Aortic dissection natural history, complications and prognosis

Aortic dissection Microchapters
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Case #1

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Aortic dissection carries a very poor prognosis. 90% of patients who are untreated will be dead at one year. Type A dissection is associated with a worse prognosis than type B dissection. Aortic dissection can be complicated by extension to the coronary arteries resulting in myocardial infarction, involvement of the aortic arch to cause stroke, dilation of the route to cause aortic insufficiency, extension into the pericardium to cause pericardial tamponade, and heart failure, and aortic rupture.

Natural History

If the patient remains untreated, the mortality is:

• 1% per hour during the first day
• 75% at 2 weeks
• 90% at 1 year

Complications

The complications of aortic dissection include:

Cardiac

Aortic Rupture

Aortic rupture leads to massive blood loss, hypotension and shock often resulting in death. Indeed, aortic dissection accounts for 3-4% of sudden deaths.

Pericardial Tamponade

Pericardial tamponade can occur due to extension of the dissection into the pericardium.

Acute Aortic Regurgitation

Acute aortic regurgitationdue to the aortic dilation and dissection into the valve structure which can then cause acute pulmonary edema. Aortic insufficiency (AI) occurs in 1/2 to 2/3 of ascending aortic dissections, and the murmur of aortic insufficiency is audible in about 32% of proximal dissections. The intensity (loudness) of the murmur is dependent on the blood pressure and may be inaudible in the event of hypotension. There are multiple etiologies for AI in the setting of ascending aortic dissection. The dissection may dilate the annulus of the aortic valve, so that the leaflets of the valve cannot coapt. Another mechanism is that the dissection may extend into the aortic root and detach the aortic valve leaflets. The third mechanism is that if there was an extensive intimal tear, the intimal flap may prolapse into the LV outflow tract, causing intimal intussusception into the aortic valve preventing proper valve closure.

Myocardial Infarction

Myocardial ischemia or myocardial infarction due to dissection into either the right or left coronary ostium (but most commonly the right coronary artery). Myocardial infarction (heart attack) occurs in 1-2% of aortic dissections. The etiology of the infarction is involvement of the coronary arteries (the arteries that supply the heart) in the dissection. The right coronary artery is involved more commonly than the left coronary artery. If the myocardial infarction is treated with thrombolytic therapy, the mortality increases to over 70%, mostly due to hemorrhage into the pericardial sac causing pericardial tamponade. Because aortic dissection may present to the emergency room physician similar to a myocardial infarction, the physician must be careful to make the proper diagnosis prior to initiating treatment for myocardial infarction, since the treatment regimen for myocardial infarction can be lethal to an individual presenting with aortic dissection.

Thoracic Aortic Aneurysm

Redissection and aortic diameter enlargement as well as aneurysmal dilatation and saccular aneurysm chronically.

Kidney

Renal ischemia due to dissection into the ostium of the renal vessels can lead to hematuria, renal infarction, acute renal failure

Messentery

Visceral ischemia can occur due to extension of the dissection into the superior mesenteric artery.

Lungs

Pleural effusion

A pleural effusion (fluid collection in the space between the lungs and the chest wall or diaphragm) can be due to either blood from a transient rupture of the aorta or fluid due to an inflammatory reaction around the aorta. If a pleural effusion were to develop due to an aortic dissection, it is more commonly in the left hemithorax rather than the right hemithorax.

Peripheral Arterial

Claudication can occur due to an extension of the dissection into the iliac arteries.

Neurologic

• Ischemic cerebrovascular accident (CVA) due to dissection into the head vessels
• Hemiplegia due to dissection into the spinal arteries
• Hemianesthesia due to dissection into the spinal arteries

Compression of Nearby Organs

• Swelling of the neck and face (compression of the superior vena cava or Superior vena cava syndrome)
• Horner syndrome (compression of the superior cervical ganglia)
• Dysphagia (compression of the esophagus)
• Stridor and wheezing (compression of the airway)
• Hemoptysis (compression of and erosion into the bronchus)
• Vocal cord paralysis and hoarseness (compression of the recurrent laryngeal nerve)

Prognosis

The mortality rate is in large part determined by the patient's age and comorbidities.

Pre-Operative and Immediate Post-Operative Prognosis

• 30% in hospital mortality
• 60% 10-year survival rate among treated patients

Type A aortic dissection

• Surgical treatment-30% mortality rate
• Medical treatment-60% mortality rate

Type B aortic dissection

• Surgical treatment-10% mortality rate
• Medical treatment- 30% mortality rate

Long Term Post-Operative Prognosis

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.