Aortic dissection

Aortic dissection is a tear of the aorta (the largest artery of the body). This tear causes blood to flow between the layers of the wall of the aorta and dissects the layers apart. Aortic dissection is an extremely serious medical emergency and can quickly lead to death.

Treatment

The risk of death due to aortic dissection is highest in the first few hours after the dissection begins, and decreases afterwards. Because of this, the therapeutic strategies differ for treatment of an acute dissection compared to a chronic dissection. An acute dissection is one in which the individual presents within the first two weeks. If the individual has managed to survive this window period without death, his prognosis is improved. About 66% of all dissections present in the acute phase.

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In all individuals with aortic dissections, medication should be used to control high blood pressure, if present.

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In the case of an acute dissection, once diagnosis has been confirmed, urgent surgical consultation is warranted to repair the tear in the aorta. Surgical management is superior to medical management for an acute ascending aortic dissection. In the case of acute distal aortic dissections (abdominal aortic dissections), surgical and medical management are equivalent if there are no complications.

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Individuals who present 2 weeks after the onset of the dissection are said to have chronic aortic dissections. These individuals have been self-selected as survivors of the acute episode, and can be treated with medical therapy as long as they are stable.

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Medical management is appropriate in individuals with an uncomplicated distal dissection, a stable dissection isolated to the aortic arch, and stable chronic dissections. Patient selection for medical management is very important. Stable individuals who present with an acute distal dissection (typically treated with medical management) still have an 8 percent 30 day mortality.

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Medical management

The prime consideration in the medical management of aortic dissection is strict blood pressure control. The target blood pressure should be a mean arterial pressure (MAP) of 60 to 75 mmHg. Another factor is to reduce the shear-force dP/dt (force of ejection of blood from the left ventricle).

Related Topics:
Mean arterial pressure - MmHg - Left ventricle

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To reduce the shear stress, sodium nitroprusside should be used with a non-selective beta blocker, such as esmolol, propranolol, or labetalol. The alpha-blocking properties of labetalol make it especially attractive in this situation.

Related Topics:
Shear stress - Sodium nitroprusside - Beta blocker - Esmolol - Propranolol - Labetalol

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Calcium channel blockers can be used in the treatment of aortic dissection, particularly if there is a contraindication to the use of beta blockers. The calcium channel blockers typically used are verapamil and diltiazem, because of their combined vasodilator and negative inotropic effects.

Related Topics:
Calcium channel blocker - Verapamil - Diltiazem

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If the individual has refractory hypertension (persistent hypertension on the maximum doses of three different classes of antihypertensive agents), involvement of the renal arteries in the aortic dissection plane should be considered.

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Surgical management

Indications for the surgical treatment of aortic dissection include an acute proximal aortic dissection and an acute distal aortic dissection with one or more complications. Complications include compromise of a vital organ, rupture or impending rupture of the aorta, retrograde dissection into the ascending aorta, and a history of Marfan's syndrome.

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A number of comorbid conditions increase the surgical risk of repair of an aortic dissection. These include:

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• Prolonged pre-op evaluation (increased length of time prior to surgery)
• Advanced age
• Comorbid disease states (ie: coronary artery disease)
• Aneurysm leakage
• Cardiac tamponade
• Shock
• Past history of myocardial infarction or CVA
• History of renal failure (either acute or chronic renal failure)

The objective in the surgical management of aortic dissection is to resect (remove) the most severely damaged segments of the aorta, and to obliterate the entry of blood into the false lumen (both at the initial intimal tear and any secondary tears along the vessel). While excision of the intimal tear may be performed, it does not significantly change mortality.

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Long term follow-up

The long term follow-up in individuals who survive aortic dissection involves strict blood pressure control. The relative risk of late rupture of an aortic aneurysm is 10 times higher in individuals who have uncontrolled hypertension, compared to individuals with a systolic pressure below 130 mmHg.

Related Topics:
Aortic aneurysm - Hypertension

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The risk of death is highest in the first two years after the acute event, and individuals should be followed closely during this time period. 29% of late deaths following surgery are due to rupture of either the dissecting aneurysm or another aneurysm. In additions, there is a 17 to 25% incidence of new aneurysm formation. This is typically due to dilatation of the residual false lumen. These new aneurysms are more likely to rupture, due to their thinner walls.

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Serial imaging of the aorta is suggested, with MRI being the preferred imaging technique.

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