Thromboses

Thromboses are the formation of blood clots within blood vessels, which can obstruct blood flow and lead to tissue ischemia. The term thromboses is often used to describe clots occurring in various vessels and can be venous or arterial. Common clinical scenarios include deep vein thrombosis, pulmonary embolism, myocardial infarction, ischemic stroke, and cerebral venous sinus thrombosis.

Pathophysiology and risk factors are summarized by Virchow's triad: hypercoagulability, endothelial injury, and abnormal blood flow. Clots are composed of platelets and fibrin, with arterial thrombi often rich in platelets and venous thrombi more fibrin- and red blood cell–rich. Risk factors include cancer, surgery, immobilization, pregnancy and postpartum state, estrogen therapy, antiphospholipid syndrome, and inherited thrombophilias (such as factor V Leiden). Clots may extend locally, propagate, or embolize to distant sites, most notably the lungs in pulmonary embolism.

Diagnosis and treatment rely on imaging and anticoagulation. Duplex ultrasound is routinely used for suspected deep vein thrombosis; CT pulmonary angiography is standard for suspected pulmonary embolism; MRI or CT can diagnose cerebral venous thrombosis. D-dimer testing aids evaluation in selected patients. First-line treatment is anticoagulation, typically starting with heparin or a low-molecular-weight heparin and transitioning to a direct oral anticoagulant or warfarin. In selected life-threatening cases, thrombolysis or mechanical thrombectomy may be indicated. The duration of therapy depends on the provoking factors and recurrence risk.

Prevention focuses on risk reduction and prophylaxis in high-risk settings. Long-term complications include post-thrombotic syndrome after deep vein thrombosis and chronic thromboembolic pulmonary hypertension after pulmonary embolism. Outcomes depend on the thrombosis location, extent, and timeliness of treatment.