Fact-sheet: Aortic dissection


Updated on 07/01/2020 at 9:54 AM

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Definition

Intimal tear resulting in longitudinal cleavage of the aortic media, creating a true lumen and a false lumen separated by the intimal flap

Clinical features

The clinical presentation is nonspecific:

Population at risk:

- Most common: male + age > 60 years + personal history of hypertension

- In practice: patients of ANY AGE can be affected:

  • 17 to 59 years: 27% of cases (particularly young adults with connective tissue disease or Marfan syndrome)
  • 60 to 74 years: 40% of cases
  • over 75 years: 33% of cases

Onset pattern:

  • most common: within 2 hours after onset of lesions
  • less commonly: delayed onset more than 12 hours after onset of lesions (50% of patients do not undergo surgical treatment within 24 hours)

Physical examination:

  • acute pain (85% of cases), severe (90% of cases), anterior chest (44–71% of cases) or posterior chest (33–41% of cases) or back (47–64% of cases) or abdominal (22–43% of cases)
  • absence of pain (2–6% of cases)
  • aortic regurgitation (12–44% of cases)
  • loss of a peripheral pulse (9–30% of cases)
  • ischemic complications: stroke (cerebral infarction) ++, acute coronary syndrome (due to myocardial ischemia) (sometimes the presenting feature +++)

Laboratory findings

Elevated troponin level (in cases of coronary ischemia)

Radiography

- Normal in 10 to 40% of cases

- Mediastinal widening

- Abnormal aortic contour

- Displacement of aortic calcifications

- Left pleural effusion

Allows exclusion of differential diagnoses of acute chest pain (notably pneumothorax)

Ultrasound

Transthoracic echocardiography (TTE) can allow diagnosis of ascending aortic dissection by demonstrating the intimal flap.

The sensitivity of TTE is between 78 and 100% for the diagnosis of type A dissection, but only 31 to 55% for dissections involving the descending thoracic aorta.

TTE also allows diagnosis of aortic regurgitation and hemopericardium.

CT

Performed with 2 thoracic phases and one acquisition at the portal phase of the abdomen and pelvis

1- without injection of iodinated contrast material, mandatory for the diagnosis of intramural hematoma.

2- with injection of iodinated contrast material at the arterial phase.

Positive diagnosis: visualization of the intimal flap separating the 2 lumina as a thin membrane within the aortic lumen.

Indirect signs:

  • displacement of intimal calcifications toward the aortic lumen
  • increase in aortic diameter

Complication:

  • hemopericardium
  • hemomediastinum
  • hemothorax due to rupture of the false lumen into the pleura

Assessment of the extension of the dissection to the supra-aortic trunks, the coronary arteries, the abdominal visceral arteries, down to the common femoral arteries

MRI

No recommendation for emergency use.

The diagnosis of dissection on MRI relies on demonstrating the intimal flap and the double lumen.

When the false lumen is rapidly flowing, the intimal membrane is visible as a linear band of intermediate signal on T1-weighted Spin Echo, separating two flow voids.

Visualization of this intimal flap may be more difficult if flow within the false lumen is slow.

Contrast-enhanced magnetic resonance angiography (gadolinium) (3D-Gd MRA) complements the non-contrast acquisitions. When dissection of the descending thoracic aorta extends into the abdominal aorta, extension of the dissection to the visceral branches of the abdominal aorta or compression of the intimal flap over their ostia should be sought.

Management

Medical-surgical emergency

Symptomatic treatment: analgesics + antihypertensives (IV beta-blockers)

Etiologic treatment:

  • if Stanford type A (ascending aorta involved): emergency surgical treatment
  • if Stanford type B (ascending aorta spared): medical treatment + assessment/treatment of complications

Classification

Stanford classification:
- type A = dissection originating proximal to the supra-aortic trunks, involving the ascending aorta or the aortic arch
- type B = dissection beginning distal to the supra-aortic trunks, which are spared