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Endovascular aneurysm repair (EVAR) is a type of minimally-invasive
endovascular surgery Vascular surgery is a surgical subspecialty in which diseases of the vascular system, or arteries, veins and lymphatic circulation, are managed by medical therapy, minimally-invasive catheter procedures and surgical reconstruction. The specialty ...
used to treat pathology of the
aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...
, most commonly an
abdominal aortic aneurysm Abdominal aortic aneurysm (AAA) is a localized enlargement of the abdominal aorta such that the diameter is greater than 3 cm or more than 50% larger than normal. They usually cause no symptoms, except during rupture. Occasionally, abdominal ...
(AAA). When used to treat thoracic aortic disease, the procedure is then specifically termed TEVAR for "thoracic endovascular aortic/aneurysm repair." EVAR involves the placement of an expandable stent graft within the aorta to treat aortic disease without operating directly on the aorta. In 2003, EVAR surpassed open aortic surgery as the most common technique for repair of AAA, and in 2010, EVAR accounted for 78% of all intact AAA repair in the United States.


Medical uses

Standard EVAR is appropriate for aneurysms that begin below the renal arteries, where there exists an adequate length of normal
aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...
(the ''"proximal aortic neck"'') for reliable attachment of the endograft without leakage of blood around the device ("'' endoleak''"). If the proximal aortic neck is also involved with the aneurysm, the patient may be a candidate for complex visceral EVAR with a fenestrated or branched EVAR. Patients with aneurysms require elective repair of their aneurysm when it reaches a diameter large enough (typically greater than 5.5 cm) such that the risk of rupture is greater than the risk of surgery. Repair is also warranted for aneurysms that rapidly enlarge or those that have been the source of
emboli An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel. The embolus may be a blood clot (thrombus), a fat globule ( fat embolism), a bubble of air or other gas ( gas embolism), amniotic fluid ( amn ...
(debris from the aneurysm that dislodges and travel into other arteries). Lastly, the repair is also indicated for aneurysms that are the source of pain and tenderness, which may indicate impending rupture. The options for repair include traditional open aortic surgery or endovascular repair. Endovascular procedures aim to reduce the morbidity and mortality of treating arterial disease in a patient population that is increasingly older and less fit than when major open repairs were developed and popularized. Even in the early days, significant risks were accepted in the understanding that the large open operation was the only option. That is not the case in most patients today. Studies that assign aneurysm patients to treatment with EVAR or traditional open surgery have demonstrated fewer early complications with the minimally invasive approach. Some studies have also observed a lower mortality rate with EVAR. The reduction in death, however, does not persist long-term. After a few years, the survival after repair is similar to EVAR or open surgery. This observation may be the result of durability problems with early endograft, with a corresponding need for additional procedures to repair endoleaks and other device-related issues. Newer, improved technology may reduce the need for such secondary procedures. If so, the results of EVAR may improve to the point where long-term survival benefit becomes evident. EVAR is also used for rupture of the abdominal and descending thoracic aorta, and in rare cases used to treat pathology of the
ascending aorta The ascending aorta (AAo) is a portion of the aorta commencing at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum. Structure It passes obliqu ...
.


Aortic dissection

Endografts have been used in patients with
aortic dissection Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or ...
, noting the extremely complex nature of open surgical repair in these patients. In uncomplicated aortic dissections, no benefit has been demonstrated over medical management alone. In uncomplicated type B aortic dissection, TEVAR does not seem either to improve or compromise 2-year survival and adverse event rates. Its use in complicated aortic dissection is under investigation. In the Clinical Practice Guidelines of the European Society for Vascular Surgery, it is recommended that in patients with complicated acute type B aortic dissection, endovascular repair with thoracic endografting should be the first line intervention. Before people are deemed to be suitable candidates for this treatment, they have to go through a rigorous set of tests. These include a CT scan of the complete thorax/abdomen/pelvis and blood tests. The CT scan gives precise measurements of the aneurysm and the surrounding anatomy. In particular, the calibre/tortuosity of the iliac arteries and the relationship of the neck of the aneurysm to the renal arteries are important determinants of whether the aneurysm is amenable to endoluminal repair. In certain occasions where the renal arteries are too close to the aneurysm, the custom-made fenestrated graft stent is now an accepted alternative to doing open surgery.


