Pulmonary Embolism Flashcards
What is the most common cause of a pulmonary embolism?
it is most commonly a complication of venous thromboembolism (VTE) from another source
e.g. clot in the legs (DVT) becomes dislodged and flows via the bloodstream, through the right side of the heart, and becomes lodged in the pulmonary circulation
Other than a clot, what other things can cause a pulmonary embolism?
- fat
- air
- amniotic fluid
for fat and amniotic fluid, these often resolve themselves with supportive care
air is often an iatrogenic cause
What is the mortality like for a PE caused by venous thromboembolism?
- <5% if there is no haemodynamic instability
- 30% if shock is present
- 70% with cardiac arrest (in hospital)
What lifestyle factors act as risk factors for VTE pulmonary embolism?
-
immobility
- bed rest > 24 hours
- immobiity > 48 hours
- plaster of paris (POP) over limb
- smoking
- dehydration
- obesity
- trauma / surgery (especially pelvic & orthopaedic)
- pregnancy (oestrogen)
What other medical conditions can increase the risk for VTE pulmonary embolism?
- malignancy
- infection
- previous DVT / embolism
- recent MI
- congestive heart failure
- varicose veins
- antithrombin deficiency
- protein C deficiency
- inherited clotting deficiencies (thrombophilia , factor V Leiden)
What are other risk factors for VTE pulmonary embolism?
- age
- family history
-
oestrogen therapy
- HRT or OCP
- only the combined pill, not the progesterone only one
How do clinical features for PE vary?
What question is it important to always ask about?
symptoms can be wide ranging from none at all to sudden death
symptoms are usually correlated to severity
it is important to always ask about a family history of thrombosis
What are the clinical signs of pulmonary embolism?
- pyrexia
- cyanosis
- tachypnoea
- 90% of patients have RR > 16
- tachycardia
- hypotension
- raised JVP
- pleural rub
- pleural effusion
What are the typical symptoms of pulmonary embolism?
- pleuritic chest pain (pain worse on inspiration)
- breathlessness
- cough
- haemoptysis (as a result of pulmonary infarct)
- dizziness / pre-syncope
- syncope (loss of consciousness / fainting)
- non-pleuritic chest pain
What is usually the first symptom of PE that presents?
Shortness of breath typically occurs within seconds to minutes of onset
pain then develops later
What symptom of PE is it important to pay special attention to?
patients with unexplained syncope
around 25% of patients admitted to hospital with unexplained syncope have PE
What are the 2 tools to use to help define the risk of the probability of PE?
-
PERC score
- pulmonary embolism rule-out criteria
- Well’s score
When is the PERC score used to rule out PE?
This is used to rule out PE in low-risk patients
if the patient’s score is 0, then there is a <2% chance of PE
in the absence of convincing clinical signs, you can usually safely exclude PE as a differential
What are the factors that are measured in the PERC score?
- age > 50
- heart rate > 100
- SaO2 on room air <95%
- unilateral leg swelling
- haemoptysis
- recent surgery or trauma
- previous PE or DVT
- exogenous oestrogen
- oral contraceptives, hormone replacement or other oestrogen hormones
How is the PERC score calculated?
What does it mean if someone scores more than 0?
Each factor gives a score of 1 if present
If the patient scores 0, and in the absence of convincing clinical signs, you can usually safely exclude PE
If the patient scores 1 or more, the PERC criteria CANNOT be used to safely rule out PE and the Well’s score is used
What is the purpose of calculating the Well’s score?
it will stratify patients as low or high risk
in high risk patients, you should proceed straight to imaging
in a low risk patient, you should consider a D-dimer test
How is the Well’s score calculated?
What is each factor worth?
Factors that score 3 points:
- clinically suspected DVT
- PE is the most likely diagnosis
Factors that score 1.5 points:
- tachycardia > 100 bpm
- immobilisation > 3 days or surgery in past 4 weeks
- history of DVT or PE
Factors that score 1 point:
- haemoptysis
- malignancy
How is the Well’s score interpreted?
- Score > 6.0 means high probability of PE
- Score 2.0 - 6.0 means moderate probability of PE
- Score < 2.0 means low probability of PE
What is D-dimer?
Why is it useful when there is a suspected PE?
D-dimer is a fibrin degradation product
Levels of D-dimer are raised by the presence of a blood clot in the circulation
D-dimer can be useful to RULE OUT a PE or DVT as a differential
What signs may be present on a CXR for pulmonary embolism?
- may show pulmonary oedema signs such as raised hemidiaphragm
- may show atelectasis - little areas of collapsed lung
- this occurs because there is loss of blood to some areas of the lungs, resulting in collapse fo these areas
What ECG changes can occur in PE?
ECG changes are common but often non-specific
the most common findings are T wave inversion and sinus tachycardia
(ECG shows T wave inversion)
What is shown in this CTPA image?
this CTPA shows a saddle PE
the red arrows are indicative of thrombus and show lack of contrast in the pulmonary vessels
What is shown in images A and B of VQ scans?
Image A:
- inhaled radioactive element (usually Xenon gas) showing normal perfusion throughout the bronchial tree
Image B:
- this image follows injection of technetium
- patchy update in different regions of the lungs indicates multiple areas of reduced blood flow, likely due to PE
What is a paradoxical embolism?
an embolism that goes through a defect in the heart and goes on to cause a stroke
the clot passes from a vein to an artery, through some sort of “fistula” (usually a cardiac defect such as patent foramen ovale)
