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Cardiology
Endovascular Abdominal Aortic Aneurysm Repair
Built from Cardiovascular Catheterization and Intervention: A Textbook of Coronary, Peripheral, and Structural Heart Disease
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14 sections · 157 slides
Overview
- Definition, natural history, pathogenesis of AAA Screening, surveillance, thresholds for repair Randomised evidence: EVAR versus open repair Planning, sizing, access and deployment Fenestrated and branched repair (FBEVAR) Endoleaks, complications, lifelong surveillance
Definition, epidemiology and pathogenesis
- Aortic diameter more than 3.0 cm Or 50% increase over estimated normal diameter Normal aorta varies with age, sex, body habitus Normal infrarenal aorta about 2 cm Infrarenal aorta always less than 3 cm normally
- Men aged 45-54 years: 1.3% have 2.9-4.9 cm aorta Men aged 75-84 years: 12.5% Women: 0% youngest, 5.2% oldest age groups Overwhelmingly a disease of older individuals
- CDC 2013: 15th leading cause of death 4.1 deaths per 100,000 at ages 60-64 years Most deaths occur in men Cause of death in 0.13% of males Cause of death in 0.07% of females
- Meta-analysis of 18 studies, aneurysms 3-5.4 cm Mean growth 2.21 mm per year Growth independent of age and sex Faster in smokers, slower in diabetics Rupture 0.71-11.03 per 1,000 person-years
- Smokers: pooled hazard ratio 2.02 95% confidence interval 1.33 to 3.06 Women: pooled hazard ratio 3.76 95% confidence interval 2.58 to 5.47 Sex is the stronger rupture multiplier here
- Cause not fully established Inflammatory cells migrate into the aortic wall Elastin and collagen degraded in media, adventitia Transmural inflammation is the hallmark Macrophages and lymphocytes predominate
- Most lymphocytes are CD4+ T cells T helper 1 and Th17 subsets predominate Regulatory T cells and Th2 infiltrate less Proinflammatory M1 macrophages exceed M2 Balance is tilted towards wall destruction
- Interleukin-1b, interleukin-6, interleukin-8 Interferon-gamma Tumour necrosis factor alpha Monocyte chemoattractant protein-1 (MCP-1) Raised in aneurysm tissue and in serum
- Endothelium releases DAMP molecules DAMP: danger-associated molecular pattern signal Release is Pannexin-1 channel mediated Recruits and activates M1 macrophages SPMs may mitigate wall degeneration
- Sequence of aneurysmal wall degeneration
Classification and risk factors
- Small: diameter less than 4 cm Medium: 4 to 5.5 cm Large: greater than 5.5 cm Very large: 5 cm or more, at or above 6 cm Size drives surveillance and repair decisions
- Anatomical scheme for thoracoabdominal aneurysms Extent I: left subclavian to above renal arteries Extent II: left subclavian to aortic bifurcation Extent III: sixth intercostal space to bifurcation Extent II carries the widest aortic coverage
- Extent IV: 12th intercostal space to bifurcation Extent V: below sixth space to above renals Extent IV is the abdominal-only pattern Extent defines visceral vessel involvement Guides fenestrated or branched device choice
- Crawford classification of thoracoabdominal aortic aneurysms
- Advanced age Male sex Smoking, odds ratio above 3 First-degree relative with AAA Smoking effect exceeds that in CAD or stroke
- Lower incidence in diabetics Lower incidence in non-Caucasian ethnicities Associated: greater height, hypertension Associated: coronary and cerebrovascular disease Associated: atherosclerosis, high cholesterol Evidence for several of these is inconsistent
- Loci on 3p12.3, 9p21.3, 9q33.1, 12q13.3 rs10757278 lies in the 9p21.3 noncoding region Linked to reduced CDKN2B expression Impairs efferocytosis, raises inflammation Histone modification alters MMP and TIMP balance
Clinical presentation and diagnosis
- Most patients are entirely asymptomatic Usually incidental on imaging or screening Symptomatic: abdominal, back or flank pain Thromboembolism may cause limb ischaemia Systemic symptoms: fever and malaise
- Classic triad: severe pain, hypotension, mass Pulsatile abdominal mass is the third element Triad present in about 50% of ruptures Half of ruptures therefore present atypically Also seen with rapidly expanding aneurysm
- Safe, reliable, inexpensive first-line test Sensitivity and specificity 100% above 3 cm Used for follow-up of small and medium AAA No radiation, no contrast Physical examination has poor sensitivity
