Abdominal Aortic Aneurysms: The Silent Killer

By John Paul Runyon MD, FACC


One of the leading causes of death in the United States is a condition that many people don’t even know they have.

WHAT IS AN AAA?

An abdominal aortic aneurysm is the swelling or ballooning, of the abdominal aorta, which is the main artery that carries blood from the heart to all parts of the body. It is characterized by a gradual and/or sporadic expansion (enlargement) in its diameter. Although an aneurysm can occur in any part of the body, it is most common in the abdominal aorta.

The prevalence of AAA varies with a number of demographic factors, including age, gender, family history, and tobacco use. In general, AAAs that are 2.9 cm to 4.9 cm in diameter occur in about 1.3 percent of men and 0.1 percent of women age 45 to 54, and in as many as 12.5 percent of men and 5.2 percent of women age 75 to 84.

Patients who have undergone coronary artery bypass grafting (CABG) are three times more likely to have an AAA than those who have not. Among patients with prior CABG, men have a 6.6 percent change of developing an AA, whereas women have a 3.2 percent chance.2

Some patients may also be genetically predisposed to the formation of abdominal aortic aneurysms. First-degree relatives of patients with AAA have two to four times the normal risk for AAA.3

The three most common complications of aneurysms are rupture, thromboembolic events (stroke), and the compression or erosion of adjacent structures. Rupture is the most widely recognized complication of AAAs. Ruptured abdominal aortic aneurysms result in approximately 30,000 deaths each year and are the 17th leading cause of death in the United States. Ninety percent of patients with ruptured abdominal aortic aneurysms will die.4

SIGNS AND SYMPTOMS

Although most AAAs are asymptomatic, patients may experience abdominal discomfort and back pain, and some patients become aware of abdominal pulsations. Less-frequent symptoms include pain in the legs, chest, or groin, anorexia, nausea, vomiting, constipation, or dyspnea.

Compression of the left iliac vein can cause the left leg to swell. As the aneurysm expands and compresses vertebrae and lumbar nerve roots, pain can develop in the lower back, possibly radiating to the back of the legs. Flank pain radiating to the upper left thigh or scrotum can reflect compression of the left genitofemoral nerve. Nausea and vomiting can occur as the aneurysm compresses the duodenum (first segment of the intestine). Bladder compression can cause urinary frequency or urgency.

When rupture occurs, low blood pressure, back pain, and a pulsatile abdominal mass are the classic findings.

DIAGNOSIS AND TREATMENT

Aortic diameter can be measured accurately by ultrasound imaging. Because this method of screening can potentially catch an AAA before it ruptures, it has become the focus of population-based screening programs. The Screening Abdominal Aortic Aneurysms Very Efficiently Act (SAAVE) was included in the Deficit Reduction Act of 2005 (DRA) and signed in law in February 2006. This Act provides Medicare Part B coverage for screening ultrasound examinations to detect AAA.

Beginning January 1, 2007, Medicare began offering a free one-time ultrasound AAA screening to qualified seniors as part of their Welcome to Medicare Physical Exam (WTMPE). Men who have smoked at least 100 cigarettes in their lifetime, as well as men or women with a family history of AAA, qualify for the one-time screening once they have undergone the WTMPE. The WTMPE must be completed within the first six months of Medicare eligibility, but there is no established time frame thereafter for completion of AAA screening. Providers who perform the WTMPE physical and order the AAA screening ultrasound examination need to document the AAA Risk factor.



The Society of Vascular Surgery (SVS), however, has recommended a more aggressive screening schedule for AAA: men 60 to 85; women 60 to 85 with cardiovascular risk factors; and men and women 50 or older with a family history of AAA.

At the present time, two options exist for treatment of AAAs: open surgical repair and endovascular aneurysm repair. Open surgical repair consists of isolating the abdominal aortic aneurysm vial laparotomy (abdominal incision) and replacing the aneurysm with a synthetic graft.

The second option, endovascular aneurysm repair (EVAR), utilizes small incisions made in the femoral arteries to deliver a self-expanding graft into the abdominal aorta via a catheter-based system. The stent graft is flexible and conforms to the structure of the normal aorta above the aneurysm, preventing blood from entering the aneurysm.

The AAA stent graft remains in the patient for life and is inspected during periodic follow-up using computerized tomography angiography (CTA). EVAR has been FDA-approved for the treatment of AAAs in the United States since 1999, and it offers a reliable alternative for patients who meet the vascular anatomy and AAA location requirements.

THE INFORMED PATIENT

In choosing between open repair and EVAR, patient preference is of great importance. It is essential that the patient be well informed in making such choices. Likewise, it is not appropriate to arbitrarily set a threshold diameter beyond which elective repair should be recommended. The decision for AAA repair must be individualized in each case. The risk for rupture of small (less than 5 cm) AAA is quite low, and a policy of careful surveillance up to a diameter of 5.5 cm is safe, unless rapid expansion (greater than 1 cm per year) or symptoms develop. For women or AAAs with greater-than-average rupture risk, elective repair at 4.5 cm to 5.0 cm is appropriate.5

Abdominal aortic aneurysms continue to be a leading cause of death in the United States. Endovascular abdominal aortic repair (EVAR) has gained tremendous attention for treatment of AAA. However, early detection or screening of AAAs is an equally important issue. Despite advances in diagnostic imaging and medicine in general, there has been no change in the number of patients who present to U.S. hospitals with ruptured AAAs in the last 20 years.

Early detection can be achieved through increased patient and physician awareness, in conjunction with organized screening programs. Compelling data reveal that identification of AAAs can save lives at a cost to society that compares favorably with other well-accepted interventions.



REFERENCES

1) Kent K. Zwolak R, Jaff M, et al. Screening for abdominal aortic aneurysm: A consensus statement. J. Vasc Surg 2004; 39: 267-269.

2) Dall’olmo C, Ippolito A, Mcliduff J, et al. Incidence of AAAs in CABG Patients. Endovasc Today 2005: 4: 53-58.

3) Engtsson H, Sonesson B, Lanne T, et al. Prevalence of abdominal aortic aneurysm in the offspring of patients dying from aneurysm rupture. Br J Surg 1992; 79: 1142-3.

4) Johansen K, Kohler T, Nicholls SC, et al. Ruptured abdominal aortic aneurysm: the Harborview experience. J. Vasc Sur 1991; 13: 240-5.

5) Brewster D, Cronenwett J, Hallett J, et al. Guidelines for the treatment of abdominal aortic aneurysms. J. Vasc Surg 2003; 37: 1106-17.

John Paul Runyon is a Board-certified physician with expertise in cardiovascular medicine; significant background in clinical education and training of physicians. Vast network of peer relationships with key opinion leaders in cardiology and peripheral/endovascular medicine.

Please visit Dr. Runyon on his websites, blogs and on social media;
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