DVT & PE

Question 1

What are the three main components to the haemostasis system?

Answer 1

Hemostasis is the mechanism that leads to cessation of bleeding from a blood vessel.

1. Vasoconstriction
2. Platelet plug formation
3. Blood clotting-leads to formation of fibrin

Question 2

What systems prevent blood clotting?

Answer 2

Healthy endothelium
1. Anti-thrombins-prevent thrombin formation
2. Protein C and S inactivate clotting factors
3. Fibrinolysis-Plasmin breaks down fibrin - breakdown product of this is D-dimer-used in diagnosis

Question 3

Provide a brief overview of how a platelet plug is formed.

Answer 3

Platelets stick to ruptured surface – produce A2 (inhibited by aspirin) and ADP – driving the sticking of more platelets – emergency quick response

Coagulation cascade activated to form fibrin mesh – solid/long-term clot

Question 4

Overview of the coagulation cascade.

Answer 4

Question 5

Outline how a suspected DVT is investigated.

Answer 5

Use Well’s score to calculate liklihood of DVT

D-Dimer is a thrmbus breakdown product - elevated levels indicates high levels of clotting

Doppler Ultrasound - allows for visualisation of clot

Question 6

How are DVTs treated

Answer 6

Most patients treated with

Factor Xa inhibitors e.g. apixaban - Often called Direct oral anticoagulants (DOAC)

or

Low molecular weight heparin (LMWH)

Warfarin – difficult to work with – low therapeutic window - inhibits the production of vitamin K dependent clotting factors

Question 7

What is Virchow’s triad?

Answer 7

Outlines three factors that contribute to venous thrombosis formation.

Question 8

Do tumours increase DVT risk?

Answer 8

Yes!

Tumours release tissue-factor like molecules-HYPERCOAGULABILITY (Virchows Triad)

Tumours produce molecules that damage endothelium- VESSEL WALL INJURY (Virchows Triad)

Unprovoked DVT – suspicion of cancer

Question 9

How does a pulmonary embolus typically present?

Answer 9

1. Breathlessness (most common)/Tachypnoea-rapid breathing
2. Tachycardia, including AF – look out for this – typically in a hospital environment
3. Cough
4. Calf or leg swelling
5. Crackles or reduced breath sounds in around 1/5th
6. Elevated JVP – jugular venous pressure

Less common
1. Haemoptysis
2. Syncope
3. Pleuritic chest pain

Need high degree of clinical suspicion to spot

Question 10

What is the treatment for PE?

Answer 10

Oral factor Xa inhibitor e.g. apixaban, rivaroxaban - This is option for majority

or

Low molecular weight heparin e.g. dalteparin followed by either thrombin inhibitor e.g. dabigatran or vitamin K antagonist e.g. warfarin

Treatment normally given for three months after a “provoked” PE or DVT

Question 11

Why is venothromboembolism risk increased in hospital patients?

Answer 11

1. Immobility
2. Age – likely due to a lack of mobility
3. Underlying conditions like heart failure
4. Cancer
5. Surgery-activates clotting system
6. Inflammation-release of tissue factor

Question 12

What measures can reduce the risk of venothromboembolism in hospitals?

Answer 12

1. Mobilisation
2. Adequate hydration
3. Compression stockings or pneumatic compression devices - Sufficient in low risk patients
4. Prophylactic dose low molecular weight heparin e.g. dalteparin - Treatment based on risk assessment

Question 13

How is a pulmonary embolism diagnosed?

Answer 13

CT pulmonary angiogram