What is an abdominal aortic aneurysm?
First, let us understand what is the aorta. The aorta is the major blood vessel that supplies blood to the body. It is about the size of a 3/4 inch to 1 inch garden hose and runs from your heart down through the center of your chest and abdomen and then divides and goes to each leg. In short, the aorta is the body’s main supplier of blood.
So what is an aneurysm? An aneurysm is a weakened and bulging area in an artery which in this case an abdominal aortic aneurysm occurs when the wall of the aorta becomes weak and bulges out in the part of the aorta that passes through the abdomen. This bulge is like on an old-timey tire where it bulges out in one area and may blow out.
How serious is an abdominal aortic aneurysm?
Because the aorta is the body’s main supplier of blood, a ruptured abdominal aortic aneurysm can cause life-threatening bleeding. Although you may never have symptoms, finding out you have an abdominal aortic aneurysm can be frightening.
Most small or slow-growing abdominal aortic aneurysms do not rupture. However, large or fast-growing abdominal aortic aneurysms may. Depending on the size and rate at which the aneurysm is growing, treatment may vary from watchful waiting to emergency surgery. More recently there is new technology being implemented. Endoluminal stent grafts can possibly be passed through lower abdominal incisions with a lower mortality than opening your entire abdomen, but to do this procedure you have to have specific anatomy and not everyone can undergo this procedure. Newer technology is even decreasing these limitations.
Once an abdominal aortic aneurysm is found, your doctors will help you understand what to watch for, any life-style changes you may need to make and will continue to closely monitor it so that if surgery becomes necessary it can be planned rather than become an emergency situation or an intravascular stent can be placed.
Most abdominal aortic aneurysms are found at the time of other x-rays such as a CT scan or regular x-rays of your abdomen and some even found at the time of surgery for other problems. For an aneurysm to be palpable on an abdominal examination, it usually is near 5 cm in size. If your abdomen is large, they can be impossible to feel until they are larger than 5 cm. An abdominal aortic aneurysm is found in about 1.5 to 3% of people when screened by ultrasound. Abdominal aortic aneurysm has also been detected by ultrasound screening in 8.8% of male smokers older than 65-years of age who have abdominal pain.
Approximately 70 to 75% of abdominal aortic aneurysm are asymptomatic when first detected.
Average growth of a small aneurysm is around 0.25 cm in diameter per year. One other study lists the growth rate at 0.32 cm per year when it is under 5 cm. As it gets larger, it may grow as much as 0.4 cm to 0.5 cm per year. The risk of rupture begins to increase some at around 5 cm.
The average one-year rate of risk of rupture:
|Aneurysm Size||Average Yearly Rate of Rupture (Approximately)|
|4.0 to 5.4 cm||0.5 to 1% per year|
|6.0 to 7.0 cm||6.6 %|
|Greater than 7.0 cm||19%|
This is the five-year risk of rupture of untreated aneurysm:
|Aneurysm Size||Average Yearly Rate of Rupture (Approximately)|
|5.0 to 5.9 cm||25%|
|6.0 to 7.0 cm||35%|
|Greater than 7.0 cm||75%|
The instance of rupture begins to increase really at 5.0 cm.
The ratio of aneurysm of men to women of instance of abdominal aortic aneurysm is 4:1. Cigarette smoking correlates with the presence of an aortic aneurysm with a predominance of 8:1 preponderance in smokers compared with nonsmokers.
Approximately 20 to 29 percent of patients with abdominal aortic aneurysm have a 1st degree relative with the same condition.
What are risk factors for an abdominal aortic aneurysm?
Most aortic aneurysms occur in the part of your aorta that is in your abdomen. Although the exact cause of abdominal aortic aneurysms is unknown, a number of factors may play a role.
- Advanced age
- Being male
- Family history of aortic aneurysms in first-degree relatives (parent, brother, or sister)
- Alcohol (more than 2 drinks a day)
- Tobacco use. Cigarette smoking and other forms of tobacco use appear to increase your risk of aortic aneurysms. In addition to the damaging effects that smoking causes directly to the arteries, smoking contributes to the buildup of fatty plaques in your arteries (atherosclerosis) and high blood pressure. Smoking can also cause your aneurysm to grow faster by further damaging your aorta.