Relative contraindications

A patient's anatomy can be unsuitable for EVAR in several ways. Most commonly, in an infrarenal aneurysm, a potential EVAR candidate lacks adequate length of the normal-diameter aorta between the aneurysm and the takeoff of the renal arteries, the "infra-renal neck". Another relative
contraindication In medicine, a contraindication is a condition that serves as a reason not to take a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a reason to use a certain tre ...
s include prohibitively small iliac arteries, aneurysmal iliac arteries, prohibitively small
femoral arteries The femoral artery is a large artery in the thigh and the main arterial supply to the thigh and leg. The femoral artery gives off the deep femoral artery or profunda femoris artery and descends along the anteromedial part of the thigh in the fe ...
, or circumferential calcification of the femoral or iliac arteries. In addition to a short proximal aortic neck, the neck may be angulated, large in diameter, or shaped like a funnel (conical) where the neck diameter at the top is larger than the neck diameter at the bottom. Along with a short proximal aortic neck, necks with any of these characteristics are called "hostile necks" and endovascular repair can be either contraindicated or associated with early-late complications of endoleak, or endograft migration, or both. Many of the advances in EVAR technique aim to adapt EVAR for these situations, and advanced techniques allow EVAR to be employed in patients who previously were not candidates.


Technique

The procedure is carried out in a sterile environment under
fluoroscopic Fluoroscopy () is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object. In its primary application of medical imaging, a fluoroscope () allows a physician to see the internal structure and function ...
guidance. It is usually carried out by a vascular surgeon, interventional radiologist or
cardiac surgeon Cardiac surgery, or cardiovascular surgery, is surgery on the heart or great vessels performed by cardiac surgeons. It is often used to treat complications of ischemic heart disease (for example, with coronary artery bypass grafting); to corr ...
, and occasionally,
general surgeon General surgery is a surgical specialty that focuses on alimentary canal and abdominal contents including the esophagus, stomach, small intestine, large intestine, liver, pancreas, gallbladder, appendix and bile ducts, and often the thyroid ...
or
interventional cardiologist Interventional cardiology is a branch of cardiology that deals specifically with the catheter based treatment of structural heart diseases. Andreas Gruentzig is considered the father of interventional cardiology after the development of angioplasty ...
. The procedure can be performed under general, regional (spinal or epidural) or even local anesthesia. Access to the patient's femoral arteries can be with surgical incisions or percutaneously in the groin on both sides. Vascular sheaths are introduced into the patient's femoral arteries, through which guidewires, catheters, and the endograft are passed. Diagnostic angiography images are captured of the aorta to determine the location of the patient's renal arteries, so the stent-graft can be deployed without blocking these. Failure to achieve this will cause kidney failure. With most devices, the "main body" of the endograft is placed first, followed by the "limbs" which join the main body and extend to the iliac arteries, effectively protecting the aneurysm sac from blood pressure. The abdominal aneurysm extends down to the common iliac arteries in about 25%-30% of patients. In such cases, the iliac limbs can be extended into the external iliac artery to bypass a common iliac aneurysm. Alternatively, a specially designed endograft, (an iliac branch device) can be used to preserve flow to the internal iliac arteries. The preservation of the hypogastric (internal iliac) arteries is important to prevent buttock
claudication Claudication is a medical term usually referring to impairment in walking, or pain, discomfort, numbness, or tiredness in the legs that occurs during walking or standing and is relieved by rest. The perceived level of pain from claudication can be ...
and impotence, and every effort should be made to preserve flow to at least one hypogastric artery. The endograft acts as an artificial lumen for blood to flow through, protecting the surrounding aneurysm sac. This reduces the pressure in the aneurysm, which itself will usually thrombose and shrink in size over time. Staging such procedures is common, particularly to address aortic branch points near the diseased aortic segment. One example in the treatment of thoracic aortic disease is revascularization of the left common carotid artery and/or the left subclavian artery from the innominate artery or the right common carotid artery to allow treatment of a thoracic aortic aneurysm that encroaches proximally into the aortic arch. These "extra-anatomic bypasses" can be performed without an invasive
thoracotomy A thoracotomy is a surgical procedure to gain access into the pleural space of the chest. It is performed by surgeons (emergency physicians or paramedics under certain circumstances) to gain access to the thoracic organs, most commonly the he ...
. Another example in the abdominal aorta is the embolization of the internal iliac artery on one side prior to coverage by an iliac limb device. Continued improvement in stent-graft design, including branched endografts, will reduce but not eliminate multi-stage procedures.


