Atherosclerosis Overview and Implications

Introduction to Arterial Sclerosis

  • Definitions:
    • Arteriosclerosis: General term for hardening of arterial walls affecting elasticity.
    • Atherosclerosis: A specific type characterized by plaque buildup primarily in medium to large arteries.
    • Arteriolosclerosis: Hardening of small arteries (arterioles).

Atherosclerosis Overview

  • Endothelium: Inner lining of blood vessels, single-cell layer. Functions:
    • Protects the blood vessel wall from blood flow.
    • Secretes proteins to inhibit clotting.
  • Damage: Caused by factors like low density lipoproteins (LDL), smoking, and high blood pressure.

Role of Low Density Lipoproteins (LDLs)

  • Entry into Endothelium:
    • Damaged endothelium permits LDL entry.
    • Monocytes (white blood cells) follow and oxidize LDLs.
  • Foam Cells Formation:
    • Macrophages consume large quantities of LDLs, die, and form foam cells.
    • Cytokines Release: Attract more monocytes, perpetuating the cycle.
  • Fatty Streaks: Accumulation of foam cells leads to formation of lesions.
    • Thrombogenic Nature: Fatty streaks facilitate blood clot formation.

Smooth Muscle Cell Response

  • Platelet Derived Growth Factor (PDGF): Released by platelets, encourages smooth muscle migration from tunica media to tunica intima.
  • Fibrous Cap Formation:
    • Growing smooth muscle cells secrete collagen and other materials, forming a protective wall around the fatty streak called a fibrous cap.
  • Plaque Structure: Combination of fatty streak and fibrous cap.

Plaque Composition and Effects

  • Calcium Deposits: Atherosclerosis leads to calcium accumulation in plaques, leading to rigidity and hardening of vessels.
  • Inflammation:
    • Atherosclerosis is an inflammatory disease.
    • Elevated C-reactive protein (CRP) indicates ongoing inflammation, presenting as a risk factor for atherosclerosis.

Complications of Atherosclerosis

  • Fibrous Cap Rupture: Can expose foam cells to blood, leading to rapid thrombus formation, further occluding the artery.
    • Effects depend on the artery affected:
    • Coronary Arteries: Can result in angina or myocardial infarction.
    • Carotid Arteries: Risk of strokes.
    • Renal Arteries: Can lead to hypertension due to activation of renin-angiotensin-aldosterone system.
    • Peripheral Arteries: E.g., popliteal artery occlusion can lead to gangrene or claudication.
  • Aneurysms: Weakened walls due to plaque can result in arterial dilations (e.g., abdominal aortic aneurysms).

Prevention Strategies

  • Lifestyle Choices: Maintaining blood pressure, and reducing intake of sugary and fatty foods is crucial.
  • Risk Factors:
    • Age and gender: Older individuals and males/postmenopausal females are at higher risk.
    • Family history increases susceptibility to the disease.