Deep Vein Trombosis
Introduction
Venous thromboembolism (VTE) is a relatively common, largely preventable, condition with a significant burden of morbidity and mortality worldwide. Clots in the deep veins or deep venous thrombosis (DVT) accounts for 2/3 of cases of VTE and pulmonary embolism (PE) for 1/3.
The pathogenesis of DVT is based on 3 contributing factors, classically referred to as Virchow’s Triad:
1. Venous stasis (often the most clinically significant factor)
2. Vascular Injury
3. Hypercoagulability
Risk Factors for DVT
Common
Prolonged immobility – eg long journeys, lower limb fractures
Active malignancy
Recent major surgeries
Pregnancy or recent childbirth
Previous DVT - The residual abnormality can act as a focus for recurrent thrombi
Less Common
Pro-thrombotic Disorders.
Factor 5 Leiden, Antithrombin deficiency, Protein C and Protein S deficiency, Antiphospholipid syndrome
Oestrogen containing products
e.g. OCP, HRT
Active Inflammatory Bowel Disease
Complications
Pulmonary Embolism
Limb ischaemia secondary to clot burden
phlegmasia alba dolens
swollen and white leg because of early compromise of arterial flow secondary to extensive DVT.
phlegmasia cerulea dolens
more advanced and considered a precursor of frank venous gangrene. It is characterised by severe swelling and cyanosis and blue discolouration of the extremity.
Chronic venous insufficiency
Post-thrombotic syndrome
Clinical Features
The clinical presentations of DVT can vary significantly depending on the site and size of the thrombus
Symptoms
Acute onset of calf pain worsened by movement
Progressive swelling of the leg
Difficulty walking and weight bearing
Progression to pulmonary embolism may cause
Pleuritic chest pain
Cough
Shortness of breath on exertion
Dizziness or syncope
Haemoptysis
Signs
Unilateral calf swelling +/- pitting oedema
classically described as >3 cm in calf circumference discrepancy based on measurements 10 cm below the tibial tuberosity.
swelling may be confined to the ankle if the thrombus is in the lower calf.
Tenderness on palpation of the calf or distribution of the deep venous system of the lower limb.
Thrombosed veins may be felt as hard masses
Superficial varicose veins
Erythema
Differential Diagnosis
Vascular
Superficial thrombophlebitis
Changes of venous insufficiency
Post-phlebitic syndrome
Lymph-oedema
IVC obstruction secondary to pelvic malignancy
Infection/Inflammation
Cellulitis
Lymphadenitis
Local inflammation secondary sting/insect bite
Musculoskeletal
Ruptured Baker’s Cyst
Gastrocnemius muscle strain/tear
Achilles tendon rupture
Post-traumatic haematoma
Clinical Decision Tool
Well’s Score for DVT
Calculates the risk of DVT based on a patient’s clinical criteria
It is used in the ED and outpatient setting and is not reliable in hospitalised patients
This scoring system divides patients into DVT likely and DVT unlikely and aids the decision to progress to further testing
Score of 0 = low probability
Score of 1-2 = intermediate probability
Score of 3 or more = high probability
Clinical Investigations
Bedside
POCUS
As a rule-in test only. An experienced operator may be able confirm the diagnosis
Urinary Beta-hCG on all women of childbearing age
ECG if concerned about PE
Laboratory
FBC
assess Hb and platelets prior to anticoagulation
elevated WCC more likely in cellulitis
D Dimer
Highly sensitive but not specific
A negative D Dimer is useful for ruling out DVT in those in whom you have low or moderate suspicion for DVT (as per Wells Score)
CRP
more likely to be elevated if infectious or inflammatory cause for leg swelling
Coagulation profile and LFTs
prior to commencing anticoagulation
U&E
prior to commencing anticoagulation. Impaired renal function influences choice and dose of anticoagulant.
Radiology
Vascular Ultrasound of the venous system
first line imaging modality for proximal DVT
CT Venography and MR venography may also be used but are not common due to cost and availability
CT Pulmonary Angiogram
if concerned about concurrent PE
Management & Disposition
Initial Resuscitation
Resuscitation may be required in cases where the severe complications of PE or limb ischaemia occur
Specific Treatment
If there is delay in obtaining definitive diagnosis empiric anticoagulation should be commenced until a diagnosis is confirmed.
typically treatment dose subcutaneous low molecular weight heparin (LMWH)
Once diagnosis is confirmed patient should be started on oral anticoagulation. Choice is based on patient co-morbidities and risk factors.
DOAC (apixiban, rivaroxiban) vs Warfarin vs subcut LMWH (tinzaparin)
Symptomatic Treatment
Analgesia as required
Elevation
Disposition
Most patients who present with a confirmed or suspected below knee lower limb DVT will be suitable for outpatient management with anticoagulation and oupatient haematology follow up
If the DVT is unprovoked i.e. no cause readily identifiable the patient will need to be worked up for possible underlying clotting disorders or malignancy as an outpatient
Patients who meet the following criteria are not suitable for outpatient management and should be admitted to hospital.
Symptoms suggestive of PE
High thrombotic load e.g. Limb ischaemia, extension into IVC, severe limb pain
Active bleeding
Significant risk of bleeding e.g. active peptic ulceration, liver disease, Uncontrolled HTN, CNS surgery or haemorrhagic stroke in past month, platelet count <100.
References
Stone J et al. Deep venous Thrombosis: pathogenesis, diagnosis and medical management. 2017. Cardiovascular diagnosis and Therapy. 7(3):S276-S284
Hirsh J, Hoak J. 1996. Management of DVT and PE. Circulation. 93:2212-2245
Sprigings D, Chambers B. Acute Medicine, A Practical Guide to the Management of Medical Emergencies
NICE Guideline Venous Thromboembolic Disease: diagnosis, management and thrombophilia testing. 2020 (NG158)
Wilbur J, Shian B. Deep Venous Thrombosis and PE: Current Therapy. Am Fam Physician. 1;95(50:295-302)
SJH Ambulatory DVT care pathway. Nov 2016