Aortic Dissection

Definition

Aortic dissection is a rare, but potentially fatal, condition in which blood passes through the inner lining and between the layers of the aorta. The dissecting aorta usually does not burst, but has an abnormal second channel within it.

Description

A defect in the inner lining of the aorta allows an opening or tear to develop. The aorta is the main artery of the body and is an area of high blood pressure. When a defect develops, blood pressure can force the tear to open and allow blood to pass through. Since the blood is under pressure, it eventually splits (dissecting) the middle layer of the blood vessel, creating a new channel for blood. The length of the channel grows over time and can result in the closing off of connection points to other arteries. This can lead to heart attack, strokes, abdominal pain, and nerve damage. Blood may leak from the dissection and collect in the chest an around the heart.

A second mechanism leading to aortic dissection is medial hemorrhage. A medial hemorrhage occurs in the middle layer of the blood vessel and spills through the inner lining of the aorta wall. This opening then allows blood from the aorta to enter the vessel wall and begin a dissection. Approximately 2,000 cases of aortic dissection occur yearly in the United States.

Causes and symptoms

Aortic dissection is caused by a deterioration of the inner lining of the aorta. There are a number of conditions that predispose a person to develop defects of the inner lining, including high blood pressure, Marfan's disease, Ehlers-Danlos syndrome, connective tissue diseases, and defects of heart development which begin during fetal development. A dissection can also occur accidentally following insertion of a catheter, trauma, or surgery. The main symptom is sudden, intense pain. The pain can be so intense as to immobilize the patient and cause him to fall to the ground. The pain is frequently felt in both the chest and in the back, between the shoulder blades. The extent of the pain is proportional to the length of the dissection.

Key terms

Dissection — A cut or divide.

Hemorrhage — A large discharge of blood, profuse bleeding.

Diagnosis

The pain experienced by the patient is the first symptom of aortic dissection and is unique. The pain is usually described by the patient as "tearing, ripping, or stabbing." This is in contrast to the pain associated with heart attacks. The patient frequently has a reduced or absent pulse in the extremities. A murmur may be heard if the dissection is close to the heart. An enlarged aorta will usually appear in the chest x rays and ultrasound exams of most patients. The use of a blood dye in angiograms and/or CT scans (computed tomography scans) will aid in diagnosing and visualizing the dissection.

Treatment

Because of the potentially fatal nature of aortic dissection, patients are treated immediately. Drugs are administered to reduce the blood pressure and heart rate. If the dissection is small, drug therapy alone may be used. In other cases, surgery is performed. In surgery, damaged sections of the aorta are removed and a synthetic graft is often used to reconstruct the damaged vessel.

Prognosis

Depending on the nature and extent of the dissection, death can occur within a few hours of the start of a dissection. Approximately 75% of untreated people die within two weeks of the start of a dissection. Of those who are treated, 40% survive more than 10 years. Patients are usually given long term treatment with drugs to reduce their blood pressure, even if they have had surgery.

Resources

Books

Alexander, R. W., R. C. Schlant, and V. Fuster, editors. The Heart. 9th ed. New York: McGraw-Hill, 1998.

dissection

[dĭ-sek´shun]

1. the act of dissecting.

2. a part or whole of an organism prepared by dissecting.

aortic dissection a dissecting aneurysm of the aorta; the usual site is the thoracic aorta. There are two types, classified according to anatomical location: Type A involves the ascending aorta; Type B originates in the descending aorta. Acute aortic dissection is often fatal within one month of onset. Surgical treatment may be delayed in aneurysms involving the descending aorta until the blood pressure has been controlled and edema and friability of the aorta are diminished. The usual course of treatment for an aneurysm of the ascending aorta is immediate surgery. The surgical procedure for either type is aimed at either repairing the intimal tear or removing the affected portion of the aorta. This may be done by suturing the separated aortic layers back together or by removing the damaged section of the aorta and replacing it with a synthetic graft.

axillary dissection (axillary lymph node dissection) surgical removal of axillary lymph nodes, done as part of radical mastectomy.

