Deep vein thrombosis and plumonary embolism

Question 1

What is a ‘clot’ made up of?

Answer 1

• Fibrin
• Platelets
• Red blood cells

Question 2

How is a clot formed?

Answer 2

Damage to endothelium etc > Tissue factor > X reacts with Prothrombin to produce Thrombin > Thrombin reacts with Fibrinogen to produce Fibrin which reacts with factor XIII to produce cross-linked fibrin

Question 3

Mechanisms in Arterial vs Venous thrombosis

Answer 3

Arterial
- Usually rupture of atherosclerotic plaque

Venous
- Combination of Virchow’s triad, especially stasis and hypercoagulability

Question 4

Location of origin in Arterial vs Venous thrombosis

Answer 4

Arterial
- Arteries, left heart chambers

Venous
- Venous valves and venous sinusoids of muscles

Question 5

Results in Arterial vs Venous thrombosis

Answer 5

Arterial
- Ischaemia and infarction

Venous
- Back pressure

Question 6

Disease in Arterial vs Venous thrombosis

Answer 6

Arterial

• Acute coronary syndrome
• Ischaemic stroke
• Limb claudication/ischaemia

Venous

• Deep vein thrombosis
• Pulmonary embolism

Question 7

Composition in Arterial vs Venous thrombosis

Answer 7

Arterial

• “white thrombus”
• Platelets and fibrin

Venous

• “red thrombus”
• Red blood cells and fibrin

Question 8

Features of Virchow’s Triad

Answer 8

• Stasis
• Hypercoagulability
• Endothelial damage

Question 9

What is an embolism?

Answer 9

Intravascular material that migrates from its original location to a distal vessel
E.g. blood clot, fat, air, tumour

Question 10

What is a thromboembolism?

Answer 10

Movement of blood clot along a vessel

Question 11

Examples of venous thromboembolism (VTE)

Answer 11

• Limb deep vein thrombosis (DVT)
• Pulmonary embolism (PE)
• Visceral venous thrombosis
• Intracranial venous thrombosis

Question 12

Epidemiology of venous thromboembolism

Answer 12

• DVT: 1 in 1000 patients
• PE: 1 in 3000-5000 patients
• Leading cause of direct maternal death in UK
• Case fatality rate: 1 to 5% - untreated PE: 30%
• PE in 20% of autopsies

Question 13

Risk factors for VTE

Answer 13

• Major abdominal/pelvic surgery
• Hip/knee replacement
• Late pregnancy
• Fracture
• Malignancy
• Congenital heart disease
• Hypertension
• COPD
• Obesity

Question 14

Symptoms and signs of DVT

Answer 14

• Unilateral limb swelling
• Persistent discomfort
• Calf tenderness
• Warmth
• Redness-erythema
• Prominent collateral veins
• Unilateral pitting oedema

May be clinically silent!!

Question 15

What is a potential long-term consequence of DVT?

Answer 15

Post Thrombotic Syndrome

• Damage to venous valves
• Incidence of 20-60% within 2 years of DVT
• Swelling
• Discomfort
• Pigmentation
• Ulceration in severe form

Question 16

Diagnosis of DVT

Answer 16

• Clinical assessment and pretest probability score (Wells score)
• Blood test: D-dimer if low pre-test probability score
• Imaging: compression ultrasound if positive D-dimer or high pre-test probability score

Question 17

Learn wells score for DVT

Answer 17

kinda know about it

Question 18

What is a D-Dimer?

Answer 18

• Breakdown product of cross-linked fibrin: produced during fibrinolysis
• High sensitivity for VTE
• Low specificity for VTE: trauma, malignancy, sepsis, bleeding, cancer, recent surgery

Question 19

How is a D-Dimer formed?

Answer 19

Plasmin combines with Fibrin producing fibrin degradation products (FDPs), including D-dimer

Question 20

Symptoms and signs of pulmonary embolism

Answer 20

• Pleuritic chest pain
• Breathlessness (dyspnoea)
• Blood in sputum (haemoptysis)
• Rapid heart rate (tachycardia)
• Pleural rub on auscultation: usually due to pulmonary infarction

Question 21

Symptoms and signs of massive pulmonary embolism

Answer 21

• Severe dyspnoea of sudden onset
• Collapse
• Blue lips and tongur (cyanosis)
• Tachycardia
• Low blood pressure
• Raised jugular venous pressure
• May cause sudden death!!

Question 22

Diagnosis methods of pulmonary embolism

Answer 22

• Clinical assessment and pretest probability score (Wells score or Geneva score)
• Blood test: D-dimer if low pre test probability score
• Imaging: If D-dimer positive or high pre test probability score: Isotope ventilation/perfusion scan, CT pulmonary angiogram

Question 23

Look over Wells score for PE

Answer 23

Do it

Question 24

What is a potential long-term consequence of pulmonary embolism?

Answer 24

• Pulmonary arterial hypertension

- Most recover fully

Question 25

What is the aims of treatment of VTE?

Answer 25

• Prevent clot extension
• Prevent clot embolisation
• Prevent recurrent clot

Question 26

What are the treatment options for VTE?

Answer 26

Anticoagulation is the main treatment

• Parental options: unfractionated heparin, low molecular weight heparin
• Enteral options: warfarin, direct oral anticoagulants (DOACs)

Thrombolysis is reserved for massive PE: e.g. Alteplase

Question 27

Prevention methods of VTE in hospital

Answer 27

• Early mobilisation
• ‘Anti-embolism stockings’ - help with the flow of blood
• Other mechanical methods of thromboprophylaxis
• Pharmacological thromboprophylaxis

Question 28

Summary learning outcomes

Answer 28

• VTE is common and deadly
• Aim to prevent VTE in patients at significant risk
• Need to be aware of suggestive symptoms and signs
• Apply diagnostic and treatment pathway

Question 29

How do you develop a pulmonary infarction after a PE?

Answer 29

Pulmonary infarction = rare due to dual vascular supply to lungs with anastomoses
- Blockage to a branch of the pulmonary artery = increase in pressure within pulmonary vasculature

• Force within bronchial artery may be insufficient to overcome this
• ‘Leakage’ of blood into alveolar space occurs, and leads to infarction