Deep vein thrombosis

Question 1

What is a deep vein thrombosis?

Answer 1

Formation of a thrombus within the deep veins (most commonly in the calf or thigh) 

Question 2

Describe the aetiology of a deep vein thrombosis

Answer 2

Deep veins in the legs are more prone to blood stasis, hence clots are more likely to form (Virchow’s triad - stasis, hypercoagulation and endothelial damage) 

Question 3

What are some risk factors for deep vein thrombosis?

Answer 3

1. Stasis :
   - Post-surgery (within 2 months) 
   - Immobility 
   - Obesity (BMI >30) 
   - Age (> 60 yrs.) 
   - Long-haul travel 
2. Hypercoagulability:
   - Active malignancy 
   - Pregnancy 
   - OCP 
   - Nephrotic syndrome 
   - IBD 
   - Thrombophilia 
   - Polycythaemia vera 
3. Endothelial damage :
   - Dehydration 
   - Smoking 
   - HTN 

Question 4

What presenting symptoms of deep vein thrombosis can be found in the history?

Answer 4

• Swollen limb, red 
• Calf tenderness and erythema 
• May be painless- 50% asymptomatic 
• Mild fever 
• Pitting oedema  

Question 5

What signs of deep vein thrombosis can be found on physical examination?

Answer 5

• Local erythema, warmth and swelling 
• Measure the leg circumference 
• Varicosities (swollen/tortuous vessels) 
• Skin colour changes 
• Homan’s Sign- forced passive dorsiflexion of the ankle causes deep calf pain 
• Examine for PE: Check respiratory rate, pulse oximetry and pulse rate 
• Pitting oedema  

Question 6

What investigations are used to diagnose a deep vein thrombosis?

Answer 6

Risk is stratified using the 2-Level DVT WELLS CRITERIA 
(NOTE: this is different from the PE Wells criteria) :

1. ≥ 2= DVT Likely 
   - Leg vein USS doppler (if -ve, perform D-dimer, if d-dimer +ve, repeat USS 6-8 days later) 
   - D-dimer is not useful in pregnancy - high false positive rate! 
2. < 2 = DVT unlikely 
   - D-dimer test (if +ve, perform leg vein USS) 

(if imaging is not available within 4 hours. pt should be given anti-coagulation during the wait- DOACs first-line)

If PE suspected:
- ECG 
- CXR 
- ABG 

Question 7

How are deep vein thrombosis managed?

Answer 7

apixaban or rivaroxaban (DOACs)

• if neither apixaban or rivaroxaban are suitable then either LMWH followed by dabigatran or edoxaban OR LMWH followed by a vitamin K antagonist (VKA, i.e. warfarin)
• if the patient has active cancer: DOAC, unless this is contraindicated
• if renal impairment is severe (e.g. < 15/min) then LMWH, unfractionated heparin or LMWH followed by a VKA
• if the patient has antiphospholipid syndrome (specifically ‘triple positive’ in the guidance) then LMWH followed by a VKA should be used
• in an emergency, initial parenteral therapy with LMWH or unfractionated heparin, then long term use with DOACs

Provoked DVT (e.g. caused by surgery) = 3 months of DOACs

Unprovoked DVT (occurring in the absence of a transient risk factor/ risk factor that is persistent and not easily correctable (such as active cancer or thrombophilia).)= 6 months pf DOACs

Question 8

What are the scores you can get on a DVT wells score?

Answer 8

1 point= any RF of DVT:
- cancer
- immobility for 3 days
- surgery without anaesthesia within 12 weeks
- prev DVT
1 point= symptoms
- paralysis/ paraesis
- tenderness
- swelling
- pitting oedema
- superficial veins
2 points= if any other diagnosis is likely