Vascular: Aortic Dissection

Aortic Dissection

Basics

  • Intimal Disruption Allows Blood Extravasation Between the Layers of the Wall
  • Origination
    • Ascending Aorta (50-65% – Most Common)
    • Descending Aorta (20-30%)
    • Aortic Arch (< 10%)
  • High Mortality
    • Ascending Dissection – From Cardiac Failure (Tamponade, Regurgitation/Insufficiency or Coronary Occlusion)
      • Most Common Cause of Death: Cardiac Failure
    • Descending Dissection – From End Organ Failure by Vessel Obstruction

Pathophysiology

  • Initial Lesion: Intimal Tear
  • Blood Extravasation Between the Layers of the Vessel Wall
    • Typically Spreads Antegrade but Can Spread Retrograde
    • “False Lumen” Created Between “Intimal Flap” & Remaining Wall
    • May Have Distal Fenestrations (Intimal Connections) to Maintain Patency
  • Malperfusion Syndrome
    • Occurs When Branch Occlusion Causes End-Organ Ischemia
    • Dynamic Obstruction
      • More Common (80%)
      • Etiologies:
        • Insufficient Flow Through the True Lumen – Varies with Vessel Circumference, Blood Pressure, Heart Rate and Peripheral Resistance
        • Mobile Intimal Flap Prolapse Occluding Branch Vessel Ostium
      • Obstruction is Intermittent in Nature & Responds Better to Beta-Blocker Management
    • Static Obstruction
      • Etiology: Narrowing/Occlusion of Branch Vessels from False Lumen Protrusion into the Branch Vessel with Associated Thrombosis
      • Obstruction is Consistent

Aortic Dissection Specimen and Intravascular Imaging 1

Classification

  • DeBakey Classification Mn
    • Type I: Both – Tear Originates in Ascending & Extends to Descending
    • Type II: Ascending – Tear Originates in Ascending & Confined to Ascending
    • Type III: Descending – Tear Originates in Descending
      • IIIa: Confined to Thoracic Aorta
      • IIIb: Originates in Thoracic Aorta & Extends to the Abdominal Aorta
  • Stanford Classification Mn
    • Type A Aortic Dissection (TAAD): Originates in the Ascending Aorta
      • Includes DeBakey Type I & II
    • Type B Aortic Dissection (TBAD): Originates in the Descending Aorta
      • Includes DeBakey Type III

DeBakey Classification 1

Stanford Classification 1

Risk Factors

  • Hypertension (70%)
  • Male Sex (4:1)
  • Aortic Wall Abnormality (Bicuspid Aortic Valve, Coarctation)
  • Cystic Medial Necrosis
  • Connective Tissue Disorders (Marfan & Ehlers-Danlos)
  • Pregnancy
  • Cocaine
  • Trauma

Presentation

  • Pain (Back/Chest/Abdomen) – Most Common
  • Pulse Deficit
  • Limb Ischemia
  • Mesenteric Ischemia
  • Cardiac Tamponade
  • Aortic Insufficiency
  • Myocardial Infarction
  • Syncope/Stroke

Diagnosis

  • Gold Standard: CTA
  • Highest Sensitivity: TEE

Aortic Dissection on CTA 1

Aortic Dissection – Treatment

Initial Management

  • Initial Tx: β-Blockers & Vasodilator (Sodium Nitroprusside)
    • Reduce Systolic Blood Pressure & Pulsatile Load/Aortic Stress (dP/dt – Derivative of Pressure/Time from Left Ventricle)
    • Give β-Blockers Before Vasodilator – Avoid Reflex Sympathetic Stimulation
    • Agent of Choice: Esmolol for Goal Systolic Blood Pressure < 120 mmHg within 20 Minutes

Type A

  • Repair All Type A Aortic Dissections Mn
  • Access: Median Sternotomy
    • May Need Cervical/Supraclavicular Incisions to Visualize Great Vessels
  • Procedure: Excision with Interposition Synthetic/Dacron Graft
    • May Also Require Aortic Valve Replacement/Repair

Type B

  • Uncomplicated: Medical Management
    • *Role of Endovascular Stenting in Uncomplicated Patient’s is Evolving
  • Complicated: Thoracic Endovascular Aortic Repair (TEVAR)
    • Indications:
      • Malperfusion Syndrome
      • Refractory Severe Hypertension
      • Refractory Severe Chest Pain
      • Progression/Expansion
      • Impending Rupture
  • Ruptured: Open Surgical Repair
    • Access: Left Posterolateral Thoracotomy
      • May Need Thoracoabdominal Incision

Postoperative Complications

  • Aortic Aneurysm
    • Risk: 30%
  • Paraplegia
    • From Intercostal Artery Occlusion
  • Recurrent Dissection
    • Most Common in Marfan Syndrome
  • “Bird’s Beaking” of Endograft
    • Proximal Edge Pulled Away from Aortic Wall
    • Allows for Recurrent Dissection
    • Risks Graft Migration, Collapse or Occlusion

Mnemonics

DeBakey Classification

  • Dissections are B.A.D.
    • 1 – Both
    • 2 – Ascending
    • 3 – Descending

Stanford Classification

  • A-A: Type A – Ascending

Repair of Aortic Dissections

  • A-A: All Ascending Are Repaired

References

  1. Tran TP, Khoynezhad A. Current management of type B aortic dissection. Vasc Health Risk Manag. 2009;5(1):53-63. (License: CC BY-NC-3.0)