Advances in Fenestrated and Branched Endografts for Complex Aortic Aneurysm Repair

Complex aortic aneurysms involving branch vessels have historically presented significant therapeutic challenges, often requiring extensive open surgical procedures with substantial morbidity and mortality. The development of fenestrated and branched endovascular aortic repair (F-EVAR and B-EVAR) technologies represents one of the most significant advances in vascular surgery over the past two decades, offering minimally invasive options for patients with anatomically challenging aneurysms previously considered unsuitable for standard endovascular approaches. This comprehensive guide explores the evolution, technical considerations, outcomes, and future directions of these sophisticated endovascular technologies, providing evidence-based insights for healthcare professionals navigating this rapidly evolving field.

Evolution and Technological Development

Historical Context

From concept to clinical reality:

The concept of fenestrated endografts emerged in the late 1990s as a solution to the anatomical limitations of standard endovascular aortic repair (EVAR), which requires adequate non-aneurysmal “neck” segments for secure proximal and distal fixation. Many patients, particularly those with juxtarenal, pararenal, or thoracoabdominal aneurysms, lack these landing zones, as the aneurysm extends to or involves critical branch vessels such as the renal, superior mesenteric, or celiac arteries.

The pioneering work of Australian vascular surgeon Michael Lawrence-Brown and engineer David Hartley led to the first custom-made fenestrated device, with initial clinical applications reported in 1999. These early devices featured precisely positioned openings (fenestrations) in the graft fabric aligned with branch vessel origins, allowing blood flow to these critical vessels while excluding the aneurysm from circulation. The technology evolved rapidly through collaboration between innovative clinicians and industry partners, leading to the first commercially available fenestrated system (Zenith Fenestrated, Cook Medical) receiving European approval in 2007 and FDA approval in 2012.

Branched endografts emerged as a complementary technology, particularly suited for thoracoabdominal aneurysms where the angulation and distance between the main aortic lumen and branch vessels make fenestrations less optimal. These devices incorporate dedicated side branches that extend from the main body of the endograft, allowing connection to target vessels using covered stents. Early clinical experiences with branched devices were reported in the early 2000s, with continued refinement leading to current-generation systems.

The evolution of these technologies has been characterized by iterative improvements in device design, delivery systems, and planning software, expanding both the anatomical applicability and technical success rates while reducing procedural complexity. This progression represents a remarkable example of collaborative innovation between clinicians, engineers, and industry partners addressing a significant unmet clinical need.

Device Design and Types

Understanding technological variations:

Fenestrated and branched endografts share the fundamental goal of preserving flow to essential branch vessels while excluding the aneurysm, but differ significantly in design approach and anatomical applications:

Fenestrated endografts feature precisely positioned openings in the graft fabric that align with branch vessel origins. These fenestrations may be:
– Small (6-8mm) reinforced fenestrations for renal arteries
– Larger (8-12mm) reinforced fenestrations for mesenteric vessels
– Scallops (U-shaped cutouts at the graft edge) typically used for the superior mesenteric artery or celiac axis when these originate near the proximal edge of the graft

Once deployed, fenestrations are typically secured with balloon-expandable covered stents (bridging stents) that extend from the fenestration into the target vessel, creating a seal and preventing endoleak. The precise positioning required for fenestrated grafts makes them most suitable for vessels originating from relatively normal aortic segments with limited angulation between the aorta and branch vessel.

Branched endografts incorporate dedicated side branches extending from the main body of the endograft, connected to target vessels using covered stent-grafts. These branches may be:
– Antegrade (downward-facing) branches typically used for renal arteries
– Retrograde (upward-facing) branches typically used for mesenteric vessels
– External branches that extend outside the main body, requiring separate catheterization
– Internal branches contained within the main body lumen

Branched designs accommodate greater distances and angulation between the aorta and target vessels, making them particularly suitable for thoracoabdominal aneurysms where the spatial relationships are more complex. They also provide greater flexibility in accommodating anatomical variations and vessel tortuosity.

Hybrid designs combining fenestrations and branches within the same device have emerged to address complex anatomies requiring both approaches. Additionally, physician-modified endografts (PMEGs) represent an alternative when commercial custom devices are unavailable or time-constrained, involving modification of standard devices in the operating room immediately before implantation.

Planning and Customization

The foundation of successful outcomes:

The planning process for fenestrated and branched endovascular repair represents one of the most complex and critical aspects of the entire treatment pathway, requiring meticulous attention to anatomical detail and three-dimensional spatial relationships.

