S6) Pulmonary Embolism Flashcards
What is an embolism?
An embolism is the movement of material from one part of the circulation to another
What is a pulmonary embolism?
A pulmonary embolism is when and embolism passes through the right side of the heart and lodges in the pulmonary arteries
Identify 6 types of material that can cause an embolism
- Thrombus
- Tumour
- Air
- Fat
- Amniotic fluid
- Bullet
What is the most common cause for a pulmonary embolism?
90% of PE arise from a deep vein thrombosis (DVT) in the legs, particularly the popliteal vein and more proximal veins including pelvic veins
How many patients with a PE show signs/symptoms of a DVT?
25%
In terms of causes of death, where does PE fall?
- 3rd commonest cause of vascular death (after MI and stroke)
- Commonest cause of preventable death in hospital patients
Identify 8 risk factors for thrombo-embolism
- Pregnancy (6x)
- Contraceptive pill (3x)
- Prolonged immobilisation (3x)
- Previous thromboembolism (3x)
- Cancer (2.8x)
- Obesity (2.4x)
- Surgery > 30 minutes (2.3x)
- Age > 40 years (2.1 x)
Describe the presence of risk factors in patients with PE
- 50% have an identifiable ‘temporary’ risk factor (surgery, oestrogen treatment, etc)
- 25% have cancer (permanent risk factor)
- 25% have no identifiable risk factor
What is the likelihood of sudden death after PE?
20%
Identify 3 effects of PE
- Right ventricular overload
- Respiratory failure
- Pulmonary infarction
In four steps, explain how right ventricular overload occurs in the pathophysiology of PE
⇒ Pulmonary artery pressure increases if more than 30% of the total cross section of the pulmonary arterial bed is occluded
⇒ Right ventricular dilatation and strain
⇒ Inotropes are released to maintain systemic BP
⇒ Pulmonary artery vasoconstriction
What effect does right-to-left shunting through the foramen ovale have on the pathophysiology of PE?
May lead to severe hypoxaemia and an increased risk of paradoxical embolisation and stroke
How does respiratory failure occur in the pathophysiology of PE?
Respiratory failure is due to areas of ventilation perfusion mismatch and low right ventricle output
How does pulmonary infarction occur in the pathophysiology of PE?
Pulmonary infarction occurs as small distal emboli create areas of alveolar haemorrhage resulting in haemoptysis, pleuritis, and small pleural effusion
Identify 7 symptoms of PE
- Dyspnoea (50%)
- Pleuritic chest pain (39%)
- Cough (23%)
- Fever (10%)
- Haemoptysis (8%)
- Syncope (6%)
- Unilateral leg pain (6%)
What are the main differential diagnosis for PE?
- Myocardial infarction
- Pneumothorax
- Pneumonia/pleurisy
Identify 2 physical signs in PE
- Pleural rub in cases of pulmonary infarction
- Raised JVP
Identify and describe 4 investigations for PE
- Chest X-ray used to exclude other diagnoses as (PE has normal CXR)
- ECG may show signs of right ventricular strain (T wave inversion)
- Blood gases may show hypoxaemia and hypocapnia due to hyperventilation
- D-dimer as a negative value rules out PE in patients with a low likelihood
What are D-dimers?
D-dimer is a fibrin degradation product, a small protein fragment released into the blood when a thrombus is degraded by fibrinolysis
What imaging can be used for PE?
- CT Pulmonary angiography
- Ventilation perfusion lung scintigraphy
What form of treatment is given to patients with both low and high risk of PE?
Immediate heparinisation as this reduces mortality
How does heparinisation reduce mortality of PE?
- Stops thrombus propagation in the pulmonary arteries
- Allows the body’s fibrinolytic system to lyse the thrombus
- Stops thrombus propagation at the embolic source
- Reduces the frequency of further PE
Identify 5 types of treatment in high risk patients for PE?
- Haemodynamic support
- Respiratory support
- Exogenous fibrinolytics (streptokinase/tPA)
- Percutaneous catheter directed thrombectomy
- Surgical pulmonary embolectomy
