24th July 2024

Venous thromboembolism

Definition of VTE

Venous thromboembolism (VTE) is a common disorder defined as the formation of a clot within vessels which carry deoxygenated blood. VTE can occur anywhere in the venous system but is most often found within the deep veins of the legs (deep vein thrombosis, DVT) and in the pulmonary arteries (pulmonary embolism, PE).

DVT

Clinical features of DVT

Presentation is typically with an acutely swollen, erythematous leg. Differentials include cellulitis or knee bursitis.

Risk factors include: recent immobilisation, recent surgery, dehydration, active malignancy, pro-thrombotic conditions, trauma, intrinsic compression of veins, Covid-19, medications such as the oral contraceptive pill, nephrotic syndrome, obesity and inflammatory bowel disease. A risk factor history must be taken for anyone with suspected VTE.

If there is doubt about the diagnosis, the Well’s score for DVT can be used (see online calculators, e.g. MDCalc.com). With a low score, D-dimer should be performed. If negative, no further investigations are required; if positive, US Doppler should be performed. With a higher Well’s score, US Doppler should be performed directly.

Management of DVT

Management is predominantly with DOACs, but warfarin and LMWH are also used. The duration of treatment is determined by whether the clot was provoked (typically treated for three months) or unprovoked. For VTE with no obvious cause, treatment must be continued for a minimum of 6 months and can be indefinite.

PE

Clinical features of PE

Presentation is typically with dyspnoea, pleuritic chest pain, haemoptysis or collapse. Examination may be normal.

Scoring systems to aid diagnosis and choose investigations include Well’s score for PE and PERC (both can be found online).

Investigations findings may include:

• ECG: the most common finding is sinus tachycardia; there may be evidence of right heart strain such as new onset right bundle branch block; the classical finding of S1Q3T3 can be caused by PE, but is uncommon and not diagnostic
• CXR: unremarkable in the majority of patients, however PEs can cause pleural effusions (normally exudative) or, if severe, can cause pulmonary infarction which can be seen on CXR
• Troponin and BNP: if positive, demonstrate heart strain
• CT pulmonary angiogram (CTPA) is the gold standard test to investigate PE

Management of PE

The vast majority of patients with PE will be anticoagulated, however for those in which this is contraindicated, inferior vena cava (IVC) filters can be considered. Thrombolysis (usually with alteplase) and thrombectomy are considered for patients with haemodynamic compromise.

Aetiology of VTE

Another important consideration when managing VTE is working out the underlying cause. This is important as it will help determine the duration of treatment and change management (e.g. if medication related, the offending agent may have to be stopped). Common causes include: immobility, surgery, combined oral contraceptive pill, malignancy and prothrombotic conditions including inherited. If a VTE is considered to be provoked, then a 3-month duration of anticoagulation is sufficient, however if unprovoked, 6 months of treatment may be indicated.

If a cause is not obvious, further investigations may be warranted. Malignancy is a common cause of VTE, however NICE only recommends investigating for cancer if the history or examination is suggestive.

References

• Bauer K, Lip G. Overview of the causes of thromboembolism [Internet]. Leung L,  Mandel J, editors.  UpToDate; 2021 [cited Dec 17 2021]. Available from: https://www.uptodate.com/contents/overview-of-the-causes-of-venous-thrombosis
• NICE Guidelines. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. March 2020 [cited December 17 2021]. Available from: https://www.nice.org.uk/guidance/ng158/chapter/Context