endograft.

Obtain completion angiographic images (see the images below). If necessary, the left subclavian artery can be bypassed and/or occluded with coil embolization to prevent endoleaks.

Angiogram performed following endograft deployment Angiogram performed following endograft deployment.
Coil embolization of left subclavian artery to pre Coil embolization of left subclavian artery to prevent endoleak.

Carefully remove delivery catheters and sheaths, with the contralateral guide wire remaining in position. The "delivery" femoral or iliac artery is repaired by tightening the polypropylene sutures preplaced with the Perclose device or by performing primary repair in patients requiring open femoral exposure/iliac conduit.

Remove the guide wire from the "imaging" femoral artery, and seal the femoral artery access point.

Confirm distal pulses before leaving the operating suite.

Transfer patients to the cardiac intensive care unit for monitoring of neurologic and hemodynamic function.

Pearls

Multidisciplinary collaboration between skilled vascular and cardiac surgeons is critical for safe and successful development of an endovascular aortic treatment program. Although the incidence of intraoperative surgical conversion remains low, late complications and remedial secondary procedures may necessitate complex thoracic aortic reconstructions. Despite the seeming simplicity of such procedures, unforeseen anatomic and device-related complexities can transform these cases into highly complicated ones that demand advanced endovascular skills on the part of the practitioner in order to bring the procedure to a safe and successful conclusion.

Maintaining proper guide wire access throughout the procedure is vital to the safety of the procedure. The guide wire is analogous to "proximal" control of a blood vessel during open vascular surgery. As long as guide wires remain in position, life-saving occlusion balloons can be passed proximal to iliac or femoral artery sites that may tear during sheath retrieval.

Catheter and guide wire "hygiene" is important for avoiding air embolism and thromboembolism of clot and fibrin debris that tends to collect around the guide wires. The guide wires should be wiped, and the catheters should be flushed frequently with heparinized saline during the procedure.

Implanting appropriate-sized endografts is critical; if too large a device is deployed, it can collapse or infold and cause endoleaks and even aortic occlusion.

Complications

As with any surgical therapy, complications may arise. The most severe complications of TEVAR include the following[3] :

  • Stroke (4%)
  • Paraplegia/paraparesis (2-15%)
  • Peripheral vascular injury
  • Death 

Stroke can occur because the guide wires that are placed in the aortic arch to direct the endografts into position can dislodge a thrombus or atheroma, which can embolize via the cerebral vasculature to the brain. For that matter, emboli can also lead to limb and mesenteric ischemia.

Spinal cord ischemia (SCI) occurs when the intercostal blood vessels supplying the spinal cord are covered by the stent grafts. A bundled SCI prevention protocol that includes cerebrospinal fluid (CSF) drainage, blood pressure targets (mean arterial pressure >90 mm Hg), transfusion goals (hemoglobin >9 g/dL), and pharmacologic adjuncts (eg, steroids or naloxone) is utilized in patients preoperatively deemed to be high risk for SCI.[17]

In patients with small iliac arteries (access vessels), passage of the stent grafts can damage the femoral and iliac arteries. The most worrisome concern is complete avulsion of the arteries, which can be controlled with balloon occlusion; this is the reason why guide wires must be left in position until the very end of the case. Concern regarding these rare but major vascular catastrophes is one reason why TEVAR should be performed only by surgeons experienced with open repair techniques.

Endoleaks occur when the aneurysm is not completely isolated from the bloodstream. In the TAG trial, such leaks were found in 6% of patients at 1 year and in 9% at 2 years.[3]  Although device improvements have led to significant reductions in endoleak rates, this potential complication remains a strong consideration in evaluating patients' anatomy and determining the appropriate device selection for each individual anatomic configuration. Accordingly, it is important to emphasize that patients undergoing TEVAR require lifelong follow-up with CT scans (eventually annually but initially more frequently).[18]  

Endoleaks are commonly classified into four types as follows:

  • Type I endoleaks occur when the seal on either end of the stent graft is incomplete
  • Type II endoleaks occur because of back-bleeding from smaller vessels (typically intercostals) that are covered with the endograft
  • Type III endoleaks occur when leakage develops between overlapping stent grafts
  • Type IV endoleaks were seen with earlier stent grafts when porosity of the graft material led to seepage of blood components through the graft walls, resulting in tension within the excluded aneurysmal segment; they are rarely seen today