Pulmonary Embolism Flashcards
What is an embolism?
An obstruction of a blood vessel by a foreign substance or blood clot that travels through the bloodstream and lodges in a distal blood vessel
What is a pulmonary embolism?
An ebolism where the material passes through the right side of the heart and lodges in the pulmonary arteries
Aside from blood clots, what other things can embolise?
- Tumour
- Air
- Fat (after bone fracture)
- Amniotic fluid
- Bullets
What is fat embolism syndrome?
A serious manifestation of fat emboli that affects the lungs, CNS and skin and may cause death!
Where do 90% of pulmonary embolism arise from?
DVT
Predominantly the popliteal vein and more proximal veins including pelvic veins
What 3 primary factors make up Virchow’s triad and predispose to blood clotting?
- Endothelial injury
- Stasis or turbulence of blood flow
- Blood hypercoagulability
Explain the normal clotting cascade
Give some risk factors for thromboembolism
- Pregnancy
- Prolonged immobolisation
- Previous VTE
- Contraceptive pill
- Long haul travel >4 hrs
- Cancer
- Heart Failure
- Obesity
- Surgery >30 mins
- HRT
- Thrombophilia
Which cancer has the highest risk of someone getting PE?
Pancreatic Cancer
Which conditions make a patient hypercoaguable
- Antithrombin III deficiency
- Protein C or protein S deficiency/ resistance
- Lupus anticoagulant
- Homocystinuria
- Occult neoplasm
- Connective tissue disorders such as RA
What is the most common risk factor for DVT/ PE in younger people?
Factor V Leiden mutation causing resistance to activated Protein C
What is the main cause of death if someone has PE?
Acute right sided heart failure leading to:
- cardiogenic shock and/or
- cardiac arrest secondary to arrythmia
How does PE cause acute right ventricular overload?
- PE causes an increase in pulmonary artery pressure if >30% of the pulmonary artery bed is occluded
- Increased right ventricular dilation and strain
- Inotropes released by the body in an attempt to maintain systemic BP cause further pulmonary artery vasoconstriction which further exacerabates the situation
What increases risk of severe hypoxaemia, paradoxical emboli and stroke?
Patent Foramen Ovale
How does PE lead to respiratory failure?
- Areas of V/Q mismatch
- Right ventricle has low output
- R → L shunt if patent foramen ovale causes deoxygenated blood to go into systemic circulation causing profound hypoxaemia
How does pulmonary embolism cause pulmonary infarct?
- Small distal emboli may create areas of alveolar haemorrhage
- Results in haemoptysis, pleuritis and small pleural effusion
- Only happens in 10-20% cases
- May be visible of CXR as a wedge shape
What are some of the symptoms of PE?
- Dyspnoea (60-75%)
- Pleuritic chest pain (40-65%)
- Substernal chest pain (15%)
- Cough (25-35%)
- Haemoptysis (8-15%)
- Syncope (6%)
- Unliateral leg pain (6%)
- Fever (10-15%)
- Chest wall tenderness on palpation
What are some of the physical signs of PE?
- Tachypnea (>16 resp rate) (90-96%)
- Rales/ decreased breath sounds (50%)
- Accentuated second heart sounds loud P2 (50-55%)
- Tachycardia >100bpm (44-50%)
- Fever (30-45%)
- Siaphoresis
- Clinical signs and symptoms of thromboplebitis
- Lower exremity oedema
- Cardiac murmor
- Cyanosis
What investigations would you you carry out to diagnose PE?
- Blood gases
- CXR
- ECG
- D dimers
What may you see on blood gases that would indicate PE?
- Hypoxaemia and hypocapnia (respiratory alkalosis) due to hyperventilation
- PaO2 may be normal in a minority
What would you see on CXR if someone has PE?
Chest X-Ray will be normal!!
Done to exclude other diagnoses
What might you see on ECG if someone has PE?
Signs of right ventricular strain
- T wave inversion in right precordial leads (V1-V4 and the inferior leads II, III and aVF)
- Classical finding is SI QIII TIII
What are D-dimers?
D dimers are products of fibrin degredation that are released into the blood when a thrombus is degreated by fibrinolysis
A normal D-Dimer would rule out PE
What is the criteria used for assessing PE?
Well’s Criteria
A score >4 = PE is likely and imaging is recommended
A score <4 and D dimers + = imaging recommended
A score <4 and D dimers are negative = PE unlikely
