What Happens During an EVAR Procedure for Aortic Aneurysms?

Endovascular aneurysm repair, commonly called EVAR, is a minimally invasive procedure used to treat abdominal aortic aneurysms by threading a fabric-and-metal tube graft through the blood vessels and anchoring it inside the weakened section of the aorta, bypassing the bulging wall without opening the abdomen. Compared with traditional open surgery, EVAR dramatically reduces early death rates and shortens recovery, but its long-term picture is more complicated than the upfront numbers suggest. The procedure has evolved considerably since its first human application in the late 1980s, and understanding what it involves, what it fixes, and what it leaves unresolved gives you a much clearer framework for evaluating it.

What Happens During the Procedure

An aortic aneurysm is a balloon-like bulge in the body’s largest artery, typically in the abdomen. If it grows large enough, the wall can rupture, which is often fatal. EVAR avoids the large abdominal incision of open repair. Instead, a vascular surgeon makes small incisions in the groin to access the femoral arteries. A compressed stent graft, a tube of synthetic fabric supported by a metal skeleton, is loaded onto a delivery catheter and guided up through the arteries under real-time X-ray imaging. Once positioned across the aneurysm, the graft is deployed so that blood flows through the new channel instead of pressing against the weakened aortic wall.

Modern stent grafts are modular, meaning they come in separate pieces that lock together inside the body. A main body sits in the aorta, and two limb extensions reach down into each iliac artery. This modularity lets surgeons adjust sizing to fit each patient’s anatomy. Deployment demands precision: surgeons may use a step-by-step technique, alternately releasing parts of the graft to ensure it tracks the curves of the aorta rather than sliding out of position along the outer wall of a bend.¹ Certain graft designs introduce their own quirks. The Ovation system, for instance, sometimes arranges its limb openings front-to-back instead of side-by-side, which can make threading a wire into the opposite limb tricky enough to require access from the arm rather than the groin.²

Who Qualifies and Who Does Not

Not every aneurysm is shaped right for a standard EVAR. The “neck” of the aneurysm, the stretch of normal aorta just below the kidney arteries where the top of the graft needs to seal, has to meet several geometric requirements. Standard manufacturer guidelines call for a neck at least 15 mm long, with limited angulation and a diameter that falls within the graft’s range.³ Necks that are too short, too wide, or too sharply angled raise the risk of a poor seal and future problems. Some surgeons push beyond those boundaries using extended criteria, accepting necks as short as 10 mm and steeper angles, but doing so trades wider eligibility for a higher chance of complications down the road.

Early Results Compared with Open Surgery

EVAR’s headline advantage is a substantially lower risk of dying in the first 30 days after surgery. The landmark UK EVAR Trial 1 found that operative mortality was roughly 1.7% for EVAR versus 4.7% for open repair, a reduction of about two-thirds.⁴ A large Medicare-matched analysis confirmed this pattern, reporting 30-day mortality of about 1.2% for EVAR versus 4.0% for open repair.⁵ Heart and lung complications are also less common after EVAR. One comparative study found cardiac complications in about 11% of EVAR patients versus 22% after open repair, and pulmonary complications in 3% versus 16%.⁶

Hospital stays are shorter, too. Most EVAR patients go home after one or two days, while open repair typically means a longer recovery in the hospital and a higher rate of discharge to a rehabilitation facility rather than straight home.⁷

The Long-Term Trade-Off

Here is where the EVAR story gets complicated. The early survival benefit fades over time, and in some studies it reverses. The 15-year follow-up of EVAR Trial 1 found no overall difference in total mortality between the two groups. Worse, beyond eight years the open-repair group actually had lower death rates, including a sharply lower rate of aneurysm-related death. Much of this was driven by secondary ruptures of the aneurysm sac in the EVAR group: about 7% of EVAR patients eventually died from a late sac rupture, compared with only 1% in the open-repair group.⁸ The Dutch DREAM trial told a similar story: by the end of follow-up, no significant difference in overall mortality, but higher graft-related complications and reinterventions in the EVAR arm.⁹

The Medicare-matched analysis found that open repair was associated with lower long-term mortality, lower rupture rates, and fewer reinterventions over a follow-up period that averaged several years, even after adjusting for patient characteristics.¹⁰ None of this means EVAR is the wrong choice. For older patients, those with serious heart or lung disease, or anyone who might not tolerate a major abdominal operation, the early survival edge of EVAR may be worth the long-term trade-offs. But for younger, healthier patients who can handle open surgery, the calculus is more nuanced, and the discussion with a surgeon should reflect that.

Endoleaks and Why They Matter

The most characteristic complication of EVAR is the endoleak, blood finding its way into the aneurysm sac outside the graft. Endoleaks come in several flavors, and they range from harmless to potentially fatal.

