Pulmonary emolism

Question 1

What is a pulmonary embolism?

Answer 1

Pulmonary embolism (PE) is a condition where a blood clot (thrombus) forms in the pulmonary arteries. This is usually the result of a deep vein thrombosis (DVT) that developed in the legs and travelled (embolised) through the venous system and the right side of the heart to the pulmonary arteries in the lungs. Once they are in the pulmonary arteries they block the blood flow to the lung tissue and create strain on the right side of the heart.

Question 2

Risk factors for venous thromboembolism

Answer 2

Virchow’s triad

• Hypercoaguability
  
  • Active cancer
  • Oestrogen: pregnancy, COCP, HRT
  • Sepsis
• Venous stasis
  
  • Recent surgery (within 2 months)
  • Deep vein thrombosis or varicose veins
  • Significant immobility
• Endothelial damage
  
  • Lower limb trauma
  • Previous venous thromboembolism

Question 3

If a patient has an increased risk of DVT what prophylactic treatment would they recieve?

Answer 3

A low molecular weight heparin such as enoxaparin unless contraindicated.

Anti-embolic compression stockings are also used unless contraindicated.

Question 4

Contraindications to VTE prophylaxis with low molecular weight heparin

Answer 4

Active bleeding or existing anticoagulation with warfarin or a DOAC

Question 5

Contraindications to anti-embolic compression stockings

Answer 5

Significant peripheral arterial disease

Question 6

Pulmonary embolism presentation

Answer 6

Symptoms

• Dyspnoea
• Cough with or without haemoptysis
• Pleuritic chest pain
• Low grade fever
• Syncope (a red flag symptom)

Signs:

• Tachypnoea and tachycardia
• Hypoxia
• DVT: swollen, tender calf
• Haemodynamic instability causing hypotension (<90 suggests massive PE)
• Raised JVP: suggests cor pulmonale
• Right parasternal heave: suggests right ventricular strain

Question 7

Which score predicts the risk of VTE?

Answer 7

Wells Score

Question 8

How is a pulmonary embolism diagnosed?

Answer 8

NICE recommend assessing for alternative causes with a:

• History
• Examination
• Chest xray

Perform a Wells score and proceed based on the outcome:

• Likely: perform a CT pulmonary angiogram
• Unlikely: perform a d-dimer and if positive perform a CTPA

Question 9

Apart from a CT-pulmonary angiogram, what investigation can be performed to establish a definitive diagnosis of pulmonary embolism and why may this option be preferred?

Answer 9

Ventilation-perfusion (VQ) scan involves using radioactive isotopes and a gamma camera to compare the ventilation with the perfusion of the lungs.

They are used in patients with renal impairment, contrast allergy or at risk from radiation where a CTPA is unsuitable.

Question 10

What might the ABG of someone with a PE show?

Answer 10

↓ PaCO2

↓ PaO2

Question 11

Initial management of pulmonary embolism

Answer 11

• Oxygen as required
• Analgesia if required
• Apixaban or Riveroxaban (DOACs)
• Low molecular weight heparin is an alternative where these are not suitable (enoxaparin, dalteparin)

Question 12

Management of PE in antiphospholipid syndrome

Answer 12

Low molecular weight heparin (enoxaparin, daleteparin)

Question 13

Anticoagulation options for PE in patient with renal impairment

Answer 13

One of:

• LMWH
• Unfractionated heparin
• LMWH or unfractionated heparin and warfarin for at least 5 days (or INR stable at 2.0), then warfarin alone

Question 14

Long term anticoagulation in VTE

Answer 14

Warfarin, DOAC or LMWH

Question 15

Target INR for warfarin

How would you switch from a DOAC to warfarin?

Answer 15

INR 2-3

When switching to warfarin continue LMWH for 5 days or until the INR is in the therapeutic range (2-3) for 24 hours (whichever is longer)

Question 16

What does DOAC stand for and what are the three main DOACs used?

Answer 16

Direct-acting oral anticoagulants

The main three options are apixaban, dabigatran and rivaroxaban

Question 17

Which anticoagulation is used in the treatment of VTE in cancer or pregnancy?

Answer 17

LMWH

Question 18

How long should anticoagulation be continued for?

Answer 18

• 3 months if there is an obvious reversible cause (then review)
• Beyond 3 months if the cause is unclear, there is recurrent VTE or there is an irreversible underlying cause such as thrombophilia. This is often 6 months in practice.
• 6 months in active cancer (then review)

Question 19

What is the treatment for a massive PE where there is haemodynamic compromise?

SBP < 90 mmHg

Answer 19

Thrombolysis eg alteplase - this involves injecting a fibrinolytic medication that rapidly dissolves clots. There is a significant risk of bleeding.

Question 20

Examples of thrombolytic agents

Answer 20

Streptokinase, alteplase and tenecteplase

Question 21

What are the two ways that thrombolysis can be performed?

Answer 21

• Intravenously using a peripheral cannula.
• Directly into the pulmonary arteries using a central catheter. This is called catheter-directed thrombolysis

Question 22

Managment of patients with recurrent PEs despite anticoagulation, or if anticoagulation is contraindicated

Answer 22

Inferior vena cava filter

Question 23

What might the ECG of someone with a PE show?

Answer 23

• Sinus tachycardia is the most common finding
• RBBB and right axis deviation suggest right heart strain
• S1Q3T3: large S wave in lead I, large Q wave in lead III, inverted T wave in lead III (a classic finding but only seen in 20% of patients)