Percutaneous EVAR

Standard EVAR involves a surgical cut-down on either the femoral or iliac arteries, with the creation of a 4–6 cm incision. Like many surgical procedures, EVAR has advanced to a more
minimally invasive Minimally invasive procedures (also known as minimally invasive surgeries) encompass surgical techniques that limit the size of incisions needed, thereby reducing wound healing time, associated pain, and risk of infection. Surgery by definition ...
technique, by accessing the femoral arteries percutaneously In percutaneous EVAR (PEVAR), small, sub-centimeter incisions are made over the femoral artery, and endovascular techniques are used to place the device over a wire. Percutaneous EVAR has been systematically compared to the standard EVAR cut-down femoral artery approach. Moderate quality evidence suggests that there are no differences in short-term mortality, aneurysm sealing, long and short-term complications, or infections at the wound site. Higher quality evidence suggests that there are no differences in post-repair bleeding complications or haematoma between the two approaches. The percutaneous approach may have reduced surgical time.


Fenestrated EVAR

In certain circumstances, a specially designed custom-made graft, which has holes, or fenestrations, on the graft body to maintain the patency of the visceral arteries, is used for the procedure, which is called FEVAR (fenestrated endovascular aortic/aneurysm repair). When the aneurysm begins close to the renal arteries, standard EVAR may be
contraindicated In medicine, a contraindication is a condition that serves as a reason not to take a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a reason to use a certain tre ...
since there will be an inadequate length of suitable aorta for the endograft attachment. In these cases, a fenestrated endograft may be useful, where the attachment of the endograft to the aorta may be placed above the renal arteries with each fenestration aligned with a renal artery so that blood flow to the kidneys is maintained. Fenestrated EVAR has been in use in the United Kingdom for over a decade and early results were published in Jun 2012.


Branched EVAR

Thoracoabdominal aortic aneurysms (TAAA) involve the aorta in the chest and abdomen. As such, major branch arteries to the head, arms, spinal cord, intestines, and kidneys may originate from the aneurysm. An endovascular repair of a TAAA is only possible if blood flow to these critical arteries is preserved. Hybrid procedures offer one option, but a more direct approach involves the use of a branched endograft. However, the complex anatomy associated with the supra-aortic vessels is particularly difficult to accommodate with branched endograft devices. Dr. Timothy Chuter pioneered this approach, with a completely endovascular solution. After partial deployment of the main body of an endograft, separate endograft limbs are deployed from the main body to each major aortic branch. This procedure is long, technically difficult, and currently only performed in a few centers. When the aneurysm begins above the renal arteries, neither fenestrated endografts nor "EndoAnchoring" of an infrarenal endograft is useful (an open surgical repair may be necessary). Alternatively, a "branched" endograft may be used. A branched endograft has graft limbs that branch off of the main portion of the device to directly provide blood flow to the kidneys or the visceral arteries.


Hybrid procedures

On occasion, there is inadequate length or quality of the proximal or distal aortic neck. In these cases, a fully minimally invasive option is not possible. One solution, however, is a hybrid repair, which combines an open surgical bypass with EVAR or TEVAR. In hybrid procedures, the endograft is positioned over major aortic branches. While such a position would normally cause problems from disruption of blood flow to the covered branches (renal, visceral, or branches to the head or arms), the prior placement of bypass grafts to these critical vessels allowed the deployment of the endograft at a level that would otherwise not be possible. If a patient has calcified or narrow femoral arteries that prohibit the introduction of the endograft transfemorally, an iliac conduit may be used. This is typically a piece of PTFE that is sewn directly to the iliac arteries, which are exposed via an open retroperitoneal approach. The endograft is then introduced into the aorta through the conduit. In patients with thoracic aortic disease involving the arch and descending aorta, it is not always possible to perform a completely endovascular repair. This is because head vessels of the aortic arch supplying blood to the brain cannot be covered and for this reason, there is often an inadequate landing zone for stent-graft delivery. A hybrid repair strategy offers a reasonable choice for treating such patients. A commonly used hybrid repair procedure is the "frozen elephant trunk repair". This technique involves midline sternotomy. The aortic arch is transected and the stent-graft device is delivered in an ante-grade fashion in the descending aorta. The aortic arch is subsequently reconstructed and the proximal portion of the stent-graft device is then directly sutured into the surgical graft. Patients with anomalies of the arch and some disease extension into the descending aorta are often ideal candidates. Studies have reported successful use of hybrid techniques for treating Kommerell diverticulum and descending aneurysms in patients with previous coarctation repairs. In addition, hybrid techniques combining both open and endovascular repair are also used in managing emergency complications in the aortic arch, such as retrograde ascending dissection and endoleaks from previous stent grafting of descending aorta. A "reverse frozen elephant trunk repair" is shown to be particularly effective.


