Flashcards in Session 6 - Pulmonary Embolism Deck (19)
What is the most common cause of pulmonary embolism?
Deep vein thrombosis in the legs (particularly the popliteal vein and pelvic veins)
What are the risk factors for thromboembolism?
Long haul travel (>4 hours)
What are the three possible causes of death in pulmonary embolism?
1. Right ventricular overload
2. Respiratory failure
3. Pulmonary infarction
Explain the pathophysiology of right ventricular overload in pulmonary embolism.
Pulmonary artery is occluded, increase in pressure. This leads to right ventricular dilatation and strain.
What are the possible symptoms of pulmonary embolism?
Pleuritic chest pain
Substernal chest pain
Unilateral leg pain
What is meant by pulmonary infarction?
Small distal emboli may create area of alveolar haemorrhage resulting in haemoptysis, pleuritic and small pleural effusion. This clinical presentation is know as pulmonary infarction.
What are the signs of pulmonary embolism?
Pleural rub in cases of pulmonary infarction
Why is a chest X ray not useful as a primary diagnostic tool for pulmonary embolism?
By far the commonest finding in PE is a normal CXR. A CXRE may be done to exclude other diagnoses.
What might an ECG show in pulmonary embolism?
An ECG may show signs of right ventricular strain - T wave inversion in the right precordial leads (V1-V4 and the inferior leads, II, III and aVF).
Not useful as a primary diagnostic tool.
What may blood gases show in pulmonary embolism?
May show hypoxaemia and hypocapnia (due to hyperventilation)
What is the significance of D-dimer in pulmonary embolism?
A normal D-dimer effectively rules out PE in those at low likelihood of having PE. In those with high likelihood of having a PE the negative predictive value of D-dimmer is too low to use.
What is D-dimer?
D-dimer is a fibrin degradation product released into the blood when a thrombus is degraded by fibrinolysis. D-dimers are not normally present in the blood except when the coagulation system has been activated.
A negative D-dimer result practically rules out thrombosis in patients with a low clinical likelihood of PE.
What is the best imaging technique to use to diagnose PE?
CT Pulmonary angiography
What is a saddle embolus?
A form of large pulmonary embolism that straddles the main pulmonary arterial trunk at its bifurcation.
How is pulmonary embolism treated?
Immediate intravenous heparin
Later started on oral anticoagulant (warfarin), for 3 months if there’s an identifiable ‘temporary’ risk factor, indefinitely if cancer or no identifiable risk factor
How does heparinisation reduce mortality?
1. Stops thrombus propagation in pulmonary arteries and allows the body’s fibrinolytic system to lyse the thrombus
2. Stops thrombus propagation at the embolism source and reduces the frequency of further pulmonary embolism
How would treatment of high risk patients differ to normal treatment?
Exogenous fibrinolytics (streptokinase/tPA) - delivered directly via a percutaneous catheter into the pulmonary arteries
Percutaneous catheter directed thrombectomy
Surgical pulmonary embolectomy
Give examples of conditions that would mean patients cannot be safely anticoagulated?
Oesophageal varices, previous haemorrhaging stroke, severe thrombocytopenia)