Venous thromboembolism (VTE) is a common and potentially fatal condition. It involves blood clots (thrombosis) developing in the circulation. This usually occurs secondary to stagnation of blood and hyper-coagulable states. When a thrombosis develops in the venous circulation it is called a deep vein thrombosis (DVT). Once a thrombosis has developed, it can mobilise (embolise) from the deep veins and travel through the right side of the heart and into the lungs where it becomes lodged in the pulmonary arteries. This blocks blood flow to areas of the lungs and is called a pulmonary embolism (PE).
If the patient has a hole in their heart (for example an atrial septal defect) the blood clot can pass through to the left side of the heart and to the systemic circulation. If it travels to the brain it can cause a large stroke.
There are a number of factors that can put patients at higher risk of developing a DVT or PE. In may of these situations (e.g. surgery) we give patients prophylactic treatment to prevent VTE.
- Recent surgery
- Long haul flights
- Hormone therapy with oestrogen (combined oral contraceptive pill and hormone replacement therapy)
- Systemic lupus erythematosus
TOM TIP: In your exams when a patient is presenting with possible features of a DVT or PE, ask about risk factors such as periods of immobility, surgery and long haul flights to score extra points.
Thrombophilias are conditions that predispose patients to develop blood clots. There are a large number of these:
- Antiphospholipid syndrome (this is the one to remember for your exams)
- Antithrombin deficiency
- Protein C or S deficiency
- Factor V Leiden
- Prothombin gene variant
- Activated protein C resistance
Every patient admitted to hospital should be assessed for their risk of venous thromboembolism (VTE). If they are at increased risk of VTE they should receive prophylaxis with low molecular weight heparin such as enoxaparin unless contraindicated. Contraindications include active bleeding or existing anticoagulation with warfarin or a NOAC. Anti-embolic compression stockings are also used unless contraindicated. The main contraindication for compression stockings is significant peripheral arterial disease.
DVTs are almost always unilateral. Bilateral DVT is rare and bilateral symptoms are more likely due to an alternative diagnosis such as chronic venous insufficiency or heart failure. DVTs can present with:
- Calf or leg swelling
- Dilated superficial veins
- Tenderness to the calf (particularly over the site of the deep veins)
- Colour changes to the leg
To examine for leg swelling measure the circumference of the calf 10cm below the tibial tuberosity. More than 3cm difference between calves is significant.
Always ask questions and examine with the suspicion of a potential pulmonary embolism as well.
The Wells score predicts the risk of a patient presenting with symptoms actually having a DVT or pulmonary embolism. It takes in to account risk factors such as recent surgery and clinical findings such as unilateral calf swelling 3cm greater than the other leg.
D-dimer is a sensitive (95%) but not specific blood test for VTE. This makes it useful for excluding VTE where there is a low suspicion. It is almost always raised if there is a DVT, however other conditions can also cause a raised d-dimer:
- Heart failure
Ultrasound doppler of the leg is required to diagnose deep vein thrombosis. NICE recommend repeating negative ultrasound scans after 6-8 days if there is a positive D-dimer and the Wells score suggest a DVT is likely.
Pulmonary embolism can be diagnosed with a CT pulmonary angiogram or ventilation–perfusion (VQ) scan.
Initial Management (LMWH)
The initial management is with treatment dose low molecular weight heparin (LMWH). It should be started immediately before confirming the diagnosis in patients where DVT or PE is suspected and there is a delay in getting the scan. Examples are enoxaparin and dalteparin.
Switching to long term anticoagulation:
The options for long term anticoagulation in VTE are warfarin, a NOAC or LMWH.
The target INR for warfarin is 2-3. When switching to warfarin continue LMWH for 5 days or the INR is 2-3 for 24 hours on warfarin (whichever is longer).
NOACs or DOACs are essentially oral anticoagulants that are not warfarin. They are an alternative option for anticoagulation that does not require monitoring. Originally they were called “novel oral anticoagulants” but this has been changed to “non-vitamin K oral anticoagulants” because they are no longer novel. This is changing to DOACs, standing for “direct-acting oral anticoagulants”. The main three options are apixaban, dabigatran and rivaroxaban.
LMWH long term is first-line treatment in pregnancy or cancer.
Continue anticoagulation for:
- 3 months if there is an obvious reversible cause (then review)
- Beyond 3 months if the cause is unclear, there is recurrent VTE or there is an irreversible underlying cause such as thrombophilia. This is often 6 months in practice.
- 6 months in active cancer (then review)
Inferior Vena Cava Filter
Inferior vena cava filters are devices inserted into the inferior vena cava designed to filter the blood and catch any blood clots traveling from the venous system towards the heart and lungs. They act like a sieve, allowing blood to flow through whilst stopping larger blood clots. They are used in unusual cases of patients with recurrent PEs or those that are unsuitable for anticoagulation to prevent emboli traveling to the lungs.
Investigating Unprovoked DVT
When patients have their first VTE without a clear cause then NICE recommend investigating them for possible cancer. To screen for cancer they recommend:
- History and examination
- Chest X-ray
- Bloods (FBC, calcium and LFTs)
- Urine dipstick
- CT abdomen and pelvis in patients over 40
- Mammogram in women over 40
They also recommend testing for antiphospholipid syndrome by checking for antiphospholipid antibodies.
In patients with an unprovoked VTE with a family history of VTE they recommend testing for hereditary thrombophilias:
- Factor V Leiden (most common hereditary thrombophilia)
- Prothrombin G20210A
- Protein C
- Protein S
Budd-Chiari syndrome is where a blood clot (thrombosis) develops in the hepatic vein, blocking the outflow of blood. It is associated with hyper-coagulable states. It causes an acute hepatitis.
It presents with a classic triad of:
- Abdominal pain
Management involves anticoagulation (heparin or warfarin), investigating for the underlying cause of hyper-coagulation and treating the hepatitis.
Last updated April 2019