Thoracic Endovascular Aortic Repair (TEVAR) Technique

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

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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.

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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
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