Aortic Aneurysmal Disease

Background

Aneurysmal disease spans abdominal (4Aneurysms), thoracic (6Thoracic Aortic), thoracoabdominal (6Thoracic Aortic), and peripheral arterial beds ^[1] and remains a leading cause of sudden vascular death due to rupture. AAA prevalence in men ≥65 years is approximately 1.5–4.5% ^[2] and lower in women, who have higher rupture risk at smaller diameters ^[3]. Thoracic aneurysms are less common but carry high lethality, particularly in connective tissue disorders (Marfan, Loeys–Dietz, vascular Ehlers–Danlos) ^[1]. Peripheral aneurysms (popliteal, femoral, visceral, renal) often coexist with AAA ^[4]. Population screening of older men reduces AAA-related mortality and emergent repairs, and contemporary guidelines define who to screen and how to surveil detected AAAs ^{[5] [3] [1]}. For peripheral arterial disease management, see 10PAD.

Etiology

Aneurysm development results from the interplay of genetic predisposition, hemodynamic stress, and degenerative changes in the arterial wall ^[6]. The most common etiology is atherosclerosis, which leads to intimal injury, medial degeneration, and loss of elastic fibers ^[6]. Genetic factors play a significant role, with hereditary connective tissue disorders (Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome) causing abnormalities in extracellular matrix proteins ^[1]. Additional etiologies include infection (mycotic aneurysms), inflammatory conditions (Takayasu arteritis, giant cell arteritis), trauma, and iatrogenic injury ^[1]. Management of infected aneurysms is discussed in the complications section, and genetic thresholds for repair are detailed in 6the thoracic aneurysm chapter.

Pathophysiology

1. Proteolysis of extracellular matrix → loss of elastin and collagen ^[6].
2. Inflammatory infiltration (macrophages, CD4+ T cells) → cytokine release, oxidative stress ^[6].
3. Biomechanical stress → wall shear stress, Laplace law: ↑ diameter → ↑ wall tension → progressive dilation ^[6].
4. Genetics and epigenetics → TGF-β signaling pathways in 6Thoracic Aortic/6Thoracic Aortic ^[1].
5. Intraluminal thrombus (ILT) acts as a bioreactor sustaining hypoxia, protease activity, and mural neovascularization, contributing to wall weakening in 4Aneurysms ^[6].
6. Distinct biology in 6Thoracic Aortic/6Thoracic Aortic (medial degeneration, smooth muscle apoptosis, TGF-β signaling abnormalities) vs atherosclerotic 4Aneurysms; clinical implications include different thresholds in genetic aortopathy ^[1].

Diagnostics

Measurement standards should be applied consistently to improve reproducibility. For AAA, measure the outer-to-outer diameter in the anteroposterior plane at the point of maximal dilation. For EVAR planning, centerline-of-flow measurements are essential for accurate device sizing ^[7]. These standardized approaches reduce interobserver variability and ensure comparable surveillance data across imaging studies ^[3].

Complex Anatomy Challenges

• Hostile neck features: short (<10–15 mm), severe angulation (>60°), conical shape, heavy thrombus/calcification—associated with higher Type Ia endoleak/migration ^[3].
• TAAA: classify extent (Crawford I–V); enumerate visceral involvement; plan for spinal cord protection and access.
• Implications include the balance of off-IFU EVAR risk against FEVAR/BEVAR or open repair ^{[8] [9] [3]}.

Abdominal Aortic Aneurysm

Screening and surveillance of intact AAA: Population-based screening programs target men aged 65–75 years with a history of smoking, as this group demonstrates the highest prevalence and cost-effectiveness for one-time ultrasound screening. Selective screening may be considered for men ≥65 years without smoking history and for women ≥65 years with smoking history or family history of AAA. First-degree relatives of AAA patients should be offered a one-time ultrasound screening at age ≥65 years. Once detected, small AAAs require systematic surveillance: aneurysms measuring 3.0–3.9 cm should be monitored annually, those measuring 4.0–4.9 cm every 6 months, and those measuring 5.0–5.4 cm every 3 months or proceed directly to repair planning if appropriate ^[3],[5].

Key Trials and Registries

Landmark RCTs (EVAR-1/2, DREAM, OVER, ACE) ^[10] showed lower 30-day mortality with EVAR vs open repair ^[11], with no long-term survival advantage and higher late reinterventions for EVAR. Fifteen-year EVAR trial follow-up and OVER trial long-term results ^[12] inform counseling and surveillance. Complex repairs (FEVAR/BEVAR/PMEG/ChEVAR) ^[13] lack RCTs; multicenter registries demonstrate high technical success and acceptable early/medium-term outcomes in experienced centers ^{[14] [15] [16] [9] [8]}.

General Principles

• rAAA, rTAA, and ruptured iliac aneurysms are life-threatening emergencies with overall mortality often >50% including prehospital deaths ^[17].
• Regionalized pathways with 24/7 CTA, endovascular capability, blood products, and hybrid ORs are recommended ^[3].
• Initial management: permissive hypotension, massive transfusion protocol, and rapid CT-based triage in stable or semi-stable patients; an EVAR-first strategy is feasible in many rAAA and supported by randomized strategy data ^[18].

