Advances in Elective Repair of Abdominal Aortic Aneurysms

Points to remember

• Abdominal aortic aneurysm affects an estimated 12 to 15 per 100,000 persons per year and causes considerable risk for mortality because of the potential risk of rupture.
• Screening via CT scan or ultrasound is recommended for men aged 65 years or older who have been or still are tobacco users and for men older than 50 years and women older than 60 years whose parent or sibling had an aortic aneurysm.
• Repair is recommended for aneurysms with a diameter of 5 cm or more in women and 5.5 cm or more in men, or if the aneurysm has enlarged by more than 5 mm in less than 6 months.
• Endovascular aortic aneurysm repair is the preferred treatment for patients older than 65 years, for patients who are considered to be at high risk because of other medical conditions, and for those who have undergone prior aortic operations.

The challenge

In the hands of experienced surgeons, open surgical repair of an abdominal aortic aneurysm (AAA) is generally safe and provides durable results that are well suited to younger patients. During this procedure, the aorta is clamped above and below the aneurysm, and the abnormal segment is replaced with a polyester graft.

Open repair of abdominal aortic aneurysm

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Perioperative complications (including cardiac and pulmonary problems, incisional hernia, sexual dysfunction, lower extremity paralysis, and death) and recovery time associated with traditional elective open repair can make this procedure less than ideal in elderly or higher-risk patients.

First introduced in 1991, endovascular aortic aneurysm repair (EVAR) using a stent graft now provides a less invasive alternative to open repair. The procedure has excellent results in appropriately selected patients with good anatomy.

Monitoring and treatment

Aneurysms are often asymptomatic. AAAs are frequently discovered via examination of the abdomen or through an x-ray, CT scan, or ultrasound study of the abdomen performed for another purpose.

If the aneurysm is small (d4.5 cm in diameter) and there are no symptoms, monitoring annually with Doppler ultrasound is recommended. Optimal medical management should include careful control of hypertension and smoking cessation.

Repair is recommended for aneurysms with a diameter of 5 cm or more in women and 5.5 cm or more in men, or if there has been growth of more than 5 mm in less than 6 months.

The groin (femoral) arteries can be exposed using small incisions or the procedure may be performed totally percutaneously. Following puncture of the femoral artery, a guidewire is passed across the dilated portion of the aorta and the stent graft is advanced over the wire. Once the stent graft is correctly positioned, the device is released and the graft expands to exclude the aneurysm just below the renal arteries.

Endovascular repair of abdominal aortic aneurysm

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To ensure a proper seal between the stent graft and the aorta, most stents currently available require the aneurysm to have a proximal neck length of at least 1.0 to 1.5 cm below the renal arteries. However, repair can be done in patients with aneurysms that have shorter necks or no neck by using a fenestrated stent graft with side holes and branches to the renal or intestinal arteries.

Suitable iliac arteries are required for introduction of the devices, although deployment through a polyester chimney graft sutured to the iliac artery via a small retroperitoneal incision has increased the number of candidates for EVAR.

When compared with traditional open surgical repair, EVAR offers several advantages, including:

• Decreased operative time
• Decreased blood loss and transfusion requirements
• Shorter intensive care unit (ICU) and hospital stays
• Decreased risk of complications

The use of contrast has decreased, and often procedures can be performed with less than 60 mL of contrast. Operative and early (30-day) mortality are also lower for EVAR than for open repair.

The average ICU stay for open surgical repair is about 3 days, with a total hospital stay of 7 to 10 days and a postdischarge recovery time of 8 to 12 weeks. Most patients treated with EVAR no longer require admission to the ICU and are dismissed home the day after surgery. A higher percentage of patients undergoing EVAR are discharged to home rather than to nursing homes. These patients have a faster return to normal level of function, with postdischarge recovery time of 1 to 2 weeks.

Properly selected EVAR patients also have a relatively low incidence of secondary problems, but some complications specific to this technique do occur. Early conversion to open repair is exceedingly rare. Problems related to the stent graft occur in 5% to 10% of patients and require CT or ultrasound surveillance.

Migration of the device is rare, with the newer-generation devices that have hooks or a suprarenal uncovered stent to improve fixation. And endoleaks—when blood perfuses between the stent graft and the native aorta—are reported in 5% to 10% of patients. The majority of these are type II endoleaks from a lumbar artery that continues to perfuse the aneurysm sac. These are not treated unless there is growth of the aneurysm, in which case outpatient treatment can be done using coils to exclude the lumbar artery with the patient under local anesthesia.

The risk of late conversion or rupture is exceedingly low with proper imaging surveillance. For this reason, patients must be willing to comply with follow-up care that includes a CT scan of the endovascular graft 4 to 6 months after the repair and yearly thereafter. Other less common complications are stent fracture or infection.

The current prognosis for healthy patients who undergo elective aneurysm repair is excellent. EVAR represents an exciting advance in the treatment in patients with suitable anatomy and is the preferred method of treatment for elderly and higher-risk patients.

Mayo Clinic's highly experienced vascular surgery team performs more than 300 aneurysm repairs annually, including complex open and EVAR procedures, making Mayo Clinic one of the largest and most experienced centers for both procedures.