Pulmonary Embolism Flashcards
What is the cause of a PE in the majority of cases?
Thrombus- from the venous system passing through the right heart into the pulmonary vasculature
What are some other causes of PE other than thrombus? (One is during pregnancy)
Air embolus
Marrow embolus- following large bone fracture
Tumour embolus- part of tumour breaks off and travels in the vasculature
Amniotic fluid embolus- during pregnancy/child birth
What type of respiratory failure is seen in PE?
Type 1 Respiratory failure- due to V/Q mismatch
Explain the findings on an ABG for a PE
Hypoxia with a normal/low PaCO2
Hypoxia occurs due to V/Q mismatch, this leads to hyperventilation which reduces the PaCO2
Is respiratory acidosis or alkalosis seen in a PE?
Respiratory alkalosis occurs due to a reduced PaCO2
How could a DVT bypass the pulmonary circulation and cause an embolic stroke?
If there is an atrial septal defect
What percentage vasculature obstruction can be used to define a massive PE?
50% or more
How does the American Heart Association define a massive PE?
Acute PE with sustained hypotension, pulselessness or persistent profound bradycardia
Describe the cascade that occurs during a PE that eventually leads to reduced LV output
- Pulmonary artery pressure increases due to clot obstruction and vasoconstriction due to hypoxia
- Increased pre load and after load for RV
- Leads to RV stretch, hypokinesis and eventually tricuspid regurgitation
- Bulging of the IV septum occurs during diastole
- Bulging into the LV impairs diastolic filling
- Reduced LV output
What two factors contribute to the pulmonary artery pressure increase that is seen in PE?
Vasculature obstruction
Vasoconstriction in response to hypoxia
Why might there be a rise in cardiac troponins in a PE?
Compression of the RCA can occur leading to cardiac ischaemia
How might a patient present with a PE?
Pleuritic chest pain (and other chest pain) Sudden onset breathlessness Haemoptysis Dry cough Syncope
What are some major risk factors for PE?
Immobility- Prolonged hospital stay, care home
Major surgery
Lower limb problems- varicose veins, fracture
Late pregnancy/c-section/post-partum
Malignancy
Previous proven VTE
What are some minor risk factors for PE?
CV- CHD, CCF, HTN Oestrogen exposure- Hormone Replacement, Oral Contraceptive Pill COPD Long distance travel Obesity Thrombotic disorders
What are the clinical features someone with a PE might have?
Tachypnoea Hypotension Hypoxia- low oxygen saturations Pleural rub Decreased CRT (reduced CO)
What might be heard on auscultation of the chest for a patient with PE?
Pleural Rub
What is the gold standard investigation for PE?
CT Pulmonary Angiogram
What initial investigations might you request if suspecting a PE?
ECG- Changes are rarely seen, Sinus Tachycardia most common
CXR- Exclude other causes of breathlessness/ pleuritic chest pain (e.g. Pneumonia, Pleural effusion, Pneumothorax)
ABG- Type I Respiratory Failure
What scoring system do NICE recommend using if suspecting a PE?
WELLS Score
What is the WELLS score used for?
To calculate the clinical possibility that the patient has a pulmonary embolism. A score of more than 4 than four points indicates that a PE is likely.
What WELLS score indicates that a PE is likely?
More than 4
What WELLS score indicates that a PE is unlikely?
4 or less
What criteria of the WELLS score?
Signs/Sx of DVT = 3 Points
Alternative Diagnosis less likely than PE= 3
HR>100= 1.5
Immobile for >3 days or surgery in the last 4/52= 1.5
Previous DVT/PE= 1
Haemoptysis= 1
Malignancy= 1
If malignancy present what does this score for WELLS?
1 point
What does haemoptysis score for WELLS?
1 point
What does a previous DVT/PE score for WELLS?
1 Point
What does immobility for >3 days or surgery in last 4/52 score for WELLS?
1.5 points
What does a HR>100 score for WELLS?
1.5 point
What does signs/sx of a PE score on the WELLS?
3 points?
What score is given if an alternative diagnosis is less likely than PE for WELLS?
3 points
A score of more than 4 on the WELLS criteria indicates that a PE is likely, what should be done?
CTPA
If delay to CTPA give LMWH (e.g. Enoxaparin, Fondaparinux)
(Note- Never do a D-Dimer if PE likely)
A score of four or less on the WELLS criteria indicates that a PE is no likely, what should be done?
D- Dimer
How should a positive D-Dimer be interpreted?
This is not an indication that a PE is present and so further investigation (CTPA) required Give LMWH (Enoxaparin/Fondaparinux) if delay to this
How should a negative D-Dime be interpreted?
Rule out PE
What are some contraindications to CTPA?
Allergy to CT contrast
Renal Impairment
(Note- never avoid doing a scan if outcomes of avoiding it can be severe)
What might done instead of a CTPA?
V/Q Scan
- less radiation but less reliable
What cardiac investigation might you request for a patient with suspected PE?
ECHO
Can show RV dilatation, stretch, hypokinesis, IV septum bulging and reduced LV filling
How do you manage a PE? (Supportive and Definitive)
Supportive- Oxygen, Analgesia
Definitive- Anticoagulation, Thrombolysis, Thrombectomy
Why is it important to give analgesia in PE except for the obvious reduction in pain?
Reduced pleuritic chest pain will lead to greater ventilation and so help to manage the hypoxia
What anti-coagulation therapy should be given initially for the management of PE?
LMWH- Enoxaparin, Fondaparinux via SC injection initially
To reverse the effects unfractionated heparin can be given- this requires careful INR monitoring, dose adjustment and continuous infusion so requires inpatient stay
What long term anti-coagulation therapy might be given after initial treatment for a PE?
Warfarin
NOAC- Apixaban, Rivaroxaban, Dabigatran
Warfarin requires continuous INR monitoring with a target therapeutic INR of 2-3. Continue with LMWH till this is reached.
NOACs do not require regular INR monitoring and are effective from first dose. However, they are more expensive and more difficult to reverse.
When might thrombolysis be considered for PE?
- For PE with major haemodynamic instability
- Cardiac arrest or arrest imminent
- Only to be considered by a senior physician- ideally a respiratory consultant
What are some absolute contraindications to thrombolysis?
Previous haemorrhagic stroke Ischaemic stroke in the last 6/12 CNS damage or neoplasms Recent major surgery/head injury (3/52) Known GI bleed in the last month Current known bleeding
If a PE is suspected in pregnancy and leg symptoms are also present what is the first investigation that should be done? What should be done if it is positive/negative?
Ultra sound doppler of the leg to investigate for DVT- if positive treatment for DVT/PE is the same = LMWH
If negative request a CXR
(Aim is to reduce radiation exposure)
If leg symptoms are absent what should be done for a pregnant lady with suspected PE?
CXR first
In a pregnant lady with suspected PE what should be done if the CXR is normal and abnormal?
Normal- V/Q Scan (if non-diagnostic do a CTPA)
Abnormal- CTPA
Can warfarin be given to a pregnant woman?
Absolutely not- it is teratogenic
Can be given 3 days after delivery
