An aortic dissection is a small tear in the tunica intima (the inside layer of the aortic wall in contact with blood).
- Aortic dissection occurs when a tear occurs in the inner muscle wall lining of the aorta, allowing blood to split apart the muscle layers of the aortic wall.
- Symptoms of aortic dissection include
- a tearing or ripping pain in the chest,
- sweating,
- nausea,
- shortness of breath,
- weakness, or
- syncope (fainting).
- Abdominal aortic dissection can present with abdominal pain radiating to the flank or back.
- Mortality is high for both types of aortic dissection.
- Reducing the risk factors for aortic dissection are key to prevention of this condition, including
- high blood pressure,
- elevated cholesterol,
- diabetes, and
- quitting smoking.
The aorta
- The aorta is the large blood vessel that leads from the heart and carries blood to the rest of the body.
- It originates at the aortic valve at the outlet of the left ventricle of the heart and ascends within the chest to an arch where blood vessels branch off to supply blood flow to the arms and head.
- The aorta then begins to descend through the chest and into the abdomen where it splits into two iliac arteries that provide blood flow to the legs.
- Along its descent, more small arteries branch out to supply blood to the stomach, intestine, colon, kidneys, and the spinal cord. Also, at its origin at the aortic valve, coronary arteries branch from the aorta to supply the heart muscle with blood.
- The aorta has a thick wall with three layers of tissue that allow the blood vessel to withstand the high pressure that is generated when the heart pumps blood to the body.
- The three layers are
- the tunica intima,
- tunica media, and the
- tunic adventitia.
- The intima is the inside layer that is in contact with the blood, the media is in the middle, and the adventitia is the outermost layer.
Aortic Dissection
- In an aortic dissection, a small tear occurs in the tunica intima (the inside layer of the aortic wall in contact with blood).
- Blood can enter this tear and cause the intima layer to strip away from the media layer, in effect dividing the tissue layers of the aortic wall and forming a false channel, or lumen.
- This channel may be short or may extend the full length of the aorta.
- Another tear more distal (further along the course of the aorta than the initial tear) in the intima layer can let blood re-enter the true lumen of the aorta.
- In some cases, the dissection will cross all three layers of the aortic wall and cause immediate rupture and almost certain death.
- In most other cases, the blood is contained between the wall layers, usually causing pain felt in the back or flanks.
Types of Aortic Dissection
While there have been different historic classifications of aortic dissection, the Stanford classification is now most commonly used.
There are two types of dissection:
- Type A—dissections involving the ascending aorta and arch, which is treated surgically, and
- Type B—dissections involving the descending aorta, which is treated with medical management.
A patient can have a type A dissection, type B dissection, or a combination of both.
Some patients may experience an aortic dissection without pain and it may be found incidentally on imaging studies performed for other purposes.
What are the aortic dissection causes?
It is uncertain as to why the initial tear (rent) occurs in the intima layer of the aortic wall. Aortic dissection tends to occur most commonly in men between the ages of 50 and 70.
High blood pressure: Most cases are associated with high blood pressure (hypertension). The aorta has to withstand significant pressure changes with each heartbeat, and it may be that over time with hypertension, a weakening of an area of the intima will occur.
Some conditions increase the risk of aortic dissection or are associated with the condition, including:
- Bicuspid aortic valve (a congenital abnormality of the aortic valve)
- Marfan syndrome
- Ehlers-Danlos syndrome
- Turner syndrome
- Syphilis
- Cocaine use
Pregnancy: Pregnancy is a rare associated risk factor, especially in the third trimester and early in the postpartum period.
Trauma: Blunt trauma is known to cause aortic dissection, which is often seen after car wrecks in which the patient's chest hits the steering wheel.
Surgical complications: Aortic dissection can be a complication of medical operations including coronary artery bypass grafting and aortic and mitral valve repairs. It can also be a complication of heart catheterization.
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What are the signs and symptoms of aortic dissection?
- Pain is the most common symptom of aortic dissection and is often described as tearing or ripping and often begins suddenly. If the aortic dissection occurs in the chest, the pain is usually centered in the chest and radiates directly into the upper back. If the dissection occurs in the abdominal aorta, the pain may occur in the mid back or low back and radiate to the flanks.
- There may be associated nausea, sweating, shortness of breath, and weakness.
- The patient may pass out (syncope).
- Other symptoms may be related to the location of the dissection within the aorta and whether it affects some of the branch arteries and occludes their blood supply. For example, if an artery that supplies blood to the brain is involved, there may be signs of stroke. Or if the dissection affects the anterior spinal artery and blood supply to the spinal cord, the patient may present with paraplegia.
- The coronary arteries that supply blood to the heart begin at the origin of the aorta at the aortic valve. If the coronary arteries are involved, the aortic dissection may cause a heart attack (myocardial infarction) as its presenting symptom.
- The patient may present with congestive heart failure with fluid building up in the lungs. If the aortic dissection involves the aortic valve and causes it to fail, blood flows back into the heart with each beat and causes blood flow to back up into the lungs.
