Venous Thromboembolism Overview

Study Notes

VTE is the formation of a blood clot in a vein, commonly in the deep veins of the lower extremities.
DVT (deep vein thrombosis) is a blood clot in a deep vein.
Pulmonary embolism (PE) is a blood clot that travels to the lungs.
100,000 people die annually in the US from PE, often within 1 hour post the event.
PE is frequently preceded by a DVT in 80% of cases.
VTE is a preventable cause of death in hospitalized patients.
Associated complications include poor quality of life (QoL), post-thrombotic syndrome, and chronic venous insufficiency.

Platelets play an important role in the formation of blood clots.
Exposure to subendothelial substances activates platelets, which stick together to form a platelet plug.
The clotting cascade is activated in response to vascular injury, involving a series of protein interactions.
Intrinsic and extrinsic clotting pathways converge to activate factor X, then factor II (prothrombin), to factor IIa (thrombin), and factor I (fibrinogen) to factor Ia (fibrin).
Clotting is controlled by inhibitors like antithrombin, protein C, protein S, plasminogen, and plasmin.

Factors affecting blood flow, like immobilization and atrial fibrillation, increase clot risk.
Hypercoagulable states, such as antiphospholipid syndrome or protein C/S deficiency, contribute to increased risk.
Endothelial injury from catheters or tumors can promote clot formation.

Symptoms often include unilateral leg swelling, tenderness, and warmth.
Pain may be present.
Homans' sign (pain on dorsiflexion of the foot) is sometimes present but not always significant.
Increased D-dimer levels, a nonspecific marker of clot formation, may be detected.
Duplex/Doppler/Ultrasound, echocardiogram are used for diagnosis.

Symptoms may include shortness of breath (tachypnea), fast heart rate (tachycardia), and chest pain.
Pleuritic chest pain, anxiety, cough, or hemoptysis are additional symptoms.
Increased D-dimer, chest X-ray (CXR), electrocardiogram (EKG), arterial blood gases (ABG), V/Q scan, or CT angiography are diagnostic tests.

Nonpharmacologic methods include graduated compression stockings, intermittent pneumatic compression, early ambulation after surgery, and leg exercises.
Parenteral and oral pharmacologic prophylaxis are options.
Independent risk factors for bleeding include cancer, bleeding history, thrombocytopenia, age >65, renal/liver failure, and the use of anti-platelets or NSAIDs.

Initial therapy is often with heparin or low molecular weight heparin (LMWH) and bridging to warfarin, if needed, for the long term.
Different agents can be used for the long term in acute VTE management.
Direct oral anticoagulants (DOACs) provide an alternative to warfarin and may be chosen in specific circumstances and with appropriate patient stratification.
Thrombolytics, like alteplase, can be used in life-threatening situations or to treat massive PE, but have significant contraindications.
Patients should be evaluated for risk factors and managed accordingly. Monitoring strategies should be developed depending on the therapeutic agent to ensure efficacy and safety of the chosen treatment.