Ruptured Abdominal Aortic Aneurysm

• Epidemiology & outcomes: rAAA carries near-universal mortality without repair; contemporary 30-day mortality after repair is ~30–40% across series ^[17].
• Guidelines: An EVAR-first approach is recommended when anatomically feasible and resources are available ^[3]; open repair remains essential for unsuitable anatomy or lack of endovascular capability ^[2].
• Evidence: Randomized strategy trials (e.g., IMPROVE) found similar 30-day mortality between EVAR-first and open strategies overall ^[17], validating CT-based triage and showing benefits in process measures (faster discharge home, cost) and in EVAR-capable centers ^[18]. Absolute mortality reductions should be interpreted with caution in the absence of center-specific data.
• Technical considerations: Prioritize local/regional anesthesia, percutaneous access, and rapid proximal seal for rEVAR; for open repair, expeditious clamp placement and hemorrhage control. Post-repair: aggressive hemodynamic optimization, renal protection, abdominal compartment syndrome surveillance, and early imaging when feasible.

Related: For comprehensive management of abdominal compartment syndrome (ACS) following rAAA repair, see Ch. 17.

Ruptured Iliac Artery Aneurysms

• Ruptured iliac aneurysms are uncommon; many coexist with AAA and are treated within an aorto-iliac repair strategy.
• Endovascular repair is preferred when anatomy allows, with hypogastric preservation via iliac branch devices if feasible; internal iliac embolization may be necessary but increases risk of buttock claudication and pelvic ischemia ^[19].
• Open repair remains important when endovascular seal/access is not possible or in infection. Consider thresholds for intact disease (common iliac ≥3.5 cm) in elective contexts ^[3].

Peripheral Aneurysms

• Popliteal aneurysm: Consider elective repair for asymptomatic PAAs ≥25 mm (2.5 cm) ^[20]; earlier repair at 20–24 mm if substantial mural thrombus, documented distal embolization, or poor runoff ^[19]. Symptomatic PAAs (thromboembolism, compression) warrant repair regardless of size. Prefer open bypass with autogenous vein in good-risk patients; endovascular stent-grafts for select high-risk/anatomy ^[21]. For detailed management, see 5Chapter 5.
• Common femoral aneurysm: Consider repair at ≥2.5–3.0 cm or symptomatic; favor open repair ^[19].
• Visceral artery aneurysms: Splenic, hepatic, renal, SMA—repair when ≥2.0–3.0 cm (artery-specific), symptomatic, enlarging, or in women of child-bearing potential; endovascular therapy (coil/plug/covered stent) is increasingly first-line in suitable anatomy ^[19].

Complications

Endoleaks are classified into five types based on their source and mechanism ^[3]. Type I (proximal or distal attachment site) and Type III (fabric tear or component separation) endoleaks represent device failure with ongoing pressurization of the aneurysm sac and require urgent reintervention ^[3]. Type II endoleaks (from branch vessels such as lumbar or inferior mesenteric arteries) are common (15–25% of cases) ^[22] and typically managed with observation unless associated with sac growth >5 mm, in which case selective embolization may be indicated ^[23]. Type IV (graft porosity) endoleaks usually resolve spontaneously. Type V endoleaks, or endotension, describe persistent sac expansion without identifiable leak on imaging and may warrant conversion to open repair.

Migration and limb occlusion occur when inadequate fixation or progressive neck dilation allows device movement or when limb stenosis/kinking develops. Risk factors include short necks, severe angulation, large initial neck diameter, and lack of proximal fixation (suprarenal vs infrarenal devices). Management includes extension cuffs, relining with aortic extenders, or limb thrombectomy with adjunctive femorofemoral bypass when endovascular salvage is not feasible.

Branch vessel occlusion after fenestrated or branched EVAR represents a serious complication requiring prompt recognition and intervention. Renal or mesenteric artery occlusion may present with acute kidney injury, flank pain, or abdominal symptoms. Salvage techniques include catheter-directed thrombolysis, mechanical thrombectomy, angioplasty with stenting, or open revascularization depending on the timing and extent of occlusion.

Spinal cord ischemia (SCI) remains the most feared complication of thoracoabdominal aortic repair, with incidence ranging from 3–15% depending on extent of coverage ^[1]. Prevention strategies include preoperative risk stratification, selective cerebrospinal fluid (CSF) drainage (maintain CSF pressure <10 mmHg), maintenance of mean arterial pressure >80–90 mmHg, correction of anemia (hemoglobin >10 g/dL), and revascularization of the left subclavian artery and hypogastric arteries when appropriate ^[19]. Treatment involves immediate optimization of spinal cord perfusion through the same principles. For detailed 6Thoracic Aortic management, see 6Chapter 6.

Colonic ischemia after aortoiliac repair results from interruption of mesenteric collateral flow, particularly when inferior mesenteric and hypogastric arteries are sacrificed simultaneously. Recognition requires high clinical suspicion with symptoms of left-sided abdominal pain, bloody diarrhea, or peritoneal signs. Early colonoscopy aids diagnosis; management ranges from supportive care for mucosal ischemia to emergent laparotomy and resection for transmural infarction.

