DVT what all things I should know for FMGE exam
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I now have comprehensive content from multiple authoritative textbooks to compile a high-yield FMGE answer on DVT. Let me put it all together.
Deep Vein Thrombosis (DVT) — High-Yield FMGE Notes
1. Pathophysiology — Virchow's Triad
The three primary factors leading to DVT (Virchow's triad):
| Component | Examples |
|---|---|
| Endothelial injury | Trauma, surgery, catheter, inflammation |
| Stasis / turbulent flow | Immobility, bed rest, pregnancy, CHF, long flights |
| Hypercoagulability | Factor V Leiden, Protein C/S deficiency, ATIII deficiency, malignancy, OCP, antiphospholipid syndrome |
Stasis is the dominant factor in venous thrombosis. Arterial thrombi are platelet-rich (white); venous thrombi are fibrin/RBC-rich (red, "currant jelly"). — Robbins & Kumar Basic Pathology
2. Risk Factors
Acquired:
- Prolonged immobility, post-surgery (especially orthopedic), trauma, burns
- Malignancy (Trousseau syndrome = migratory thrombophlebitis in disseminated cancer)
- Pregnancy & postpartum (stasis from uterine compression + hypercoagulable state)
- OCP / HRT, obesity, CHF
- Prior DVT, age >50, male sex
Inherited (Thrombophilia):
- Factor V Leiden mutation — most common inherited thrombophilia (APC resistance)
- Prothrombin G20210A mutation
- Protein C deficiency, Protein S deficiency
- Antithrombin III (ATIII) deficiency
- Hyperhomocysteinemia
3. Clinical Features
- Unilateral leg pain, swelling, erythema, warmth
- Tenderness along deep venous distribution
- Pitting edema confined to the symptomatic leg
- Dilated collateral superficial veins
- Rarely: palpable venous cord
Special situations:
- Left leg > right leg (due to May-Thurner syndrome — left iliac vein compressed by the right iliac artery)
- Bilateral DVT in <10% of cases
- Upper extremity DVT: almost always associated with central venous catheter/pacemaker wire. Without a device → Paget-Schroetter syndrome (effort-induced thoracic outlet compression of subclavian vein, dominant arm of young athletes)
Homans sign (calf pain on dorsiflexion): poor predictive value — do NOT use for diagnosis!
4. Differential Diagnosis
- Cellulitis (concurrent DVT only ~3%)
- Ruptured Baker cyst — clinically mimics DVT exactly
- Venous insufficiency
- Gastrocnemius muscle tear, Achilles tendon injury
- Calf muscle hematoma
- Asymmetric edema from systemic causes (CHF, hypoalbuminemia)
5. Wells Score for DVT (Pre-test Probability)
Each criterion = +1 point, except the last:
| Criterion | Points |
|---|---|
| Active cancer (Rx within 6 months / palliative) | +1 |
| Paralysis, paresis, or recent plaster immobilization | +1 |
| Bedridden ≥3 days OR major surgery within 12 weeks | +1 |
| Localized tenderness along deep venous system | +1 |
| Entire leg swollen | +1 |
| Calf swelling ≥3 cm more than asymptomatic side (measured 10 cm below tibial tuberosity) | +1 |
| Pitting edema confined to symptomatic leg | +1 |
| Collateral superficial veins (non-varicose) | +1 |
| Previously documented DVT | +1 |
| Alternative diagnosis at least as likely | −2 |
Score <2 = low probability; ≥2 = high probability — Rosen's Emergency Medicine
6. Diagnosis
D-Dimer
- High sensitivity, low specificity — good for ruling OUT DVT in low pre-test probability
- False positives with: pregnancy, malignancy, recent surgery, advanced age, SLE, sickle cell, rheumatologic disease
- False negatives: warfarin use
- Algorithm: Low Wells score + negative D-dimer → DVT excluded; no imaging needed
Imaging
- Gold standard: Compression Duplex Ultrasonography
- Non-compressibility of the vein = DVT
- 3-point ultrasound: common femoral, femoral, popliteal veins
