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30. Endovascular Aortic Repair (EVAR and TEVAR)
Endovascular aortic repair (EVAR) and thoracic endovascular aortic repair (TEVAR) are minimally invasive modalities for the treatment of aneurysms, dissections, penetrating ulcers, and traumatic aortic injury. Aortic stent grafts can be used to exclude an aneurysm sac, encourage thrombosis of a false lumen, cover an entry tear or penetrating ulcer, or seal a transection.
Preoperative Considerations
Preoperative Testing and Procedures
EVAR and TEVAR patients should have baseline laboratory testing including serum creatinine and coagulation parameters. In the elective setting, cardiac evaluation can be undertaken. Depending on the functional status of the patient, testing may include chemical or exercise stress testing or coronary angiography, depending on risk stratification. Preoperative hydration should be considered in patients with elevated serum creatinine to avoid contrast-associated nephropathy. General anesthesia is typically employed, but sedation with local anesthesia can utilized if patients are unable to tolerate general anesthesia.
In the setting of descending thoracic aortic dissection, aggressive impulse control should be undertaken with intravenous antihypertensives. For patients with planned significant thoracic or thoracoabdominal stent coverage, placement of a prophylactic lumbar drain should be considered to help mitigate risks of spinal ischemia by reducing lumbar cerebrospinal fluid pressure and increasing spinal cord perfusion pressure. Complications of lumbar drain placement are rare but include neuraxial hematoma, subdural hematoma, catheter fracture, meningitis, intracranial hypotension, and spinal headache.
Stent Graft Sizing and Selection
Access
When available, preoperative cross-sectional imaging should be evaluated to determine the proper approach to navigating the aorta. Current sheath size ranges from 12 to 26 French, corresponding to an outer diameter of 4.7–9.5 mm, depending on the device. Vessel size and quality and tortuosity should dictate which side the main graft body is deployed over.
Evaluation of iliofemoral tortuosity, caliber, or intraluminal disease can determine eligibility for percutaneous versus open access, or the need for concurrent endarterectomy or open or endovascular conduit. Arteries with circumferential or anterior calcification are difficult to close percutaneously, and suture-mediated closure devices may have difficulty navigating a tortuous iliofemoral system.
A conduit is typically a Dacron graft that is sewn end-to-side onto either the common femoral artery or external iliac artery during open exposure, but another alternative is the endo-conduit, in which placement of an external iliac stent graft followed by serial dilation and balloon angioplasty is undertaken to treat pre-existing iliofemoral disease. Brachial access can be obtained as well, to assist in left subclavian embolization, renal artery intervention, or celiac embolization, if indicated.
Landing Zones
In general, landing zones should be at least 15–20 mm proximal and distal to the pathological aortic segment depending on the pathology as well as the quality of the landing zone. In TEVAR, anatomical boundaries include the left subclavian artery and the celiac artery, although adjunctive maneuvers such as embolization, bypass, or branched configurations can allow for extension beyond these vessels. In EVAR, the anatomical boundaries are the renal arteries superiorly and the hypogastric arteries inferiorly. Chimney, snorkel, branched, or fenestrated approaches can allow for extension into the suprarenal segment, and iliac branch devices allow for treatment beyond the origin of the hypogastric artery. 3D reconstruction preoperatively can assist in accurately measuring the image intensifier angles to maximize the seal zones visualized during stent graft deployment.
Landing zone length may need to be extended in the setting of non-parallel walls, tortuosity, circumferential thrombus, or extensive calcification, as these factors make it more challenging to obtain adequate seal.
Sizing
Anatomic measurements should be taken from the preoperative CT angiography (CTA) scan for appropriate stent graft sizing and selection. Three-dimensional reconstructive software is extremely useful for measurements (particularly in the setting of tortuosity) and for deciding how a device may land proximally and distally. Stent diameter is typically oversized by 10–20% at the proximal and distal landing zones in aneurysmal disease, whereas oversizing is usually not necessary in the setting of chronic dissection or traumatic injury of a previously healthy aorta.
Currently available stent grafts range in diameter from 22 to 46 mm. Given the traditional 10–20% rule of device oversizing, these devices are designed to safely treat aortas with landing zones ranging from 18 to 44 mm in diameter.
Operative Technique
Setting Up the Operating Room
The patient is positioned supine on the operating room table, with bilateral groins prepped. If the left arm is to be accessed, it can be abducted and prepped circumferentially.
Access
Percutaneous Access
In percutaneous access, the mid-common femoral artery is punctured under ultrasound guidance with a micropuncture needle, which is exchanged for a low-profile micropuncture sheath over a 0.018 wire.
Confirmation of puncture into healthy common femoral artery below the inguinal ligament and above the femoral bifurcation should be obtained with a sheathogram. A starter wire is then advanced into the abdominal aorta and the sheath is exchanged for a 7 Fr sheath.
At this point, pre-closure can be performed with a variety of techniques. We prefer the “pre-close” technique using two suture-mediated closure devices. If performed, the 7 Fr sheath is removed and the suture-mediated closure devices are serially deployed with device orientation in the 10 o’clock and 2 o’clock positions to facilitate closure of the arteriotomy at the conclusion of the procedure. The suture ends are clamped together to avoid premature cinching of the knots, and a sterile towel can be placed over them to avoid tangling. A 9 Fr sheath can then be placed to continue dilation.
Femoral Cutdown
For a femoral cutdown, a longitudinal or transverse incision can be made over the common femoral artery, which can be identified by palpation, ultrasound guidance, or anatomical landmarks (classically two thirds medially along the inguinal ligament when moving from lateral to medial). The incision is deepened through the femoral sheath and the common femoral artery is circumferentially dissected to expose adequate area for percutaneous access and proximal/distal control.
This approach is required if endarterectomy or a conduit is needed. Longitudinal endarterectomy is performed in the standard fashion and can be patched with Dacron or bovine pericardium. Then the pericardial patch is punctured with the micropuncture kit. If feasible, place the patch at the end of the case, because putting a large-bore sheath through the patch and fresh suture line might cause bleeding or even disruption of the suture line.
If a Dacron conduit is needed in the common femoral, we prefer the femoral “chimney conduit”, but splitting the Dacron graft longitudinally to create cranial and caudal tapered ends much like a patch, allowing for a mobile graft that can be flipped retrograde and antegrade (Fig. 30.1). The graft is then clamped distally and punctured with the micropuncture kit, and at the end of the case the femoral chimney is transected and oversewn or stapled.
