Rapid Review·Cardiovascular
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PHARMACOLOGY
T1Must knowDeep Venous Thrombosis & Anticoagulation
P321
Focus on
Virchow’s triad, and which anticoagulant belongs to which moment.
Key takeaways
The clot
Deep venous thrombosis
a clot within a deep vein, causing swelling, redness, warmth, and pain.Virchow triad, by "SHE"
- Stasis: post-operative state, a long drive or flight, immobilization.
- Hypercoagulability: factor V Leiden, oral contraceptives, pregnancy, malignancy.
- Endothelial damage: exposed collagen triggering the clotting cascade.
Embolic risk depends on location
it is highest in the proximal veins (femoral, iliac, popliteal). Distal calf DVT is much less likely to embolize and often resolves on its own.| Component | Clinical examples |
|---|---|
| Stasis | Post-operative, long flight or drive, immobilization |
| Hypercoagulability | Factor V Leiden, oral contraceptives, pregnancy, malignancy |
| Endothelial damage | Exposed collagen: trauma, surgery, indwelling catheters |
Proving it
Pretest probability first
it decides which test comes next.D-dimer
rules out DVT when the pretest probability is low or moderate, because it has high sensitivity but low specificity. It cannot rule anything in.Compression ultrasound with Doppler
the imaging test of choice, and the first test when the probability is high.Which anticoagulant when
Prophylaxis and acute management
unfractionated heparin or LMWH (enoxaparin).Treatment and long-term prevention
direct oral anticoagulants (rivaroxaban, apixaban).| Setting | Drug |
|---|---|
| Prophylaxis and acute management | Unfractionated heparin or LMWH (enoxaparin) |
| Treatment and long-term prevention | Direct oral anticoagulants: rivaroxaban, apixaban |
A young woman on oral contraceptives has her second unprovoked DVT. Which arm of the triad, and which inherited cause is the exam after?
Hypercoagulability, and the name they want is factor V Leiden.
How it's tested
A post-operative or long-haul-flight patient with a swollen, warm calf is the stem, and the decision point is pretest probability. At low or moderate probability a negative D-dimer ends the workup, because the test is sensitive but not specific; at high probability you go straight to compression ultrasound with Doppler regardless of the D-dimer. The other favourite is a young woman on oral contraceptives with recurrent clots, where factor V Leiden is the hypercoagulability the question wants named.
Go deeper
First Aid 2026 — CV/Pharmacology (p.321) · B&B — Anticoagulants · Mehlman — HY Heme/Onc (heparin vs warfarin, HIT, factor V Leiden)
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