High-resolution computed tomography angiography (CTA) with thin slices (≤1mm) forms the foundation of planning, ideally with both arterial and delayed phases to optimize visualization of vessel origins and the true lumen in cases with mural thrombus. Advanced post-processing with multiplanar reconstructions, centerline analysis, and three-dimensional volume rendering is essential for accurate measurement and spatial understanding.

Key measurements include:
– Precise clock-face positions of each target vessel relative to the centerline
– Longitudinal distances between vessel origins
– Vessel diameters, angulation, and tortuosity
– Extent of healthy aortic segments for proximal and distal sealing

These measurements inform the custom design of each device, with fenestration or branch positions precisely matched to the patient’s unique anatomy. The planning process typically involves collaboration between the implanting physician and the device manufacturer’s planning team, with multiple review stages to ensure accuracy.

The customization process typically requires 4-8 weeks for commercial devices, necessitating stable aneurysms suitable for elective repair. This timeline represents a significant limitation for urgent or emergent cases, driving interest in “off-the-shelf” fenestrated and branched systems with adjustable components that can accommodate a range of anatomies without custom fabrication.

Advanced planning software has evolved to support this complex process, with tools for semi-automated centerline generation, vessel origin mapping, and virtual device deployment simulation. These technologies continue to improve, potentially reducing planning time and enhancing precision in device design and implantation strategy.

Technical Considerations and Procedural Aspects

Procedural Steps

Navigating complex endovascular deployment:

Fenestrated and branched endovascular procedures share common elements but differ significantly from standard EVAR in complexity, duration, and technical demands. The typical procedure involves several distinct phases:

Access establishment typically requires multiple entry points, including large-bore femoral access for the main device delivery and additional access (femoral, brachial, or axillary) for branch vessel catheterization. Percutaneous approaches have become increasingly common for suitable anatomy, though surgical cutdown remains necessary for hostile access vessels or very large delivery systems.

Main body deployment represents the initial and often most critical phase, requiring precise positioning to align fenestrations or branches with their target vessels. Modern delivery systems incorporate features to enhance positioning accuracy, including staged deployment mechanisms and repositionable designs that allow limited adjustment before final commitment.

Branch vessel catheterization follows main body deployment, involving selective catheterization of each target vessel through its corresponding fenestration or branch. This phase often represents the most technically challenging aspect, particularly for vessels with unfavorable angles or origins obscured by the deployed endograft. Various catheter and wire techniques have evolved to address these challenges, including use of steerable sheaths, buddy wires, and specialized catheters.

Bridging stent deployment connects each fenestration or branch to its target vessel, typically using balloon-expandable covered stents for fenestrations and self-expanding covered stents for branches. Precise positioning is essential, with the stent extending adequately into both the main graft and the target vessel to ensure sealing while avoiding excessive coverage of branch vessel length.

Completion steps include balloon molding at all connection points, final angiography to confirm technical success and identify any immediate issues requiring correction, and removal of delivery systems with access site closure. The entire procedure typically requires 3-6 hours depending on complexity, with advanced cases involving four or more vessels potentially extending longer.

Technical Challenges

Navigating procedural complexities:

Several technical challenges distinguish fenestrated and branched procedures from standard EVAR, requiring specific strategies and advanced endovascular skills:

Vessel catheterization difficulties represent perhaps the most common intraoperative challenge, particularly for renal arteries with downward angulation or origins obscured by the deployed main body. Strategies to overcome these challenges include use of preshaped catheters, steerable sheaths, “buddy wire” techniques to maintain access during sheath exchanges, and in some cases, creation of “gutters” alongside the main graft to facilitate access.

Sheath interactions and management become increasingly complex as the number of target vessels increases, with potential for interference between multiple sheaths and displacement of the main body during manipulation. Techniques to address these issues include sequential rather than simultaneous vessel catheterization, careful sheath management to minimize interactions, and in some cases, use of alternative access sites such as axillary or brachial approaches for upper vessels.

Bridging stent selection and positioning requires balancing competing priorities of adequate overlap for sealing, sufficient vessel coverage for stability, and preservation of branch vessel length and flexibility. Balloon-expandable covered stents (e.g., Atrium Advanta, Gore VBX) are typically preferred for fenestrations due to their precise deployment and radial strength, while self-expanding covered stents (e.g., Gore Viabahn, Fluency) are often used for branches due to their flexibility and conformability to tortuous anatomy.