- High blood pressure. High blood pressure, especially if poorly controlled, increases the risk of developing an aortic aneurysm or your aneurysm blowing out. This is because high blood pressure can damage and weaken your arteries.
- Infection in the aorta (vasculitis). In rare cases, an aortic aneurysm may be caused by an infection or inflammation that weakens a section of the aortic wall.
Growth rate is recognized as related to tobacco use. Smoking is the most important risk factor associated with abdominal-aortic ratio with abdominal aortic aneurysm (odds ratio 5.57) followed by positive family history (odds ratio 1.95), age, height, coronary artery disease, atherosclerosis, high cholesterol level and hypertension.
Findings of the Multicenter Aneurysm Screening Study (MASS) demonstrated that screening in male patients older than 65 is cost effective. Therefore, most vascular surgeons agree that all men over age 65 and women who do not smoke should systematically be offered abdominal ultrasound screening. This should be done by age 55 if there is a family history of abdominal aortic aneurysm. Rupture is strongly correlated with persistent tobacco use, female gender, aneurysm size, diminution FEV 1 (chronic obstructive pulmonary disease from smoking) HTN and in presence of a transplant.
Simon et al. demonstrated prevalence of abdominal aortic aneurysm of 11% in male patients age 60 to 75 with systolic blood pressure greater than 175 mmHg. No patient with uncomplicated hypertension had an abdominal aortic aneurysm. Claudication was the only cardiovascular complication associated independently with an AAA (relative risk of 5.8). Baxter et al. found a prevalence of 9% in patients older than 65 years regardless of cardiovascular risk factors.
What are the symptoms of an abdominal aortic aneurysm?
Most abdominal aortic aneurysms are said to be asymptomatic meaning you have no symptoms. Often they are found incidentally on ultrasound or CT scan when that test was ordered for other conditions. They may also be identified on an abdominal ultrasound screening exam which you should do when you are 50 years old if you have a family history of first-degree relatives with aneurysms, but this may need to be done earlier. The most common symptoms are:
- Abdominal pain that may radiate into the back
- Abdominal pulsation
- They occasionally break loose clots that have formed within the aneurysm and these can go to your feet and legs
When an abdominal aortic aneurysm does cause symptoms, the most common symptom is abdominal pain that is felt in the middle of the abdomen and can radiate to the back. The pain may be deep, aching, gnawing, or throbbing, and may last for just minutes or hours or days. It is generally not affected by movement, although certain positions may be more comfortable than others. It may become more severe as it increases in size causing pressure on surrounding organs.
However, a rapidly expanding abdominal aortic aneurysm can cause sudden severe, steady and worsening middle abdominal pain and back pain. A rapidly expanding aneurysm is also at imminent risk of life-threatening rupture. Actual rupture of an abdominal aortic aneurysm is life threatening and carries a high mortality of 50 to 80 percent. If you develop this pain and it goes away, you are still in trouble. Go to the emergency room immediately. The next pain may be associated with a devastating experience.
The person may also become aware of an abnormally prominent abdominal pulsation.
If you suspect you may have an abdominal aortic aneurysm, screening is imperative. Ultrasound is the screening test for an abdominal aortic aneurysm and due to the nature of an aneurysm it is easily seen on ultrasound or CT scan. This screening is fast and painless. You simply lie on a table while a technician does the test and can usually be done in the doctor’s office or at a hospital.
What should I do If I think I may be at risk?
You should see your doctor if your symptoms are minor or if you have any of the symptoms described above go to the emergency room immediately. Occasionally pain lessens before the final event. Do not wait for the final event because it may be too late to save your life. Do not put it off until Monday.
Anyone age 50 and older who has risk factors for developing an aortic aneurysm should consider regular screening. Men ages 65 to 75 who have never smoked cigarettes should have a one-time ultrasound screening for abdominal aortic aneurysm.
