VTE (Venous Thromboembolism)

Question 1

What is a thrombus?

Answer 1

A blood clot within the body

Question 2

What is an embolus?

Answer 2

Material which is transported in the blood stream and lodges in a blood vessel at a different site

• An embolus can be gaseous, e.g. an air bubble, or solid, e.g. part of a thrombus
• When it impedes or blocks blood flow in the artery it causes an embolism, the consequences of which are infarction of the tissue supplied by the artery
• The bigger the embolus the bigger the artery it blocks and the bigger the area of infarction

Question 3

Where do most VTE develop?

Answer 3

In the deep veins of the leg (e.g. DVT)

Question 4

What is Virchow’s triad?

Answer 4

Stasis of blood flow (e.g. due to being immobile in bed)
Endothelial injury
Hypercoagulabitly

All hospital patients are at risk

Question 5

How can VTE be prevented mechanically?

Answer 5

Anti-embolism stockings (AES)

Intermittent pneumatic compression sleeves (IPC) - put on during surgery

Question 6

How can VTE be prevented pharmacologically?

Answer 6

Low dose low molecular weight heparin - LMWH
Low dose unfractionated heparin (IV) - UFH
Direct anti-Xa and anti-thrombin drugs (oral) - DOACs

Question 7

How is VTE managed acutely?

Answer 7

• Once suspected according to clinical signs and symptoms (Wells scores) then treat immediately
• Do NOT investigate first unless this can be done within 1 hour for PE or 4 hours for DVT
• Use Heparin - usually LMWH but sometimes particularly post-op it may be preferred to use UFH because UFH can be immediately reversed (Protamine Sulphate) or just stopped (T1/2 @20 minutes) if post-op bleeding or redo surgery required
• At the same time as starting heparin begin oral warfarin (except in some post-op patients) Warfarin takes 48 to 72 hours to reach its therapeutic range at which time the heparin can be discontinued

Question 8

How may a DVT present?

Answer 8

Lower limb DVT will present with:
- a unilateral, swollen, painful leg
It can be caused by a clot, but also cellulitis (infection of skin of leg), a ruptured baker’s cyst, muscle haematoma

Question 9

What would be seen on examination for a DVT?

Answer 9

Warm, swollen leg
Tenderness in calf > worse with dorsiflexion of the ankle (Homan’s sign)
Calf circumference greater than 3cm compared with unaffected leg
- To ensure you’re comparing like for like – get a tape measure and make a mark at 10cm from tibial tuberosity on each leg. Then use this mark to measure circumference

Question 10

What score on DVT Wells score means a DVT is likely?

Answer 10

DVT likely - 2 points or more

DVT unlikely - 1 point or less

Question 11

What are risk factors for PE?

Answer 11

• DVT
• Previous DVT or PE
• Active cancer
• Recent surgery
• Lower limb trauma
• Significant immobility (e.g. due to hospitalisation)

Question 12

What are some symptoms of PE?

Answer 12

• Dyspnoea, chest pain, haemoptysis, features of DVT (e.g. leg pain and swelling - usually unilateral, lower abdominal pain, redness), dizziness and syncope
• Tachypnoea (increased respiratory rate), tachycardia, tachyarrythmias (commonest sinus tachycardia but might be atrial fibrillation), hypoxia, pyrexia, elevated JVP, hypotension, pleural rub

Question 13

What investigations may be done for PE?

Answer 13

CTPA (CT pulmonary angiogram) - investigation of choice for most people with a high probability of PE, or low probability and raised D-Dimer
V/Q scan
Clotting screen - for baseline clotting
CXR - exclude other causes such as pneumothorax
ECG - to assess rhythm in any tachycardia patient; in a big PE, it might show signs of R heart strain (S wave in I, Q waves in III, inverted T waves in III)
ABGs - ABGs are normal in 20% of patients with PE
FBC - useful prior to anticoagulation and to rule out infection, good as a baseline test
UE - indicated if starting anticoagulation therapy
LFT - indicated if starting anticoagulation therapy

Question 14

What Wells score for PE means it is likely?

Answer 14

PE likely - 4 points or more

PE unlikely - 3 points or less

Question 15

What are diagnostic tests may be done for PE?

Answer 15

If Wells score is ‘low clinical probability’ (less than 4 points) the next test is a blood test for D-Dimer
- If it is within normal range (or D-Dimer negative) then because D-Dimer test is highly sensitive for VTE, a DVT or PE can be safely excluded without further testing
- If D-Dimer test is positive (i.e. a raised blood level of D-Dimer) then further imaging must be done
Further imaging - usually an US doppler scan of the leg for DVT and usually a CT pulmonary angiogram (CTPA) for PE, both of which are highly specific tests
If Wells score is ‘high clinical probability’ (4 points or more) then the recommendation is to go straight for highly specific imaging tests

Question 16

What is the Pulmonary Embolism Rule-out Criteria (PERC)?

Answer 16

• PE can be ruled out if none of the 8 PERC criteria are present in patients with a low pre-test probability of PE (e.g. Wells < 2 or 3 in keeping with the clinical gestalt of a senior physician)

• Age < 50 years
• Pulse < 100 BPM
• SaO2 > 95%
• No Haemoptysis
• No oestrogen use
• No surgery/trauma requiring hospitalisation within 4 weeks
• No prior VTE
• No unilateral leg swelling

Question 17

What are the treatment options for PE?

Answer 17

LMWH - low molecular weight heparin e.g. dalteparin
- Potassium levels should be monitored when patients take LMWH for longer than 7 days
- Those patients that have diabetes, chronic renal impairment and on medication that can increase potassium levels are more susceptible to hyperkalamia
Fondaparinux (not a licensed indication but can be used based on personal, religious and/or cultural views of the patient)
Unfractionated heparin
DOAC - Apixaban or rivaroxaban
LMWH + DOAC (e.g. dabigatran or edoxaban)