60. Thrombosis. Causes and consequences

Thrombosis, formation of blood clots where they're not physiologically necessary, is an important component of various common disorders. Thrombi can cause problems locally or they can loosen and travel to other vessels, a process called embolisation. Thrombi can form in veins or arteries.

Etiology

Virchow’s triad described the major risk factors for thrombosis:

• Impaired blood flow (stasis)
  • Immobilization (bed-ridden people, long flights)
  • Varicose veins
  • Obesity
  • Pregnancy
  • Polycythaemia vera (viscosity increased)
  • Stroke
• Endothelial damage
  • Hypertension
  • Phlebitis
  • Vasculitis
  • Ischemic injury
• Hypercoagulability
  • Leiden mutation of factor V
  • Smoking
  • Antithrombin-III deficiency
  • Protein C or S deficiency
  • Polycythaemia vera (viscosity increased)
  • SLE
  • Oestrogen therapy
  • Obesity
  • Cancer

Consequences

Deep vein thrombosis

When a clot forms in the deep veins of the leg, the condition is called deep vein thrombosis (DVT). This can cause pain and swelling of the leg.

Pulmonary embolism

One major consequence of venous thrombosis is pulmonary embolism. The thrombus usually forms in the deep veins of the leg (deep vein thrombosis, DVT) from where it loosens and travels to the pulmonary circulation. Common symptoms of partial pulmonary embolisms include:

• Dyspnoea
• Chest pain
• Haemoptysis
• Cough
• Tachypnoea
• Tachycardia

Many pulmonary embolisms are asymptomatic. Multiple microembolisms can progressively decrease the total diameter of pulmonary vessels, which causes type 4 pulmonary hypertension and cor pulmonale. Total and sub-total pulmonary embolisms are deadly.

Laboratory findings show increased amount of D-dimers, a breakdown product of fibrin. Echocardiography, CT, pulmonary angiography and doppler ultrasound can also be used.

Acute myocardial infarction

Acute myocardial infarction occurs when thrombosis occurs on a ruptured atherosclerotic plaque in a coronary artery.