Pulmonary emolism Flashcards
What is a pulmonary embolism?
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.
Risk factors for venous thromboembolism
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
If a patient has an increased risk of DVT what prophylactic treatment would they recieve?
A low molecular weight heparin such as enoxaparin unless contraindicated.
Anti-embolic compression stockings are also used unless contraindicated.
Contraindications to VTE prophylaxis with low molecular weight heparin
Active bleeding or existing anticoagulation with warfarin or a DOAC
Contraindications to anti-embolic compression stockings
Significant peripheral arterial disease
Pulmonary embolism presentation
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
Which score predicts the risk of VTE?
Wells Score
How is a pulmonary embolism diagnosed?
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
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?
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.
What might the ABG of someone with a PE show?
↓ PaCO2
↓ PaO2
Initial management of pulmonary embolism
- Oxygen as required
- Analgesia if required
- Apixaban or Riveroxaban (DOACs)
- Low molecular weight heparin is an alternative where these are not suitable (enoxaparin, dalteparin)
Management of PE in antiphospholipid syndrome
Low molecular weight heparin (enoxaparin, daleteparin)
Anticoagulation options for PE in patient with renal impairment
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
Long term anticoagulation in VTE
Warfarin, DOAC or LMWH
Target INR for warfarin
How would you switch from a DOAC to warfarin?
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)
What does DOAC stand for and what are the three main DOACs used?
Direct-acting oral anticoagulants
The main three options are apixaban, dabigatran and rivaroxaban
Which anticoagulation is used in the treatment of VTE in cancer or pregnancy?
LMWH
How long should anticoagulation be continued for?
- 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)
What is the treatment for a massive PE where there is haemodynamic compromise?
SBP < 90 mmHg
Thrombolysis eg alteplase - this involves injecting a fibrinolytic medication that rapidly dissolves clots. There is a significant risk of bleeding.
Examples of thrombolytic agents
Streptokinase, alteplase and tenecteplase
What are the two ways that thrombolysis can be performed?
- Intravenously using a peripheral cannula.
- Directly into the pulmonary arteries using a central catheter. This is called catheter-directed thrombolysis
Managment of patients with recurrent PEs despite anticoagulation, or if anticoagulation is contraindicated
Inferior vena cava filter
What might the ECG of someone with a PE show?
- 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)