- High-resolution CT is standard for planning Test of choice in symptomatic, impending rupture Contrast not usually needed for diagnosis Contrast shows extravasation in rupture Also defines neck, branches, access vessels
- Crescent sign in the mural thrombus Breaks in circumferential wall calcification Aortic blebs All indicate instability of the aneurysm wall Prompt urgent rather than elective repair
Screening, surveillance and thresholds for repair
- Three linked guideline sets are used Who to screen, and once or repeatedly How often to re-image a known aneurysm When the aneurysm should be repaired Each carries a strength and evidence grade
- The Society for Vascular Surgery Screening Guidelines for Abdominal Aortic Aneurysm (Aaa)
- The Society for Vascular Surgery Surveillance Guidelines for Patients with Known Aaa
- The Society for Vascular Surgery Threshold for Repair Guidelines for Aaa
Randomised trials: EVAR versus open repair
- 1,252 patients across 37 UK hospitals Maximum aneurysm diameter above 5.5 cm Randomised to open or endovascular repair Elective, anatomically suitable patients Largest elective randomised comparison
- 30-day death: 1.8% EVAR versus 4.3% open P = 0.02, a clear early advantage All-cause survival curves converge at 2 years Aneurysm-related curves converge at 6 years No long-term survival advantage for EVAR
- 351 patients, 30 Dutch and Belgian centres Maximum aneurysm diameter above 5 cm 30-day death: 1.2% EVAR versus 4.6% open Risk ratio 3.9, 95% CI 0.9 to 32.9 All-cause survival converged at 1 year
- 881 patients, 42 US Veterans Affairs centres Aneurysm above 5 cm, or iliac aneurysm above 3 cm Or AAA above 4.5 cm with rapid enlargement Rapid enlargement: above 0.5 mm in 6 months Or saccular morphology
- 30-day death: 0.5% EVAR versus 3.0% open P = 0.004 All-cause survival converged at 2 years EVAR: shorter procedure, less blood loss Fewer transfusions, less ventilation time Shorter hospital and intensive care stay
- Short-term mortality clearly better with EVAR Short-term morbidity also clearly better Long-term outcomes similar in both groups Benefit is early and then erodes Trade is early survival for late reintervention
- Summary of the Results from the Randomized Controlled Trials for Both Ruptured and Nonruptured Abdominal Aortic Aneurysm (Aaa) Treated Either with Endovascular Aneurysm Repair (Evar) or Open Repair
- Summary of the Results from the Randomized Controlled Trials for Both Ruptured and Nonruptured Abdominal Aortic Aneurysm (Aaa) Treated Either with Endovascular Aneurysm Repair (Evar) or Open Repair (continued)
- Elective EVAR compared with open repair
Ruptured abdominal aortic aneurysm
- Overall mortality rates broadly similar Some evidence favours EVAR at 30 days Recommended for high-risk suitable anatomy Registry mortality EVAR 16% to 31% Registry mortality open 34% to 44%
- Registry comparisons were not randomised Stable ruptures were selected for EVAR Unstable ruptures went straight to open repair Bias inflates the apparent EVAR advantage Randomised trials show a much smaller gap
- Largest ruptured AAA trial, 613 patients 30 centres in the United Kingdom and Canada 30-day death: 35.4% EVAR versus 37.4% open Odds ratio 0.92, 95% CI 0.66-1.28, P = 0.62 1-year death: 41.1% versus 45.1%, P = 0.325 Reintervention rates similar in both arms
- AJAX: 116 Dutch patients, anatomy-based arms AJAX 30-day death: 21% EVAR versus 25% open Absolute risk reduction 4.4%, CI -11% to +20% ECAR: 107 French patients, stable ruptures only ECAR 30-day death: 19% versus 24% ECAR 1-year death: 33% versus 35%
- Minimally invasive, avoids laparotomy Reduces physiological stress of blood loss Reduces ischaemia-reperfusion insult Lowers cardiac, pulmonary, renal morbidity No reliable score predicts rupture mortality
- Confirmed rupture demands emergent transfer Particularly with concomitant hypotension Go directly to an operating room Or to a regional vascular centre Protocol-driven care improves outcomes
- Decision algorithm for suspected or confirmed ruptured AAA
- Rapid airway, breathing, circulation assessment Two large-bore peripheral intravenous lines Permissive hypotension, systolic 70-90 mmHg Avoid elective endotracheal intubation Prepare blood products immediately Active patient warming measures
- Ninety-minute framework from presentation to intervention
