D: Occlusion of pulmonary vessels, most commonly by a thrombus that has travelled to the vascular system from another site.
A: Thrombus (> 95% originating from DVT of the lower limbs and rarely from right atrium in patients with atrial fibrillation). Other agents that can embo-lise to pulmonary vessels include amniotic fluid embolus, air embolus, fat emboli, tumour emboli and mycotic emboli from right-sided endocarditis.
A/R: Risk factors for DVT (Virchow's triad*), e.g. surgical patients, immobility, obesity, OCP, heart failure, malignancy.
E: Relatively common, especially in hospitalised patients, they occur in 10-20% ^^ of those with a confirmed proximal DVT.
H: Depends on the size and site of the pulmonary embolus: Small: May be asymptomatic.
Moderate: Sudden onset dyspnoea, cough, haemoptysis and pleuritic chest pain.
Large (or proximal): All of the above plus severe central pleuritic chest pain, shock, collapse, acute right heart failure or sudden death. Multiple small recurrent: Symptoms of pulmonary hypertension.
E: Small: Signs may be absent. Low-grade pyrexia and tachycardia. Low saturation O2.
Moderate: Tachypnoea, tachycardia (may be atrial fibrillation), pleural rub, low saturation O2 (despite oxygen), signs of DVT (see Deep vein thrombosis). Massive PE: Shock, cyanosis, signs of right heart strain (" JVP, left parasternal heave, accentuated S2).
Multiple recurrent PE: Signs of pulmonary hypertension and right heart failure.
P: Moderate PE: Occlusion of pulmonary artery branches causes pulmonary infarction and a peripheral wedge-shaped haemorrhagic area. There may be a coexisting compromised collateral bronchial artery circulation. Massive PE: Large emboli may wedge at the pulmonary artery bifurcation (saddle embolus).
I: Bloods: ABG, D-dimer tests (for cross-linked fibrin degradation products released into the circulation following fibrin breakdown; it is not very specific, especially if post-surgical but negative result makes PE very unlikely); thrombophilia screen if indicated prior to starting anticoagulation. ECG: May be normal or more commonly show a tachycardia, right axis deviation or RBBB. Classical S|, Qui, Tm pattern is relatively uncommon. CXR: Often normal. May show a wedge-shaped peripheral opacity, pulmonary oligaemia (# vascular markings), linear atelectasis or a small pleural effusion. Mainly to exclude other differential diagnoses.
Ventilation-perfusion scan: Administration of IV 99mTc macro-aggregated albumin and inhalation of 81krypton gas. This identifies any areas of ventilation and perfusion mismatch that would indicate infarcted lung. May be difficult to interpret if there is coexisting lung disease.
Spiral CT pulmonary angiogram: Non-invasive. Poor sensitivity for small emboli, but very sensitive for medium to large emboli. Investigation of choice if there is underlying lung disease.
Pulmonary angiography: Gold standard, but invasive. May be done prior to surgery for massive emboli.
Doppler USS of the lower limb: To examine for venous thrombosis. Echocardiogram: May show thrombus in heart or pulmonary artery.
M: Primary prevention: Graduated pressure stockings (TEDs) and heparin prophylaxis in those at risk (e.g. undergoing surgery). Early mobilisation and adequate hydration post surgery.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...