If you have a family history of aortic aneurysm, your doctor may recommend regular ultrasound screening. If you are found to have an abdominal aortic aneurysm, the frequency for follow up studies will be determined by the size and rate of growth and your vascular specialist will explain this to you.
If you are found to have an abdominal aortic aneurysm, you should notify your brothers, sisters and children so they, too, can begin early screening. Some of the disease process that causes these aneurysms can be inherited.
What is the treatment for an abdominal aortic aneurysm?
The goal of treatment is to prevent your aneurysm from rupturing. At present, there are three options for treatment:
- Medical monitoring (Watchful Waiting) when it is small and the risk of treatment is greater to your life expectancy than the risk of rupture
- Open surgery
- Endovascular surgery and placement of a covered stent graft
The decision as to which of these three is recommended depends on the size of the aortic aneurysm and how fast it is growing.
Medical monitoring (watchful waiting)
If your aneurysm is small, your doctor may recommend medical monitoring, which includes regular appointments to make sure your aneurysm is not growing, and management of other medical conditions that could worsen your aneurysm.
It is again recommended that you have serial duplex ultrasound every six months for aneurysms 4.0 to 4.9 cm and every three months for aneurysms of 5.0 to 5.5 cm. Do not miss an appointment.
We have learned much in the management of aneurysms from the U.K. Small Aneurysm Trial which attempted to shed much light on this subject. It has also been confirmed and accepted in this country. The U.K. Trial concluded that early surgical intervention did not offer any long-term survival advantages for an aneurysm under 5.5 cm. Their recommendation was based on trial methodology with serial duplex ultrasound every six months for aneurysms of size 4.0 to 4.49 cm and every three months for aneurysms of size 5.0 to 5.5 cm.
There was another large trial that set 5.5 cm range that the long-term survival is improved by surgery. The operative mortality for surgery is 1/5% (lower than this for endovascular stent graft repair). The risk of rupture must be weighed against the operative mortality and for you to come out ahead and most agree that 5.5 cm is that dividing line. An asymptomatic aneurysm of 5.5 cm is recommended for repair if you have a life expectancy of two years or more. It may be considered for repair with it smaller than this if you live in a remote area that has no medical care capable of treating an aneurysm. This also varies some with the shape of the aneurysm and rate of growth documented on ultrasound. If your aneurysm is 5.0 to 5.5 cm and there is a documented enlargement of more than 0.5 cm in less than 6 to 12 months, then repair may be considered.
There is one thing that you must be aware of and that is coronary artery disease is the most frequent cause of death in patients with small abdominal aortic aneurysms.
It is likely your doctor will order regular imaging tests such as abdominal duplex Doppler (ultrasound) or a CT scan to check the size of your aneurysm at specific intervals. Do not miss an appointment.
If you have high blood pressure or blockages in your arteries, it is likely that your doctor will prescribe medications to lower your blood pressure and reduce your risk of complications from your aneurysm. These medications could include:
- Beta blockers. Beta blockers which lower your blood pressure partially by slowing your heart rate and forcefulness of heart contraction. Examples of beta blockers include metoprolol (Lopressor, Toprol-XL), atenolol (Tenormin) and bisoprolol (Zebeta) and numerous others. Beta blockers particularly are protective to your heart since coronary artery disease is the most frequent cause of death in patients with small aortic aneurysms.
- Angiotensin II receptor blockers. Your doctor may also prescribe these medications if beta blockers are not enough to control your blood pressure. Examples of angiotensin II receptor blockers include losartan (Cozaar), valsartan (Diovan) and olmesartan (Benicar) and numerous others. You can also use a first generation ACE inhibitor such as lisinopril. These two categories are the only medications that have been shown to slow the rate of aneurysmal growth. The mechanism is not clear.
- Statins. These medications can help lower your cholesterol, which can help slow the rate of progression of blockages in your arteries and reduce your risk of aneurysm complications. Examples of statins include atorvastatin (Lipitor), lovastatin (Mevacor), simvastatin (Zocor) and others.