Type I: Blood leaks around the top or bottom seal where the graft meets the aortic wall. These are high-pressure leaks that keep the aneurysm sac pressurized, and they usually require prompt treatment. Options include inserting a cuff extension, placing a balloon-expandable stent to shore up the seal, or relining the graft entirely.¹¹
Type II: Blood flows backward into the sac through small branch arteries, typically lumbar arteries that feed the back muscles or the inferior mesenteric artery that supplies part of the colon. These are the most common endoleaks and often seal on their own. Intervention is reserved for cases where the sac keeps growing. Patients with a larger inferior mesenteric artery (above 4 mm), more lumbar arteries, or who take blood thinners are at considerably higher risk of needing treatment for a type II leak.¹²
Type III: Blood leaks through a defect in the graft fabric or at a junction between modular components. Like type I, these repressurize the sac and typically need repair.

A more puzzling phenomenon is endotension: the aneurysm sac keeps expanding even though no endoleak is visible on imaging. Proposed explanations include pressure transmitted through thrombus or the graft material itself, along with possible neovascularization in the aortic wall. One imaging study using high-resolution X-ray tomography found evidence of tiny new blood vessels growing through the thinned aortic wall in sacs that were expanding, suggesting the boundary between the sac and the bloodstream may not be as sealed as conventional imaging suggests.¹³ Endotension is not benign: in one comparative analysis, the rupture rate in conservatively managed endotension patients reached about 27%, and reintervention (usually relining the graft) was associated with better sac stabilization and a trend toward lower mortality.¹⁴

Reinterventions Over Time

One of the realities of EVAR that patients sometimes hear too late is the ongoing need for additional procedures. A large analysis from the Vascular Quality Initiative found the five-year reintervention rate was about 21%, starting with a rapid jump to 5% in the first three months and then climbing steadily at roughly 3 to 4 percentage points per year, with no sign of leveling off.¹⁵ Patients with larger aneurysms, those treated urgently, and Black patients all faced higher reintervention rates. Patients with large aneurysms (6 cm or above) also had lower five-year freedom from rupture compared with smaller aneurysms.¹⁶

Structural problems with the graft itself can also force reintervention. Limb occlusion, where one of the graft’s legs blocks off, usually results from kinking of the stent graft, use of a too-narrow limb, or migration and dislocation of a component.¹⁷ This is a serious event that typically causes sudden leg pain or loss of pulses and requires urgent treatment. Predictive models using aneurysm sac growth rate after EVAR have shown reasonable ability to identify patients at highest risk of rupture or needing a preventive reintervention, which may help clinicians target surveillance more intelligently.¹⁸

The Graft Material Question

Stent grafts are not all made of the same stuff, and the choice of fabric influences more than just durability. The two main graft fabrics are woven polyester and expanded polytetrafluoroethylene (ePTFE). A notable difference shows up in the body’s inflammatory response after implantation. A systematic review found that post-implantation syndrome, a constellation of fever, elevated inflammatory markers, and sometimes cardiac events in the days after EVAR, occurred in about a quarter of patients overall but was overwhelmingly concentrated in those who received polyester grafts.¹⁹ One earlier study reported the syndrome in about 56% of polyester-graft patients versus roughly 18% of ePTFE patients, with polyester carrying more than five times the risk after adjusting for other factors.²⁰

Post-implantation syndrome is not just uncomfortable. Patients who develop it have higher rates of major cardiac events and longer hospital stays, and the syndrome is an independent predictor of adverse events within the first 30 days.²¹ Interestingly, when patients undergo a secondary endovascular procedure after a previous EVAR, the rate of this syndrome drops compared with first-time repairs.²²

Anesthesia and Access

One of EVAR’s practical advantages over open surgery is flexibility in anesthesia. While many procedures are done under general anesthesia, data from large registries show that local anesthesia with sedation is associated with shorter operative times, fewer lung complications, shorter hospital stays, and even lower mortality. An analysis of emergency EVAR found that local anesthesia was associated with lower 30-day mortality (about 11% versus 14% after general anesthesia) and fewer pulmonary, renal, and wound complications.²³ For ruptured aneurysms specifically, 30-day mortality was about 15.5% with local anesthesia versus 23.3% with general anesthesia.²⁴ In elective cases, a national database analysis found that general anesthesia roughly quadrupled the odds of pulmonary complications compared with spinal anesthesia and more than doubled them compared with local/sedation.²⁵

