Aneurysm Overview

An aneurysm refers to a weakening of an artery wall that creates a bulge, or distention, of the artery.

Most aneurysms do not show symptoms and are not dangerous. However, at their most severe stage, some can rupture, leading to life-threatening internal bleeding.

The Centers for Disease Control and Prevention (CDC) advise that aortic aneurysms contribute to over 25,000 deaths in the United States (U.S.) each year.

Around 30,000 brain aneurysms rupture in the U.S. each year. An estimated 40 percent of these cases cause death within 24 hours.

Types of Aneurysms

Aneurysms are classified by their location in the body. The arteries of the brain and heart are the two most common sites of a serious aneurysm.

The bulge can take two main shapes:

• Fusiform aneurysms bulge all sides of a blood vessel
• Saccular aneurysms bulge only on one side

The risk of rupture depends on the size of the bulge.

Aortic aneurysm

The aorta is the large artery that begins at the left ventricle of the heart and passes through the chest and abdominal cavities. The normal diameter of the aorta is between 2 and 3 centimeters (cm) but can bulge to beyond 5 cm with an aneurysm.

The most common aneurysm of the aorta is an abdominal aortic aneurysm (AAA). This occurs in the part of the aorta that runs through the abdomen. Without surgery, the annual survival rate for an AAA of over 6 cm is 20 percent.

AAA can rapidly become fatal, but those that survive the transfer to a hospital have a 50 percent chance of overall survival.

Less commonly, a thoracic aortic aneurysm (TAA) can affect the part of the aorta running through the chest. TAA has a survival rate of 56 percent without treatment and 85 percent following surgery. It is a rare condition, as only 25 percent of aortic aneurysms occur in the chest.

Cerebral aneurysm

Aneurysms of the arteries that supply the brain with blood are known as intracranial aneurysms. Due to their appearance, they are also known as “berry” aneurysms.

A ruptured aneurysm of the brain can be fatal within 24 hours. Forty percent of brain aneurysms are fatal, and around 66 percent of those who survive will experience a resulting neurological impairment or disability.

Ruptured cerebral aneurysms are the most common cause of a type of stroke known as subarachnoid hemorrhage (SAH).

Peripheral aneurysm

An aneurysm can also occur in a peripheral artery. Types of peripheral aneurysm include the following:

• Popliteal aneurysm: This happens behind the knee. It is the most common peripheral aneurysm.
• Splenic artery aneurysm: This type of aneurysm occurs near the spleen.
• Mesenteric artery aneurysm: This affects the artery that transports blood to the intestines.
• Femoral artery aneurysm: The femoral artery is in the groin.
• Carotid artery aneurysm: This occurs in the neck.
• Visceral aneurysm: This is a bulge of the arteries that supply blood to the bowel or kidneys.

Peripheral aneurysms are less likely to rupture than aortic aneurysms.

Causes of Aneurysm

An aneurysm can happen in any part of the body. Blood pressure can more easily distend a weakened arterial wall.

Further research is necessary to confirm why an artery wall weakens to cause an aneurysm. Some aneurysms, though less common, are present from birth as an arterial defect.

Aortic Dissection

Aortic dissection is one identifiable cause of an aortic aneurysm. The arterial wall has three layers. Blood can burst through a tear in the weakened wall of the artery, splitting these layers. It can then fill the cavity surrounding the heart.

If the tear occurs on the innermost layer of the arterial wall, blood channels into and weakens the wall, increasing the risk of rupture.

People with aortic dissection often describe abrupt and excruciating chest pain. This pain can travel as the dissection progresses along the aorta. It may, for example, radiate to the back.

Dissection leads to compression. Compression prevents blood from returning to the heart. This is also known as a pericardial tamponade.

Risk Factors of Aneurysm

There are some lifestyle choices and physical characteristics that can increase the chance of an aneurysm.

• Hypertension, or high blood pressure
•  Inactive lifestyle
• Obesity
• Poor Diet
• Smoking tobacco

Tobacco smoking is by far the most common risk factor, especially in cases of AAA. Tobacco use has been shown not only to increase cardiovascular disease and the risk of an aneurysm but also increase the risk of rupture once an aneurysm has taken effect.

Diagnosis of Aneurysm

Aneurysms often remain undetected. Screening aims to identify people who need monitoring or treatment.

The US Preventive Services Task Force (USPSTF) recommends ultrasound screening for signs of AAA for all men aged 65 to 75 years who have smoked 100 cigarettes or more in their lives.

The taskforce does not recommend routine screening for women, whether they have smoked or not, as women have a lower risk of AAA.

