31. Venous Thromboembolism

Question 1

What is meant by ‘thrombosis’?

Answer 1

Pathological clot (thrombus) formation within a blood vessel

Question 2

What is an ‘embolism’?

Answer 2

This is when the clot breaks off and travels through the blood circulation until it is obstructed by vessels of a smaller diameter

Question 3

Briefly describe venous thrombi

Answer 3

These thrombi are more commonly the ones that cause deaths i.e. lead to heart attacks and strokes - predominantly formed of platelets

Question 4

Briefly describe arterial thrombi

Answer 4

These are predominantly formed of fibrin

I.e. in the case of DVT and PE

Question 5

What is the epidemiology of PE?

Answer 5

The epidemiology is age dependent: 1 per 5000 for 20 year olds, 1 per 1000 for 50 year olds and 1 per 100 in 90 year olds

Third most common cause of cardiovascular disease

Second leading cause of death in cancer patients

Question 6

What is the main reason for the cause of death in patients with venous thromboembolism (VTE)?

Answer 6

Because a diagnosis is not made (rather than treatment failure) - this is because the symptoms can often be similar to that from other conditions

Question 7

What are the causes of VTE?

Answer 7

Virchow’s triad:
Reduced blood flow - stasis i.e. in patients in hospital beds, planes
Vessel wall disorder
Hypercoagulability

These can be due to heritable or acquired disorder although the majority of patients have it due to both a heritable and an acquired cause
Some causes are idiopathic

Question 8

What are the main genetic risk factors for VTE?

Answer 8

Antithrombin deficiency
Protein C deficiency
Protein S deficiency
Factor V Leiden

Question 9

What are some strong acquired risk factors for WTE?

Answer 9

Fracture of hip/pelvis
Hip or knee replacement surgery
Major general surgery, especially for malignancy
Major trauma

Question 10

What are some moderate acquired risk factors for VTE?

Answer 10

Previous VTE
Cancer
Respiratory failure
Pregnancy
Combined pill/HRT

Question 11

What are some weak risk factors for VTE and why is this important?

Answer 11

Bed rest for more than three days
Travel-related e.g. a long haul flight
Obesity
Varicose veins

These are important because although they are weak risk factors, the population is generally widely exposed to these factors

Question 12

How does DVT generally present?

Answer 12

Pain
Erythema - superficial reddening of the skin
Tenderness
Swelling
Palpable cord i.e. thrombosed vein
Warmth
Ipsilateral odoema
Superficial venous dilation

Question 13

Why is the correct diagnosis of DVT ridiculously important?

Answer 13

Because about 90% of patients that present with a query DVT are found not to have DVT
The drugs used to treat DVT can cause serious/fatal side effects SO must not be given to someone who does not have it

Question 14

What is the differential diagnosis for DVT?

Answer 14

Musculo-tendinous - trauma
Ruptured Baker's (popliteal) cyst
Post-thrombotic syndrome
Congestive heart failure
Acute arterial occlusion

Question 15

How can you diagnose DVT?

Answer 15

Pre-test i.e. the Well’s scoring system

D-dimer test

Confirm the diagnosis with radiology - a compression ultrasound radiograph

Question 16

What is a D-dimer test and what is it testing for?

What is the problem with this test?

Answer 16

When a clot forms, insoluble fibrin is produced
When the clot is lysed by the embolytic process, D-dimer protein is produced SO indicates presence of a clot

BUT this is a non-specific marker - is commonly raised in other conditions too e.g. infection, cancer, inflammation, pregnancy

Question 17

Give the Well’s scoring system

Answer 17

Clinical characteristic Score
Active cancer within last 6 months 1
Paralysis, paresis, recent plaster immobilisation 1
Recently bedridden ≥ 3 days, major surgery <12 weeks 1
Localised tenderness along distribution of deep veins 1
Entire leg swollen 1
Calf swelling ≥ 3 cm (10 cm below tibial tuberosity) 1
Pitting oedema confined to symptomatic leg 1
Collateral superficial veins (non-varicose) 1
Previous documented DVT 1
Alternative diagnosis at least as likely as DVT -2

Total score: ≥ 2 – DVT likely; ≤ 1 – DVT unlikely

Question 18

What complications can arise from DVT?

