Blood Clots (Thrombus): Formation, Risks, and Complications

What Is a Thrombus?

A thrombus is a blood clot that forms inside a blood vessel (vein or artery) and remains attached to the vessel wall. It is composed of platelets, fibrin, red and white blood cells.

Pathophysiology (Virchow's Triad)

• Endothelial injury: Trauma, surgery, atherosclerosis, inflammation.
• Stasis/turbulent flow: Immobility, heart failure, atrial fibrillation, varicose veins.
• Hypercoagulability: Genetic (Factor V Leiden, prothrombin mutation), acquired (cancer, pregnancy, OCP, antiphospholipid syndrome).

Major Clinical Consequences

• Venous thromboembolism (VTE): Deep vein thrombosis (DVT) → pulmonary embolism (PE).
• Arterial thrombosis: Myocardial infarction, ischemic stroke, limb ischemia.
• Post-thrombotic syndrome: Chronic venous insufficiency after DVT.

Prevention and Treatment

• Anticoagulants (heparin, DOACs, warfarin) for treatment and prophylaxis.
• Mechanical prophylaxis (compression stockings, intermittent pneumatic compression).
• Early mobilization after surgery/illness.
• Thrombolytics or thrombectomy for massive PE or arterial occlusion.

Risk assessment tools (Wells score, Caprini score) guide prophylaxis decisions in hospitalized and surgical patients.