Endovascular Aortic Repair (EVAR): Techniques, Outcomes, and Advances in Minimally Invasive Aneurysm Management

Endovascular aortic repair (EVAR) has revolutionized the treatment of aortic aneurysms over the past three decades, offering a minimally invasive alternative to traditional open surgical repair. This transformative approach involves the transfemoral deployment of stent-grafts to exclude aneurysms from circulation, thereby preventing rupture without the physiological stress of major open surgery. Since its introduction in the early 1990s, EVAR has evolved significantly through technological innovations, expanded anatomical applications, and refined patient selection criteria. This comprehensive guide explores the principles, techniques, outcomes, and ongoing developments in endovascular aortic repair, providing evidence-based insights for healthcare professionals navigating this important aspect of vascular intervention.

Principles and Evolution of EVAR

Historical Development

The journey to modern practice:

Endovascular aortic repair represents one of the most significant paradigm shifts in vascular surgery over the past century. The concept was first introduced by Ukrainian surgeon Nicholas Volodos in 1986, though Juan Parodi’s 1991 publication is widely credited with bringing the technique to international attention. These pioneering efforts demonstrated the feasibility of excluding abdominal aortic aneurysms using stent-grafts delivered through femoral artery access, avoiding the physiological stress of aortic cross-clamping and extensive surgical exposure.

Early devices were custom-made, physician-modified systems with limited applicability and high complication rates. The first commercially approved devices emerged in the late 1990s, with subsequent generations addressing limitations through improved delivery systems, fixation mechanisms, and graft materials. The evolution from first to current-generation devices has been marked by enhanced conformability, lower profile delivery systems, and more reliable fixation methods, expanding both the applicability and durability of the procedure.

The adoption of EVAR accelerated rapidly following publication of early randomized trials demonstrating reduced perioperative mortality compared to open repair. In many centers, EVAR now represents the predominant approach for anatomically suitable infrarenal abdominal aortic aneurysms, and technological advances continue to expand applications to increasingly complex anatomies and pathologies.

Basic Components and Design Principles

Understanding stent-graft architecture:

Modern aortic stent-grafts share fundamental design elements while incorporating manufacturer-specific features. The basic structure includes a metallic skeleton (typically nitinol or stainless steel) providing structural support and radial force, covered by a fabric graft material (usually polyester or expanded polytetrafluoroethylene) that excludes the aneurysm from circulation. This combination creates a new conduit for blood flow, relieving pressure on the aneurysm wall and preventing rupture.

Proximal and distal fixation mechanisms are critical for long-term stability and prevention of migration. These may include bare metal stents with hooks or barbs engaging the vessel wall, suprarenal fixation components, and radial force-dependent friction. Modular designs with separate main body and limb components allow customization to individual anatomy while facilitating delivery through smaller access vessels.

Delivery systems have evolved significantly, with current platforms featuring hydrophilic coatings, controlled deployment mechanisms, and increasingly lower profiles to accommodate smaller access vessels and more tortuous anatomies. These refinements have expanded the proportion of patients anatomically suitable for endovascular repair while reducing access-related complications.

Anatomical Considerations and Planning

The foundation of successful intervention:

Detailed anatomical assessment is essential for appropriate patient selection, device selection, and procedural planning. Modern planning relies heavily on high-resolution computed tomography angiography (CTA) with multiplanar reconstructions and three-dimensional modeling. Key anatomical considerations include:

1. Proximal neck: Length (typically ≥10-15mm required), diameter, angulation (<60° preferred), shape (conical vs. straight), calcification, and thrombus burden
2. Aneurysm sac: Maximum diameter, length, thrombus distribution, and presence of branch vessels
3. Distal landing zones: Common iliac artery diameter, length, tortuosity, and aneurysmal involvement
4. Access vessels: Diameter, tortuosity, calcification, and previous interventions

These measurements inform device selection, sizing, and deployment strategy. Oversizing of 10-20% relative to the native vessel diameter at landing zones is typically recommended to ensure adequate seal and prevent migration, though specific recommendations vary by device. Advanced planning software allows virtual device deployment and prediction of final positioning, particularly valuable for complex anatomies.