- EVAR is first line if anatomy allows Aortic occlusion balloon for instability Also if anatomy prevents rapid repair Transfemoral access with a long sheath Advance sheath to supraceliac aorta Intermittent balloon deflation may be needed
- Bifurcated and aorto-uni-iliac both feasible AUI needs cross-femoral bypass afterwards Preprocedural imaging is ideal for planning Intraoperative angiography defines landing zones IVUS identifies intramural thrombus
Preprocedure planning and endograft sizing
- High-resolution CT with 3D reconstruction Defines aortic and branch vessel anatomy Measures access vessel diameter Assesses neck length and angulation Assesses aortic tortuosity Identifies calcification and mural thrombus
- Landing zone, that is proximal neck length Angle of the neck Diameter of healthy aortic segment Iliac and common femoral artery diameter Tortuosity of aorta and access vessels Calcification and mural thrombus burden
- Identify inferior mesenteric artery Identify patent lumbar arteries Identify internal iliac artery origins Coiling reduces later type II endoleak risk Preserve branches to avoid ischaemia Balance is between endoleak and ischaemia
- Modular bifurcated: Endurant, Excluder, Zenith Also Ovation, Aorfix and Treo Unibody configuration: AFX AUI for severe unilateral iliac calcification Also for a small terminal aortic diameter AUI needs cross-femoral bypass and occluder
- Conventional aortic stent grafts: materials and neck limits
- Conventional aortic stent grafts: angulation, access and fixation
- Conventional aortic stent grafts: unique device features
- Conventional grafts seal a 10-15 mm neck Measure shortest transverse diameter on axial CT From lowest renal orifice to 15 mm caudal Take measurements at 5 mm intervals Oversize the endograft by 10% to 20%
- Significant calcification of the aortic neck Circumferential mural thrombus in the neck Conical neck morphology Short neck below device instructions for use Extremes of neck angulation
- Endoanchor application is an available adjunct Used with the Endurant II and IIs device Extends approved minimum neck length to 4 mm Adds active mechanical fixation to the wall Supplements radial force alone
- Defined by more than 10% transverse dilation Measured over 15 mm caudal from lowest renal Sizing to the small end under-sizes distally Sizing to the large end over-sizes proximally Split the difference between the two diameters Aim 10% minimum and 30% maximum oversize
- Measure proximal to distal landing site Also proximal landing site to aortic bifurcation Tortuosity makes lengths underestimated Centreline measurement corrects for this Upsize iliac limbs by 10% to 20% Use the shortest transverse iliac diameter
Access and intraoperative imaging
- Choice rests with the operator and anatomy Percutaneous closed with suture-based devices Prostar XL and Perclose ProGlide are approved Devices deployed before sheath placement Open cut-down exposes common femoral artery
- Significant scarring in the groin High femoral bifurcation Severe anterior femoral wall calcification Proximal iliac calcific disease Small vessel calibre Need for frequent sheath exchanges
- Vertical or oblique skin incisions both used Wound complication rate 2% to 2.8% in EVAR Swinnen et al: fewer infections with vertical Vertical 2.6% versus transverse 8.7% P = 0.062, not conventionally significant
- Focal lesions: balloon angioplasty first Stents distal to the graft placed at the end Prevents iliac stent displacement by the sheath Conduit needed for calcified or small iliacs Retroperitoneal end-to-side to common iliac Tunnelled under the inguinal ligament
- Low-osmolar nonionic contrast agents used Standard method for deployment landmarks Confirms adequate aneurysm exclusion Digital subtraction gives best visualisation Preoperative imaging can guide wires and grafts
- Dilute the contrast to reduce nephrotoxic load Carbon dioxide can substitute as contrast agent IVUS gives anatomy with no iodinated contrast Aortic IVUS uses 8-15 MHz transducers Lower frequency: whole artery, less resolution
Main device deployment and limb management
- Bilateral femoral access obtained first Heparin 100 units per kilogram intravenously Target activated clotting time 300 seconds Floppy 0.035 inch J-wire to descending aorta Exchange for a stiff Lunderquist wire
