Orientation notes for study. Doses are typical adult doses: check renal function, interactions and your hospital protocol before prescribing.
Definitions
- Deep vein thrombosis (DVT): a blood clot in a deep vein, usually of the leg (calf, popliteal, femoral, iliac veins).
- Pulmonary embolism (PE): a clot (usually from a leg DVT) lodges in the pulmonary arteries.
- Venous thromboembolism (VTE) = DVT + PE: one disease with two faces.
Pathophysiology: Virchow's triad
- Stasis of blood (immobility, surgery, long travel, heart failure, pregnancy, obesity).
- Endothelial injury (trauma, surgery, central lines, previous DVT, inflammation).
- Hypercoagulability (cancer, pregnancy and the pill, thrombophilia, nephrotic syndrome, sepsis, HIV, TB).
Risk factors
- Provoked: recent surgery (hip and knee, abdominal, pelvic), trauma or fracture, immobility (bed rest, long travel, stroke), hospitalisation, cancer and chemotherapy, pregnancy and the postpartum period, oestrogen (combined pill, HRT), central venous catheter.
- Medical: age over 60, obesity, heart failure, nephrotic syndrome, inflammatory bowel disease, HIV, TB, polycythaemia, antiphospholipid syndrome.
- Inherited thrombophilia: factor V Leiden, prothrombin mutation, protein C or S and antithrombin deficiency.
- Previous VTE and family history.
Clinical features
DVT: unilateral calf or leg pain, swelling, tenderness, warmth, redness, pitting oedema and dilated superficial collateral veins; calf circumference more than 3 cm larger than the other side (measured 10 cm below the tibial tuberosity). Severe cases: phlegmasia cerulea dolens, venous gangrene.
PE: sudden dyspnoea, pleuritic chest pain, cough, haemoptysis, tachycardia, tachypnoea, fever (low grade), syncope; massive PE: hypotension, shock, cyanosis, raised JVP, cardiac arrest.
Clinical probability: Wells scores
DVT (Wells): active cancer · paralysis or recent plaster immobilisation · recently bedridden 3 days or more or major surgery within 12 weeks · localised tenderness along deep veins · entire leg swollen · calf swelling more than 3 cm · pitting oedema · collateral superficial veins · previous DVT; minus 2 if an alternative diagnosis is as likely. 2 or more: DVT likely; below 2: unlikely.
PE (Wells): clinical signs of DVT · PE is the most likely diagnosis · HR above 100 · immobilisation or surgery in the last 4 weeks · previous DVT or PE · haemoptysis · malignancy. Above 4: PE likely; 4 or below: unlikely.
Investigations
- Unlikely probability: D-dimer (highly sensitive, low specificity; a negative result excludes VTE). Raised in infection, cancer, pregnancy, surgery, age.
- Likely probability (DVT): compression duplex ultrasound of the leg (non-compressible vein, absent flow).
- Likely probability (PE): CT pulmonary angiogram (CTPA): filling defects in the pulmonary arteries; V/Q scan if CT is not possible (renal failure, contrast allergy, pregnancy).
- Other tests in suspected PE:
- ECG: sinus tachycardia (commonest), S1Q3T3, right bundle branch block, T-wave inversion V1–V4 (right heart strain).
- Chest X-ray: often normal (excludes pneumothorax, pneumonia); wedge-shaped infarct, small effusion.
- ABG: hypoxaemia with low PaCO2.
- Troponin and BNP (right ventricular strain), echocardiogram (right ventricle dilatation).
- Thrombophilia screen only in selected patients (young, unprovoked, recurrent, family history).
- Look for occult cancer in unprovoked VTE (history, examination, basic tests).
Management
Anticoagulation (the mainstay): start immediately if suspicion is high, before the test result.
- DOACs (first-line): rivaroxaban 15 mg twice daily for 21 days, then 20 mg daily; apixaban 10 mg twice daily for 7 days, then 5 mg twice daily.
