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.
## 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)
## 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.
## 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.
## 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).
## 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.
## 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.