Medical uses
Standard EVAR is appropriate for aneurysms that begin below theAortic dissection
Endografts have been used in patients with aortic dissection, 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 contraindications include prohibitively small iliac arteries, aneurysmal iliac arteries, prohibitively smallTechnique
The procedure is carried out in a sterile environment underPercutaneous 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 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 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,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 atSpinal 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.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
References
{{DEFAULTSORT:Endovascular Aneurysm Repair Diseases of the aorta Interventional radiology Vascular surgery