1. Look for key symptoms suggestive of a likely DVT when making your diagnosis, and start treatment accordingly.
History:
- Sudden onset of calf pain, swelling or skin cyanosis, often worsened by exertion.
- Not all of these features might be present.
Clinical examination:
- Tenderness, deep in the upper calf, popliteal fossa or medial thigh, with or without ankle swelling should raise the possibility of DVT.
- Classical tests for DVT such as Homan’s sign lack the sensitivity or specificity to be reliable.
- The two-level DVT Wells score should be used to differentiate between likely and unlikely DVT.1
- If a DVT is considered likely urgent investigation is warranted.
Investigations:
- Duplex ultrasound within four hours of suspected diagnosis is recommended for patients in whom a DVT is likely.
- D-dimer test can substitute if an ultrasound cannot be performed, but beware of the possibility of a positive D-dimer due to acute arterial thrombosis – a vascular emergency in its own right.
- Treatment with fractionated heparin should be started immediately, unless contraindicated; pending confirmation of the diagnosis.
2. Consider whether it is a provoked or unprovoked DVT
Unprovoked DVT occurs in patients with no risk factors in the previous three months such as malignancy, surgical procedure, immobility, previous history of DVT, first degree family history of DVT, or taking oral contraceptives or HRT. Otherwise, this is a provoked DVT.
In all patients with proximal (above knee) DVT, anticoagulation should be continued for at least three months. In unprovoked DVT you should consider continuing treatment beyond three months. In those with underlying malignancy this should be low-molecular weight heparin (LMWH) for six months.
3. Aim to diagnose or rule out underlying pathology
It is important not to miss a sinister cause for an unprovoked DVT. Pelvic malignancy in particular may first present with DVT. Clinical examination of the abdomen and pelvis should be undertaken. A high clinical suspicion of underlying malignancy should be maintained, especially in higher risk patients. All should have chest X-ray, FBC, serum calcium, LFT and urinalysis. Consider mammogram and abdominopelvic CT in over 40s.
DVT can occur as a result of extrinsic venous compression. The most common example of this is May-Thurner syndrome, in which the left common iliac vein is compressed by the overlying common iliac artery. Radiological intervention with stent insertion can reduce chronic symptoms. This is especially helpful as this syndrome tends to affect younger female patients and can give rise to recurrent DVT.
4. Do not overlook other conditions such as acute limb ischaemia in the differential diagnosis
While a DVT seems a fairly obvious diagnosis to make it is important not to miss acute limb ischaemia or severe cellulitis. Although swelling is unusual in acute limb ischaemia, colour changes can vary and pain is often vague initially. Examining for peripheral pulses and recording these in both lower limbs is helpful in excluding underlying PAD.
Cellulitis is normally associated with pyrexia and tachycardia.
Increasing numbers of patients undergoing varicose vein treatment are having endovenous thermal ablation procedures, either endovenous laser ablation (EVLA) or radio frequency ablation (RFA). Inflammatory changes in the saphenous vein can mimic symptoms of DVT and cause concern for both patient and GP alike. Pain in the line of the treated vein peaking at 48-72 hours is common. This is accompanied by modest tenderness in some patients. This will normally respond to NSAIDs and compression stockings. Propagation of thrombus into the deep vein is possible a phenomenon known as endothermal heat-induced thrombosis (EHIT). It is usually self-limiting but a more extensive DVT should be excluded by duplex ultrasound. D-dimers are unhelpful as this test is invariably positive due to the saphenous vein treatment.
5. Testing for thrombophilia is recommended in only a few patients
Routine thrombophilia testing in patients with a provoked DVT is not currently recommended.
Hereditary thrombophilia testing should only be undertaken in patients with an unprovoked DVT and a first degree relative with a history of DVT, if planning to stop anticoagulation. A positive result is likely to lead to lifelong anticoagulation, in discussion with the patient and local haematology service.
6. Low molecular weight heparin is needed in pregnancy or patients with malignancy. Otherwise consider the benefits of a novel oral anticoagulant for your patients
LMWH is the anticoagulant recommended in patients with malignancy, based on safety and efficacy in this cohort, and in pregnant or breastfeeding patients. Choice of vitamin K antagonist, either warfarin or NOAC, is dependent on patient preference, pre-existing renal disease (NOACs are renally excreted), concomitant medication interaction.
NOACs seem to have lower bleeding risk than warfarin with non-inferior efficacy, but long-term administration is less well studied.
7. In patients with severe symptoms, thrombolysis should be considered. Direct referral to a vascular specialist is advised. Often a telephone discussion is helpful
Increasingly, patients are being considered for endovascular intervention to reduce late complications by catheter-directed thrombolysis of the DVT. Case selection is important, one factor in improving outcome is earlier referral. It is important to consider this treatment in patients soon after diagnosis. Risk factors contraindicating treatment include recent surgery, active/advanced malignancy or history of bleeding.
Presently, severe symptomatic iliofemoral DVT of less than 14 days duration, patients with more than one year life expectancy and low risk of bleeding are deemed suitable for treatment.
The standard pathway via A&E or haematology builds delays in the pathway that can cause patients to miss the opportunity for the most effective treatment.
8. Prescribing good quality compression stockings will help to prevent late complications
Chronic venous insufficiency results from incomplete recanalisation of the deep veins after a DVT. The severity of symptoms is variable and depends on extent of initial DVT. More proximal iliofemoral DVT is more likely to cause worse late complications.
Graduated compression hosiery has been shown to reduce late symptoms. Patients should be encouraged to wear these daily for two years following a DVT.
The level of compression is important. The German RAL standard class II (23-32mmHg) gives greater compression than the UK grade (18-24mmHg). This higher level of compression is preferred and should be specified on FP10 prescription
Although this recommendation is not suggested by NICE, it is listed as an area for further research, and is the advice given to my patients in Sheffield.
9. Recommend the use of flight socks for long-haul air travel
The risk of DVT associated with air travel is small, approximately 1 in 50,000 for long-haul flights over six hours. Several randomised studies have shown benefit from wearing knee-length graduated compression stockings on long-haul flights. There is no evidence for aspirin use. In addition, LMWH can be considered in high-risk individuals.
10. Don’t miss an upper limb DVT, in patients with new onset of upper limb pain or swelling
Effort induced thrombosis (Paget-Schroetter syndrome) is an uncommon condition, affecting 2-3 per 100,000 per year. Patients typically present with upper extremity swelling, superficial venous engorgement and pain. The history is usually of excessive activity involving the upper limb, often held above the head, for example decorating, or in younger patients may occur as result of weight-training causing overdevelopment of the neck and shoulder muscles.
Early intervention to perform thrombolysis and venous decompression, by surgical first rib resection, is now considered to be the preferred standard of care. Delayed diagnosis makes successful thrombolysis less likely and persistent upper limb venous insufficiency more likely.
Mr Dominic Dodd is a consultant vascular surgeon at Sheffield Teaching Hospitals NHS Foundation Trust
Reference
1. NICE. CG144: Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. London: NICE; 2012
