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Aortic Dissection

Symptoms & Signs

  • Chest pain
    • Sudden onset
    • Severe, sharp and tearing
    • May be localized to the front or back of the chest
      • Often the interscapular region
    • Typically migrates with propagation of the dissection
  • Diaphoresis
  • Syncope
  • Dyspnea
  • Weakness
  • Physical findings (frequencies from registry data[1])
    • Reflect complications resulting from the dissection occluding the major arteries
      • Hypertension (more common in type B) or hypotension (more common in type A)
      • Loss of pulses
        • ~30 % of type A
        • ~20% of type B
      • Acute aortic regurgitation
        • ~44% of type A, 12% of type B
        • Bounding pulses
        • Wide pulse pressure
        • Diastolic murmur, often radiating along the right sternal border
        • Congestive heart failure
      • Pulmonary edema (rales)
      • Neurologic findings due to carotid artery obstruction or spinal cord ischemia
        • Hemiplegia
        • Hemianesthesia
        • Paraplegia
      • Bowel ischemia
      • Renal ischemia with hematuria
      • Myocardial ischemia
    • Reflect complications resulting from compression of adjacent structures (superior cervical ganglion, superior vena cava, bronchus, esophagus) by the expanding dissection causing aneurysmal aortic dilatation
      • Horner’s syndrome
      • Superior vena cava syndrome
      • Hoarseness
      • Dysphagia
      • Airway compromise
    • Cardiac tamponade
  • 10% of patients present without typical chest pain and pulse deficits.[1]

Differential Diagnosis

  • Other causes of chest pain
    • Myocardial infarction (MI)
      • An electrocardiogram (EEG) that shows no evidence of myocardial ischemia is helpful in distinguishing aortic dissection from MI.
      • Rarely, dissection involves the right or left coronary ostium and causes acute MI.
    • Unstable angina
    • Aortic aneurysm without dissection
    • Pulmonary disorders
    • Pericardial disease
    • GI disorders

Diagnostic Approach

  • A high index of suspicion is important in:
    • Patients with evolving signs and symptoms
    • Patients with simultaneous multiple neurologic and vascular complaints
    • Up to 30% of patients with dissection are initially suspected to have other conditions.[2]
  • Transesophageal echocardiography, CT, and MRI are the diagnostic procedures of choice over contrast aortography.
    • Their relative utility depends on availability and expertise in individual institutions as well as on the hemodynamic stability of the patient.
    • CT and MRI are less suitable for unstable patients; echocardiography should be the initial test in these patients.
    • CT has advantage of being able to exclude other diagnoses (e.g., pulmonary embolism) simultaneously.
    • Transesophageal echocardiography is a more sensitive test than transthoracic echocardiography, but the latter is better tolerated by unstable patients.
  • Chest x-ray is not a reliable test to rule in or rule out aortic dissection, but will be abnormal in a majority of patients.

Laboratory Tests

  • No laboratory tests are helpful in diagnosing aortic dissection.
  • D-dimer
    • A negative d-dimer test has been proposed as a useful test for ruling out dissection.
      • However, data currently do not support the use of d-dimer as the sole modality in diagnosis.[3]
  • Laboratory abnormalities depend on the vascular sequelae of the dissection.

Imaging

  • Chest radiography
    • Abnormal in 60–90%
    • May be normal, particularly in type A dissections[2]
    • Widened mediastinum
    • Pleural effusion (usually left-sided) may be present.
    • Dissections of the descending thoracic aorta: Descending aorta may appear to be wider than the ascending portion.
  • Dissection can be confirmed by CT, MRI, or ultrasonography (especially transesophageal echocardiography).
  • CT and MRI
    • Highly accurate in identifying the intimal flap and the extent of the dissection
    • Each has a sensitivity and specificity > 90%.
    • Useful in recognizing intramural hemorrhage and penetrating ulcers
    • CT reconstructions can be used to guide surgery.
    • MRI can detect blood flow.
      • May be useful in characterizing antegrade vs retrograde dissection
  • Echocardiography
    • Transthoracic echocardiography
      • Imaging technique of choice in unstable patients
      • Overall sensitivity of 60–85%
        • Sensitivity > 80% in diagnosing proximal ascending aortic dissections
        • Less useful for detecting dissection of the arch and descending thoracic aorta
    • Transesophageal echocardiography
      • Requires greater skill and patient cooperation
      • Very accurate in identifying dissections of the ascending and descending thoracic aorta, but not the arch
        • 98% sensitivity and ~90% specificity
    • Echocardiography provides important information on the presence and severity of:
      • Aortic regurgitation
      • Pericardial effusion
  • Aortography
    • Recommended if results of noninvasive imaging techniques are not definitive
    • May be used to:
      • Document diagnosis
      • Identify entry point, intimal flap, and the false and true lumina
      • Establish extent of dissection into the major arteries
    • Sensitivity
      • 70% for an intimal flap
      • 56% for the site of intimal tear
      • 87% for false lumen
      • Cannot recognize intramural hemorrhage
  • Coronary angiography
    • May be performed concomitantly with aortography in high-risk patients in evaluation and preparation for surgery

Diagnostic Procedures

  • EGC
    • If no evidence of myocardial ischemia, helpful in distinguishing aortic dissection from myocardial ischemia
    • However, ECG changes can mimic those of acute coronary syndrome.

Classification

  • Anatomic classification
    • DeBakey classification
      • Type I: Dissection involves both ascending and descending aorta.
        • Intimal tear occurs in the ascending aorta but involves the descending aorta as well.
      • Type II: Dissection is limited to the ascending aorta.
      • Type III: Dissection is limited to the descending aorta.
    • Stanford classification
      • Type A: Dissection involves the ascending aorta (proximal dissection).
        • Independent of site of tear and distal extension
      • Type B: Dissection is limited to the descending aorta (distal dissection).
  • From a management standpoint, classification into type A or B is more practical and useful because DeBakey types I and II are managed in a similar manner.
  • Mechanistic classification
    • Svensson classification
      • Class 1: classic dissection with true and false lumen
      • Class 2: intramural hematoma or hemorrhage
      • Class 3: subtle dissection without hematoma
      • Class 4: atherosclerotic penetrating ulcer
      • Class 5: iatrogenic or traumatic dissection

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Last updated: September 20, 2009
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