Venous Thrombosis

Blood clot which forms in a vein

Aetiology

Hypercoagulable state

• Malignancy

• Pregnancy and peripartum

• Oestrogen therapy

• IBD

• Sepsis

• Thrombophilia

Endothelial injury

• Venous disorders

• Venous valvular damage (e.g. from previous DVT/PE - very strong RF)

• Trauma or surgery

• Indwelling catheters

Circulatory stasis

• Left ventricular dysfunction

• Immobility or paralysis

• Venous insufficiency/varicose veins

• Venous obstruction - tumour, obesity, pregnancy

Pathophysiology

• Low pressure system, platelets not activated → activates coagulation cascade → clot rich in fibrin

Formation of DVTs

• DVTs form predominantly in the venous valve pockets and other sites of assumed stasis

• Distal vein thrombosis: refers to DVT of the calves

• Proximal vein thrombosis: DVT of the popliteal or femoral vein, more likely to embolise

Pulmonary embolism

• Usually the result of a DVT (95%)

• Can also be caused by embolism of a blood clot from the atria in a patient with AF - ARTERIAL THROMBOSIS NOT VENOUS

Clinical presentation

Deep vein thrombosis

• Limb feels hot, swollen, tender, erythema (unilateral)

• Pitting oedema

• Mild fever

Pulmonay emobolism

• Dyspnoea - often acute onset

• Pleuritic chest pain

• Symptoms of DVT - leg pain, swelling etc.

• Collapse (/sudden death)

• Fever

• Haemoptysis

• Tachycardia

• Hypoxia

• Cyanosis

• Low BP

Investigations

DVT

• D-dimer - rule out test for patients considered unlikely to have a DVT based on the Wells score

• US Doppler leg scan is diagnostic - indicated if patient has raised D-dimers, or if they have a high Wells score (in which case US would be first line)

PE

• If Wells score indicates a PE is likely - perform a CTPA

• If Wells score indicates a PE is unlikely - perform D-dimer and if positive perform a CTPA

• A V/Q scan is an alternative to a CTPA used in patients with renal impairment, contrast allergy or at risk from radiation where a CTPA is unsuitable
• Try to avoid using CTPA for pregnant women (use USS or V/Q), however if patient is very unwell CTPA is the best modality so accept risk of radiation

• Other imaging:
• CXR - will be normal early on in PE (before infarction), often used to rule out other causes, ‘wedge-shaped infarct’ indicates PE
• USS leg - if radiation to be avoided or DVT suspected

• Other tests:
• ECG - sinus tachycardia, S1Q3T3 (right heart strain pattern)
• Troponin - may be raised due to strain on right ventricle, raised troponin is associated with worse outcomes
• ABG - type I resp failure, respiratory alkalosis
• Investigate underlying cause - USS, cancer screen, autoantibodies (SLE), thrombophilia screen

Management

Acute management

• The initial management for a suspected or confirmed DVT or PE is with anticoagulation

• Apixaban or rivaroxaban (DOACs) first line in the majority of patients
• May be outpatient if patient considered low-risk
• If neither apixaban or rivaroxaban are suitable then either LMWH followed by dabigatran or edoxaban OR LMWH followed by a vitamin K antagonist (VKA, i.e. warfarin)

• Thrombolysis is recommended as the first-line treatment for massive PE where there is circulatory failure (e.g. hypotension)

Secondary prevention

• The options for long term anticoagulation are warfarin, a DOAC or LMWH
• Warfarin first line in antiphospholipid syndrome
• LMWH first line in pregnancy

• Treatment with a should be continued for at least three months
• Provoked DVT with reversible factors - 3 months
• Provoked DVT with irreversible factors, or unprovoked DVT - 3-6 months, potentially life-long depending on patient factors (e.g. genetic clotting disorder)