Radiation exposure represents a significant concern given the prolonged fluoroscopy times required for complex cases, with potential risks to both patients and operators. Strategies to minimize exposure include optimal equipment settings, collimation, intermittent fluoroscopy, use of fusion imaging to reduce fluoroscopy requirements, and attention to operator protection through appropriate shielding and positioning.

Adjunctive Techniques

Expanding applicability and addressing complications:

Various adjunctive techniques have evolved to expand the applicability of fenestrated and branched technology to challenging anatomies and address potential complications:

Parallel graft techniques (chimneys, snorkels, and periscopes) involve deployment of covered stents parallel to the main body to maintain branch vessel perfusion. Originally 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. These techniques create deliberate “gutters” between the main graft and parallel stents, with associated endoleak risks requiring careful oversizing strategies and appropriate patient selection.

Iliac branch devices (IBDs) extend the principles of branched technology to the iliac bifurcation, preserving internal iliac artery flow when aneurysmal disease extends to this level. These devices prevent buttock claudication and pelvic ischemia complications associated with internal iliac artery sacrifice, particularly important in younger, active patients and those with bilateral disease.

Temporary sac perfusion branches represent an emerging technique for thoracoabdominal aneurysms, involving deliberate maintenance of controlled aneurysm perfusion during the initial procedure with planned secondary intervention for complete exclusion. This staged approach may reduce spinal cord ischemia risk by allowing collateral network development before complete aneurysm exclusion.

Fusion imaging combines preoperative CTA with intraoperative fluoroscopy, creating overlay images that enhance visualization of vessel origins and reduce contrast and radiation requirements. This technology is particularly valuable for complex cases with multiple target vessels, potentially reducing procedural time and complications while improving technical precision.

Outcomes and Evidence Base

Short-term Outcomes

Perioperative results and learning curve:

Short-term outcomes of fenestrated and branched endovascular repair have been extensively documented in single-center series, multicenter registries, and limited comparative studies, demonstrating the safety and efficacy of these approaches in appropriately selected patients and experienced centers.

Technical success rates, defined as successful deployment with patent target vessels and absence of type I or III endoleak, typically exceed 95% in contemporary series from experienced centers. This high success rate reflects improvements in device design, delivery systems, and operator experience, though remains dependent on appropriate patient selection and anatomical suitability.

Perioperative mortality ranges from 2-5% for fenestrated repairs of juxtarenal aneurysms to 5-10% for more extensive thoracoabdominal repairs, comparing favorably to historical results of open surgical repair for these complex anatomies. Mortality risk correlates strongly with the extent of repair, patient comorbidities, and center experience, highlighting the importance of appropriate patient selection and referral to high-volume centers.

Major complications include:
– Spinal cord ischemia (1-10%, increasing with extent of coverage)
– Renal function deterioration (10-30%, typically mild and often transient)
– Access vessel complications (5-10%)
– Branch vessel occlusion (2-5%)
– Type I or III endoleak requiring reintervention (3-7%)

The learning curve for these procedures is substantial, with studies suggesting at least 10-15 cases required to achieve consistent outcomes and up to 50 cases for optimization. This learning curve affects not only the primary operator but the entire team involved in planning, device preparation, and perioperative care, supporting the concentration of these procedures in specialized centers with adequate volume to maintain proficiency.

Long-term Durability

The critical question of sustainability:

Long-term outcomes data for fenestrated and branched repairs continue to accumulate, with several centers now reporting follow-up extending beyond 10 years for early-generation devices. These data provide important insights into the durability of these repairs while acknowledging the continuous evolution of device design and techniques.

Branch vessel patency represents a primary concern, with contemporary series reporting primary patency rates of 90-95% at 5 years for renal branches and slightly higher for mesenteric vessels. Secondary interventions can successfully salvage many threatened branches if detected early, highlighting the importance of vigilant surveillance imaging. Factors associated with branch compromise include severe vessel angulation, small vessel diameter (<4mm), and extensive atherosclerotic disease in the target vessel.

Freedom from reintervention ranges from 70-85% at 5 years, with most reinterventions performed for branch vessel stenosis or occlusion, type I or III endoleaks, or disease progression in untreated aortic segments. While higher than reintervention rates after standard infrarenal EVAR, these figures must be contextualized against the complexity of the initial pathology and the likely outcomes of alternative treatment approaches.

