What are the anatomical constraints for an Endovascular Aneurysm Repair (EVAR)?

From the Guidelines

The anatomical constraints for Endovascular Aneurysm Repair (EVAR) are primarily determined by the proximal neck, which should be at least 10-15mm in length, less than 32mm in diameter, and have angulation less than 60 degrees, as well as adequate iliac arteries for access, to ensure proper seal and fixation of the stent graft. The key factors that determine patient eligibility for EVAR include the morphology of the proximal neck, defined as the segment of aorta between the most caudal renal artery and the proximal boundary of the aneurysm 1. Unfavorable neck anatomy, such as diameter, length, angulation, morphology, and presence of calcification, is the most frequent cause of exclusion from EVAR 1. Some of the specific anatomical constraints for EVAR include:

• Proximal neck length of at least 10-15mm and diameter less than 32mm 1
• Angulation of the proximal neck less than 60 degrees to prevent device migration and endoleak 1
• Iliac arteries with a minimum diameter of 7mm without excessive tortuosity or calcification to allow passage of the delivery system
• Landing zones in the iliac arteries should be at least 15-20mm in length and less than 20mm in diameter
• Excessive thrombus in the aneurysm neck (>50% circumference) can compromise seal and fixation 1
• Accessory renal arteries originating from the aneurysm sac may be sacrificed but can lead to partial renal infarction
• Severe neck angulation (>60 degrees) increases the risk of endoleak and migration These anatomical constraints are crucial because they affect the durability of the repair and risk of complications such as endoleak, migration, and device failure 1. When these constraints are not met, traditional open surgical repair or more complex endovascular techniques like fenestrated or branched grafts may be necessary 1.

From the Research

Anatomical Constraints for Endovascular Aneurysm Repair (EVAR)

The anatomical constraints for EVAR are crucial in determining the suitability of patients for this procedure. The following are some of the key constraints:

• Proximal neck diameter: The diameter of the proximal neck should be between 18-32 mm 2, 3.
• Proximal neck length: The length of the proximal neck should be greater than 10-15 mm 2, 3, 4.
• Proximal neck angulation: The angulation of the proximal neck should be less than 60° 2, 3, 4.
• Iliac diameter: The diameter of the iliac arteries should be greater than 7 mm 2 or 6 mm 3.
• Iliac tortuosity: Severe iliac tortuosity can make EVAR challenging or impossible 3.
• Renal artery orientation: The orientation of the renal arteries can affect the feasibility of EVAR, with caudal orientation being more favorable 2.
• Aortic morphology: The morphology of the aorta, including the presence of thrombus or calcifications, can impact the suitability of EVAR 2, 3.

EVAR Suitability Criteria

The suitability of patients for EVAR is determined by the presence of favorable anatomical characteristics. The following are some of the key criteria:

• The presence of a healthy aortic area greater than 15 mm between the renal arteries and celiac trunk 2.
• The presence of a healthy descending thoracic aorta 2.
• The absence of severe iliac pathology, such as calcifications or stenosis 2.
• The presence of a suitable proximal neck, with a diameter between 18-32 mm and a length greater than 10-15 mm 2, 3.

Techniques for Challenging Anatomy

Several techniques have been developed to address challenging anatomy, including:

• The chimney technique, which involves the use of a stent graft with a fenestrated design to accommodate the renal arteries 2.
• The cross-wire technique, which involves the use of a guidewire to cannulate the contralateral limb of the stent graft in cases with tortuous proximal aortic neck 5.
• The use of suprarenal fixation devices and proximal cuffs to secure the stent graft in place 4.