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
What is the gold-standard investigation for PE?
CT Pulmonary Angiogram (CTPA) - poor sensitivity for small emboli, very high for medium-large emboli
What do you do next if 2-level PE Wells score >4?
- arrange immediate CTPA
- if delay in getting CTPA - interim therapeutic anticoagulation with DOACs
- positive CTPA = PE diagnosed
- negative CTPA = consider proximal leg vein ultrasound if DVT suspected
What do you do next if 2-level PE Wells score is 4 points or less?
- arrange a D-dimer test (if not pregnant)
- if +ve arrange immediate CTPA (if delay in getting CTPA give interim DOACs)
- if -ve then PE is unlikely - stop anticoagulation and consider alternative diagnosis
What is the indication for doing CTPA for PE?
- Wells score >4
- or Wells score </=4 but +ve D-dimer
What do we do for haemodynamically unstable patients with potential PE who cannot have CTPA?
Echocardiography
What do we do whilst waiting for results of CTPA for suspected PE?
Start DOAC
When is a V/Q scan preferred to CTPA for suspected PE? (3)
- renal impairment
- contrast allergy
- pregnant
What does a V/Q scan do?
Identifies areas of ventilation and perfusion mismatch, indicating area of infarcted lung
Start patient on treatment-dose anticoagulant while awaiting results
What would ECG show in PE? (3)
- sinus tachycardia
- RBBB and right axis deviation
- S1Q3T3 (rarely seen) - S wave in lead I, Q waves in lead III, inverted T waves in lead III
What are some differential diagnoses for PE? (12)
- unstable angina (ECG, troponin elevated in PE)
- MI
- pneumonia
- acute bronchitis (wheeze/rhonchi, purulent sputum, normal D-dimer)
- COPD/asthma exacerbation
- congestive heart failure exacerbation
- pericarditis (ECG)
- cardiac tamponade
- pulmonary hypertension due to chronic thromboembolic disease (bruits, swelling, RAD)
- pneumothorax
- costochondritis
- panic disorder
What is the initial management for PE in haemodynamically stable patients?
- DOAC (Apixaban or Rivaroxaban)
- LMWH followed by vitamin K antagonist if eGFR<15 / antiphospholipid syndrome
- LMWH if patient pregnant
How long do you continue anticoagulation for provoked vs unprovoked PE?
- provoked - 3 months (3-6 months if active cancer)
- unprovoked - 6 months
What can you prescribe for PE if DOAC contraindicated?
- warfarin
- LMWH if pregnant
What is the target INR for recurrent PE?
3.5
What is the management for PE in haemodynamically unstable patients (<90mmHg)?
Thrombolysis (Alteplase) - contraindicated if Hx haemorrhagic stroke
What surgical treatment options are there for PE? (3)
- embolectomy - when thrombolysis contraindicated (e.g. Hx haemorrhagic stroke)
- percutaneous catheter-directed treatment
- IVC filters - recurrent PEs despite adequate anticoagulation/when anticoagulation contraindicated
What are some complications of PE? (7)
- recurrent VTE/PE
- signs of pulmonary HTN
- signs of right heart failure
- acute bleeding during treatment
- death
- pulmonary infarction
- heparin-induced thrombocytopenia (HIT) - low platelets, normal Hb, normal WCC
What is mortality from PE often due to?
Cardiogenic shock secondary to right ventricular collapse