- Pigtail catheter via contralateral groin Position at infrarenal level, L1 to L2 bodies Aortogram confirms lowest renal artery origin Also confirms both internal iliac origins Check contralateral gate orientation carefully Check before and during endograft delivery
- Depends on access vessel diameter And on iliac artery tortuosity And on main body and iliac limb length Iliac stenosis: deliver body via larger side Tortuosity hinders gate cannulation too Match vessel size to available device sizes
- Deploy close to the renal arteries Place within a neck of uniform diameter Suprarenal or infrarenal fixation options Mural thrombus guides device selection Avoid embolisation, migration, seal loss
- Isolated suprarenal disease: avoid suprarenal stent Reduces renal and distal embolisation Circumferential neck thrombus: relative contraindication Mild thrombus: consider suprarenal fixation Fix to healthy aortic tissue where possible
- Most grafts contraindicated above 60 degrees Aorfix approved for 60 to 90 degree necks Aortic diameter at the gate must be adequate Narrow segments risk limb constriction Circumferential calcification prevents expansion Main body may be rotated up to 180 degrees
- Main body rotation aids gate access Rotation also shortens the iliac limbs slightly Freestyle cannulation: angled catheter and wire If that fails, use an ipsilateral approach Or a brachial approach with a snare Snare pulls wire through the gate
- Lumbar arteries Inferior mesenteric artery Internal iliac arteries Renal and accessory renal arteries All are potential type II endoleak sources Most stable type II leaks treated expectantly
- Unilateral occlusion has minimal sequelae Especially with a patent contralateral vessel Bilateral occlusion sometimes unavoidable Needed for iliac aneurysm or poor distal seal Visceral, pelvic, spinal ischaemia risk is low Buttock claudication and impotence persist
- Transarterial embolisation is the usual route Coils placed at the branch origin Occludes the orifice, preserves collateral flow Amplatzer plug an alternative device Allows controlled occlusion, small or large vessel
- Assess after molding balloon inflation Digital subtraction angiography or IVUS used Immediate type IA endoleak rate about 6% First treat with balloon angioplasty Then proximal graft extension cuffs Bare stents can appose graft to aortic wall
- Early type II leaks usually observed Reintervene if symptomatic or sac enlarges Mild limb compression: angioplasty, selective stent Severe problems: AUI converter device Combined with a cross-femoral bypass Open conversion with explantation if all fails
- Elective type II leak often observed first Majority correct spontaneously over time After ruptured repair the behaviour differs Type II leak will not tamponade spontaneously Open surgical ligation of back-bleeding vessel
- Withdraw sheaths while maintaining wire access Occlusive balloons for sudden haemodynamic change Also if artery is avulsed with the sheath Open access: standard arteriotomy repair Layered closure of the groin wound
- Maintain proximal manual pressure Rinse wounds and sutures free of thrombus Confirm the tract is fully dilated Tie knots down to, not into, the artery Remove wire before tying the second suture Percutaneous closure success about 95%
- Emergent repair if haemorrhage or ischaemia Risk raised by calcification and groin scarring Also by operator inexperience Perform lower limb pulse examination Ankle-brachial index and Doppler on the table Compare with preoperative measurements
- Plan access and device delivery route Manage large aortoiliac branches Orient the graft, deploy the main body Cannulate the gate, deploy the limbs Assess for endoleak and limb compression Then close the arteriotomy and wound
Fenestrated and branched endovascular repair
- Hostile proximal neck anatomy Paravisceral aneurysm morphology Juxtarenal aneurysm morphology Standard EVAR not feasible in these patterns Abbreviated FBEVAR in the literature
- Physician-modified endografts, or PMEGs Custom-made devices, or CMDs Off-the-shelf devices PMEG made on the back table, same day CMD manufactured to patient measurements Off-the-shelf available immediately
- Construction of a physician-modified endograft
- Fenestrations sited from patient CT measurements Bridging stent sewn on gives a branch Used when fenestration will not oppose wall Device constrained and resheathed for delivery Main advantage over CMD is immediate availability
