Lecture 10: Pulmonary embolism Flashcards
What is an embolism?
Obstruction of a blood vessel by a forgein substance or blood clot that travels through the bloodstream, loding in a vessel and plugging it.
What can embolise?
- thrombus
- tumour
- air
- fat
- amniotic fluid
What is a pulmonary embolism?
The material passes through the right side of the heartand lodges in the pulmonary arteries
Where do pulmonary embolisms usually arise from?
DVT in the legs, particularly the popliteal vein and more proximal veins, including pelvic veins
-you can have no symptoms of DVT
What are the risk factors for a thromboembolism?
Virchow's triad -endothelial injury -stasis or turbulence of blood flow -blood hypercoagulability (you can have more than one)
- pregnancy
- prolonged immobilisation
- contraceptive pill
- long haul travel
- cancer
- heart failure
- obesity
- previous venous thrombolic embolism
- surgery >30mins
- thrombophilia
- hormone replacement therapy
- age
What can a DVT cause?
- stroke
- pulmonary embolism
- heart attack
How do you treat DVT/pulmonary embolisms?
Anticoagulants
What is the presence of risk factors in patients with PE?
-50% have an identifiable ‘temporary’ risk factor
-25% have cancer (pancreatic cancer most common for DVT/PE)
-25% no indentifiable risk factor
If someone has a DVT with no risk factor, you need to consider if there is an undetected malignancy
What are some hypercoagulable conditions (except pregnancy)?
- antithrombin 3 deficiency
- protein C or S deficiency causing resistance to activated protein C is most common risk factor for DVT/PE in young people
- lupus anticoagulant
- homocystinuria
- occult neoplasm
- rheumatoid arthritis (connective tissue disorders)
What is the outcome after a PE?
- sudden death (20%)
- respiratory failure (due to areas of V/Q mismatch/low right ventricular output/shunt via patent foramen ovale)
- pulmonary infarction (not as common as lungs receive blood from systemic system as well)
How does a PE cause acute right ventricular overload?
- pulmonary artery pressure increases if more than 30% of the total cross section of it is occluded
- leads to acute right ventricular dilatation and strain
- inotropes are released by the body to maintain systemic bp, causing pulmonary artery constriction which exacerbates the situation
- also the increased pumping of the right ventricle pushes on the left ventricle and makes the EDV lower, this leads to cardiogenic shock
- it also can cause arrythmias, which can lead to cardiac arrest
Why is a patent foramen ovale dangerous?
Right to left shunting through a patent foramen ovale
-leads to hypoxaemia and increased risk of paradoxial embolisation and stroke
What symptoms do you get in PE?
Common -dyspnoea -pleuritic chest pain (when you take a deep breath in) -cough Rarer -substernal chest pain -syncope -unilateral leg pain -haemoptysis (coughing of blood) -low grade fever -chest wall tenderness on palpation
(may have no symptoms)
What signs do you see in PE?
- tachypnoea (resp rate <16)
- decreased breath sounds
- accentuated second heart sound (pulmonary valve which you don’t usually hear, but you do here because right side is working harder)
- tachycardia
- fever
- diaphoresis (sweating)
- lower extremity oedema
- caridac murmur
- cyanosis
What are the main differential diagnoses for PE?
- pneumothorax
- pneumonia
- MI
- pericarditis
- pleurisy (fluid in pleura)
- musculo-skeletal chest pain
