What is an aortic dissection?
Aortic dissection occurs when a small tear develops in the wall of the aorta. The tear forms a new channel between the inner and outer layers of the aortic wall. This causes bleeding into the channel and can enlarge the tear. Aortic dissection is a life-threatening condition.
Aortic dissection can be caused by atherosclerosis (hardening of the arteries) and high blood pressure, traumatic injury to the chest, such as being hit by the steering wheel of a car during an accident, and conditions that are present at birth, such as Marfan's syndrome or Ehlers-Danlos syndrome.
What causes aortic dissection, and how can it be prevented?
Any one or any combination of the following may cause aortic dissection:
- High blood pressure. Most patients with an aortic dissection have had high blood pressure for many years. The high blood pressure accelerates the natural processes of tissue aging and damage to the tissue, promoting a weakness of the aortic wall and increasing the risk for a tear.
- Processes associated with high blood pressure. A variety of processes is associated with high blood pressure and therefore increases the risk of developing an aortic dissection. These include pregnancy, lupus, polycystic kidney disease, Cushing's syndrome, giant cell arteritis, and cocaine abuse. In pregnancy, the increased frequency of aortic dissections is caused by the combination of hormonal effect on the tissue structure (elastin fibres) and additional high blood pressure stress.
- Diseases of the connective tissue. Either Marfan's syndrome or Ehlers-Danlos syndrome can damage the connective tissue in the middle of the aortic wall. This damage can lead to aortic dissection.
- Chest injury. Severe chest injury, such as might occur in an automobile accident, may also cause aortic dissection.
A family history of aortic dissection is also a risk factor.
The key point in prevention of aortic dissection is dealing with high blood pressure. Minimizing this and other risk factors for atherosclerosis significantly reduces the risk of developing an aortic dissection. Lifestyle changes, quitting smoking, and a strict dietary regimen, supported by a well-controlled medical therapy, can reduce high blood pressure.
What are the symptoms of aortic dissection?
Pain is the leading symptom of aortic dissection. You will generally have a sudden onset of pain at the moment of dissection. The pain is usually described as ripping or tearing and as the worst pain ever experienced. It is usually in between the shoulders on the back and might radiate to the arms or the neck. Less frequently, the pain can be felt as chest pain. The pain is very difficult to distinguish from that of angina or a heart attack.
Other symptoms may include:
- Numbness and the inability to move the legs.
- Lack of pulse.
- Pale skin.
If you experience these symptoms, you should call 911 or other emergency services immediately.
Do not drive yourself as time is important and stress and movement should be reduced to a minimum. Do not try to take pain medication or heart medication. Taking aspirin with aortic dissections has had fatal consequences.
If you witness a person become unconscious, call 911 or other emergency services and start cardiopulmonary resuscitation (CPR). The emergency operator can coach you on how to perform CPR.
How is aortic dissection diagnosed?
Your doctor will ask you questions about your symptoms, medical history, lifestyle, and family medical history and perform a physical exam. He or she may ask if you have been hit hard in the chest or been in an automobile accident. Several specialists may see you.
Your doctor will listen to your heart sounds with a stethoscope, take your pulse and evaluate your circulation, and evaluate your neurological status (nerve and brain function). As the symptoms of aortic dissection mimic many other conditions, you may need several tests.
If you have an aortic dissection, you may need:
- Blood tests. These tests can give your doctor clues about what is causing your symptoms.
- A chest X-ray.
- An angiogram. This test can help determine the size of your dissection and if you have blood clots or other blood vessel involvement.
- Computed tomography scanning (CT) and magnetic resonance imaging (MRI) to help your doctor know if your dissection is growing.
- A transthoracic echocardiography and transesophageal echocardiography (TEE) to let your doctor look at blood vessels inside your chest.
- An intravascular ultrasound to get a better look at your blood vessels.
How is aortic dissection treated?
The treatment of aortic dissection depends in part on where the dissection is located:
- Dissections involving the aorta where it goes up from the heart (with or without the arch) are known as type A dissections and are generally surgically treated.
- Dissections involving the rest of the aorta are known as type B dissections. If there are no complications, type B dissections are generally treated with medicines.
Initial emergency treatment and the treatment for type A dissections are widely accepted, but treatment for uncomplicated type B dissections remains controversial.
Initial emergency treatment
Treatment for aortic dissection should be made immediately following the diagnosis. The goal of initial emergency treatment is to relieve pain and to reduce the blood pressure on the dissection (reduction of the pulsatile load). This helps prevent additional bleeding and reduces the risk of a rupture.
Generally, you are put immediately in an intensive care unit (ICU) or taken to the operating room. Your doctor will continuously monitor and control your blood pressure, pulse, and heart activity.
Medicine that aims to reduce pain and blood pressure will be used and may include:
- Nitroprusside, which lowers blood pressure. Your mean arterial blood pressure should be between 60 and 70 mm Hg. This pressure normally guarantees a constant organ blood flow and minimizes the pressure on the dissection. Nitroprusside causes a widening of the vessels arteries and veins. The pressure in the whole body system is reduced.
- Beta-blockers, to lower your heart rate. Lowering the blood pressure will lead to a natural heart reflex that increases heart contraction and heart rate. This can increase the risk of rupture, so beta-blockers will be administered. You should receive this before the nitroprusside.
- Pain medicine. If the control of the hypertension does not reduce your pain, strong pain medicines may be provided, including morphine.
Treating type A dissections
Traditionally, the first line of treatment for type A dissections (dissection of the aorta involving the ascending aorta) is surgery.
The goal of the operation is to prevent death due to bleeding and to reestablish blood flow into the extremities and inner organs (if branches of the aorta are involved in the dissection process).
In this open-heart procedure, your chest is opened and the surgeon removes the part of the aorta where the tear is found. The portion of the aorta removed can be replaced with synthetic material, such as a Dacron tube graft. Another approach uses a similar graft that is placed inside the aorta; in this approach the ascending aorta is not replaced but internally reinforced.
If heart valves are involved in the dissection, they must be repaired to guarantee a regular blood flow and function of the heart. In some cases the aortic valve cannot be repaired and has to be replaced. If dissection involves the coronary arteries, these arteries may have to be disconnected from the original aorta and sewed back on to reestablish blood flow to the heart (coronary artery reinsertion).
An additional operation is often needed.
The surgery cannot be performed if you are already suffering from a severe complication in the process of dissection, such as a stroke. In this situation an operation would lead to severe bleeding in the brain.
Possible complications of aortic dissection and its surgery include:
- Kidney (renal) failure.
- Infections in the lung and lung failure.
- Decreased heart function and heart attack.
It is sometimes not possible to use surgery in type A dissections. In this case, the same procedures and medicines outlined in the initial emergency treatment section are used.
Treating type B dissections
Type B dissections are usually treated with medicines. In rare cases, a procedure or surgery may be necessary if:
- Your aorta has ruptured.
- You have pain or high blood pressure that cannot be controlled.
- You have a lot of bleeding.
- Other arteries or organs are damaged.