Endovascular Aneurysm Repair (EVAR)

Endovascular aneurysm repair (EVAR) is a minimally invasive therapeutic intervention designed to address abdominal aortic aneurysms (AAAs), which are focal dilations of the abdominal aorta caused by weakening of the vessel wall. The indication for repair includes either symptomatic aneurysms or aneurysms with a diameter greater than 5.4 cm. Patients require a pre-EVAR computed tomography angiogram for pre-operative planning.

Abdominal aortic aneurysms (AAAs) often develop asymptomatically and are incidentally discovered during routine medical examinations or imaging studies. However, in some cases, patients with AAAs may experience symptoms, especially when the aneurysm becomes large or starts to expand rapidly. The symptoms of abdominal aortic aneurysms may include:

Abdominal or back pain: Pain is one of the most common symptoms associated with AAAs. The pain is typically located in the abdomen or lower back and can vary in intensity, ranging from mild discomfort to severe, constant pain. The pain may be dull, throbbing, or sharp.
Pulsating sensation: Some patients may feel a pulsating or throbbing sensation in their abdomen, especially if the aneurysm is large and close to the abdominal wall. This pulsation is caused by the expansion and contraction of the aneurysm with each heartbeat.
Abdominal tenderness: Palpation of the abdomen may reveal tenderness, especially over the area where the aneurysm is located.
Gastrointestinal symptoms: Large AAAs can sometimes exert pressure on the surrounding organs, leading to gastrointestinal symptoms such as loss of appetite, feeling full quickly, or a sense of abdominal bloating.
Compression of nearby structures: An expanding AAA can put pressure on nearby structures, including nerves, causing pain or discomfort in the legs, hips, or groin.
Acute rupture: In some cases, an AAA may rupture, leading to a life-threatening medical emergency. Symptoms of a ruptured AAA include sudden, severe abdominal or back pain, dizziness, rapid heart rate, low blood pressure, and loss of consciousness. Ruptured AAAs require immediate medical attention and surgery.

The EVAR stent graft typically consists of a metal frame covered with a synthetic fabric, which effectively reinforces the weakened aortic wall while providing a new channel for blood flow, effectively excluding the aneurysmal segment. The placement of the stent graft in a precise manner is crucial to achieving optimal sealing and anchoring, reducing the risk of potential complications such as endoleaks - persistent blood flow within the aneurysm sac.

Post-procedure, the patient is closely monitored in the intensive care unit or a specialized unit for a designated period to ensure stability and to promptly address any potential complications. Compared to traditional open surgical repair, EVAR offers several advantages, including reduced invasiveness, shorter hospital stays, faster recovery times, and a potentially lower risk of perioperative morbidity and mortality.

Complex EVAR's may include fenestrated grafts when the aneurysm extends beyond the bilateral renal arteries, or EVARs that are combined with thoracic grafts.

A&I Protocol

Seldinger technique is used to access into bilateral common femoral arteries using ultrasound guidance. Two perclose devices are prepared on each puncture site (for closure at the end of the procedure).
A stiff 0.035" wire are advanced through both access points.
Both long, stiff wires are anchored in the aortic arch, and are checked using fluoroscopy of the thorax.
A calibrated pigtail catheter is advanced on the right side, directed towards the abdominal aorta at the vertebral level of L1/2. An aortogram is performed using the contrast injector (15 mls at 15 ml/sec) to demonstrate the abdominal aorta, aortic bifurcation, bilateral renal arteries, and bilateral iliac arteries. A prolonged x-ray exposure is required to demonstrate the AAA, with use of anaesthetic breath-hold technique.
This DSA run is used as a roadmap to map the arteries and AAA, particularly the renal arteries.
Large 16F introducer sheaths are exchanged on both common femoral artery puncture sites.
The main body is advanced on the right puncture site and the radiopaque markers on the EVAR graft are visualised using fluoroscopy and the DSA roadmap, such that these are situated infra-renally.
Once confirmed, the EVAR graft is deployed under fluoroscopic guidance to monitor for migration.
A DSA with manual hand contrast injection is performed on the right side, and with the calibrated pigtail catheter in place, the length of the right limb graft is determined. The DSA run shows the right internal iliac artery which should not be covered, and also shows length required with enough overlap between the right limb graft and the EVAR main body.
The right limb graft is advanced over the wire and deployed under fluoroscopic guidance.
A DSA with manual hand contrast injection is performed on the left side, and with the calibrated pigtail catheter in place, the length of the left limb graft is determined. The DSA run shows the left internal iliac artery which should not be covered, and also shows length required with enough overlap between the left limb graft and the EVAR main body.
The left limb graft is advanced over the wire and deployed under fluoroscopic guidance.
Following the deployment of all three graft pieces, aortic balloon occlusion is performed from the top of the EVAR main body, and along both sides of the limbs.
Following angioplasty, the calibrated pigtail is advanced up to the vertebral level of L1/2 and a contrast injector (15 mls at 15 ml/sec) is performed with anaesthetic breath hold technique and a long x-ray exposure with DSA to check for the graft integrity and any potential endoleak sources.
If an endoleak is suspected in the last few frames of the DSA run, aortic balloon occlusion along the graft and a contrast injector run are repeated.
Following the successful EVAR procedure, the perclose devices are deployed and stitch the common femoral artery on both sides for closure.

Pre-intervention Aortogram using a pig-tail flush catheter, showing the Abdominal Aortic Aneurysm (AAA).

Angiogram showing the Endovascular Aortic Repair (EVAR) of the AAA with a main body and bilateral iliac artery covered grafts.

References

Khoury MK, Thornton MA, Heid CA, Babb J, Ramanan B, Tsai S, et al. Endovascular Aortic Repair in Patients of Advanced Age. J Endovasc Ther. 2022 Jun;29(3):381–8.
Hajibandeh S, Hajibandeh S, Antoniou SA, Child E, Torella F, Antoniou GA. Percutaneous access for endovascular aortic aneurysm repair: A systematic review and meta-analysis. Vascular. 2016 Dec;24(6):638–48.
Endovascular aortic repair in patients with challenging anatomies: the EXTREME study - PubMed [Internet]. [cited 2023 Jul 24]. Available from: https://pubmed.ncbi.nlm.nih.gov/31793884/
Ullery BW, Lee JT. Considerations for patients undergoing endovascular abdominal aortic aneurysm repair. Anesthesiol Clin. 2014 Sep;32(3):723–34.
Khoury MK, Thornton MA, Weaver FA, Ramanan B, Tsai S, Timaran CH, et al. Selection criterion for endovascular aortic repair in those with chronic kidney disease. J Vasc Surg. 2023 Jun;77(6):1625-1635.e3.