An aneurysm (an-your-ism) is excessive (abnormal) stretching of the wall of an artery, vein or the heart. By definition this is usually 1.5-2 times the normal diameter (distance across) of an artery. This may result from weakening of the wall by injury, disease, or an abnormality present at birth. Arterial aneurysms may occur in any blood vessel and are often caused or aggravated by high blood pressure. Aneurysms aren't always lifethreatening, but bad things can happen if an aneurysm bursts in the wrong place. A stroke (or brain attack) may occur if one bursts in the brain. If an aneurysm on a large blood vessel or the heart wall bursts, a person could bleed to death. Venous aneurysms, such as varicose veins in the legs, may be annoying but are not life threatening. Further discussion will focus on arterial aneurysms.

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An aneurysm can be detected by angiography (x-ray using dye injected into an artery) or by imaging techniques such as echocardiography , an M.R.I. (magnetic resonance imaging) or a computed tomography (C.T.) scan. The aneurysm may be small and not cause symptoms. The person's doctor will want to check it regularly to see if it is enlarging. Which study is used may depend on where the size and location of the aneurysm.

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Although aneurysms can occur in any blood vessel, artery or vein, three areas are responsible for most serious aneurysms. These areas include:

1. Abdominal aorta
2. Brain arteries
3. Heart and thoracic aorta.

Each type will be discussed below.

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The aorta is the largest artery in the body. It carries oxygen rich blood directly from the heart. All arteries in the body arise from the aorta or other arteries that are branches of the aorta. Aortic aneurysms may occurring in the chest (near the heart) are called thoracic aortic aneurysms. Those occurring in the portion of the aorta in the abdominal cavity (below the diaphragm but above the point where the aorta branches into femoral [leg] arteries) are called abdominal aortic aneurysms.

Abdominal aortic aneurysms- Occur in 5-7 percent of people over 60 in the United States. About 15,000 Americans die each year from ruptured abdominal aortic aneurysms (12th to 13th leading cause of death).The incidence increases with age and is 3 to 11 times more common in men. 75% of abdominal aortic aneurysms occur in people over 60 years of age.

Risk factors include:

• High blood pressure
• Smoking
• Coronary artery disease / atherosclerosis (hardening of the arteries).

Detection

Most abdominal aortic aneurysms (75%) do not cause any symptoms but are are detected on routine physical exam (when the doctor feels or hears a pulsation in the abdomen between the solar plexus and belly button) or during an unrelated x-ray or ultrasound exam.

Diagnosis can be confirmed using ultrasound, CT scan or MRI- ultrasound is most commonly used for screening purposes. Some health care providers recommend screening all men between 60-80 years of age at least once. The exam is not repeated in men having no evidence of aneurysm. Routine screening is not currently recommended in women without symptoms.

Symptoms

A common symptom of aneurysm is pain in the area where it is located. Symptoms may be caused by stretching or rupture of the aneurysm, pressure on nearby organs, or decreased blood flow below the aneurysm. Symptoms include:

• Severe abdominal, back or flank pain that is not relieved by changing position
  
  
• Anorexia (loss of appetite), nausea and vomiting may occasionally occur.
  
  
• Rarely, pain or coolness in the leg or foot may happen if blood flow below the aneurysm is blocked.

20% of abdominal aortic aneurysms presenting with the above symptoms rupture (burst). Most aneurysms that rupture are contained within the tissue between the abdominal cavity and aorta. Because bleeding is contained most patients receiving proper medical care survive. Infrequently an aneurysm breaks through this tissue and bleeds into the abdominal cavity. Because this space is much larger bleeding is not controlled and a patient usually dies (70-90%) quickly from excess blood loss.

Treatment

Depends on the size of the aneurysm and whether or not symptoms are present. The risk of rupture increases as the aneurysm gets larger. Most aneurysms are small enough to be followed with ultrasound exam on a yearly basis.

Aneurysms increase in size from 0.3 to 0.5 centimeters (1/8 to 1/4 inch) per year on average. Risk of rupture increases greatly when size is greater than 5.5 centimeters or the size increases greater then 0.5 centimeters in less than six months). The risk of heart attack during surgical repair is as high as 20% during surgical repair done emergently (after the appearance of symptoms).

Medical follow up is appropriate for patients who are asymptomatic with an aneurysm less than 3.5 centimeters (yearly ultrasound), asymptomatic and have an aneurysm 3.5 to 5 centimeters (twice yearly ultrasounds).