Anatomical limitations remain the primary contraindication to EVAR, though expanding device options and adjunctive techniques have progressively reduced the proportion of patients deemed unsuitable for endovascular approaches.

Technical Aspects and Procedural Considerations

Standard EVAR Procedure

Step-by-step approach:

The standard EVAR procedure for infrarenal abdominal aortic aneurysms follows a systematic approach, though specific techniques vary based on institutional preference, device selection, and anatomical considerations. Procedures are typically performed in hybrid operating rooms or angiography suites with high-quality fixed imaging systems. General anesthesia, regional techniques, or local anesthesia with sedation may be employed depending on patient factors and institutional practice.

Bilateral femoral artery access is obtained, traditionally through surgical cutdown though percutaneous approaches have become increasingly common with improved closure devices. Following access, the contralateral limb is typically cannulated from the ipsilateral approach using catheter and wire techniques to establish through-and-through wire access. The main body of the stent-graft is then advanced over a stiff guidewire and positioned precisely at the planned deployment location, typically immediately below the lowest renal artery for infrarenal aneurysms.

Deployment techniques vary by device but generally involve staged release of the main body followed by contralateral limb cannulation and deployment of iliac extensions as needed. Balloon molding at attachment sites and overlap zones ensures optimal apposition and sealing. Completion angiography assesses technical success, confirms aneurysm exclusion, and identifies any immediate complications requiring additional intervention.

Complex EVAR Techniques

Expanding anatomical applications:

Advances in device design and adjunctive techniques have progressively expanded EVAR applications to more complex anatomies. Fenestrated EVAR (FEVAR) incorporates custom-made fenestrations or scallops in the graft fabric to accommodate branch vessels such as renal and mesenteric arteries, allowing treatment of juxtarenal and pararenal aneurysms with inadequate infrarenal necks. These fenestrations are aligned with target vessels and typically reinforced with balloon-expandable stents to ensure durable patency.

Branched EVAR extends these principles to thoracoabdominal aneurysms, incorporating dedicated side branches that are connected to target vessels using covered stents, creating a branched reconstruction of the aortic segment. These advanced techniques require meticulous planning, specialized inventory, and significant technical expertise, typically limiting their application to high-volume centers.

Chimney/snorkel techniques represent alternative approaches for preserving branch vessel flow, involving parallel stent-grafts deployed from target vessels alongside the main aortic stent-graft. While initially developed as rescue procedures for inadvertent coverage or in emergent settings, they have evolved into planned approaches for selected anatomies, particularly when custom fenestrated or branched devices are unavailable.

Adjunctive Procedures and Techniques

Optimizing outcomes through complementary approaches:

Various adjunctive techniques may enhance EVAR applicability and outcomes in challenging anatomies. Iliac conduits provide alternative access when femoral and iliac vessels are too small or diseased for device delivery, involving surgical creation of a temporary or permanent prosthetic conduit from the common iliac artery. Iliac branch devices preserve internal iliac artery flow when aneurysmal disease extends to the iliac bifurcation, preventing buttock claudication and pelvic ischemia complications.

Embolization procedures frequently complement EVAR, including coil embolization of internal iliac arteries when preservation is not feasible, treatment of type II endoleaks from lumbar or inferior mesenteric arteries, or preemptive embolization of these vessels to prevent subsequent endoleaks. Increasingly, percutaneous access and closure techniques have been adopted to reduce wound complications and facilitate earlier mobilization, though these approaches require specific expertise and suitable anatomy.

EndoAnchors represent another important adjunct, providing transmural fixation to enhance proximal seal and prevent migration, particularly valuable in hostile neck anatomy or as a treatment for type Ia endoleaks. These helical anchors are deployed through dedicated catheter systems and function similarly to surgical sutures, securing the stent-graft to the aortic wall.

Outcomes and Complications

Short-term Outcomes

Perioperative advantages and considerations:

Multiple randomized controlled trials have consistently demonstrated significant short-term benefits of EVAR compared to open repair. The landmark EVAR-1, DREAM, OVER, and ACE trials all showed substantially reduced perioperative mortality, with pooled analyses suggesting a reduction from approximately 4.5% with open repair to 1.5% with EVAR for elective infrarenal aneurysm repair. Additional short-term benefits include reduced blood loss, lower transfusion requirements, shorter intensive care and overall hospital stays, and faster functional recovery.