Adjunctive procedures

* Snorkel: A covered stent placed into a visceral vessel adjacent to the main body of the EVAR device. The aortic lumen of the visceral stent is directed superiorly, resembling a snorkel. * Chimney: In TEVAR, a covered stent placed from the ascending aorta to a great vessel (e.g., innominate artery) and adjacent to the main body of the EVAR is termed a chimney. In anatomic position, blood flows superiorly through a chimney-stent graft into the great vessel, just as smoke flows up a chimney. * Periscope: Like a snorkel, a periscope stent graft provides flow to a visceral vessel, but in a retrograde fashion, with the aortic lumen inferior to the main body of the EVAR device. * Stents: Large bare-metal stents have been used to treat proximal endoleaks, as have aortic extension cuffs to treat endograft migration. * Glue: Trans-catheter embolic glue has been used to treat type I endoleaks, with inconsistent success. * EndoAnchors: Small, helically shaped devices are screwed through the endograft and into the aortic wall. EndoAnchors have been used successfully to treat endoleaks and, in concert with an aortic extension endograft, to treat migration of the original endograft. Rigorous evaluations and long-term outcomes of this technique are not yet available.


Risks

The complications of EVAR can be divided into those that are related to the repair procedure and those related to the endograft device. For example, a myocardial infarction that occurs immediately after the repair is normally related to the procedure and not the device. By contrast, the development of an endoleak from degeneration of endograft fabric would be a device-related complication. Durability and problems such as 'endoleaks' may require careful surveillance and adjuvant procedures to ensure the success of the EVAR or EVAR/hybrid procedure. CT angiography (CTA) imaging has, in particular, made a key contribution to planning, success, durability in this complex area of vascular surgery. A major cause of complications in EVAR is the failure of the seal between the proximal, infra-renal aneurysm neck and the endovascular graft. Risk of this form of failure is especially elevated in adverse or challenging proximal neck anatomies, where this seal could be compromised by unsuitable geometric fit between the graft and vessel wall, as well as instability of the anatomy. New recent techniques have been introduced to address these risks by utilizing a segment of the supra-renal portion of the aorta to increase the sealing zone, such as with fenestrated EVAR, chimneys and snorkels. These techniques may be suitable in certain patients with qualifying factors, e.g., configuration of renal arteries, renal function. However, these are more complex procedures than standard EVAR and may be subject to further complications. An approach that directly augments the fixation and sealing between the graft and aorta to mimic the stability of a surgical anastomosis is EndoAnchoring. EndoAnchors are small, helically shaped implants that directly lock the graft to the aortic wall with the goal to prevent complications of the seal, especially in adverse neck anatomies. These EndoAnchors may also be used to treat identified leaks between the graft and proximal neck.


Procedure-related

Arterial dissection, contrast-induced kidney failure, thromboembolizaton, ischemic colitis, groin hematoma, wound infection, type II endoleaks, myocardial infarction, congestive heart failure, cardiac arrhythmias, respiratory failure.


Device-related

Endograft migration, aneurysm rupture, graft limb stenosis/kinking, type I/III/IV endoleaks, stent graft thrombosis, or infection.


Endoleaks

An endoleak is a leak into the aneurysm sac after endovascular repair. Five types of endoleaks exist: * Type I - Perigraft leakage at
proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...
or
distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
graft attachment sites (near the renal and iliac arteries) * Type II - Retrograde flow to the aneurysm sac from branches such as the
lumbar In tetrapod anatomy, lumbar is an adjective that means ''of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum.'' The lumbar region is sometimes referred to as the lower spine, or as an area of the back i ...
and inferior mesenteric arteries. Type II endoleaks are the most common, and least serious type of endoleak. Type II endoleaks do not require immediate treatment, as a portion will resolve spontaneously. * Type III - Leakage between overlapping parts of the stent (i.e., the connection between overlapping components) or rupture through graft material. * Type IV - Leakage through the graft wall due to the quality (porosity) of the graft material. As seen in first-generation grafts, changes in graft material in modern devices have decreased the prevalence of type IV leaks. * Type V - Expansion of the aneurysm sac without an identifiable leak. Also called "endotension". Type I and III leaks are considered high-pressure leaks and are more concerning than other leak types. Depending on the aortic anatomy, they may require further intervention to treat. Type 2 leaks are common and often can be left untreated unless the aneurysm sac continues to expand after EVAR.


Spinal cord injury

Spinal cord injury is a devastating complication after aortic surgery, specifically for thoracoabdominal aortic aneurysm repair; severe injury could lead to urine and fecal incontinence, paresthesia and even paraplegia. The risk varies between studies with two metanalysis demonstrating a pooled incidence of spinal cord injury 2.2% and 11%. Predictive factors include increasing extent of coverage, hypogastric artery occlusion, prior aortic repair and perioperative hypotension. Spinal cord injury related to aortic repair occurs due to impaired blood flow to the spine after coverage of blood vessels, important to the blood circulation of the spine, namely intercostal- and lumbar arteries. A few methods exist for potentially reversing spinal cord injury, if it arises, elevated blood pressure, increased oxygenation, blood transfusion and cerebrospinal fluid drainage.