If symptoms appear, an magnetic resonance imaging (MRI) can identify an aneurysm that has not yet ruptured. computerized tomography (CT) scans are usually preferred for ruptured aneurysms, especially if there is a risk of bleeding on the brain.

In cases of a severe or ruptured aneurysm in the brain or heart that needs emergency surgery, an angiogram can identify the exact area in need of repair. A catheter is inserted into a blood vessel in the thigh, under local anesthetic, and the catheter is then threaded through to the relevant part of the body.

The doctor applies a dye, helping to identify the area of the heart or brain that needs treatment.

Treatment of Aneurysm

Not all cases of unruptured aneurysm need active treatment. When an aneurysm ruptures, however, emergency surgery is needed.

Aortic Aneurysm Treatment Options

The doctor may monitor an unruptured aortic aneurysm, if no symptoms are evident. Medications and preventive measures may form part of conservative management, or they may accompany active surgical treatment.

A ruptured aneurysm needs emergency surgery. Without immediate repair, patients have a low chance of survival.

The decision to operate on an unruptured aneurysm in the aorta depends on a number of factors related to the individual patient and features of the aneurysm.

These include:

• Age, general health, coexisting conditions and personal choice of the patient
• The size of the aneurysm relative to its location in the thorax or abdomen, and the aneurysm’s rate of growth
• Presence of chronic abdominal pain or risk of thromboembolism, as these may also necessitate surgery

A large or rapidly growing aortic aneurysm is more likely to need surgery. There are two options for surgery:

• open surgery to fit a synthetic or stent graft
• endovascular stent-graft surgery.

In endovascular surgery, the surgeon accesses the blood vessels through a small incision near the hip. Stent-graft surgery inserts an endovascular graft through this incision using a catheter. The graft is then positioned in the aorta to seal off the aneurysm.

In an open AAA repair, a large incision is made in the abdomen to expose the aorta. A graft can then be applied to repair the aneurysm.

Endovascular surgery for the repair of aortic aneurysms carries the following risks:

• Bleeding around the graft
• Blockage of the stent 
• Bleeding before or after the procedure
• Erectile dysfunction
• Kidney failure
• Nerve damage, resulting in weakness, pain or numbness in the leg
• Reduced blood supply to the legs, kidneys or other organs
• Slippage of the stent
• Unsuccessful surgery that then needs further open surgery

Some of these complications, such as bleeding around the graft, will lead to further surgery.

Cerebral Aneurysm Treatment Options

In the case of a brain aneurysm, the surgeon will normally operate only if there is a high risk of rupture. The potential risk of brain damage resulting from surgical complications is too great.

As for AAA, the likelihood of a rupture depends on the size and location of the aneurysm.

Instead of surgery, patients receive guidance on how to monitor and manage the risk factors for a ruptured brain aneurysm, for example, monitoring blood pressure.

If a ruptured cranial aneurysm results in a subarachnoid hemorrhage, surgery is likely. This is considered a medical emergency.

This procedure would aim to close off the ruptured artery in the hope of preventing another bleed.

Complications of Aneurysm

The first signs of a previously undetected aneurysm could be complications upon rupture. Symptoms tend to result from a rupture rather than the aneurysm alone.

Most people living with an aneurysm do not experience any complications. However, in addition to thromboembolism and rupture of the aorta, complications can include:

• Severe chest or back pain: Severe chest or back pain may arise following the rupture of an aortic aneurysm in the chest.
• Angina: Certain types of aneurysm can lead to angina, another type of chest pain. Angina can lead to myocardial ischemia and heart attack.
• A sudden extreme headache: If a brain aneurysm leads to SAH, the main symptom is a sudden, severe headache.

Any rupture of an aneurysm may cause pain, low blood pressure, a rapid heart rate, and lightheadedness. Most people with an aneurysm will not experience any complications.

Prevention of Aneurysm

Preventing an aneurysm is not always possible, as some are congenital, meaning they are present from birth.

However, some lifestyle choices can affect the risk:

Smoking is a risk factor for both aortic aneurysms and the rupture of an aneurysm anywhere in the body. Quitting smoking can reduce the risk of a severe aneurysm.

Managing blood pressure can also minimize the risk of an aneurysm. Healthful blood pressure can be achieved through dietary measures, regular exercise, and medications.

Obesity can put extra pressure on the heart, so taking these steps is important for reducing stress on the artery walls.

A healthful diet can also reduce cholesterol and decrease the risk of atherosclerosis. Fusiform aneurysms are often linked to atherosclerosis.

Anyone diagnosed with an aneurysm and prescribed a conservative treatment plan can work with a healthcare practitioner to address any risk factors.

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