Aneurysm-related mortality remains low after successful repair, with most late deaths attributed to patients’ underlying comorbidities rather than aneurysm-related complications. This finding supports the value of these interventions in preventing aneurysm rupture while acknowledging the significant comorbidity burden in this patient population.

Device integrity concerns have emerged with some early-generation systems, including component separation, stent fractures, and fabric tears. Modern designs have addressed many of these issues through reinforced connections, more durable materials, and improved understanding of in vivo forces. Ongoing surveillance remains essential, as the long-term behavior of current-generation devices continues to be defined.

Masomo Linganishi

Contextualizing within treatment options:

Few randomized trials have compared fenestrated/branched repair to open surgical alternatives, reflecting the challenges of randomizing patients with complex anatomy and the rapid evolution of endovascular technology. Available comparative data come primarily from institutional series, administrative databases, and propensity-matched analyses.

Compared to open repair of juxtarenal and pararenal aneurysms, fenestrated EVAR consistently demonstrates lower perioperative mortality (2-4% vs. 5-8%), reduced blood loss, shorter intensive care and overall hospital stays, and faster functional recovery. These advantages appear most pronounced in older patients and those with significant cardiopulmonary comorbidities. Open repair may offer advantages in younger, lower-risk patients due to concerns about long-term durability and reintervention rates with endovascular approaches.

For thoracoabdominal aneurysms, the comparison is more nuanced. Branched EVAR demonstrates clear advantages in perioperative mortality and major complications for high-risk patients, but the durability comparison remains less definitive. Centers of excellence in open thoracoabdominal repair report excellent outcomes in selected patients, while branched repair offers particular advantages for those with hostile anatomy for open repair (e.g., previous aortic surgery) or prohibitive medical risks.

Cost-effectiveness analyses suggest that despite higher device costs, fenestrated and branched repairs may be economically reasonable when accounting for reduced intensive care utilization, shorter hospital stays, and faster return to baseline function. However, these analyses are sensitive to assumptions about long-term durability and reintervention rates, highlighting the need for continued long-term follow-up data.

The optimal approach for individual patients requires careful consideration of anatomical factors, patient characteristics and preferences, and institutional expertise with different techniques. A multidisciplinary team approach involving vascular surgeons, interventional radiologists, anesthesiologists, and critical care specialists provides the most comprehensive assessment and personalized treatment recommendations.

Future Directions and Emerging Approaches

Ubunifu wa Kiteknolojia

The next generation of solutions:

Rapid innovation continues in the field of complex endovascular aortic repair, with several emerging technologies addressing current limitations:

“Off-the-shelf” fenestrated and branched systems represent perhaps the most significant development, aiming to overcome the 4-8 week manufacturing delay for custom devices. These systems incorporate adjustable components that can accommodate a range of anatomical variations within certain parameters. Early clinical experiences with devices such as the Cook p-Branch, Medtronic Valiant TAAA, and Gore TAMBE systems show promising technical success rates while significantly reducing time to treatment. While not suitable for all anatomies, these systems may eventually address 70-80% of cases currently requiring custom fabrication.

Novel branch designs continue to evolve, including externalized branches that facilitate catheterization, precannulated systems that incorporate preloaded wires to simplify vessel access, and directional branches with predefined angulation to better match target vessel orientation. These innovations aim to reduce procedural complexity and time while improving technical success rates, particularly for challenging vessel configurations.

Improved delivery systems focus on enhanced accuracy and control during deployment, with features including staged release mechanisms, partial repositioning capabilities, and integrated imaging markers. Lower-profile systems continue to expand applicability to patients with smaller or more diseased access vessels, while maintaining the necessary column strength and stability for precise deployment.

Advanced imaging integration represents another frontier, with systems incorporating intraprocedural fusion of preoperative CT data with fluoroscopy, automated vessel detection algorithms, and real-time guidance for optimal device positioning and branch vessel catheterization. These technologies aim to reduce contrast requirements, radiation exposure, and procedural time while improving precision.

Training and Dissemination

Expanding expertise responsibly:

The complexity of fenestrated and branched procedures presents significant challenges for training and dissemination, requiring balanced approaches that expand access while maintaining quality and safety:

Simulation-based training has emerged as a valuable adjunct to traditional apprenticeship models, allowing operators to develop and refine skills in a risk-free environment before applying them clinically. High-fidelity simulators incorporating patient-specific anatomy derived from CT data can recreate the technical challenges of complex cases, while virtual reality systems offer immersive training experiences. These approaches are particularly valuable for the early portion of the learning curve, potentially reducing the number of supervised clinical cases required for proficiency.