blunt dissection separation of tissues along natural lines of cleavage, by means of a blunt instrument or finger.

lymph node dissection lymphadenectomy.

lymph node dissection, retroperitoneal (RPLND) retroperitoneal lymphadenectomy.

sharp dissection separation of tissues by means of the sharp edge of a knife or scalpel, or with scissors.

a·or·tic dis·sec·tion

a pathologic process, characterized by splitting of the media layer of the aorta, which leads to formation of a dissecting aneurysm. Classified according to location as follows: type I involves the ascending aorta, transverse arch, and distal aorta; type II is confined to the ascending aorta; type III extends distally in the descending aorta, usually from a starting point just distal to the left subclaviar artery.

aortic dissection

A condition affecting ±2,000 people/year (US), characterised by the presence of a second (false) lumen in the aortic wall. Dissection occurs when blood flows into a torn tunica intima of an aortic wall weakened by cystic medial necrosis, usually in a background of chronic hypertension (HTN), which follows degeneration of the elastic tissue and collagen of the tunica media.

Clinical findings
Hypotension with loss of consciousness due to compromised brachiocephalic vessels, reactive HTN, pulse-blood pressure dissociation and focal neurologic defects due to involvement of the spinal arteries.

High risk groups
Older men, pregnant women, Blacks, HTN, connective tissue diseases, vasculitis or congenital aortic coarctation; AD may be induced by the trauma of the cardiac catheterisation and exercise.

Management
Sodium nitroprusside, β-blockers, ganglion blockers (e.g., trimethaphan camsylate), CCBs; blood flowing into a dissection may re-flow into the aortic lumen if there is a second intimal tear, or may rupture into the pleural or pericardial cavities, with potential fatal consequences.

Mortality
21% of ruptured AD die in the first 24 hours; 90% within three months if not managed surgically.

aortic dissection

Aortic dissection of hematoma, dissecting aneurysm of aorta Cardiovascular disease A condition which affects ±2000 people/yr–US, characterized by the presence of a second–false lumen in the aortic wall; dissection occurs when blood flows into a torn tunica intima of an aortic wall weakened by cystic medial necrosis, usually in a background of chronic HTN, which follows degeneration of the elastic tissue and collagen of the tunica media High risk groups Older ♂, pregnant ♀, blacks, HTN, connective tissue diseases, vasculitis or congenital aortic coarctation; AD may be induced by the trauma of the cardiac catheterization and exercise Clinical Hypotension with loss of consciousness due to compromise of the brachiocephalic vessels, reactive HTN, pulse-blood pressure dissociation and focal neurologic defects due to involvement of the spinal arteries Radiology Abnormal chest films with widening of the mediastinal silhouette, an abnormal aortic contour, left-sided pleural effusion, a disparity of the luminal diameter between the ascending and descending aorta and separation of intimal calcification ≥ 0.5 cm from the outer edge of the soft tissue border of the aorta–'calcium sign'; other defects may be seen by aortic angiography, echocardiography, CT, MRI Management Sodium nitroprusside, β-blockers, CCBs; blood flowing into a dissection may re-flow into the aortic lumen if there is a 2^nd intimal tear or may rupture into the pleural or pericardial cavities, with potential fatal consequences Mortality 21% of ruptured AD die in the first 24 hrs; 90% within 3 months. See Cystic medial necrosis.

a·or·tic dis·sec·tion

(ā-ōr'tik di-sek'shŭn)

A pathologic process, characterized by splitting of the media layer of the aorta, which leads to formation of a dissecting aneurysm.

aortic dissection

A dangerous and painful disorder in which blood under pressure is forced into a plane within the wall of the largest artery in the body and causes a splitting effect. The condition pre-supposes some structural weakness of the wall of the artery. In about 10 per cent of cases the condition results from spontaneous rupture of one of the tiny arteries (vasa vasorum) that supply the arterial wall with blood. There is a risk of complete rupture which is usually fatal. Improved surgical management, including replacement of the aorta, has reduced the overall in-hospital death rate to below 30 per cent.