2. Epidemiology of ischaemic heart disease

• Leading cause of death in US and the world
• Higher risk in men than women
• Rising tendency in developing countries
• Accounts for nearly 30% of all disability cases
• Especially affects middle aged population
• Proposed theories
  • Lipid theory
    • Decreasing blood cholesterol decreases IHD
    • Oxidized LDL enters vessel wall
  • Blood coagulation theory
    • Increased coagulation tendency
    • Evidence:
      • Increased plasma fibrinogen
      • Increased thromboxane A2/prostaglandin ratio
      • Increased lipoprotein(a) (inhibits fibrinolysis)
  • Blood vessel wall theory
    • Collagen increases, elastic fibres decrease
    • Increases microthrombi formation and lipid infiltration
• Pathomechanism of atherosclerosis
  • Endothelial dysfunction
    • HT
    • Smoking
    • Diabetes
    • High LDL
    • Aging
  • Leukocyte migration into tunica intima
  • Proliferation of smooth muscle cells in tunica intima
  • Oxidized LDL accumulates, macrophages transform into foam cells
  • Foam cells and smooth muscle cells produce collagen -> forms fibrous plaque
  • Inflammation in fibrous plaque weakens the fibrous cap
  • Plaque ruptures, exposing thrombogenic material