Cerebrospinal fluid drainage

Cerebrospinal fluid drainage is one of the adjunct methods used to reverse spinal cord injury. With increased drainage of spinal fluid, the intrathecal pressure decreases which allows for increase blood perfusion to the spine, possibly reversing the ischemic injury of the spinal tissue due to lessened blood supply. The benefits of this procedure have been established in open aortic repair and suggested in endovascular aortic repair.


Recovery after EVAR

Unlike traditional aortic repair, standard recovery after EVAR is remarkably straightforward. Patients who have undergone EVAR typically spend one night in the hospital to be monitored, although it has been suggested that EVAR can be performed as a same-day procedure. Patients are advised to slowly return to normal activity. There are no specific activity restrictions after EVAR, however, patients typically are seen by their surgeon within one month after EVAR to begin post-EVAR surveillance. There is limited research looking at patients' experience of recovery after more complex and staged EVAR for thoracoabdominal aortic diseases. One qualitative study found that patients with complex aortic diseases struggle with physical and psychological setbacks, continuing years after their operations.


History

Dr. Juan C. Parodi introduced the minimally-invasive endovascular aneurysm repair (EVAR) to the world and performed the first successful endovascular repair of an abdominal aortic aneurysm on 7 September 1990 in Buenos Aires on a friend of
Carlos Menem Carlos Saúl Menem (2 July 1930 – 14 February 2021) was an Argentine lawyer and politician who served as the President of Argentina from 1989 to 1999. Ideologically, he identified as a Peronist and supported economically liberal policies. He ...
, the then President of Argentina. The first device was simple, according to Parodi: "It was a graft I designed with expandable ends, the extra-large Palmaz stent, a Teflon sheath with a valve, a wire, and the valvuloplasty balloon, which I took from the cardiologists." Parodi's first patient lived for nine years after the procedure and died from pancreatic cancer. The first EVAR performed in the United States was in 1992 by Drs. Frank Veith, Michael Marin,
Juan Parodi Juan Parodi was an Argentine football coach who coached the Ecuador national team at the 1941 and 1942 Events Below, the events of World War II have the "WWII" prefix. January * January 1 – WWII: The Declaration by United Natio ...
and Claudio Schonholz at
Montefiore Medical Center Montefiore Medical Center is a premier academic medical center and the primary teaching hospital of the Albert Einstein College of Medicine in the Bronx, New York City. Its main campus, the Henry and Lucy Moses Division, is located in the Norwoo ...
affiliated with
Albert Einstein College of Medicine Albert Einstein College of Medicine is a research-intensive medical school located in the Morris Park neighborhood of the Bronx in New York City. Founded in 1953, Einstein operates as an independent degree-granting institution as part of t ...
. The modern endovascular device used to repair abdominal aortic aneurysms, which is bifurcated and modular, was pioneered and first employed by Dr. Timothy Chuter while a fellow at the
University of Rochester The University of Rochester (U of R, UR, or U of Rochester) is a private research university in Rochester, New York. The university grants undergraduate and graduate degrees, including doctoral and professional degrees. The University of Roc ...
. The first clinical series of his device was published from Nottingham in 1994. The first endovascular repair of a ruptured abdominal aortic aneurysm was also reported from Nottingham in 1994. By 2003, four devices were on the market in the United States. Each of these devices has since been either abandoned or further refined to improve its characteristics ''in vivo''.


Special populations


Women

Women are known to have smaller aortas on average than men, so are potential candidates for AAA treatment at smaller maximum aneurysm diameters than men.


Transplant candidates

As immunosuppressive medications are known to increase the rate of aneurysm growth, transplant candidates are AAA repair candidates at smaller maximum aneurysm diameters than the general population.


Other animals

Due to the expense associated with EVAR stent-graft devices and their specificity to human aortic anatomy, EVAR is not used in other animals.


Videos

Stenting of Coarctation of the Aorta using a NuMed CP Stent - BVM Medical.webm, Stenting of coarctation of the aorta using TEVAR Aneurisma de aorta (terapéutica endovascular) - Dr. Marcelo Cerezo (video 19 de 33).webm, EVAR placement in the abdominal aorta


References

{{DEFAULTSORT:Endovascular Aneurysm Repair Diseases of the aorta Interventional radiology Vascular surgery