Pulmonary embolism (RESP) Flashcards
Define PE.
A thrombus which embolises to the lungs via the inferior vena cava and occludes the pulmonary vasculature
What is thrombus formation in the venous system due to (Virchow’s triad)? (3)
- venous stasis
- trauma
- hypercoagulability
What are some causes of embolus formation? (8)
- amniotic fluid
- air
- fat
- tumour
- mycotic
- parasites
- right ventricular thrombus (post-MI)
- septic emboli (right-sided endocarditis)
What can dislodgement of thrombus in pulmonary vasculature cause? (4)
Right heart failure, cardiac arrest
- increased PVR
- increased afterload + HR on RV via dilation
- decreased RV cardiac output and decreased LV preload
- lower MAP –> hypotension –> cardiogenic shock
What does the term venous thromboembolic disease refer to?
The spectrum of disease beginning with the risk factors of Virchow’s triad, progressing to DVT and resulting in life-threatening PE
What is a provoked vs unprovoked VTE?
- provoked VTE: due to an obvious precipitating event e.g. immobilisation following major surgery - this event was transient and patient is no longer at increased risk
- unprovoked VTE: occurs in absence of an obvious precipitating event i.e. there is a possibility that there are unknown factors (e.g. mild thrombophilia) making the patient at higher risk of clots
What are the clinical features of PE? (6)
- sudden pleuritic chest pain - aggravated by coughing, swallowing, deep inspiration
- dyspnoea
- hypoxaemia
- tachycardia & tachypnoea - especially in absence of respiratory signs
- signs of concurrent DVT - unilateral painful leg swelling
- haemoptysis
What is the triad of PE?
Pleuritic chest pain, dyspnoea and haemoptysis (only 10% present with this though)
How can acute right heart failure present in PE?
- increases pulmonary BP so much that RV is unable to compensate –> dilates
- such as a raised JVP, parasternal heave and loud P2
What might you find on examination in PE? (4)
- tachycardia & tachypnoea
- pleural rub
- low O2, cyanosis
- crackles
What are some risk factors for PE? (10)
- age
- DVT
- recent surgery
- bed rest / immobility
- malignancy
- pregnancy
- COCP - oestrogen increases activity of clotting factors
- thrombophilia e.g. antiphospholipid syndrome - increases coagulability
- long distance travel
- heart failure (reduced CO = reduced blood flow –> increased risk of thrombus formation)
What is the pulmonary embolism rule-out criteria (PERC)?
- age >/=50
- HR >/=100
- O2 </=94%
- previous DVT or PE
- recent surgery or trauma in past 4 weeks
- haemoptysis
- unilateral leg swelling
- oestrogen use e.g. HRT, contraceptives
If all of the above are absent the post-test probability of PE is <2% (done when low pre-test probability but want reassurance)
What is the most appropriate INITIAL investigation for PE?
- CXR - looks normal
- done to rule out other causes of chest pain e.g. pneumothorax
What scoring criteria is used to calculate clinical probability of PE?
2-level PE Wells score:
- clinical signs and symptoms of DVT (minimum of leg swelling and pain with palpation of the deep veins) - 3
- an alternative diagnosis is less likely than PE - 3
- HR>100bpm - 1.5
- immobilisation for 3+ days or surgery in previous 4 weeks - 1.5
- previous DVT/PE - 1.5
- haemoptysis - 1
- malignancy (or treatment in the last 6 months/palliative) - 1
How can we interpret 2-level PE Wells score?
- > 4 points = PE likely
- 4 points or less = PE unlikely
