Deep Vein Thrombosis

Overview

A deep vein thrombosis (DVT) is a blood clot that develops in the deep veins of the legs or pelvis. The clot can dislodge and travel to the lungs leading to a pulmonary embolism (PE) which can be fatal.

Venous thromboembolism (VTE) is a term that encompasses both deep vein thrombosis (DVT) and pulmonary embolisms (PE) due to their close relationship.

Epidemiology

• Around 2/3 of VTEs are DVTs and 1/3 are PEs
• Affects 1-2 people per 1000 per year

Risk Factors

• History of DVT
• Cancer
• Recent major surgery
• Recent hospitalisation
• Recent trauma
• Chemotherapy
• Bedbound/immobile for a prolonged amount of time
• Prolonged travel
• Trauma to a vein
• Oestrogen-containing contraception or hormone replacement therapy
• Pregnancy and the post-partum period
• Dehydration
• Acquired or familial thrombophilias
• Inflammatory conditions such as vasculitis and inflammatory bowel disease
• Varicose veins
• Smoking
• Obesity
• Heart failure
• Nephrotic syndrome

Example History

A 60-year-old woman has left leg pain and swelling of 6 days’ duration. She has hypertension and was recently hospitalised for a total hip replacement. On examination there is pitting oedema on the left and the left calm is 5 cm greater than the right when measured 10 cm below the tibial tuberosity. The left leg is more erythematous and there is tenderness on palpation of the calf.

Presentation

DVTs vary in presentation and can be difficult to diagnose clinically. Some features are:

• Unilateral calf swelling – measured 10 cm below the tibial tuberosity
• Localised tenderness to palpation along the deep vein system of the affected area
• Erythema
• Asymmetric oedema
• Prominent superficial veins
• Presence of risk factors
• Positive Wells score – see below

Wells Score

The two-level Wells score categorises patients as ‘DVT likely’ if they have a score of ≥2, or ‘DVT’ unlikely if they have a score of <2.

Table 1: The 2-level DVT Wells score

Differential Diagnoses

Cellulitis

• The leg is usually red, hot, and swollen but the area affected is smaller than a DVT that may involve the entire food, calf, or thigh
• The area of skin affected is well-demarcated compared to a DVT
• An entry route of infection may be seen (e.g. a cut or bruise)

Ruptured popliteal cyst (Baker’s cyst)

• Sudden-onset calf pain
• Tenderness present in the popliteal fossa

Investigations

If DVT likely (Wells score ≥2)

• 1^st-line: proximal leg ultrasound scan (USS) within 4 hours:
  • If positive: diagnose DVT and start anticoagulation
  • If negative: arrange D-dimer
    • If D-dimer positive: stop anticoagulation and repeat USS in a week
    • If D-dimer negative: stop anticoagulation and consider an alternate diagnosis
• If proximal leg USS cannot be performed within 4 hours: perform D-dimer + administer interim therapeutic anticoagulation while waiting for the USS
  • The scan should be done within 24 hours
  • The interim anticoagulation options are the same as ones used in managing a DVT normally – the guidance no longer recommends using LMWH instead

If DVT is unlikely (Wells score <2)

• 1^st-line: perform D-dimer within 4 hours
  • If positive: proximal leg vein USS – if this cannot be done within 4 hours of symptom onset, administer interim therapeutic anticoagulation while waiting for the results. The scan should be done within 24 hours.
• If D-dimer cannot be performed within 4 hours, administer interim therapeutic anticoagulation while waiting for the results

Management flowchart

A flowchart of the above steps is as follows:

Management

Non-pregnant patients without renal dysfunction

• 1^st-line: direct oral anticoagulant (DOAC) such as apixaban or rivaroxaban
  • If both apixaban and rivaroxaban are unsuitable then either:
    • Low molecular weight heparin (LMWH) followed by dabigatran or edoxaban
    • LMWH followed by warfarin
• If the patient has cancer: use DOAC and follow the above steps
• If the patient has antiphospholipid syndrome: LMWH followed by lifelong warfarin

Severe renal dysfunction (eGFR <15 /min)

• 1^st-line: LMWH, unfractionated heparin, or LMWH followed by warfarin

Pregnant patients

• 1^st-line: subcutaneous LMWH or IV heparin
• Warfarin is contraindicated in pregnancy
• DOACs are not used in pregnancy as there is no information surrounding their use

Length of anticoagulation in all patients

• If the DVT was provoked (there was an obvious event causing it e.g. prolonged immobilisation): continue anticoagulation for 3 months
• If the DVT was unprovoked: continue for 6 months
• If the patient has active cancer: continue for 6 months

Monitoring

• If warfarin is used, the INR target is 2.5, keeping in the range of 2.0 – 3.0
• Consider basic investigations for cancer in patients who have had an unprovoked DVT:
  • Review medical history and blood test results including FBC, U&Es, LFTs, PT, and APTT, and offer a physical examination
  • Do not offer further investigations for cancer unless the patient has relevant clinical signs or symptoms
• Consider thrombophilia testing once anticoagulation has stopped in patients with an unprovoked DVT:
  • Consider testing for antiphospholipid syndrome
  • Hereditary thrombophilias in people who have a family history of a DVT or PE

Patient Advice

• Patients should be advised on the length of duration and the importance of adherence
• If patients are taking warfarin, give advice regarding monitoring and interactions, see Anticoagulation
• DOACs do not need routine monitoring
• Patients should be safety-netted on the signs and symptoms of a DVT and PE and should be instructed to seek immediate help should they arise.

Complications

• Pulmonary embolism
• Post-thrombotic syndrome
• Bleeding associated with treatment
• Heparin-induced thrombocytopenia (HIT)

Post-Thrombotic Syndrome

Overview

Post-thrombotic syndrome can develop after a DVT. It is a chronic venous hypertension causing limb pain, swelling, hyperpigmentation, ulcers, dermatitis, and lipodermatosclerosis.

Compression stockings can be given to help. NICE states not to offer compression stockings to prevent post-thrombotic syndrome once a VTE has occurred. They should be given only if they arise.

Prognosis

• Many people who have had a VTE are likely to have another episode
• Thrombosis of the iliofemoral veins has a worse prognosis with an increased incidence of complications such as post-thrombotic syndrome