- Generated through industry partnership Historically built on Zenith and TX2 platforms Modified to individual patient requirements May carry preloaded catheters and wires Preloading eases target vessel cannulation
- Zenith fenestrated device
- Off-the-shelf fenestrated option Instructions for use: 4 to 10 mm neck Range of fenestration sizes for renal origins Anterior scallop for superior mesenteric artery Renal fenestrations supported by bridging stents
- Thoracoabdominal multibranch endoprosthesis
- Proximal seal zone of 20 to 40 mm desired Angulation tolerance narrower, 45 degrees or less Extreme angles make cannulation very difficult Delivery systems 18 to 26 French Iliac diameter, tortuosity, occlusion all matter
- Greater thoracolumbar aortic coverage Higher spinal cord ischaemia risk than EVAR Stratify patients by spinal cord ischaemia risk CSF drain preoperatively in high-risk patients Bundle: naloxone infusion, perioperative steroids Elevated mean arterial pressure targets
- Routes to a fenestrated or branched repair
Complications of endovascular aneurysm repair
- Up to 20% need a secondary intervention Usually performed to treat endoleaks Overall complication rates as high as 30% Late complications needing repair 2% to 3% Repetitive intervention in 12% to 35% of cases Most late complications are asymptomatic
- Endoleak Graft migration Limb kinking or thrombosis Endograft infection Renal complications and bowel ischaemia Access site complications and delayed rupture
- Found in 15% to 25% within the first 30 days Often entirely asymptomatic Lifelong imaging surveillance is necessary Classified by the origin of blood flow CTA better for identifying an endoleak Catheter angiography better shows flow dynamics
- Endoleak Classification
- Physiology of endoleak after endovascular repair
- Flow into the sac from an attachment site Type IA proximal, type IB distal Type IC at a target vessel in FBEVAR Occurs in about 10% of EVAR procedures Hooks and barbs reduce loss of fixation Oversizing 10% to 20% aids adequate seal
- Early intervention needed to reduce rupture risk Secure attachment sites with angioplasty balloon Then stents or endograft extension cuffs Coil embolisation and glue effective in some Enlarged neck: fenestrated or chimney graft May avert open surgical conversion
- The most common endoleak type Arises in 10% to 25% of cases Retrograde flow from collateral vessels Usually inferior mesenteric or lumbar arteries Pre-EVAR IMA coiling may reduce incidence Up to 40% thrombose spontaneously
- Delayed leaks arise beyond 1 year after EVAR Treatment usually indicated for delayed leaks Risk is sac pressurisation and rupture Threshold: 5 to 10 mm of sac expansion Rupture reported without sac expansion Onyx with contrast used for embolisation
- Structural stent-graft failure Or disconnection between graft components Estimated incidence 4% at one year CTA: contrast beside the graft, not sac periphery Pulsation and sac shrinkage cause displacement Repair with a stent-graft extension or cuff
- Type IV: porosity of the graft material Seen on angiography immediately after placement Resolves when coagulation is normalised Mostly an early-generation device phenomenon Type V: endotension, sac grows with no visible leak Diagnosis of exclusion, may need open conversion
- Migration of 5 to 10 mm is significant Measure against SMA and renal artery landmarks Risk depends on device type and neck diameter Also on configuration and landing zone length Suprarenal fixation lowers migration rate Treated with extension cuffs
- Follows migration or sac shrinkage Causes migration, thrombosis, type I or III leak Predisposed by neck angulation, narrow aorta Reported incidence 1.7% to 3.7% Low-profile devices may kink more often High-radial-force bare stents straighten kinks
- Follows excessive oversizing and fabric folding Twisting of limbs during deployment contributes Reported incidence 0.5% to 11% Small iliacs: consider AUI with surgical bypass Thrombectomy and stenting may salvage a limb Otherwise femoro-femoral bypass restores flow
- Snorkel stents preserve internal iliac flow Bifurcated iliac side-branch devices also used Applied when common iliac is aneurysmal Surveillance must check limbs for thrombosis Bilateral IIA occlusion causes buttock claudication
