Term | Definition and examples |
No identifiable risk factor (unprovoked) | VTE where no identifiable provoking event or risk factor is evident |
Identifiable risk factor (provoked) | VTE caused by a known event or risk factor (eg, surgery, hospital admission, estrogen) |
Transient risk factor | Risk factors for VTE that are reversible - Major risk factors (ie, transient factors that favor limited-duration anticoagulation):
- Major surgery >30 minutes, hospitalization or confined to bed with "bathroom privileges" for ≥3 days due to acute illness, trauma with fractures, estrogen therapy, pregnancy or puerperium
- Minor risk factors (ie, transient factors that favor continuing anticoagulation):
- Minor surgery <30 minutes, hospitalization <3 days, reduced mobility at home ≥3 days due to acute illness, lower extremity injury without fracture with reduced mobility ≥3 days, long-haul flight
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Persistent risk factor | Risk factors that persist over a prolonged period of time - Examples include irreversible conditions such as active malignancy, obesity, active inflammatory bowel disease, active autoimmune disease, continued hormonal therapy, nephrotic syndrome, recurrent long-haul flights
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Proximal DVT of lower extremity | VTE in the popliteal, femoral, or iliac veins |
Distal DVT of lower extremity | VTE without a proximal component and confined to the calf veins (peroneal, posterior, anterior tibial, and muscular veins). The popliteal vein is not involved. |
Pulmonary embolism | Thrombus in the main, lobar, segmental, or subsegmental branches of the pulmonary artery |
Phases of anticoagulation therapy | - Initiation phase (initial therapy) – Administered immediately following a diagnosis of VTE.
- Treatment phase (also called "maintenance phase" or "long-term") – Administered for a finite period beyond initiation, usually 3 to 6 months and occasionally up to 12 months.
- Extended phase (indefinite) – Administered beyond the finite period, sometimes indefinitely.
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DOACs | Includes direct factor Xa and thrombin inhibitors. Also known as newer/novel oral anticoagulants (NOAs), non-vitamin K antagonist oral anticoagulants (NOACs), and target-specific oral anticoagulants (TOACs, TSOACs). |