Deep vein thrombosis, also called ‘travellers thrombosis’, is associated in the public mind with long distance air travel. However, symptomatic DVT post flight occurs relatively infrequently (0 -0.28%). In contrast, the DVT risk in hospitalised medical patients who do not receive prophylactic medication approaches 25% (with 70 -79 year olds 7 to 10 times more likely to develop a DVT than those aged 30 – 49 . DVT is actually the third commonest cardiovascular pathology after coronary heart disease and stroke.
A deep vein thrombosis occurs when a clot (or thrombus) forms in one of the deep veins, usually in the leg. This must be distinguished from superficial thrombophlebitis (e.g. affecting long/short saphenous systems or unnamed superficial veins), which carries less risk of progression to DVT (e.g. by extension into the common femoral vein), and therefore by default, much less risk of pulmonary embolism. In the upper limb intravenous cannulation predisposes. It can be treated symptomatically with anti-inflammatory medication and support hosiery.
Who is at Risk
Different circumstances increase the risk of DVT. The most common is immobility, often associated with hospitalisation or bed rest from illness.
Other risk factors include obesity, pregnancy, previous DVT, inflammatory bowel disease and heart disease, malignancy, the oral contraceptive pill, and genetic disorders associated with an increased risk of thrombosis .
DVT diagnosis can be complex
The classic signs and symptoms are warmth, pain or tenderness and swelling of the affected limb, accompanied by redness or discoloration but only 25% of patients with this clinical picture have a thrombus. Screening using the Two-level DVT Well’s score which is a 9 point questionnaire of risk factors, can assess the likelihood of DVT
Initial investigation, includes a D-dimer blood test for fibrin degradation fragments – a negative test rules out DVT but results can be positive in other conditions such as infection, pregnancy, trauma and malignancy. Diagnosis can be confirmed by ultrasound. Differential diagnoses include cellulitis, ruptured Baker’s cyst, venous insufficiency and post thrombotic syndrome.
The aims of treatment
These aim to avoid thrombus propagation and pulmonary embolism. Patients require anticoagulants. Low molecular weight heparin by injection is frequently chosen initially, until an INR of 2.5 has been achieved for 24 hours. This commonly takes 5 – 7 days. The majority of patients then continue with oral anticoagulant medication for a period of months.. Oral medications may consist of a vitamin K agonist (e.g. Warfarin) or a factor Xa inhibitor (e.g. rivaroxaban).
Post thrombotic syndrome (PTS) affects 50% of people two years after a lower limb DVT, with leg ulceration developing in 10%. It results from chronic venous hypertension secondary to venous reflux, venous obstruction and valvular dysfunction that manifests as a painful, swollen, heavy leg with venous claudication. The disability and quality of life impairment is significant – for example the management of venous leg ulcers costs Australia $500 million a year.
More recently, percutaneous catheter based techniques (CBT) have been trialled for major iliofemoral DVT, and although results seem to reduce the clot burden and symptoms, larger long-term studies are required to ascertain whether this also reduces PTS and its associated morbidity. Methods include lytic therapy and pharmacomechanical methods.
Current Clinical Practice Guidelines of the Society for Vascular Surgery and the American Venous Forum are:
- Early thrombus removal in patients who meet these criteria: (i) first episode of acute iliofemoral DVT (ii) symptoms <14 days (iii) low risk of bleeding (iv) ambulatory with good functional capacity and an acceptable life expectancy.
- Early thrombus removal with limb threatening venous ischaemia due to iliofemoral DVT with or without associated femoropopliteal venous thrombosis (phlegmasia cerulae dolens).
- Isolated femoropopliteal DVT treated with anticoagulation alone as evidence is lacking for CBT in this group.
- Recommended percutaneous techniques are pharmacologic (lysis) or pharmacomechanical (rotational, rheolytic or ultrasound enhanced), or a combination of both.
- Self-expanding venous stenting for chronic iliocaval compressive or obstructive lesions that are uncovered, but not in femoral or popliteal veins.
- Standard anticoagulation post procedure.
NICE recommendations are similar . Ongoing research is needed to clarify who, if any require prophylactic IVC filter insertion before CBT. Results of two RCTs (CaVenT, ATTRACT) are eagerly awaited
References available on request. Suggested further reading:
- Thompson AE. Deep Vein Thrombosis. JAMA. 2015;313(20):2090-.
- National Institute for Health and Clinical Excellence. Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing. 2012; 144.
- Kyrle PA, Eichinger S. Deep vein thrombosis. The Lancet. 2005;365(9465):1163-74.