Surgical repair consists of removal of the aneurysm and replacement of the affected part of the aorta with a synthetic graft. Repair is best done electively (before symptoms or rupture occur while a patient is in relatively good health) . Repair should be strongly considered for all low risk patients ( those without severe heart or lung disease and a life expectancy greater than 3-5 years) with an aneurysm larger than 5 centimeters, patients with aneurysms of any size that are symptomatic, aneurysms between 4 to 5 centimeters with an enlargement greater than 0.5 centimeters in less than six months, or high risk patients (severe heart or lung disease) with aneurysms that are either symptomatic or larger than 7 centimeters.

Complications of surgical repair include heart attack /death (uncommon during elective repair), excessive bleeding or injury to the bowel-ureters-kidney, intestines, or spinal cord (due to blood flow interruption).

Percutaneous Graft Implant is a new and still experimental techique that passes a synthetic graft through the arteries in the groin to form a "tube within a tube". That is it expands and lines the inside of the aortic vessel while allowing blood to pass through the hollow center. Results thus far look very promising with recovery often taking only several days instead of the several weeks typical for surgical repair.

Thoracic aortic aneurysms occur in the chest and are usually detected on chest x-ray or other imaging studies done for an unrelated reason (i.e.-accidently discovered). Most have no symptoms. Rupture almost always causes death because of rapid blood loss into the chest cavity.

It should be stressed that thoracic aneurysms are much less common than brain or abdominal aortic aneurysms.

Dissecting aortic aneurysm- A much more common occurrence in the chest is a "dissecting aneurysm". Dissecting aneurysms occur when blood pumped from the heart creates a tear between the tissue layers of the aorta. Blood is then pumped between the layers of the arterial wall as well as through the normal artery channel. This tear usually occurs in the aorta a short distance from the heart. The aorta often is not excessively dilated before the dissection occurs. Risk factors include high blood pressure, particularly high diastolic blood pressure. Dissection can also occur from trauma such as motor vehicle accidents.

Symptoms

Include severe sudden tearing pain in the back between the shoulder blades, chest pain or flank pain.

Treatment

A dissecting aneurysm is a medical emergency requiring surgery if a patient's health permits. Complications include paralysis in the lower body (because the arteries supplying blood to the lower spinal cord arise from the thoracic aorta), heart attack, kidney failure or rupture (causing death).

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Aneurysms aren't always dangerous, but if one bursts in the brain, a stroke results. They're often caused or aggravated by high blood pressure but may occur in young otherwise healthy people. Brain aneurysms (called berry aneurysms) usually occur at points where the brain arteries branch or are just about to enter brain tissue in an area known as the subarachnoid space. Rupture in this area is often very serious because the blood pressure is higher in this area than in smaller arteries that have already entered the brain tissue. Ruptured subarachnoid aneurysms cause about 10% of all strokes but cause a higher percent of strokes in younger people (under 40 years).

Symptoms

Stretching or a small leak from a berry aneurysm may cause sudden severe onset of a headache. The headache is often on the top or back portion of the head. Neck stiffness may also be present.

Many people describe these headaches as "the worst of my life" or "it feels like my head is going to explode". If the leaking is more severe symptoms can vary from mild drowsiness to deep coma. It is important to realize that many people get headaches, some more frequently than others.

Physical activities, including sexual intercourse, may precipitate headache due to aneurysm stretching.

A person having a headache that is much more severe or different than previous headaches should contact their doctor or go to an emergency room immediately.

Diagnosis

Patients with the above symptoms will usually receive a CT scan in the emergency department. Newer CT scanners will detect upto 90-95% of leaking aneurysms. If the CT scan is normal but the doctor still suspects an aneurysm is present further tests may be ordered.

If there is concern the aneurysm is leaking (small amount of bleeding into subarachnoid space) a lumbar puncture (spinal tap) may be performed. Spinal fluid in the lower spinal cord mixes with spinal fluid from the subarachnoid space; therefore, bleeding into the subarachnoid spinal fluid will be detected by lumbar puncture.

Alternatively, a brain angiogram may instead be performed. Dye is injected into an artery near the brain and a series of x-ray pictures is used to make a "movie" of the blood as it circulates in brain blood vessels. Special equipment (not available at most hospitals) is required to perform a biplanar (3 dimensional) angiogram.

MRI is usually the preferred way to follow an aneurysm electively. That is an aneurysm is present but does not have to be operated on because it is small enough and not causing symptoms.

Treatment

Is determined by a patient's doctor. This will often be a neurologist in consultation with a neurosurgeon. Small asymptomatic aneurysms may be followed with yearly or twice yearly imaging studies. Larger or frequently symptomatic aneurysms are treated surgically by "clipping" the aneurysm.

See "Stroke" for more information

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