PULMONARY EMBOLISM Flashcards
What are the usual causes of pulmonary infarction?
A pulmonary embolus is the normal cause of a pulmonary infarct, however, only a few PEs lead to infarction. For a PE to cause infarction it is normally in conjunction with hypotension or shock, or because there is increased pulmonary venous pressure (for example in left ventricle failure).
Which vessels are more likely to end up with pulmonary infarction if they are hit with a pulmonary embolus?
Infarction, as a result of a PE, usually happens in smaller vessels (<3mm).
Why do only a minority of pulmonary emboli result in infarction?
Following a pulmonary embolus, the bronchial arteries often feed the pulmonary capillary network through anastomoses. The higher pressure of the bronchial arteries compared to the pressure in the capillary system, in combination with locally increased vascular permeability and capillary endothelial injury leads to an extravasation of blood cells into the alveolar and bronchial cavities. Usually the blood cells will be reabsorbed and the tissue regenerates with restitute ad integrum.
What percentage of pulmonary emboli lead to pulmonary infarction?
Only about 10-15% of pulmonary emboli result in infarction.
What are the possible causes of the embolus?
Thrombus - most often from a deep vein thrombosis in the leg
Fat - following a lone bone fracture
Amniotic fluid
Air - following neck vein cannulation or bronchial trauma
Infection
What are the risk factors for thrombosis and hence pulmonary emboli?
Smoking
Period of reduced movement - such as air travel
IV drug use
Fracture
Malignancy
Varicose veins
Major abdominal or pelvic surgery or joint replacement
Late pregnancy
Hypercoagulability of blood (thrombophilia)
Infection
Define pulmonary embolism.
Pulmonary embolism (PE) is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream.
How might someone with a suspected pulmonary embolism present? (Name 5 symptoms)
Sudden onset Pleuritic chest pain Dyspnea/Tachypnea Cough Haemoptysis
On examination, what signs might be detected in someone with suspected PE? (Name at least 5 signs)
Tachycardia Central cyanosis (if severe) Anxiety Impaired consciousness Raised JVP Gallop rhythm Split S2 Tricuspid regurgitation murmur Hypotension Low grade fever Pleural rub Pleural effusion LUNGS OFTEN NORMAL
What would form the rest of your differential diagnosis with someone who presents with chest pain, dyspnoea and collapse?
ACS (STEMI, NSTEMI and Unstable angina) Aortic dissection Cardiac tamponade Pneumonia Pneumothorax Sepsis
What is the name of the score used to work out the clinical probability of the correct diagnosis being a PE?
The two level Well’s score.
What is taken into account in the two level Well’s score? For each component give the number of points that it signifies.
Signs and symptoms of DVT - 3 points
Alternative diagnosis less likely - 3 points
Tachycardia >100 - 1.5 points
Immobilisation for more than 3 days or surgery in previous 4 weeks - 1.5 points
Previous PE/DVT - 1.5 points
Haemoptysis - 1 point
Malignancy - 1 point
What is the cut off in terms of point in the two-level Well’s score?
More than 4 points likely to be PE
4 points of less unlikely to be PE
What investigations should someone with suspected PE have?
FBC O2 sats Troponin ECG Chest x-ray ABG CTPA - computed tomography pulmonary angiogram D-dimer - used more to discount PE Consider Pulmonary angiography Echocardiogram
What investigation could be used for a patient who is allergic to contrast media?
Ventilation/perfusion single-photon emission computed tomography (V/Q SPECT)