If you smoke or chew tobacco, it is important that you quit. Using tobacco can worsen your aneurysm and your state of health. At a time of very critical illness it is important that the rest of your body function perfectly or as perfectly as possible. The single most important thing you can do is stop smoking.
Surgical repair to prevent rupture
Traditional open surgery
The traditional method involves making an abdominal incision. The segment of the aorta above and below the bulging aneurysmal section is clamped and the aneurysm segment is opened. Tubes made out of artificial material are positioned inside the artery and sewn to the aorta above and below the aneurysm. This essentially replaces the aneurysmal segment of the aorta with an artificial one that then acts as a bridge for the blood flow and no longer allows the direct pulsation pressure of the blood to further expand the weak aorta wall.
Less invasive repair: endovascular stent grafting
Instead of an open aneurysm repair, your surgeon may consider a newer procedure called an endovascular aneurysm repair. Endovascular means that surgery is performed inside your aorta using thin, long tubes called catheters. However, this procedure is not for everyone and you should discuss this with your vascular specialist. If it is determined that you are a candidate for this procedure, your surgeon will enter through small incisions in the groin and, using catheters to guide and deliver a stent-graft through the blood vessels to the site of the aneurysm with X-ray guidance, position a graft made of artificial material to the area of the aneurysm. The graft then is expanded inside the aorta and held in place with metallic hooks and stents rather than sutures. This can be used in many anatomic conditions. Fortunately, these can sometimes be used even when an aneurysm is leaking and ruptured.
Although it is possible to repair a ruptured aortic aneurysm with emergency surgery, the risk is much higher and there is less chance of survival. Many people who have a ruptured aortic aneurysm die before they reach the hospital (50%).
Because treatment for abdominal aortic aneurysm mainly consists of surgery to prevent rupture, there is a conspicuous absence of alternative therapeutic strategies. However, you may be able to reduce your risk of an aortic aneurysm by controlling your risk factors for atherosclerosis with the following:
- If you smoke, quit now
- If you have high cholesterol:
- Eat a diet low in fats and cholesterol
- If necessary, take cholesterol-lowering medication
- If you have high blood pressure:
- Maintain a healthy weight or reduce caloric intake if you are over weight
- Decrease salt intake
- Eat a diet rich in fruits and vegetables
- Take medication to control your blood pressure as needed particularly ACE inhibitors and beta-blockers to decrease the pulsatility of arterial flow
- If you have diabetes:
- Monitor your blood sugar frequently
- Follow a healthy diet
- Keep your blood pressure in the normal range
- Aim for an LDL cholesterol less than 100 mg/dL, using medication if necessary
- Also, exercise regularly and maintain an ideal weight.
Additional screening guidelines:
- All men ages 60 to 65 years should have a one-time screening ultrasound if they have ever smoked at any time
- Men ages 65 to 75 who have never smoked should have a one-time screening ultrasound
- All women ages 60 to 65 years with cardiovascular risk factors
- All men and women ages 50 to 55 and older with a family history of abdominal aortic aneurysm
Please review again the average yearly rate of risk of rupture. These can rupture under 5.5 cm in diameter, but this must be weighed against your operative mortality. Clearly, by the time they reach 5 cm the risk of rupture is worse than the operative mortality during an unruptured repair.
If you are diagnosed with an abdominal aortic aneurysm, the importance of following the advice of your vascular specialist in managing your risk factors, adherence to medical treatment and/or surgical recommendations cannot be underestimated.
DO NOT MISS A SCHEDULED SCREENING EXAM. Do not forget that coronary artery disease is the most common cause of death in patients with small abdominal aortic aneurysms.
We hope the information on these pages is both informative and helpful, but it is intended for education only. Please do note that no web site, no matter how much information is shared, can replace a consultation with your doctor and a vascular specialist. Medical technology and treatment are continually improving and evolving so before making any decision on treatment, it is always advisable to see your doctor first for a comprehensive evaluation of your vascular disease and other medical conditions.
At the Vascular Center of Wichita Falls, we work closely with your other physicians. If you have concerns about your arteries or veins, contact us. A referral is not necessary to make an appointment.