Answer 18

PE - fatal or non-fatal
Extension of a clot
Recurrent episode of VTE
Post-thrombotic syndrome

Question 19

What is post thrombotic syndrome and how common is this?

Answer 19

Recurrent pain and swelling in the leg - can lead to leg ulceration which can prove to be fatal
Occurs due to venous hypertension
Effects 30-40% of individuals with DVT

Question 20

What is the clinical presentation of PE?

Answer 20

Pulmonary infarction/haemorrhage - breathlessness, pleuritic chest pain, haemoptysis
Isolated breathlessness - this is the hardest to be recognised as there are no other presenting features - can get treated for e.g. asthma instead
Collapse/syncope
Hypotension
Shock

Question 21

What are the signs of PE?

Answer 21

Tachypnoea
Tachycardia
Crepitations and pleural rub

Question 22

What investigations are used for PE?

Answer 22

ECG - sinus tachycardia, right heart strain, T-wave inversion
Chest x-ray - often normal, small pleural effusion
Arterial blood gasses - hypoxia, low CO2, can often be normal

Question 23

What differential diagnoses are possible for PE?

Answer 23

Pneumonia or bronchitis
Asthma
COPD exacerbation
Acute coronary syndrome
Anxiety
Pneumothorax
Aortic dissection
Lung cancer

Question 24

Give the Well’s score for PE

Answer 24

Risk factor					Score
Clinical signs and symptoms of DVT		3.0
Alternative diagnosis less likely than PE	3.0
Pulse >100					1.5
Immobilisation or surgery in previous 4 wks	1.5
Previous DVT or PE				1.5
Haemoptysis					1.0
Cancer (within last 6 months)			1.0

Probability: > 4 PE likely; ≤ 4 PE unlikely

Question 25

What is the prognosis of a PE?

Answer 25

10% mortality within 1 hour of symptom onset
30% mortality within 2 weeks if not treated

If treated, PE mortality reduces to less than 5%

All cause mortality at one year is 25% due to cancer and cardiorespiratory disease

Question 26

What is the management plan for venous thromboembolism?

Answer 26

Start LMWH whilst confirming the diagnosis
Once this is confirmed, start warfarin
Stop heparin after a minimum of five days once the INR is in the therapeutic range
Continue warfarin and review this at three months

Fondaparinux

Question 27

Describe LMWH

Answer 27

Low molecular weight heparin
Agent of choice for VTE - more effective and safer than unfractionated heparin (UFH) and more predictable anticoagulant response
Subcutaneous administration
Half life of about four hours
No monitoring unless the patient has renal failure, is pregnant or obese

Half life of four hours

Question 28

What is Fondaparinux and when can it not be used

Answer 28

Anticoagulant - synthetic pentasaccharide
Half life of eighteen hours
Fixed dose
Unsuitable if renal impairment

Question 29

What are the side effects of Heparin usage?

Answer 29

Major bleeding occurs in 1-5% in the first week of treatment
Heparin-induced thrombocytopenia (deficiency of platelets in the blood causing bleeding into the tissues, bruising and slow blood clotting after injury)
Osteoporosis with exposure to heparin for several weeks or more

Question 30

Describe Warfarin

Answer 30

Vitamin K antagonist
Oral administration
Long half life of 36 hours
Delayed onset of action
Primarily affects INR (prothrombin time converted to ratio)
Multiple drug interactions
This is teratogenic so should avoid in pregnant women
BUT reduces the risk of recurrence during treatment by 90%

Question 31

What surgical treatments can be used for venous thromboembolism?

Answer 31

Thrombolysis - ‘clot bursting therapy’ used in massive PE or limb-threatening DVT
Inferior vena cava filter used if major contraindication to anticoagulation or if recurrence of PE despite adequate anticoagulation

Question 32

What is a practical treatment used for VTE?

Answer 32

Graduated knee stockings can help the symptoms