Acute Aortic Dissection - Quick Consult
Last Updated / Reviewed: June 2022
Definitions
Pathophysiology
Key History
Key Physical Exam
Risk Factors for AAD / AoD
Classification Systems
Differential Diagnosis
Laboratory & Imaging

Definitions

Acute Aortic Syndromes:
  • Aortic Dissection (AoD). This includes Acute Aortic Dissection (TAD), and the abbreviations may be used interchangeably. AoD is defined as disruption of the media layer of the aorta with bleeding within and along the wall of the aorta resulting in separation of the layers of the aorta. In the majority of patients (90%), an intimal disruption is present that results in tracking of the blood in a dissection plane within the media.
  • Intramural Hematoma (IMH). When the term IMH is used strictly, there is no intimal defect such as a tear or an ulcer. On noninvasive imaging, 15% of patients with aortic dissection syndromes have an apparent IMH without evidence of an intimal tear. Autopsy studies show only 4% have no visible intimal tear; indeed, at the time of surgery, a tear is found in most patients.
  • Penetrating Atherosclerotic Ulcer (PAU). Extensive atheromatous disease of the aorta may lead to PAU or a localized IMH. PAU may then lead to more severe aortic disease, including IMH and AoD.

Timing of Onset of Initial Symptoms to Presentation
  • Acute dissection is defined as occurring within 2 weeks of onset of pain.
  • Subacute is defined as occurring between 2 and 6 weeks from onset of pain.
  • Chronic is defined as occurring more than 6 weeks from onset of pain.

Thoracoabdominal Aneurysm (TAA): Aneurysm involving the acute and abdominal aorta

Abdominal Aortic Aneurysm (AAA): Aneurysm involving the infradiaphragmatic abdominal aorta
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Pathophysiology

The aorta, like most other arteries, consists of three layers: the intima, the media, and the adventitia. Aortic dissection involves separation of the intima from the adventitia within the aortic wall by a dissecting column of blood propagating through the media via longitudinal cleavage.

Once the dissecting hematoma is established in the media of the aorta, migration can occur either in an antegrade or retrograde fashion, creating a false lumen within the outer half of the media.

The dissection progresses until it ruptures, either back into the true lumen resulting in a "double barrel" aorta and a rare "spontaneous cure," or more commonly, the dissection may rupture out of the adventitia into the pericardium or pleural cavity.

The majority of deaths from aortic dissection are due to rupture of the aorta into the pericardium with subsequent death due to tamponade, or rupture into the pleural cavity with death due to exsanguination.

The severity of the dissection is proportional to the blood pressure and the velocity of ventricular contraction. This fact is utilized in the initial medical treatment of aortic dissection.

The most common site of dissection is the first few centimeters of the ascending aorta, with 90% occurring within 10 centimeters of the aortic valve. The second most common site is just distal to the left subclavian artery. Between 5% and 10% of dissections do not have an obvious intimal tear.

Location: 65% in ascending aorta; 10% in aortic arch; 25% in descending aorta (upper portion)

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Key History

  • Sudden or abrupt onset of pain
  • Ripping or tearing pain in the intrascapular area
  • Key: Movement or migration of pain from chest or upper back to the lower back or abdomen
  • Acute, severe chest pain (anterior chest pain can mimic acute myocardial infarction)
  • Pain extending to the neck or jaw
  • Altered mental status
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Key Physical Exam
  • Diplopia
  • Dysphagia
  • Dyspnea
  • Flank pain if the renal arteries are involved
  • Abdominal findings related to mesenteric ischemia
  • Horner’s syndrome
  • Hypertension
  • Hypotension if associated with cardiac tamponade, hypovolemia, excessive vagal tone
  • Limb paresthesias
  • Pulse deficit carotid, brachial or femoral pulse (i.e., weak or no pulse)
  • A difference of 20 mm Hg between the arms
  • Syncope
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Risk Factors for Development of Acute Aortic Dissection

Conditions Associated With Increased Aortic Wall Stress

Hypertension, particularly if uncontrolled
Pheochromocytoma
Cocaine or other stimulant use
Weightlifting or other Valsalva maneuver
Trauma
Deceleration or torsional injury (e.g., motor vehicle crash, fall)
Coarctation of the aorta

Conditions Associated With Aortic Media Abnormalities
  • Genetic

    Marfan syndrome
    Ehlers-Danlos syndrome, vascular form
    Bicuspid aortic valve (including prior aortic valve replacement)
    Turner syndrome
    Loeys-Dietz syndrome
    Familial acute aortic aneurysm and dissection syndrome

  • Inflammatory Vasculitides

    Takayasu arteritis
    Giant cell arteritis
    Behçet arteritis

  • Other

    Pregnancy
    Polycystic kidney disease
    Chronic corticosteroid or immunosuppression agent administration
    Infections involving the aortic wall either from bacteremia or extension of adjacent infection
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AoD Graphic
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Classification Systems

DeBakey Classification
The DeBakey classification divides aortic dissection into three types:

Age Frequency
Type I Dissections begin in the ascending aorta and extend distally to involve the aortic arch and the descending aorta.
Type II Dissections involve only the ascending aorta.
Type III Dissections involve the descending aorta, distal to the left subclavian artery. Dissections may also propagate in a retrograde fashion to involve the proximal aorta.
Type IIIA Dissections stop above the diaphragm.
Type IIIB Dissections propagate below the diaphragm.

Stanford Classification
In the Stanford classification, all dissections involving the ascending aorta are Type A. All other dissections are Type B.ii

Type A Any dissection involving the proximal aorta. Corresponds to DeBakey Types I and II. Accounts for about 70% of cases.
Type B Dissection of the distal aorta. Corresponds to DeBakey Type III. Accounts for about 30% of cases.
Type A = Surgical emergency w/mortality 15%-20%; if medically treated, 70%-80%; type B managed medically, 11%
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Differential Diagnosis
  • Acute sickle cell chest syndrome
  • Cholecystitis
  • Anxiety disorder
  • Aortic stenosis
  • Cholelithiasis
  • Congestive heart failure
  • Coronary artery disease
  • Costochondritis
  • Esophageal rupture
  • Esophagitis
  • Gastritis
  • GERD
  • Herpes zoster
  • Hiatal hernia
  • Hypertrophic cardiomyopathy
  • Kawasaki syndrome
  • Endocarditis
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Laboratory & Imaging
  • Choice of imaging test depends on clinical setting and availability.
  • CT angiogram (CTA) is most commonly used.
    • Different protocol than CTPA (pulmonary artery) that is used to rule out pulmonary embolism (PE).
    • If both PE and TAD are in the differential diagnosis, order CTA to rule out TAD and also PE. The dissection protocol is excellent at detecting PE, but it is always helpful to alert the radiologist that you are concerned about both.
  • If a high clinical suspicion exists for TAD but initial aortic imaging is negative, a second imaging study should be obtained.
  • Transthoracic echocardiography (TTE) is not sensitive enough to exclude TAD from the differential diagnosis; however, some dissections are seen on TTE—in those instances, TTE is diagnostic.
  • ECG and cardiac markers are usually normal; D-dimer is sensitive but nonspecific.
  • Chest X-ray is abnormal in 80%-90% and may include: depression of left main stem bronchus, loss of aortic-pulmonary window, left sided effusion, apical cap, obliteration of aortic knob, or trachea deviated to right.
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