Access complications include arterial dissection, occlusion, bleeding, and pseudoaneurysm formation. Prevention strategies include careful pre-procedural imaging, appropriate sheath sizing, ultrasound-guided access, and consideration of conduit placement in hostile groins. Acute kidney injury (AKI) occurs in 10–30% of complex aortic procedures ^[8] due to contrast nephropathy, atheroembolism, or renal ischemia. Prevention includes optimization of hydration status, minimization of contrast volume, use of iso-osmolar contrast agents, and selective renal artery protection during complex repairs.

Follow-up

Antithrombotic therapy after endovascular aortic repair typically consists of single antiplatelet therapy (aspirin 81–325 mg daily) unless another indication exists for dual antiplatelet therapy or anticoagulation. Contrast-sparing strategies should be employed in patients with renal dysfunction, including use of duplex ultrasound as the primary surveillance modality when feasible ^[23], judicious use of contrast-enhanced ultrasound, and reservation of CTA for specific clinical indications such as suspected complications or sac growth ^[3].

Screening and surveillance of intact small AAA (pre-repair)

Screening target populations include men aged 65–75 years with a history of ever-smoking, with selective screening for men ≥65 without smoking history and women with smoking or family history. Screening is also recommended for first-degree relatives. Surveillance intervals are determined by maximal diameter: 3.0–3.9 cm annually; 4.0–4.9 cm every 6 months; and 5.0–5.4 cm every 3 months or expedited workup for repair. Ultrasound is the primary modality. Trial data demonstrate that screening reduces AAA-related mortality ^[5], consistent with SVS 2018 schedules ^[3].

AAA Surveillance Intervals by Diameter

Explicit repair thresholds and sex-specific considerations

Elective repair of asymptomatic 4Aneurysms is generally recommended at ≥5.5 cm in men and should be considered at ≥5.0 cm in women, given the higher rupture risk at smaller diameters. Repair is also indicated for rapid growth (≥0.5 cm in 6 months or ≥1.0 cm/year) or symptoms. Shared decision-making is emphasized for elderly or frail patients ^[3].

AAA Repair Thresholds

Evidence synthesis of EVAR vs open for intact AAA with long-term outcomes

EVAR reduces 30-day mortality vs open repair, but long-term overall survival is similar with higher late aneurysm-related deaths and reinterventions in EVAR; This is supported by long-term EVAR trials ^[14] and the OVER trial ^[15]; the DREAM trial confirms early benefit with convergence over time ^[16].

IMPROVE trial and rAAA management

IMPROVE randomized strategy trial showed similar 30-day mortality between EVAR-first and open strategies, confirmed safety of CT-based triage, and suggested improved outcomes in EVAR-capable centers; 3-year data show no overall mortality difference but faster discharge home and cost advantages in EVAR-capable centers ^[18].

UK Small Aneurysm Trial (UKSAT) and ADAM context for small AAA

The UKSAT and ADAM trials demonstrated no survival advantage with early elective surgery for 4.0–5.4 cm AAAs, supporting surveillance until the threshold size is reached ^[24].

Definitions and nomenclature (infrarenal, juxtarenal, pararenal, suprarenal) and hostile neck criteria

Definitions distinguish juxtarenal (no normal neck but no involvement of renal arteries), pararenal (involves at least one renal artery), and suprarenal (extends above renal arteries) aneurysms. Hostile neck criteria include short length (<10–15 mm), >60° angulation, conical neck, and thrombus or calcification. These features have significant implications for the choice between off-IFU EVAR and FEVAR/ChEVAR ^[3].

Iliac artery aneurysm thresholds and iliac branch device strategy

Repair of common iliac artery aneurysms should be considered at ≥3.5 cm, or earlier if rapid growth or symptoms occur, while internal iliac aneurysms are typically repaired at ≥3.0 cm. Hypogastric preservation with iliac branch devices is preferred when feasible; otherwise, internal iliac embolization may be necessary, observing for buttock claudication and colonic ischemia risks ^[3].

Medical optimization and pharmacotherapy

Medical optimization includes smoking cessation (strongly recommended), statin therapy for atherosclerotic risk reduction, blood-pressure control, and antiplatelet therapy for cardiovascular indications. No pharmacotherapy has definitively slowed AAA growth ^[25]; thus, the routine use of doxycycline, beta-blockers, or ACE inhibitors solely for this indication is not recommended ^{[26] [3]}.

Post-repair antithrombotic and imaging surveillance strategy tailoring

Single antiplatelet therapy (aspirin) is recommended after EVAR/FEVAR/BEVAR unless another indication exists for DAPT or anticoagulation. Duplex-first surveillance should be adopted in low-risk EVAR patients with a stable or shrinking sac and no endoleak at 1 year. CTA is reserved for concerning findings, complex repairs, or sac growth ^[3].

Clinical Reference Tables

Table 2.1. Major Risk Factors for Aneurysm Formation

Table 2.2. Comparison of AAA Repair Options

Table 2.3. Endoleak Classification

Table 2.4. Surveillance Protocols After Aneurysm Repair