Proctoring programs facilitate controlled dissemination of these techniques, with experienced operators supervising and guiding those new to the procedures during initial cases. Structured programs typically involve case observation, followed by progressively increasing responsibility under direct supervision, and finally independent practice with remote support as needed. This approach has proven effective in expanding access while maintaining quality and safety.

Centralization versus dissemination represents an ongoing tension in the field. The complex nature of these procedures, substantial learning curve, and need for specialized inventory support arguments for centralization in high-volume centers. Conversely, geographic access challenges and institutional preferences push toward broader dissemination. Most healthcare systems have adopted hybrid approaches, with regional centers of excellence serving defined geographic areas while maintaining sufficient volume for proficiency.

Credentialing and quality monitoring systems are increasingly important as these procedures disseminate beyond initial pioneering centers. Professional societies have developed guidelines for training requirements and case volumes, while registry participation allows benchmarking of outcomes against national standards. These quality assurance mechanisms help ensure that expansion of these techniques occurs in a manner that maintains the excellent outcomes demonstrated in specialized centers.

Expanding Indications

Beyond current applications:

As technology and experience advance, applications of fenestrated and branched techniques continue to expand to new anatomical challenges and patient populations:

Arch aneurysms represent perhaps the most challenging frontier, with several approaches under investigation including inner branched arch devices, externalized arch branches, and various hybrid techniques combining surgical debranching with endovascular repair. The hemodynamic forces, anatomical constraints, and catastrophic consequences of complications in this region present unique challenges, but early experiences with specialized devices show promise for selected patients unsuitable for conventional open repair.

Aortic dissection applications are expanding beyond the traditional focus on aneurysmal degeneration to include treatment of acute and subacute dissections with branch vessel compromise. Specialized dissection-specific designs incorporate features to address the unique challenges of the dissected aorta, including true lumen collapse, multiple entry tears, and dynamic branch vessel compromise. Early experiences suggest potential for favorable aortic remodeling and improved branch perfusion in appropriately selected cases.

Pediatric and young adult applications remain controversial but are increasingly considered for conditions such as Marfan syndrome, Loeys-Dietz syndrome, and other connective tissue disorders where open surgical repair carries significant morbidity. Concerns regarding long-term durability and the need for lifelong surveillance and potential reinterventions must be balanced against the substantial perioperative risks of open repair in these challenging populations. Highly individualized decision-making involving multidisciplinary teams and detailed discussion of uncertainties with patients is essential in this evolving area.

Kanusho la Matibabu

Ilani Muhimu: This information is provided for educational purposes only and does not constitute medical advice. Fenestrated and branched endovascular aortic repair represent specialized procedures that should only be performed by qualified healthcare professionals with appropriate training and expertise in complex endovascular techniques. The approaches discussed should only be implemented under appropriate medical supervision in centers with necessary resources and experience. Individual treatment decisions should be based on patient-specific factors, current clinical guidelines, and physician judgment. If you have been diagnosed with a complex aortic aneurysm, please consult with vascular surgery specialists at experienced centers to discuss treatment options appropriate for your specific condition. This article is not a substitute for professional medical advice, diagnosis, or treatment.

Hitimisho

Fenestrated and branched endovascular aortic repair technologies have transformed the management of complex aortic aneurysms, offering minimally invasive options for patients previously limited to high-risk open surgical procedures or no treatment at all. The evolution from pioneering concepts to sophisticated, commercially available systems represents a remarkable example of collaborative innovation between clinicians, engineers, and industry partners addressing a significant unmet clinical need.

Current evidence supports the safety and efficacy of these approaches in appropriately selected patients treated at experienced centers, with perioperative advantages compared to open surgical alternatives and accumulating data supporting medium-term durability. Ongoing technological innovations continue to address existing limitations, expand anatomical applicability, and simplify procedural complexity.

The future of this field lies in responsible dissemination of expertise, continued refinement of device designs and techniques, and careful long-term evaluation of outcomes. As these technologies mature, the focus increasingly shifts from technical feasibility to optimizing patient selection, procedural efficiency, and long-term durability—ensuring that these sophisticated interventions provide lasting benefit for patients with complex aortic pathology.