Pulmonary Embolism
Aetiology
Clot breaks off and passes through the veins and right heart before lodging in the pulmonary circulation
Rare Causes
Venous thrombosis in the pelvis or legs (iliofemoral veins)
Parasite
Amniotic fluid embolism
Septic emboli (right sided endocarditis
Neoplastic cells
RV thrombus post MI
Risk Factors
Prolonged bed rest/reduced mobility
Malignancy
Leg fracture
Pregnancy, postpartum, oral contraceptive pill, HRT
Thrombophilia e.g. antiphospholipid syndrome
Previous PE
Recent surgery: especially abdominal, pelvic, hip, knee
Pathophysiology
Acute RH failure
Small embolus will impact in a terminal, peripheral pulmonary vessel - may be clinically silent unless it causes pulmonary infarction
Sudden increase in pulmonary vascular resistance
Lung tissue is ventilated but not perfused, leads to impaired gas exchange
Massive embolism obstructs RV outflow tract
Symptoms
Haemoptysis
Dizziness
Pleuritic chest pain
Syncope
Acute breathlessness
Signs
Tachypnoea
Tachycardia
Cyanosis
Hypotension
Pyrexia
Pleural effusion + pleural rub
Raised JVP
Investigations
ABG may show low PaO2 and low PaCO2
Chest X-ray: dilated pulmonary artery, small pleural effusion
D-dimer test: negative D dimer excludes PE but positive doesn't mean it's PE, further imaging is needed
CT pulmonary angiography - shows clot
FBC, baseline clotting
ECG can show tachycardia, RBBB
Treatment
Long term anticoagulation: DOAC or warfarin
If haemodynamically unstable, then thromboylse with alteplase IV
Commence LMW heparin. Stop heparin once INR >2
Treat hypotension with fluids
Start treatment before definitive investigations as most deaths occur within 1 hour
Give oxygen if hypoxic
Prevention
Stop HRT and pill pre op
Compression stockings
Give heparin to immobile patients
Early mobilization post op
Calculate risk of PE by using Wells Criteria