- The pain of aortic dissection can be confused with that of heart attack, but can sometimes be distinguished because of its sudden onset, potentially normal electrocardiogram, and abnormal findings on chest X-ray.
- The pain of an abdominal aortic dissection can be confused with the pain caused by a kidney stone. The diagnosis is made when a CT scan looking for the kidney stone reveals an aneurysm instead.
- The patient may also have a sense of impending doom.
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How is aortic dissection diagnosed?
The health care professional should always be suspicious of aortic dissection as one of the three major causes of chest pain that can cause death, in addition to heart attack and pulmonary embolism.
If the patient has unstable vital signs, poor breathing, abnormal pulse, low blood pressure, and/or a decreased level of consciousness, the ABCs of resuscitation (Airway, Breathing, Circulation) need to be addressed while the evaluation of the patient continues.
Patient History
The history is one of the important first steps in trying to make the diagnosis. It is important to consider not only the symptoms but also the risk factors of high blood pressure, genetic or family history, and the presence of other medical conditions that may predispose the patient to aortic dissection.
Physical examination may show potential complications of the aortic aneurysm and allow the health care professional to consider this as a potential diagnosis. Again, the presenting symptoms will depend upon the location of the dissection and what organs are involved. Symptoms, depending on the location of the dissection, may include:
- Blood pressure discrepancy between the arms
- Pulse delay between arms and legs
- Listening for fluid in the lung or for a new heart murmur that may help assess the aortic valve
- New stroke symptoms
- Paraplegia
Diagnostic Testing
- The initial tests for chest pain, an electrocardiogram and a chest X-ray, are usually done. Unless the dissection involves the coronary arteries, the electrocardiogram is usually normal. The chest X-ray may show an abnormal shape to the aorta and a widened mediastinum (that space where the heart, aorta, vena cava, trachea, and esophagus sit in the chest cavity).
- The diagnostic test of choice is an aortic angiogram using computerized tomography of the chest and abdomen. This test requires a contrast dye injection and visualizes the aorta and other blood vessels that branch off from it.
- Alternatively, for those people who cannot undergo computerized tomography, transesophageal echocardiography is an option. A cardiologist puts an ultrasound probe through the mouth into the esophagus and can identify potential problems with the heart, heart valves, and the aorta.
- Magnetic resonance imaging (MRI) can also be used, but is not often technically easily available with unstable patients and takes much longer to perform than a CT scan.
What is the treatment for aortic dissection?
- The ABCs of resuscitation are always a priority.
- In the emergency department, intravenous lines will be placed, monitors for heart rate and rhythm will be attached, and supplemental oxygen will be provided. Treatment and diagnostic testing usually occur at the same time until the final diagnosis is established and definitive treatment is required.
- The initial medications used for treatment of an aortic dissection are directed at lowering the blood pressure to prevent further tearing or damage to the aorta. Beta blocker medications (for example, esmolol [Brevibloc], labetalol [Normodyne, Trandate], metoprolol [Lopressor, Toprol XL]) decrease the adrenaline action on the heart and blood vessels. Nitroglycerin dilates blood vessels to decrease blood pressure. These medications cannot be used if the patient is in shock with low blood pressure because of the aortic dissection. Specific medication combinations will depend upon the patient's needs.
- Ultimately, type A aortic dissections of the ascending aorta require surgery as the treatment of choice. The area of the aorta that is damaged is replaced with an artificial graft. If the aortic valve has been damaged, it too may need replacement or repair.
- Medical management (nonsurgical) is usually preferred for type B dissection of the descending aorta, but again, each patient needs to be assessed individually as to the specific treatment suggested. Medications are prescribed to aggressively control high blood pressure to prevent further dissection and aortic injury.
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What is the prognosis for aortic dissection?
For aortic rupture, in which all three layers of the aorta are disrupted, the mortality (death) rate is up to 80% of patients. Forty percent of these patients die before reaching a hospital.
- For type A aortic dissection, the mortality rate remains high, with up to a 30% death rate after surgery.
- Type B aortic dissections, treated medically, have an initial death rate of 10%. This compares to a 25% mortality when treated surgically.
Overall, for both types of aortic dissection, the 10-year survival rate is more than 60%.
Can aortic dissection be prevented?
- As with any disease involving blood vessels, prevention is key. Controlling high blood pressure, diabetes, cholesterol, and avoiding smoking decreases the risk of all blood vessel disease. Because the majority of patients with aortic dissection have hypertension, controlling high blood pressure (one risk factor) may decrease the risk of this disease.
- The use of screening ultrasound to look for abdominal aortic aneurysm is somewhat controversial. The U.S. Preventive Services Task Force recommends a one-time ultrasound screening for males aged 65 to 75 who have ever smoked. There is no recommendation for men who don't smoke. They recommend against screening for women because of the rarity of abdominal aortic aneurysm in women.
- Any chest pain should not be ignored and medical care should be accessed immediately by activating the emergency medical services system and calling 9-1-1.
- Since the cause of the chest pain may be unknown, giving a baby aspirin to the patient is appropriate, as is providing nitroglycerin (if the patient has been prescribed this medication for chest pain).