- Whole-leg adds: great saphenous, posterior tibial, peroneal, gastrocnemius veins
- Contrast venography: historical gold standard, now rarely used
- CT venography / MRI: used in special circumstances (pelvic DVT, iliac thrombosis)
7. Treatment
Anticoagulation (first-line)
| Drug | Key Points |
|---|---|
| DOACs (rivaroxaban, apixaban) | First-choice for most patients; no bridging with LMWH needed; reversal agents available |
| LMWH (enoxaparin) | Preferred in active malignancy and pregnancy; 40 mg SC OD for prophylaxis |
| UFH | When thrombolysis/surgery planned; can be reversed with protamine |
| Warfarin | Requires 4–5 day overlap with parenteral anticoagulation; target INR 2–3; contraindicated in pregnancy |
| Dabigatran | Direct thrombin inhibitor; reversal: idarucizumab |
| Rivaroxaban/Apixaban | Factor Xa inhibitors; reversal: andexanet alfa |
Duration of Anticoagulation
| Situation | Duration |
|---|---|
| Provoked DVT (reversible risk factor) | 3 months |
| Unprovoked DVT (first episode) | 3–6 months |
| Recurrent DVT or ongoing risk factor | Indefinite |
| Cancer-associated DVT | Indefinite (while cancer active) |
Special Contraindications for DOACs
- Pregnancy, severe renal failure, liver failure, antiphospholipid antibody syndrome, high-risk PE
Thrombolysis / IVC Filter
- Catheter-directed thrombolysis: for massive iliofemoral DVT with limb-threatening ischemia
- IVC filter: indicated when anticoagulation is contraindicated or has failed; does NOT replace anticoagulation
Prophylaxis (FMGE favorite!)
- UFH 5000 units SC TDS or Enoxaparin 40 mg SC OD
- Early ambulation + compression stockings
- Extended prophylaxis in high-risk orthopedic/cancer surgery patients
8. Complications
| Complication | Details |
|---|---|
| Pulmonary Embolism (PE) | >95% of PE originates from lower limb DVT; present in ~30% of symptomatic DVT |
| Post-thrombotic syndrome | Chronic venous insufficiency, leg ulcers, skin pigmentation after DVT |
| Phlegmasia cerulea dolens | Massive iliofemoral DVT → venous gangrene (blue, painful, swollen leg) |
| Phlegmasia alba dolens | Massive DVT → white, painful, swollen leg (reflexive arterial spasm) |
9. DVT in Pregnancy
- LMWH is the drug of choice throughout pregnancy
- Warfarin is contraindicated (crosses placenta → warfarin embryopathy, teratogen)
- DOACs are not used in pregnancy (insufficient safety data)
- Risk highest in 3rd trimester and postpartum period
10. Key FMGE One-Liners
| Fact | Answer |
|---|---|
| Most common inherited thrombophilia | Factor V Leiden (APC resistance) |
| Gold standard for DVT diagnosis | Compression duplex ultrasound |
| Historical gold standard | Contrast venography |
| Best drug for DVT in pregnancy | LMWH (enoxaparin) |
| Drug contraindicated in pregnancy | Warfarin |
| DVT + migratory thrombophlebitis in cancer | Trousseau syndrome |
| Left-sided DVT predisposed by artery compression | May-Thurner syndrome |
| Effort-induced DVT of subclavian vein | Paget-Schroetter syndrome |
| Homans sign utility | Poor — not diagnostic |
| D-dimer: false negative with | Warfarin |
| Venous thrombus type | Red (fibrin + RBC rich) |
| DVT in malignancy — preferred drug | LMWH (DOACs increasingly used) |
| Reversal of warfarin | Vitamin K + FFP/PCC |
| Reversal of dabigatran | Idarucizumab |
| Reversal of factor Xa inhibitors | Andexanet alfa |
| IVC filter indication | Anticoagulation contraindicated or failed |
| Anticoagulation duration for provoked DVT | 3 months |
Sources: Rosen's Emergency Medicine, Robbins & Kumar Basic Pathology, Current Surgical Therapy 14e, Fuster and Hurst's The Heart 15e
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