Coronary Artery Dissection

Coronary artery dissection refers to a tear in the intimal layer of a coronary artery, allowing blood to enter the arterial wall and creating a false lumen.

The underlying pathogenesis can differ based on the type of dissection:

1. Spontaneous Coronary Artery Dissection (SCAD)

Pathogenesis:

• Intimal Tear or Medial Hemorrhage: SCAD occurs either from a primary tear in the intima or from spontaneous rupture of the vasa vasorum (small vessels in the arterial wall) causing an intramural hematoma.
• Compression of True Lumen: The intramural hematoma expands and compresses the true lumen, leading to reduced blood flow and myocardial ischemia.
• Underlying Predispositions:
  • Fibromuscular Dysplasia (FMD): A connective tissue disorder affecting medium-sized arteries, weakening the vessel wall.
  • Pregnancy/Postpartum: Hormonal and hemodynamic changes in pregnancy can weaken the arterial wall.
  • Inflammatory Conditions: Such as lupus or vasculitis, causing vessel wall weakening.
  • Stress or Physical Exertion: Often acts as a trigger in predisposed individuals.

2. Iatrogenic Coronary Artery Dissection

Pathogenesis:

• Mechanical Injury: Occurs during medical procedures such as percutaneous coronary intervention (PCI) or catheter manipulation, causing an intimal tear.
• Risk Factors: Tortuous arteries, high-pressure injections, or oversizing of catheters contribute to the risk.

3. Traumatic Coronary Artery Dissection

Pathogenesis:

• Blunt or Penetrating Trauma: Direct injury to the coronary arteries, typically involving the left anterior descending artery (LAD), causing intimal tears or rupture.

4. Atherosclerotic Coronary Artery Dissection

Pathogenesis:

• Plaque Erosion or Rupture: Atherosclerotic plaques may rupture or erode, creating a tear that leads to blood entry into the arterial wall.
• Weakened Vessel Wall: Chronic inflammation and lipid deposits weaken the vessel, predisposing it to dissection.

5. Underlying Pathophysiological Mechanisms:

• Loss of Structural Integrity: Weakening of the connective tissue matrix in the arterial wall.
• Shear Stress: Hemodynamic forces, especially during stress or exertion, can exacerbate the likelihood of a tear.
• Vascular Remodeling: Abnormal angiogenesis or repair processes can predispose vessels to dissection.

Clinical Implications:

Coronary artery dissection leads to myocardial ischemia, manifesting as chest pain, myocardial infarction, arrhythmias, or even sudden cardiac death. Treatment strategies depend on the type and severity, ranging from conservative management to revascularization procedures.