Pulmonary embolism Flashcards
Where do most thrombi originate?
Deep veins of calf or pelvis
How common are PEs?
Fairly common - 12% of PMs show PEs
Predisposing factors for a PE
- Immobile
- Contraceptive pill
- Malignancy (pancreas, uterus, breast and stomach)
- Heart failure
- Post operative
- Fractures of pelvis or lower limb
- Hypercoagulable states e.g. pregnancy
Clinical features of PE
- Dyspnoea
- Tachypnoea
- Pleuritic pain
- Apprehension
- Tachycardia
- Cough
- Leg pain
Discuss clinical presentation of a massive PE
- Sudden onset severe chest pain and dyspnoea
- Onset often occurs when patient goes for a poo 💩 - the idea that the act of defecation is a trigger acute embolism in patients with DVTs
- If patient has had surgery, classically occurs around a week after the op
- Signs of shock
- Right ventricular heave, prominent A wave in JVP
Why would a PE cause a prominent A wave on JVP?
Saddle PE blocks blood from leaving the right ventricle therefore there is nowhere for blood from the right atria to pump into meaning that when the atria contract there is a marked increase in the A-wave which indicates atrial contraction
What is an infarct?
Area of dead tissue/ necrosis secondary to ischaemia
What are the causes of PE other than thromboemboli?
- Fat emboli after injury to subcut fat or fatty marrow following fracture
- Air
- Tumour cells in capillary bed
- Amniotic fluid (very rare, amniotic fluid enters mother’s blood stream and causes a reaction, disseminated intravascular coagulation occurs followed by massive bleeding due to the fact that all clotting factors have been used up)
Which patients are admitted immediately when PE is suspected?
- If they are showing signs of haemodynamic instability: pallor, tachycardia, hypotension, shock and collapse
- They are pregnant or had a baby in the past 6 weeks
**If neither of the above apply but PE suspected - use the PE Wells score
What is the PE Wells score?
Used to predict clinical probability of PE
Criteria:
- Clinical signs of DVT: +3
- HR >100bpm: +1.5
- Immobilisation for 3 days or surgery in last 4 wk: +
- Previous DVT/ PE: +1.5
- Haemoptysis: +1
- Cancer: +1
- Alternative diagnosis is less likely than PE: +3
SCORE OF 5 OR MORE - PE LIKELY 😬
SCORE OF 4 OR LESS - PE UNLIKELY
What if a patient has a PE Wells score of 5+?
This means a PE is likely - admit them for an immediate CTPA (CT pulmonary angiography)
**If CTPA cannot be carried out straighaway, give therapeutic anticoagulant and arrange admission
What if your patient has a PE Wells score of 4 or less?
This means a PE in unlikely (but not impossible!)
- Offer a D-dimer test with a result within 4hrs
- If you can’t get a result within 4hrs, give anticoagulant
- D-dimer result positive - DO CTPA
- D-dimer result negative - stop any anticoagulant and consider a differnt diagnosis
Which anticoagulants are given to patients with suspected PE?
ApiXaban and RivaroXaban
What are D-dimers?
They are degradation products of cross-linked fibrin and are released into the circulation when a thrombus begins to dissolve
Is the presence of D-dimers in the blood diagnostic of PE?
No because they can be elevated in infection, malignancy and post surgery
But if a patient is suspected to have a PE, a Wells score of <4 and a + D-dimer result - arrange a CTPA
What does a negative D-dimer result indicate?
Acute PE is unlikely (high negative predictive value)
In which lung is a pulmonary infarct more likely?
Right - reason unknown 🤔
Why are pulmonary infarcts not that common?
Because the lung receive a dual blood supply (bronchial and pulmonary) - so if an emboli is present it is likely that a collateral vessel can maintain the oxygen supply to the tissue
Why does alveolar collapse occur in PE?
Area of lung isn’t perfused and therefore doesn’t produce surfactant and the alveoli stick together
What are the consequences in the heart as a result of chronic recurrent PE?
Right ventricular overload with a right ventricular heave and loud pulmonary second sound
What is a ventilation perfusion scan?
Nuclear medicine scan that uses radioactive material to examine ventilation and perfusion of the lungs
Radioactive material is breathed in and pictures or images are taken to look at the airflow in the lungs. In the second part, a different radioactive material is injected into a vein in the arm, and more images taken to see the blood flow in the lungs
What are D-dimers?
- Protein fragments released into circulation when a blood clot breaks down
- The formation of a thrombus is usually followed by an immediate fibrinolytic response, this results in the generation of plasmin which causes the release of fibrin degredation products (predominantly d-dimer) into the circulation
- A negative D-dimer assay suggest that thrombosis is not occuring
Discuss negative and positive predictive value of D-dimer
Fibrin is produced in a wide variety of conditions such as pregnancy, cancer, inflammation, bleeding, trauma, surgery and necrosis - the positive predictive value of elevated D-dimer level is low and D-dimer testing is not used for confirmation of PE.
If a D-dimer test is done and the result is normal, there is a high probability that the patient truly does not have a PE, however if a D-dimer is done and it is elevated, this does not mean that the patient does have a PE, it could be loads of other things
Why is CTPA now the recommended initial lung imaging modality for non-massive PE as opposed to V/Q scan?
Speed, easier to perform out-of-hours, a reduced need for further imaging and the possibility of providing an alternative diagnosis if PE is excluded
