Endovascular repair of abdominal aortic aneurysms
Abdominal aortic aneurysm (AAA) affects an estimated 12 to 15 per 100,000 people a year and causes considerable risk of mortality because of the potential risk of rupture. 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
Because aneurysms are often asymptomatic, they are frequently discovered via examination of the abdomen or through an X-ray examination, CT scan or ultrasound study of the abdomen performed for another purpose. If the aneurysm is less than 5 cm in diameter and there are no symptoms, monitoring annually with Doppler ultrasound is recommended. Optimal medical management should include blood pressure control and smoking cessation.
Repair is usually 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 0.5 cm in a year. During EVAR, the femoral arteries can be exposed using small incisions, or the procedure may be performed totally percutaneously. Following puncture of the femoral artery, a guide wire 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.
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 to 1.5 cm below the renal arteries. However, repair can be done in patients with aneurysms that have shorter necks 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.
Using a Mayo Clinic aortic registry, Mayo Clinic researchers recently analyzed data from 1,008 consecutive patients (133 women and 875 men) who received endovascular repair between 1997 and 2011:
- Patients ranged in age from 49 to 99 years, with a mean age of 76 years.
- Thirty-day mortality after repair of nonruptured aneurysms was 0.2 percent in low-risk patients and 2.2 percent in high-risk patients.
- The five-year survival rate was 72 percent for low-risk patients and 51 percent for those at high risk; three-fourths of those in either group were free from early and late complications, which can include post-procedure bleeding, blood clots or problems with the repair.
- Age and high surgical risk were associated with complications and early and all-cause death.
- Women were more likely than were men to have complications but were not at higher risk of death.
Most patients treated with EVAR no longer require admission to the intensive care unit and are dismissed home the day after surgery. A higher percentage of patients undergoing EVAR are discharged directly home rather than to nursing homes, and patients have a faster return to normal level of function, with post-discharge recovery time of one to two weeks.
The current prognosis for healthy patients who undergo elective aneurysm repair is excellent. Follow-up imaging studies at regular intervals are required to look for rare late complications such as graft migration or leaks around the stent (endoleaks). If a significant leak around the stent is discovered, the aneurysm sac still can rupture if no procedure to correct this is performed.
However, with low rates of operative and early (30-day) mortality, even among high-risk patients, EVAR represents an exciting and cost-effective advance in the treatment of patients with suitable anatomy.
Points to remember
- Screening for abdominal aortic aneurysm via CT scan or ultrasound is recommended for all men age 65 or older and for women age 65 years or older who have been or still are tobacco users or whose parent or sibling had an aortic aneurysm. Screening for men is recommended at age 55 years if a parent or a sibling had an aortic aneurysm.
- Repair is considered 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 0.5 cm in a year.
- Endovascular aortic aneurysm repair (EVAR) is the preferred treatment for patients with suitable anatomy. EVAR is particularly advantageous for patients older than 65 years, patients who are considered to be at high risk because of other medical conditions and patients who have undergone prior abdominal operations.
- Percutaneous EVAR is feasible and will increase in frequency as endograft technology improves.