Endovascular AAA Repair

Endovascular aneurysm repair (EVAR) was first described by Juan Parodi in 1991 as an alternative approach for patients who were deemed unable to undergo open abdominal aortic aneurysm (AAA) repair. An AAA is a ≥50% enlargement of the aorta diameter relative to the normal aorta diameter.

Indications 

• Asymptomatic AAA diameter ≥5.5 cm (males) and ≥5.0 cm (females)
• Expansion of AAA ≥5 mm in 6 months 
• Expansion of AAA ≥1 cm in 1 year
• Symptomatic or ruptured AAA

Contraindications 

• Some anatomical variation may not be amenable to endovascular repair
  • Horseshoe kidney
  • Location of renal arteries (main and accessory)
  • Mesenteric arterial occlusion (due to heavy dependence on collateral blood supply)

Preoperative Considerations

• CTA is the gold standard for preoperative imaging with 3D centerline reconstruction
• Aortic neck
  • Distance from lowest renal artery to the beginning of the aneurysm
  • Serves as the proximal landing zone 
  • Endovascular repair requires 10-15 mm length below the lowest renal artery in order to obtain an adequate proximal seal, diameter < 32 mm, and angulation < 60º
• Distal aorta
  • Allows for two limbs to pass through the distal aorta and into the iliac arteries without compressing either limb
• Access sites
  • Allows for the delivery of the device through iliofemoral vessels to the intended location
  • Ideal diameter  of iliofemoral vessels is ≥6 mm with minimal calcification, thrombus, and tortuosity 
• Distal zone
  • Located in the bilateral common iliac arteries
  • Ideal to have minimal calcification, thrombus, and tortuosity within 10-15 mm length to allow for adequate distal seal 

Relevant Information

• Risk factors
  • Age >65 years old
  • Caucasian 
  • Atherosclerosis
  • Other large vessel aneurysms
  • Male
• Most AAA are asymptomatic and discovered as incidental findings on imaging obtained for other reasons. If a patient is presenting with symptoms, it often includes acute onset of severe abdominal/back pain. If rupture of AAA has occurred, hypotension and altered mental status may also be present.
• Screening recommendations (performed via abdominal ultrasound)
  • USPSTF: males ages 65-75 with a smoking history
  • CMS:
    • Males ages 65-75 with smoking history of ≥100 cigarettes
    • Males and females with family history of AAA
• AAA prevention → cardiovascular risk reduction
  • Smoking cessation
  • Antihypertensive medication
  • Aerobic exercise

Surgical Technique

• Bilateral femoral artery access. This can be completed either via cutdown/open or percutaneous access with ultrasound guidance. Open exposure may be completed via horizontal/oblique or vertical access. Vessel puncture occurs directly on top of the artery at a 45-degree angle. Under fluoroscopy, arterial guidewires are advanced into the thoracic aorta with sequential dilation of access vessels until the appropriate sheath size is performed using Coon dilators. Once the large sheaths are in place, a heparin bolus (80-100 units/kg) is given to maintain an activated clotting time (ACT) >200.
• Main body device. Generally, the main body requires a larger sheath advanced from the “ipsilateral side” while the smaller sheath is referred to as the “contralateral side.” The decision of which femoral artery is used as the ipsilateral side includes size and tortuosity of the vessel. After this is determined, the main body is advanced to the location planned for deployment based on landmarks and intravascular ultrasound (IVUS). Before deployment an aortogram using digital subtraction angiogram (DSA) fluoroscopic imaging is obtained through a marking flush catheter from the contralateral side. 
• Main body deployment. Placed just below the lowest renal artery until the contralateral gate is opened. Then, the contralateral gate is cannulated and confirmed through several methods (IVUS, gentle balloon inflation with gate or pigtail catheter). A stiff wire is then delivered and the contralateral iliac extension stent graft is deployed into the common iliac artery after confirming the distal landing zone location. Completion of the main body deployment into the ipsilateral common iliac artery occurs after.
• Balloon molding. Performed at the proximal seal zone, distal seal zone, and other areas of the stent graft is completed to ensure full deployment. Completion DSA is performed to evaluate the patency of the visceral branches and hypogastric arteries, confirming successful seal of the aneurysm and allow for assessment of potential endoleak. Then the femoral access sites are closed.

Intraoperative Complications

• Access site complications
  • Hematoma
  • Acute thrombosis/occlusion
  • Pseudoaneurysm
  • Arteriovenous fistula
  • Hemorrhage
• Rupture of external iliac artery
• Unintentional coverage of visceral vessel

Postoperative Considerations

• Usually discharged on POD1 after uncomplicated EVAR
• Imaging surveillance
  • 1 month
  • 6 months
  • 12 months
  • Yearly

Postoperative Complications

• Endoleak
  • Type I: proximal or distal graft attachment leaks
  • Type II: retrograde flow into aneurysm sac from aortic side-branches 
  • Type III: defect in graft due to fabric tear or disconnection of modular overlap
  • Type IV: graft wall porosity
  • Type V: increase in aneurysm diameter with no identifiable endoleak