• Clinical science

Aortic dissection

Abstract

An aortic dissection is a tear in the inner layer of the aorta which leads to a progressively growing hematoma between in the intima-media space. It commonly occurs in hypertensive males between the 4th and 6th decade. Patients complain of a sudden onset and severe pain radiating into the thorax, back, or abdomen. Initial chest x-ray shows a widened mediastinum. The diagnosis is confirmed with a contrast-enhanced CT in stable patients and transesophageal echocardiography in unstable patients. Treatment options range from conservative measures (e.g., blood pressure optimization) to surgery (aortic prosthesis), depending on the localization and severity of the dissection. Complete occlusion of branching vessels and aortic rupture are common complications. Even with treatment, mortality rates associated with aortic dissection are high.

Epidemiology

References:[1][2][3]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[4][3]

Classification

Stanford classification

  • Type A; (proximal; ; DeBakey type I and II): ascending aorta dissection, including retrograde extension from the descending aorta (independent of the site of origin and propagation)
  • Type B; (distal; ; DeBakey type III): descending aorta dissection, originating distal to the left subclavian artery

Stanford A = Affects ascending aorta; Stanford B = Begins beyond brachiocephalic vessels.

DeBakey classification (rarely used)

  • Type I: involves the ascending and descending aorta, as well as all distal segments of the aorta
  • Type II: involves the ascending aorta and/or the aortic arch only
  • Type III: involves the descending aorta only

References:[5]

Pathophysiology

  • Anatomic site of origin
  • Transverse tear in the aortic intima (“entry”) → blood enters the media of the aorta and forms a false lumen in the intima-media space hematoma forms and propagates longitudinally downwards
    • → rising pressure within the aortic wall → rupture
    • → occlusion of every single branching vessel (e.g., coronary arteries, arteries supplying the brain, renal arteries, arteries supplying the lower limbs) → ischemia in the affected areas (see “Complications” below)
    • → a second intimal tear may result in a “reentry” into the primary aortic lumen.

References:[1][6]

Clinical features

  • Sudden and severe tearing/ripping pain
    • Location
      • Anterior chest (ascending) or back (descending)
      • Interscapular or retrosternal pain
      • Neck and jaw
      • Abdomen or periumbilical, colicky pain
    • Character: migrates as the dissected wall propagates caudally
  • ↑ BP (if the patient is hypotensive, consider shock from blood loss or a cardiac tamponade)
  • Asymmetrical blood pressure and pulse readings between limbs
  • Syncope, diaphoresis, confusion or agitation
  • A heart murmur (an aortic regurgitation in a proximal dissection)

References:[4]

Diagnostics

  • Initial imaging: Chest x-ray (AP view) showing a widened mediastinum (> 8 mm)
  • Definitive diagnostic tests (determine the type of lumen, location, and extent of the dissecting membrane)
    • In stable patients → Contrast-enhanced CT angiography (gold standard) High sensitivity and specificity.
    • In unstable patients, renal insufficiency, contrast allergyTransesophageal echocardiography (TEE)
    • If contrast-enhanced CT is contraindicated in stable patients → Magnetic resonance angiography (MRA)
  • ECG: in all patients, although normal or signs of left ventricular hypertrophy

References:[4][7][8][9]

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

Stanford A dissections; (involvement of the ascending aorta) require immediate surgery; , while Stanford B dissections are generally treated conservatively unless complications (e.g., rupture or occlusion) occur.

Conservative treatment

Surgery

  • Open surgery with a polyester graft implantation
  • Possibly, endovascular treatment: aortic stent implantation (only in type B dissections and if the operative risk is too high)

Avoid thrombolytic therapy in patients with suspected aortic dissection!
References:[4]

Complications

References:[4]

We list the most important complications. The selection is not exhaustive.

Prognosis

  • Generally, the 30-day mortality is high
  • Type A dissection
    • After surgery ∼ 30%
    • Conservative treatment: ∼ 60%
  • Type B dissection
    • Conservative treatment ∼ 10%
    • After surgery ∼ 30%

References:[4]

Prevention

  • Blood pressure control
  • Smoking cessation
  • Screening and repair of rapidly expanding aneurysms (also see “Therapy” and “Prevention” sections in aortic aneurysms)
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  • 4. Khan AN, Cho KJ. Aortic Dissection Imaging. In: Aortic Dissection Imaging. New York, NY: WebMD. http://emedicine.medscape.com/article/416776-overview#showall. Updated May 13, 2016. Accessed December 4, 2016.
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last updated 11/20/2018
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