- LMWH (for example enoxaparin 1 mg/kg twice daily or 1.5 mg/kg daily) then warfarin (target INR 2–3), overlapping for at least 5 days until INR is in range for 2 days: where DOACs are unavailable.
- Pregnancy: LMWH (warfarin and DOACs are contraindicated). Cancer-associated VTE: LMWH or a DOAC. Renal failure: unfractionated heparin.
- Duration: at least 3 months; provoked by a transient factor: 3 months; unprovoked: consider extended (6 months to indefinite) after weighing bleeding risk; cancer while active.
Massive PE (shock): thrombolysis (alteplase) unless contraindicated, or surgical/catheter embolectomy; supportive (oxygen, fluids with care, vasopressors).
IVC filter: if anticoagulation is contraindicated or recurrent PE despite adequate anticoagulation.
Supportive: oxygen, analgesia, early mobilisation; compression stockings only for symptom relief or established post-thrombotic syndrome (not routinely to prevent it).
Prophylaxis (in hospital): risk assess every inpatient; LMWH (enoxaparin 40 mg daily) or fondaparinux ± intermittent pneumatic compression or graduated compression stockings; early mobilisation and hydration; extended prophylaxis after major orthopaedic or cancer surgery; avoid long immobility.
Complications
- PE and death, recurrent VTE, post-thrombotic syndrome (chronic leg swelling, pain, ulcers), chronic thromboembolic pulmonary hypertension (CTEPH), bleeding from anticoagulation, phlegmasia.
Exam points
- Virchow's triad.
- Wells score first, then D-dimer or imaging.
- D-dimer rules out, it does not rule in.
- Anticoagulate before the result if probability is high.
- Sinus tachycardia is the commonest ECG change in PE.
- Massive PE with shock → thrombolysis.
- Pregnancy → LMWH only.
Pharmacology at a glance
Tap a drug name for its full card (how it works, adverse effects, cautions, dose), then use Back to this note to return to this spot. Condition guide: VTE drugs.
| Drug | Class | Role here | Watch for |
|---|---|---|---|
| Rivaroxaban | Direct oral anticoagulant (factor Xa inhibitor) | First-line treatment: 15 mg twice daily for 21 days, then 20 mg daily | Bleeding; avoid in severe kidney disease and pregnancy |
| Apixaban | Direct oral anticoagulant (factor Xa inhibitor) | First-line: 10 mg twice daily for 7 days, then 5 mg twice daily | Bleeding; interactions with rifampicin |
| Heparin | Low-molecular-weight heparin (enoxaparin) | Start at once; pregnancy and cancer; prophylaxis in hospital | Bleeding, low platelets |
| Warfarin | Vitamin K antagonist | When DOACs are unavailable: INR 2–3 | Bleeding; many interactions; teratogenic |
| Alteplase | Thrombolytic | Massive PE with shock | Major bleeding including intracranial |
| Vitamin K | Reversal agent | Reverses warfarin if bleeding or INR very high | Slow onset (hours) |
Anticoagulate first when suspicion is high: do not wait for the scan.
Practice questions
1. A 30-year-old woman on the combined pill has a swollen, painful left calf for 3 days. Wells score is 3. The next investigation is: A. D-dimer · B. Compression duplex ultrasound · C. Venography only · D. Chest X-ray · E. CT head Answer: B. A likely probability goes straight to imaging.
2. A man 5 days after hip surgery has sudden dyspnoea, pleuritic pain, HR 120, SpO2 88%. BP 130/80. The best diagnostic test is: A. CT pulmonary angiogram · B. Chest X-ray · C. Spirometry · D. Echocardiogram only · E. Peak flow Answer: A.
3. A pregnant woman with a proximal DVT should receive: A. Warfarin · B. Rivaroxaban · C. Low-molecular-weight heparin · D. Aspirin only · E. No treatment Answer: C.