Services |Aorta Dissection

Overview

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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 muscle 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.
While there have been different historic classifications of aortic dissection, the Stanford classification is now most commonly used.

  • Type A dissections involve the ascending aorta and arch.
  • Type B involves the descending aorta.
  • 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 causes of aortic dissection?

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 (over 70%) 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.

Symptoms

No one sign or symptom can positively identify acute aortic dissection. Clinical manifestations include the following:

Sudden onset of severe chest pain that often has a tearing or ripping quality (classic symptom)

  • Chest pain may be mild
  • Anterior chest pain: Usually associated with anterior arch or aortic root dissection
  • Neck or jaw pain: With aortic arch involvement and extension into the great vessels
  • Tearing or ripping intrascapular pain: May indicate dissection involving the descending aorta
  • No pain in about 10% of patients
  • Syncope
  • Cerebrovascular accident (CVA) symptoms (eg, hemianesthesia, and hemiparesis, hemiplegia)[1]
  • Altered mental status
  • Numbness and tingling, pain, or weakness in the extremities
  • Horner syndrome (ie, ptosis, miosis, anhidrosis)
  • Dyspnea
  • Hemoptysis
  • Dysphagia
  • Flank pain (with renal artery involvement
  • Abdominal pain (with abdominal aorta involvement)
  • Fever
  • Anxiety and premonitions of death

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.

Treatment

In the emergency department, intravenous lines will be placed, monitors for heart rate and rhythm will be attached, and supplemental oxygen 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.


Surgery

The surgery involved in repairing an aortic dissection is very difficult and invasive. As has been stated before, type A dissections require immediate surgical repair. In the operating room, a cardiothoracic surgeon first performs a median sternotomy, a procedure in which a patient’s chest is opened. Then, a patient is placed on cardiopulmonary bypass. This means that a patient’s blood is routed around the heart and lungs through a machine, so that the body may still receive blood and oxygen while allowing surgeons to operate on the aorta. During this time, the bypass machine can cool the patient’s blood, which in turn cools the patient’s body and reduces its oxygen requirements. To operate on the aorta, the heart cannot be pumping. Cardioplegic solution, a nutrient-rich solution that slows down the heart, is injected into the heart. This solution greatly reduces its metabolic demands, allowing the heart to be nearly stopped during the procedure yet kept alive.
Surgeons then inspect the aorta to look for the site of the tear that caused the dissection. In addition, they investigate the extent of the tear and determine if anything else, such as other vessels, may have been affected by the dissection. Surgeons suture together the layers of the aorta that were affected, closing the tear that dissected. The aorta is then reinforced with a Dacron graft–a synthetic material–that can be wrapped around the aorta. If necessary, Dacron may also be used to replace portions of the aorta. These grafts usually last an entire lifetime.
If necessary, coronary arteries can be reattached to the heart. If the aortic valve has been affected by the dissection, it may be replaced at this time with a prosthetic valve. Once all repairs are complete, the patient’s heart usually restarts on its own after the cardioplegic solution is stopped. If it does not, the heart may need to be shocked with a defibrillator to be restarted. Finally, the patient is taken off cardiopulmonary bypass. The entire procedure lasts anywhere from 5-10 hours, and recovery from surgery usually requires 7-10 days.
As described previously, patients with type B dissections are operated on only in certain situations, such as the formation of a large (>5 cm) aneurysm, organ or limb problems, or evidence of further dissection. These patients receive a similar procedure in which the aorta is reinforced with a Dacron graft and the false lumen is sealed off. However, depending on heart. This solution greatly reduces its metabolic demands, allowing the heart to be nearly stopped during the procedure yet kept alive.
Surgeons then inspect the aorta to look for the site of the tear that caused the dissection. In addition, they investigate the extent of the tear and determine if anything else, such as other vessels, may have been affected by the dissection. Surgeons suture together the layers of the aorta that were affected, closing the tear that dissected. The aorta is then reinforced with a Dacron graft–a synthetic material–that can be wrapped around the aorta. If necessary, Dacron may also be used to replace portions of the aorta. These grafts usually last an entire lifetime.
If necessary, coronary arteries can be reattached to the heart. If the aortic valve has been affected by the dissection, it may be replaced at this time with a prosthetic valve. Once all repairs are complete, the patient’s heart usually restarts on its own after the cardioplegic solution is stopped. If it does not, the heart may need to be shocked with a defibrillator to be restarted. Finally, the patient is taken off cardiopulmonary bypass. The entire procedure lasts anywhere from 5-10 hours, and recovery from surgery usually requires 7-10 days.
As described previously, patients with type B dissections are operated on only in certain situations, such as the formation of a large (>5 cm) aneurysm, organ or limb problems, or evidence of further dissection. These patients receive a similar procedure in which the aorta is reinforced with a Dacron graft and the false lumen is sealed off. However, depending on the location of the dissection, the chest cavity may not be opened. Instead, the aorta may be accessed through an incision on a patient’s sides–unfortunately, often a technically more difficult procedure.