Lecture 22 - PE Flashcards
Pulmonary embolism
Obstruction of a blood vessel by a foreign substance distal to the site of origin
Embolus substances
Thrombus Tumour Amniotic fluid Fat - fracture of long bones Air Bullet
Fat embolism syndrome
Triad of lung, brain and skin
How can fat embolism to the brain
Via a patent foramen ovale
Where do most PEs arise from
90% arise from DVTs
25% of those have symptoms of DVT
Risk factors for PE
Endothelial injury
- surgery
Stasis or turbulent blood flow
- immobile
- long haul flight
- heart failure
Blood hypercoagulabilty
- COCP
- inherited disorders e.g thrombophilia
- cancer (pancreatic)
- obesity
- pregnancy
Factor Xa
Factor Xa activates fibrin from fibrinogen to form a clot
Hypercoaguable conditions
Antithrombin III deficiency Protein C or S deficiency/ resistance (anticoagulants) Lupus anticoagulant Homocystinuria Occult neoplasm Chronic inflammation e.g RA
How does a PE cause right ventricular overload
- Pulmonary artery hypertension if more than 30% occlusion
- High right ventricle afterload
- Right ventricle hypertrophy
- Eventually the right ventricle will dilate
Inotropes
- Right sided heart failure decreases blood pressure due to decreased venous return.
- inotropes are released to increase blood pressure by causing systemic vasoconstriction
- pulmonary artery vasoconstriction further increases right sided afterload
Main cause of death in PE
- cardiogenic shock with circulatory failure
- cardiac arrest secondary to arrhythmias
PE with patent foramen ovale
- Due to the increased pressure in the right ventricle, blood flows from right to left
- causes cyanosis and hypoxaemia
Paradoxical embolism
Embolus carried from the venous system to the arterial system
Occurs due to patent foramen ovale
How does PE cause respiratory failure?
- areas of ventilation perfusion mismatch
- low right ventricle output
- shunt with patent foramen ovale
Pulmonary infarct
Not common as lungs have a collateral circulation
- small distal emboli create areas os alveolar haemorrhage
- haemoptysis, pleuritis, small pleural effusion
Symptoms of PE
Common:
Dyspnoae
Pleuritic chest pain
Less common:
Cough
Haemoptysis
Syncope
Signs of PE
Tachypnoea (16+)
Decreased breath sounds
Accentuated second heart sounds (P2) - pump against resistance
Tachycardia (100+)
Investigations
ABG
- hypoxaemia
- hypocapnia - respiratory alkalosis due to hyperventilation
Oxygen saturation
CXR
- NORMAL
- exclude other diagnosis
ECG - not diagnostic
Blood tests
- D-dimer raised - if normal can rule out if low risk for PE
ECG
- right ventricle strain (broad complex QRS)
- supraventricular tachycardia
- T wave inversion in lead III
- deep S wave in Lead I
- Q wave in Lead III
Imaging for PE
Invasive:
Pulmonary angiogram
Ventilation perfusion lung scintigraphy
Non invasive:
CT pulmonary angiography
- high specificity and sensitivity
Saddle pulmonary embolism
Large pulmonary embolism that partially occludes the bifurcation of the pulmonary trunk therefore affects the left and right pulmonary artery
Treatment of low risk PE patient
Oxygen
Immediate IV heparinisation
Oral warfarin
How does heparin treat PE
Stops propagation of embolism
Allows body’s fibrinolytic system to lose the embolus
Risk of heparin use
Heparin induced thrombocytopenia
Treatment of high risk patients
Oxygen Haemodynamic support Exogenous fibrinolytics e.g streptokinase (can only use once) Thrombectomy Embolectomy