Perioperative complications specific to EVAR include access-related issues (arterial injury, embolization, thrombosis), device-related problems (maldeployment, migration, component separation), and end-organ complications (renal dysfunction from contrast nephropathy or inadvertent coverage, bowel ischemia, spinal cord injury in more extensive repairs). Conversion to open repair is occasionally required for complications that cannot be managed endovascularly, occurring in approximately 1-2% of modern series.

Successful aneurysm exclusion, defined as absence of endoleak with complete aneurysm exclusion from circulation, is achieved in 80-95% of cases. Technical success rates have improved with device evolution and operator experience, though anatomical complexity remains an important determinant of immediate outcomes.

Long-term Durability and Surveillance

The ongoing relationship with treated patients:

Long-term outcomes after EVAR remain an area of active investigation and some controversy. While perioperative benefits are well-established, randomized trials with extended follow-up have shown convergence of survival curves between EVAR and open repair groups at 2-3 years, with some suggesting inferior long-term survival with EVAR. However, these findings must be interpreted cautiously as they largely reflect earlier-generation devices and practices, with contemporary outcomes potentially more favorable.

The primary concern with EVAR durability relates to device-related complications requiring reintervention. Endoleaks, representing persistent blood flow into the aneurysm sac outside the stent-graft lumen, occur in up to 20-30% of patients at some point during follow-up. These are classified by source: type I (attachment site), type II (branch vessel), type III (graft defect or component separation), and type IV (graft porosity). Types I and III require prompt intervention as they represent direct communication with the aneurysm sac under systemic pressure, while type II endoleaks may be observed if not associated with sac enlargement.

Other late complications include stent-graft migration, component separation, material fatigue, and infection. These concerns necessitate lifelong surveillance imaging, typically with CT angiography or duplex ultrasound at regular intervals, representing a significant distinction from open repair which generally requires less intensive follow-up. Reintervention rates range from 10-30% at 5 years, with most procedures performed endovascularly and open conversion relatively uncommon with contemporary devices.

Comparative Effectiveness

Balancing short and long-term considerations:

The comparative effectiveness of EVAR versus open repair remains nuanced and evolving. The early survival advantage of EVAR appears to diminish over time, with long-term follow-up from randomized trials suggesting similar overall survival at 5+ years. This convergence likely reflects both the burden of reinterventions after EVAR and selection of generally lower-risk patients for randomized trials.

Cost-effectiveness analyses have yielded mixed results, with higher device costs and surveillance requirements for EVAR partially offset by reduced initial hospitalization expenses. Patient-reported outcomes generally favor EVAR in the short term, with faster recovery and less impact on quality of life, though these differences also diminish over time.

The optimal approach for individual patients therefore depends on multiple factors including age, comorbidities, life expectancy, anatomical suitability, and patient preferences. Younger, lower-risk patients with longer life expectancy may benefit from the durability of open repair despite higher perioperative risk, while older or higher-risk patients may derive greater benefit from the reduced perioperative stress of EVAR despite potential for later reinterventions.

Special Applications and Considerations

Ruptured Aneurysms

Endovascular management of emergent presentations:

The application of EVAR to ruptured abdominal aortic aneurysms (rAAA) represents a significant advance in managing this life-threatening condition. Several randomized trials including IMPROVE, AJAX, and ECAR have compared endovascular and open approaches for rupture. While individual trials showed no significant mortality difference, meta-analyses suggest a modest survival benefit with endovascular repair, particularly in anatomically suitable patients reaching specialized centers.

The “rupture EVAR” approach requires specific logistical considerations, including immediate availability of appropriate inventory, experienced personnel, and imaging capabilities. Modified techniques often include permissive hypotension until aortic control is achieved, use of aortic occlusion balloons for temporary hemodynamic stabilization, acceptance of suboptimal imaging, and consideration of local anesthesia approaches. When feasible, the reduced physiological impact of EVAR appears particularly beneficial in the already compromised ruptured aneurysm patient.