- Rare, occurring in under 1% of cases Early infection from procedural contamination Late colonisation from remote infective sites Presents with leukocytosis, fever, back pain CT: perigraft fluid, air bubbles, inflammation
- Uncommon, causes massive haemorrhage May cause infection and hypovolaemic shock Sac expansion from endoleak erodes into bowel In situ repair with antibiotic-soaked graft Or autologous vein or cryopreserved graft Extra-anatomic reconstruction in high-risk cases
- Renal failure incidence after EVAR is 6.7% At least 50 to 100 mL contrast per case Use smallest dose of 50:50 diluted contrast EVAR shows greater long-term decline than open Driven by index, secondary and surveillance scans
- Ensure hydration before and after the procedure Sodium bicarbonate reduces contrast nephrotoxicity Acetylcysteine given despite limited evidence Unenhanced surveillance protocols help long term IVUS assesses anatomy and graft position IVUS considerably reduces contrast volume
- Serious but uncommon complication Suprarenal atheroma displaced during deployment Emboli reach SMA, IMA, internal iliac, legs Microemboli give patchy multifocal bowel ischaemia Inadequate mesenteric collateral also proposed
- Strong independent predictor of mortality Ruptured aneurysm repair: 8.9% of 756 patients Elective open repair: 2.2% of 983 patients EVAR: 0.5% of 202 patients P less than 0.001 across these groups
- Now uncommon, mainly early-generation devices Fatigue, corrosion, suture breakage, fabric tear Reported in up to 5.5% of cases Causes seal loss, migration and endoleak Turbulent sac flow accelerates device fatigue Metallic ring failure visible on 3D CTA
- Arise in up to 3% of percutaneous EVAR Percutaneous feasible in 76% to 96% of patients Reduces wound complications and hospital stay Risks: obesity, repeat groin access, large sheath Severe calcification, vessel under 5 mm Operator inexperience raises failure rate
- Ultrasound guidance for common femoral puncture Allows avoidance of anterior wall calcification Complications: thrombosis, dissection, pseudoaneurysm Large sheaths cause dissection and avulsion Stent an intraprocedural dissection Rupture may appear only on sheath removal
- Occurs in about 0.5% of cases per year May occur without sac enlargement on imaging Usually sudden pressurisation, type I or III leak Mortality higher for secondary procedures Treat by endovascular revision or open conversion Graft extensions used to seal landing zones
Post-repair surveillance
- Current reference standard for surveillance Primary imaging modality at most centres Detects migration, kinking, structural failure Also endoleak, infection and aneurysm growth Limited by radiation dose and contrast load
- Unenhanced, arterial and delayed phases Arterial phase at 30 second delay Delayed phase at 120 to 300 seconds Unenhanced separates calcification from leak Delayed phase detects low-flow endoleak Peak detection about 27 s after bolus threshold
- Baseline CT at 1 month after repair Then 6-month interval scans Transition to annual scans if uncomplicated Sac under 5 cm or shrunk 5 mm: extend to 1 year Sac down to 4 cm: scan every 2 to 3 years Clean 1-month scan may allow skipping 6-month
- Ultrasound limited by obesity and calcification Still shows fixation sites and sac size MRA shows patency, position, residual sac flow Nitinol stents are best suited to MRA Steel and cobalt-chromium-nickel cause artefact MRA more sensitive than CTA for endoleak
- Sac enlarges with no leak seen on imaging Type V is a diagnosis of exclusion Add ultrasound and MRA to the workup MRI is effective at detecting type II leaks Open conversion if aneurysm keeps enlarging
Conclusion
- EVAR cuts perioperative mortality about 60% Applies to patients with suitable anatomy Cost is an increased reintervention rate Upfront mortality benefit is lost on follow-up EVAR still preferred in suitable patients Open repair standard if anatomy unsuitable
- Repair at 5.5 cm in men, 5.0-5.4 cm in women Neck 10-15 mm, oversize graft by 10% to 20% Most grafts contraindicated above 60 degree neck Type I and III need repair, type II usually watched Up to 20% require a secondary intervention Lifelong imaging surveillance is mandatory
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- Cardiovascular Catheterization and Intervention: A Textbook of Coronary, Peripheral, and Structural Heart Disease
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