Aortic Dissection: Causes, Diagnosis, Management

Aortic dissection is a critical, life-threatening condition where a tear occurs in the inner layer (intima) of the aorta. This allows blood to surge through the tear, creating a “false lumen” or second channel between the layers of the aortic wall.

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## Classification Systems

Clinicians primarily use two systems to categorize dissections, which dictates the urgency and type of intervention required.

1. Stanford Classification (Most Common)

• Type A: Involves the ascending aorta. This is a surgical emergency due to the risk of aortic rupture, coronary artery occlusion, or acute aortic regurgitation.
• Type B: Involves only the descending aorta (distal to the left subclavian artery). These are often managed medically unless complications arise.

2. DeBakey Classification

• Type 1: Originates in the ascending aorta, aortic arch, and descending aorta
• Type 2: Originates in and is limited to the ascending aorta
• Type 3: Begins in the descending aorta and extends distally above the diaphragm (type 3a) or below the diaphragm (type 3b)

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## Pathophysiology & Risk Factors

The primary driver is often a combination of high wall tension and a weakened arterial media.

• Hypertension: The most significant risk factor (present in ~70-80% of cases).
• Genetic Connective Tissue Disorders: Marfan syndrome, Ehlers-Danlos syndrome, and Loeys-Dietz syndrome.
• Congenital Anomalies: Bicuspid aortic valve or Coarctation of the aorta.
• Inflammatory Conditions: Giant cell arteritis.
• Iatrogenic/Trauma: Cardiac catheterization or blunt force trauma.

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## Clinical Presentation

The “classic” presentation is often described as:

• Pain: Sudden, excruciating, “tearing” or “ripping” sensation.
• Location: Anterior chest pain (Type A) or interscapular back pain (Type B).
• Neurological Deficits: Stroke symptoms or paraplegia if branch vessels (carotids or spinal arteries) are involved.
• Pulse Deficits: A significant difference in blood pressure between arms or absent pulses in the lower extremities.
• New Diastolic Murmur: Indicative of acute aortic regurgitation.

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## Diagnostic Evaluation

Time is the most critical factor in diagnosis.

• CT Angiography (CTA): The gold standard for stable patients due to high sensitivity and specificity. It clearly visualizes the intimal flap and the extent of the dissection.
• Transesophageal Echocardiography (TEE): Preferred for unstable patients or in the OR; it is excellent for evaluating the proximal aorta and aortic valve involvement.
• ECG: Often used to rule out a myocardial infarction, though a dissection can cause an MI if it involves the coronary ostia (most commonly the RCA).

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## Management Strategies

Initial Stabilization (The “Anti-Impulse” Therapy)

The goal is to reduce the shear stress on the aortic wall by lowering heart rate and blood pressure:

• Heart Rate Target: < 60 bpm (typically using IV Beta-blockers like Esmolol or Labetalol).
• Systolic BP Target: 100–120 mmHg.

Definitive Treatment

• Stanford Type A: Requires urgent surgical repair to replace the ascending aorta and potentially the aortic arch or valve.
• Stanford Type B: Generally managed with aggressive medical therapy (BP control). However, Thoracic Endovascular Aortic Repair (TEVAR) is indicated if there is evidence of malperfusion, refractory pain, or rapid expansion.

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## Complications

• Aortic Rupture: Leading to cardiac tamponade or hemothorax.
• Malperfusion Syndrome: Ischemia to the brain, kidneys, gut, or limbs.
• Aneurysmal Dilation: The false lumen may weaken over time, leading to chronic aneurysm formation.