Implementation challenges include anatomical suitability assessment in emergent settings, availability of appropriate devices and expertise, and systems of care that facilitate rapid transfer to centers capable of endovascular rupture management. Despite these challenges, EVAR has become the preferred approach for anatomically suitable ruptured aneurysms in many high-volume centers.

Thoracic Endovascular Aortic Repair (TEVAR)

Extending principles to the thoracic aorta:

The principles of endovascular repair have been successfully applied to thoracic aortic pathologies, including aneurysms, dissections, traumatic injuries, and penetrating ulcers. Thoracic endovascular aortic repair (TEVAR) involves similar concepts of aneurysm exclusion using stent-grafts but presents unique considerations related to the thoracic aortic anatomy and pathophysiology.

Anatomical challenges include proximity to the aortic arch vessels, greater hemodynamic forces, increased tortuosity, and risk of spinal cord ischemia due to coverage of intercostal arteries supplying the anterior spinal artery. Device design has evolved to address these challenges, with increased conformability to the aortic arch, improved trackability through tortuous anatomy, and modified deployment systems for precise placement near critical branch vessels.

Outcomes after TEVAR for thoracic aortic aneurysms demonstrate similar advantages to abdominal EVAR, with reduced perioperative mortality and morbidity compared to open thoracic repair. Applications have expanded to include complicated type B aortic dissections, where TEVAR promotes false lumen thrombosis and favorable remodeling, and traumatic aortic injuries, where the minimally invasive approach is particularly advantageous in polytrauma patients.

Emerging Technologies and Future Directions

The evolving landscape of endovascular therapy:

Endovascular aneurysm repair continues to evolve rapidly, with several emerging technologies addressing current limitations. Endovascular aneurysm sealing (EVAS) represents a conceptual departure from traditional EVAR, using polymer-filled endobags to obliterate the aneurysm sac while maintaining luminal flow through covered stents. While early results showed promise for reducing certain complications, longer-term outcomes have revealed unique failure modes requiring further refinement.

Lower profile delivery systems continue to expand applicability to patients with smaller access vessels, while enhanced fixation mechanisms address migration concerns in challenging anatomies. “Off-the-shelf” fenestrated and branched systems aim to overcome the production delays associated with custom-made devices for complex anatomies, allowing treatment of urgent and emergent cases involving branch vessels.

Bioengineered stent-grafts incorporating tissue-engineered materials, drug-eluting components to promote healing, or bioabsorbable elements represent longer-term research directions. Additionally, advances in imaging and computational modeling are improving patient selection and procedural planning, with fusion imaging, augmented reality, and artificial intelligence applications enhancing procedural precision and potentially predicting complications before they occur.

Medical Disclaimer

Important Notice: This information is provided for educational purposes only and does not constitute medical advice. Endovascular aortic repair represents a specialized procedure that should only be performed by qualified healthcare professionals with appropriate training and expertise in vascular and endovascular surgery. The techniques and approaches discussed should only be implemented under appropriate medical supervision. Individual treatment decisions should be based on patient-specific factors, current clinical guidelines, and physician judgment. If you have been diagnosed with an aortic aneurysm or are experiencing symptoms such as abdominal, back, or chest pain, particularly if accompanied by lightheadedness or shortness of breath, please seek immediate medical attention as these may represent life-threatening complications. This article is not a substitute for professional medical advice, diagnosis, or treatment.

Conclusion

Endovascular aortic repair has transformed the management of aortic aneurysms, offering reduced perioperative morbidity and mortality compared to traditional open surgical approaches. The evolution from early devices to current sophisticated systems has expanded applications to increasingly complex anatomies while improving safety and efficacy. While long-term durability concerns and surveillance requirements remain important considerations, continued technological advances and refined patient selection are progressively addressing these limitations. The optimal approach for individual patients requires careful consideration of anatomical factors, patient characteristics, and institutional expertise, ideally through a multidisciplinary team approach. As technology continues to evolve, endovascular techniques will likely continue expanding their role in aortic aneurysm management, further improving outcomes for this challenging cardiovascular condition.