Surgeons also have a choice of how to access the femoral artery: a traditional open cutdown or a fully percutaneous approach using needle puncture and a closure device. Percutaneous EVAR tends to mean shorter operating times and shorter hospital stays.²⁶ Minor complication rates are comparable overall between the two approaches, though percutaneous access does carry a slightly higher rate of small bleedings that can be managed with simple compression.²⁷

Complex Variants for Trickier Anatomy

Standard EVAR works only when the aneurysm sits below the kidney arteries with enough normal aorta above it for a good seal. When the aneurysm involves or sits right next to the kidney arteries, or extends up into the chest, more sophisticated devices are needed. Fenestrated EVAR uses a custom-made graft with holes or scallops that align with branching arteries, allowing blood to continue flowing to the kidneys and gut while the aneurysm is excluded. Branched EVAR takes this further, incorporating small side tunnels that extend into the branch arteries themselves.²⁸ These are technically demanding procedures with acceptable complication rates in experienced centers.²⁹

A parallel technique called chimney EVAR offers a workaround when custom fenestrated grafts are unavailable, which is especially relevant in emergencies. Small stent grafts are placed alongside the main graft and up into the branch arteries, preserving flow to the kidneys while extending the seal zone. A multicenter registry of emergency chimney EVAR reported technical success in about 91% of patients, though 30-day mortality was roughly 18%, reflecting the severity of the cases being treated (two-thirds involved aortic rupture). Longer-term follow-up showed high rates of reintervention and mortality, underscoring that this is a rescue technique for patients with few other options.³⁰ More optimistic results come from elective series. One center reported that chimney EVAR showed acceptable long-term safety through seven years of follow-up in high-risk patients with large aneurysms.³¹

Imaging Advances in the Operating Room

Accurate graft placement depends on good imaging, and the technology has been catching up to the procedure’s demands. Three-dimensional fusion imaging, which overlays a preoperative CT scan onto live fluoroscopy during the procedure, has been shown to cut contrast dye use significantly, sometimes by more than half. For fenestrated repairs involving two vessels, fusion imaging reduced average contrast use from about 69 mL to 26 mL, and for three- or four-vessel repairs from about 90 mL to 39 mL.³² A meta-analysis confirmed the contrast reduction and found that radiation doses and procedure times trended lower in most studies using fusion guidance, though not always reaching statistical significance for every measure.³³ Less contrast means less stress on the kidneys, which matters in a patient population that often already has compromised kidney function.

Lifelong Surveillance

Unlike open repair, where the job is essentially done once the patient heals, EVAR commits you to lifelong imaging follow-up. The standard protocol involves CT angiography at regular intervals to check for endoleaks, measure the aneurysm sac, and verify graft position. This repeated radiation and contrast exposure has driven interest in alternatives. Contrast-enhanced ultrasound has emerged as a reasonable substitute in many situations. For measuring sac diameter, it agrees closely with CT, and it can pick up endoleaks comparably. One study of fenestrated EVAR patients found strong agreement between contrast-enhanced ultrasound and CT for sac measurement and endoleak detection.³⁴ Another study found that contrast-enhanced ultrasound actually detected more type II endoleaks than CT did.³⁵ Ultrasound avoids radiation entirely and uses a microbubble contrast agent rather than iodinated dye, making it easier on the kidneys.

Sex Differences in Outcomes

Women represent a small minority of EVAR patients because aortic aneurysms are far more common in men, but the evidence consistently shows that women have a harder time with the procedure. A systematic review found that women had roughly 1.7 times the odds of dying within 30 days, about twice the risk of limb ischemia, and higher rates of kidney and heart complications after standard infrarenal EVAR. Long-term all-cause mortality was also higher in women.³⁶ The reasons are partly anatomical: women tend to have smaller, more tortuous arteries, which makes device delivery harder and increases complications at the access site. In complex fenestrated and branched repairs, one study found that women had substantially higher rates of graft delivery problems, unplanned intraoperative adjustments, spinal cord ischemia, bowel ischemia, and in-hospital mortality compared with men, though six-year survival evened out between the sexes.³⁷

Cost and the Question of Value

EVAR’s initial hospitalization costs tend to be lower than open repair because of shorter stays and fewer intensive care days. But the financial picture shifts over time. A systematic review of cost-effectiveness studies concluded that EVAR was more cost-effective than open surgery for high-risk patients, where avoiding a major operation provides the greatest benefit. For low-risk patients, however, the ongoing costs of surveillance imaging, reinterventions, and occasionally conversion to open repair eroded that advantage.³⁸ The DREAM trial similarly noted that graft-related complications continued appearing as late as eight years after EVAR, contributing to persistently higher cumulative costs.³⁹ This does not make EVAR a bad deal, but it does mean the decision involves weighing a less traumatic procedure now against a greater burden of follow-up and potential re-treatment later.