Pulmonary Embolism Flashcards
What is the definition of pulmonary embolism?
Blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream
What are the 5 types of pulmonary embolism?
- thrombus (DVT)
- fat embolus
- air embolus
- amniotic fluid embolus
- foreign material
what are the non-specific symptoms associated with pulmonary embolus?
- dyspnoea
- tachypnoea
- pleuritic chest pain
- cough
- haemoptysis
What are the more severe symptoms associated with pulmonary embolus?
- haemodynamic instability
- collapse/syncope
- sudden death
What is an issue when performing an examination for a suspected pulmonary embolism?
The findings are very non specific
What are typical findings associated with pulmonary embolism?
- tachycardia
- tachypnoea
- pleural rub/effusion
- raised JVP
What is significant about the clinical findings of someone with pulmonary embolus?
they are all associated with right heart strain
this is because there is increased work load due to increased resistance in the pulmonary circulation
What is the the ECG pattern associated with pulmonary embolus?
S1 Q3 T3
S waves in lead 1
Q waves in lead 3
Inverted T waves in lead 3
How can the risk factors for VTE be classified?
By Virchow’s triad
This includes:
- stasis
- vessel wall injury
- hypercoagulability
What is meant by unprovoked and provoked VTEs?
Provoked has a clear cause - e.g. following trauma or surgery
Unprovoked has no known cause
Why is it important to know whether a VTE is provoked or unprovoked?
It affects the risk of recurrence and influences what treatment should be given to the patient
If a patient presents with signs or symptoms of a pulmonary embolism, what should be done?
carry out an assessment of their general medical history
a physical examination
a chest X-ray to exclude other causes
What should be done if a pulmonary embolism is suspected after initial assessment?
the two-level PE Wells score is used to estimate the clinical probability PE
What are the clinical features in the Wells score that are awarded 3 points?
- clinical signs and symptoms of DVT
2. an alternative diagnosis is less likely than PE
What are the clinical features in the Wells score that are awarded 1.5 points?
- heart rate > 100 beats per min
- immobilisation for more than 3 days or surgery in the previous 4 weeks
- previous DVT/PE
What are the clinical features in the Wells score that are awarded 1 point?
- haemoptysis
2. malignancy (on treatment, treated in the last 6 months, or palliative)
What does a Wells score show?
PE is likely if score is MORE than 4 points
PE is unlikely if score is 4 points or less
What test is offered if PE is unlikely and Wells score is 4 or less?
D-dimer test
What happens if the D-dimer test is negative?
assume there is no PE
What happens if the D-dimer test is positive?
Then it is treated that PE is likely and CT pulmonary angiogram is conducted
What test is performed if PE is likely and Wells score is more than 4?
CT pulmonary angiogram
What happens based on the results of the CTPA?
if it is negative, consider repeat D-dimer
if it is positive, treat as PE
What does a D-dimer test measure?
It measures fibrin degradation products that are produced when a clot is broken down
How do the clotting cascade and fibrinolysis system work at the same time during clotting?
thrombin converts soluble fibrinogen to insoluble fibrin
fibrin is crosslinked by factor 13 to form the scaffolding of the blood clot
at the same time, the fibrinolysis system involves plasmin breaking down the mesh work to form D-dimers
What is the normal concentration of D-dimer in the blood?
D-dimers are not normally present in the blood at a meaningful concentration
They are only present when the coagulation system has been activated
What is the sensitivity of D-dimer test like?
93-95% sensitivity
When may false negatives occur in the D-dimer test?
they are rare
they occur when a sample is delayed or too early
or if the patient is on anticoagulants
When may false positives occur in the D-dimer test?
- liver disease
- inflammation
- malignancy
- trauma
- pregnancy
- recent surgery
What is injected during a CTPA?
How can this identify an embolus?
Iodine based contrast is injected
All blood vessels should show up as bright white
Any dark filling detected is an embolus
What type of patients is CTPA not suitable for?
patients with renal failure, allergy to iodine, pregnancy
What is an alternative test that can be used to diagnose pulmonary embolism?
VQ scan (ventilation perfusion mismatch scan)
radioactive molecules are inhaled/injected and the difference in the 2 scans are identified
What scan is used to diagnose PE in pregnancy?
usually a doppler scan on the leg is performed to look for a DVT
What determines the acute treatment that a patient with PE receives?
The severity of the PE
What are the 4 main acute treatments for PE?
- supportive therapy - IV fluids, inotropes, respiratory support
- acute phase anticoagulation and initiate VKA
- primary reperfusion
- embolectomy
What scoring system is used to determine the severity of a pulmonary embolism?
PESI - pulmonary embolism severity index
What is an embolectomy?
the removal of a blood clot/embolism through surgery
What is the recommended anticoagulant used in treating PE?
unfractionated heparin
Why is UFH the main anticoagulant used in PE?
It has a short half life
It is reversible
It is easy to monitor
How can UFH be reversed?
Why might this happen?
reversible with protamine
e.g. if a patient is going to go to theatre
What are examples of oral anticoagulants?
Which require heparin before administration?
rivaroxaban and apixaban do not need heparin first
dabigatran and edoxaban need an initial supply of heparin to be given first
What are the benefits of oral anticoagulants?
- reduced risk of major bleeding
- rapid onset of action
- short-acting
- do not require monitoring
Which patients should UFH always be prescribed?
Obese and anorexic patients
patients with renal impairment
Which patients with PE should always be given LMWH?
- active cancer
- hepatic impairment
- coagulopathy
- pregnant patients
Why should LMWH be given to pregnant patients?
It does not cross the placenta
What is significant about Fondaparinux (oral anticoagulant)?
it carries a low risk of inducing heparin-induced thrombocytopenia (HIT)
what is HIT?
heparin induces an immune reaction
antibodies are produced to the body’s own platelets
this reduces the platelet number and leads to a DIC phenotype
What are the absolute contraindications for primary reperfusion?
- haemorrhagic stroke
- ischaemic stroke in the preceding 6 months
- central nervous system damage or neoplasms
- recent major trauma/surgery
- gastrointestinal bleeding within the last month
- known bleeding risk
What are the relative contraindications for primary reperfusion?
- transient ischaemic attack in preceding 6 months
- oral anticoagulation therapy
- pregnancy, or within 1 week postnatally
- traumatic resuscitation
- refractory hypertension
- advanced liver disease
- infective endocarditis
- active peptic ulcer
What is catheter directed therapy and when is it used?
giving the thrombolytic agent directly at the site of the thrombus
this is commonly used for large DVTs
What is the benefit of catheter directed therapy?
localising the drug minimises the bleeding risk
it can also be given at a lower dose
When is a surgical embolectomy usually performed?
if systemic thrombolysis is given and there is no improvement in the patient
What is an IVC filter and why is it used?
it is placed in the inferior vena cava in patients who have had multiple recurrent PEs
This works by trying to stop the clots reaching the lungs
What is the ongoing anticoagulation for patients with a PE provoked by surgery?
3 months at least of anticoagulation
this is usually with warfarin or UFH
What is the ongoing anticoagulation for patients with a PE provoked by a non-surgical transient risk factor?
3 months
What is the ongoing anticoagulation for patients with unprovoked PE with low or moderate bleeding risk?
extended anticoagulation therapy
What usually causes an amniotic fluid embolus?
A tear in the placental vein or defects in the gynaecological vessels
This can lead to amniotic fluid entering the maternal circulation
