Anatomic Criteria for EVAR
For a 78-year-old woman with an infrarenal AAA to be eligible for EVAR, she must have a proximal neck length ≥10-15 mm, neck diameter <30 mm, <90% circumferential thrombus/calcification coverage, favorable neck angulation, and adequate iliac landing zones with sufficient iliofemoral access. 1, 2
Proximal Neck Requirements
The proximal aortic neck is the most critical determinant of EVAR suitability and the most common reason for exclusion:
- Neck length must be ≥10-15 mm to provide adequate proximal seal and reduce risk of type I endoleak and graft migration 1, 3
- Neck diameter must be <30 mm for adequate proximal graft seal 1, 3
- Thrombus or calcification must cover <90% of the circumferential neck diameter to ensure proper seal 1, 2
- Neck angulation must be favorable – severely angulated necks are associated with increased failure risk, aneurysm sac enlargement, and should not be treated with conventional EVAR devices outside instructions for use 1
Inadequate neck anatomy accounts for approximately 88% of anatomic exclusions, with insufficient neck length being the single most common specific reason for EVAR ineligibility 4, 5.
Distal Landing Zone Requirements
- The distal landing zone should be within one or both common iliac arteries with adequate diameter and acceptable tortuosity to accommodate the delivery system 1
- Iliac artery diameter is critical for access – inadequate iliac anatomy accounts for 59% of unsuitable cases 4
- Studies demonstrate that accepting iliac diameters down to 4 mm (with low-profile delivery systems) can increase overall EVAR suitability from approximately 49% to 60% 6
Preoperative Imaging Protocol
CT angiography is the mandatory imaging modality for EVAR planning when AAA reaches intervention threshold 1:
- Use 3-D multiplanar reformatted images to measure aortic diameter perpendicular to the vessel centerline, not axial plane measurements, to avoid overestimating diameter in tortuous anatomy 1
- Angiography alone is inappropriate for AAA size assessment 1
- CTA provides comprehensive evaluation of proximal neck morphology, aneurysm extent, and access vessel dimensions 2
Overall Anatomic Suitability Rates
More than 50% of patients present with anatomy unsuitable for conventional EVAR, necessitating consideration of fenestrated/branched EVAR or open repair 2, 3. When selecting the most suitable graft model for each patient, overall suitability ranges from 48-60% depending on device specifications and acceptance of smaller iliac access vessels 6.
Critical Pitfall to Avoid
Do not use conventional EVAR devices outside instructions for use in severely angulated necks – long-term studies demonstrate increased risk of aneurysm sac enlargement and failure 1. In such cases, consider fenestrated/branched EVAR or open repair instead.
Surveillance Requirements After EVAR
Once anatomic suitability is confirmed and EVAR is performed, lifelong imaging surveillance is mandatory due to higher complication and reintervention rates compared to open repair 1, 2:
- Imaging at 1 month, 12 months, then yearly with CT/MR and duplex ultrasound 1
- Follow-up must allow measurement of aneurysm diameter, detection and classification of endoleaks, and assessment of stent graft morphology 7, 3
The patient must be able to comply with lifelong surveillance protocols – inability to do so is a relative contraindication to EVAR and should prompt consideration of open repair 2.