Thoracic Aortic Dissection

• • Often lethal event

  • Degeneration of aortic media is hallmark of disease

  • Pathogenesis controversial

  • 1. Medial degeneration leads to rupture of vasa vasorum

    2. Intimal tears allows blood to shear weakened media

  • Location of intimal tear: Ascending aorta, 62%; arch, 10%; isthmus, 16%; rest in distal aorta

  • Risk factors include:

  • -Hypertension

    -Atherosclerosis

    -Iatrogenic injury (catheter or open heart surgery)

    -Closed chest trauma

    -Marfan syndrome

    -Aortic coarctation

Classification

• • Debakey type I

  • -Originate in ascending aorta

    -Extend beyond left subclavian (Stanford type A)

  • Debakey type II

  • -Involve ascending aorta only

    -Often chronic

    -Associated with aortic valve incompetence (Stanford type A)

  • Debakey type III

  • -Occur distal to left subclavian artery

    -Often extend into abdominal aorta (Stanford type B)

Epidemiology

• • Most common cause of aortic rupture

  • 2000 cases yearly

  • Men affected more often than women

  • Usually occurs in fifth to seventh decades of life

Symptoms and Signs

• • Most common

  • -Severe, tearing chest pain often signifies intimal tear and formation of false lumen

    -Ascending: Pain anterior

    -Descending: Pain posterior between scapulas

  • Hypotension with blood loss, leak into pericardium

  • Sudden death if extends into pericardium or down a coronary artery

  • If involves aortic valve or root, aortic insufficiency and acute congestive heart failure

  • Obstruction of aortic branch vessels:

  • -Stroke

    -Asymmetric extremity pulses

    -Paraplegia

    -Renal failure

    -Acute mesenteric ischemia

    -Lower extremity occlusion

Laboratory Findings

• • ECG: Useful to rule out myocardial infarction (MI)

  • Cardiac enzymes: Rule out MI

Imaging Findings

• • Chest film

  • -50% have widened mediastinum

    -Cardiomegaly if in failure or with pericardial effusion

    -Left pleural effusion if contained rupture

  • Chest CT: Diagnostic procedure of choice

  • Transesophageal echocardiography (TEE)

  • -Information about myocardial function

    -Aortic valve competence

    -Diagnostic

    -Limited in evaluation of arch and descending dissections

  • Magnetic resonance angiography (MRA): Useful but time-consuming

Rule Out

• • MI

• • Physical exam

  • ECG

  • Chest x-ray

  • Chest CT scan

  • Transesophageal echocardiogram

  • MRA if stable

• • Aggressive blood pressure control critical; esmolol commonly used (decreases dP/dT and aortic shear force)

Ascending

• • Death occurs from cardiac tamponade, acute coronary occlusion, acute atrial regurgitation

  • Replacement of ascending aorta with resection of intimal tear

  • Resuspension of aortic valve commissures restores valve competence

Descending

• • Majority have benign course

  • Medical therapy treatment of choice

  • 20% require surgery for rupture or organ ischemia

  • 20% develop aneurysmal dilation of aorta requiring surgery

  • Endovascular stent procedure and fenestration are new approaches being studied

Medications

• • β-Blockers (esmolol)

  • Vasodilators if still hypertensive after β-blockade

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