VTE Flashcards
What is a VTE?
Clot formation within the venous circulation
What are the two types of VTE?
DVT and PE
What is a DVT?
A clot formed within a deep vein (usually in the legs)
What is PE?
A clot in the pulmonary arteries
What are the 3 primary factors influencing formation of a pathogenic clot? (Virchow’s triad)
- Damage to vessel wall
- Venous stasis
- Hypercoagulable state
What is the first step of blood clot formation?
Forming a platelet plug
How do platelets adhere to the surface of the vessel?
The glycoprotein Ib receptor on the platelet surface binds to the von Willebrand ligand
When platelets become activated, what do they release?
ADP, serotonin, and thromboxane A2
What is the purpose of ADP, serotonin, and TXA2?
To recruit other platelets to the injured site and cause aggregation
How does platelet aggregation occur?
glycoprotein IIb/IIIa on the platelet surface bind to fibrinogen
What does antithrombin inhibit?
Factors IIa, IXa, and Xa
What is the purpose of protein S?
It’s a cofactor in the activation of protein C
What does protein C do?
It inactivates factors Va and VIIIa
What does TFPI do?
Binds to factor VIIa-TF complex and inhibits activation of factor X
What is plasminogen?
A precursor to plasmin activated by tissue plasminogen activator
What does plasmin do?
It lyses fibrin to form fibrin degradation products
What are the most common places for clot formation?
The muscular veins of the calf or the valve cusp pockets of the deep calf veins
What can a DVT do once formed?
- It can spontaneously lyse
- Extend into more proximal veins
- Embolize to lungs and cause PE
What are the symptoms of a DVT?
- unilateral calf swelling
- calf pain/tenderness
- erythema
- warmth
- palpable cord
- positive Homan’s sign
What are the symptoms of PE?
- Dyspnea
- Pleuritic chest pain
- Anxiety
- Tachypnea
- Tachycardia
- Cough
- Hemoptysis
- Diaphoresis
What are the first steps of diagnosis?
- Risk factor assessment
2. D-dimer
What is a negative d-dimer test result?
less than 500 ng/ml or less than 0.5 mg/ml
Once you confirmed the positive d-dimer, what test is next for DVT?
A non-invasive doppler ultrasonography and B-mode compression ultrasound or an invasive, and more expensive, contrast venography
Once you confirmed the positive d-dimer, what test is next for PE?
A ventilation perfusion lung scan, chest CT scan, invasive pulmonary angiography, or ancillary test.
What examples will cause damage to the vessel wall?
- fractures/trauma
- valvular disease or replacement
- indwelling catheters
- previous DVT/PE
- malignancy
- surgery (orthopedic)
What examples will cause venous stasis?
- immobility/bed rest/paralysis
- pregnancy
- increasing age (>40)
- obesity
