Pulmonary Embolism Flashcards
What is an embolism
• The movement of material from one part of the circulation to another.
• The material may or may not be derived from the circulation itself.
• Pulmonary embolism means that the material passes through the right side of the heart and lodges in the
pulmonary arteries. Pulmoally usually goes through popliteal vein
Thrombus, tumours air, fat, amniotic fluid, bullet
Describe typical PE
• When we talk about pulmonary embolism in daily practice we mean thrombus entering the right side of the heart and pulmonary arteries
– 90% of PE arise from a deep vein thrombosis (DVT) in the legs, particularly the popliteal vein and more
proximal veins including pelvic veins
– However, only 25% of patients with a PE have symptoms or signs of a DVT
• Third commonest cause of vascular death, after
myocardial infarction and stroke • The commonest cause of preventable death in
hospital patients • The risk factors are the same as those for DVT
What are risk factors for thromboembolism
Most of the factors that precipitate it increase with age. Risk increases with age • Pregnancy 6x • Prolonged immobilisation (3x) • Previous VTE 3x • Contraceptive pill 3x • Long haul travel (> 4 hrs) (3x) • Cancer 2.8x • Heart failure 2.8x • Obesity 2.4x • Surgery > 30 mins 2.3x • HRT 2x • Thrombophilia - depends on type • Smoking 1.17x
Decsribe 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
Describe the main factor pathophysiology of PE
- Right ventricular overload
• Pulmonary artery pressure increases if more than 30% of the total cross section of the pulmonary arterial bed is occluded.
• This leads to right ventricular dilatation and strain (think of Frank Starling curve).
• Also inotropes are releases in an attempt to maintain systemic BP: these cause pulmonary artery vasoconstriction that further exacerbates the situation.
• This is the main cause of death in PE
• In about one-third of patients, right to-left shunting through a patent foramen ovale is present and may lead to severe hypoxaemia and an increased risk of paradoxical embolization and stroke
What are other factors in the pathophysiology of pe
- Respiratory failure
• Areas of ventilation perfusion mismatch
• Low right ventricle output - Pulmonary infarction
• Small distal emboli may create areas of alveolar haemorrhage
• Resulting in haemoptysis, pleuritis, and small pleural effusion
Not much return circulation - infarction
What are the symptoms of PE
Dypnoea 50%, pleuritic chest pain 39%, cough 23%, substernal chest pain 15%, fever 10%, haemolysis 8%, syncope 6%, unilateral leg pain 6%
Wha are some physical signs of PE
- Obvious dyspnoea
- Tachycardia
- Low BP
- Raised JVP (due to RV failure)
- Pleural rub in cases of pulmonary infarction (pleurisy occurs after pulmonary infarcion)
- Look for evidence of DVT
What are th differential diagnoses
• Pneumothorax • Pneumonia • Pleurisy • Musculo-skeletal chest pain • Myocardial infarction • Pericarditis
What are the investigations
• Blood gases (only if concerned if quite hypoxic):
– May show hypoxaemia and hypocapnia (respiratory alkalosis) due to hyperventilation
– Undertaken if evidence of hypoxia requiring oxygen
• Chest X-ray:
– By far the commonest finding in PE is normal
– May be done to exclude other diagnoses
• 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).
– The ‘classic’ finding is SI QIII TIII
– Not useful as a primary diagnostic tool
– D-dimer is a fibrin degradation product, a small protein fragment released into the blood when a thrombus is degraded by fibrinolysis
– A normal D-dimer effectively rules out PE in those at low likelihood of having a PE
– In those at high likelihood the negative predictive value of D-dimer is too low to use
What is the commonest ecg finding in patients with PE
Comminest inning in patient with PE is sinus tachycardia
What is the wells criteria for PE
(Dont have to learn in) see slide for general idea
Tries to take into account factors for patients which might have PE - helps with diagnostic probability, helps to determine next step. If wells score >4, doesn’t matter what d dimer test is
If wells score 04-, less likely. Next step is blood test. D dimer. If d dimer is negative - rules out PE
Wat are imaging techniques used
NOT used anymore - histr: — pulmonary angiography
— ventilation perfusion lung scintography - not diagnostic
NOWuse
CT pulmonary angiography CTPA
Describe a saddle embolus
See slide
What is given to treat pe
If someone is hypoxic give oxygen
• Immediate heparinisation - blood thin
• This reduces mortality.
• Study showed that 26% of patients with PE and no treatment died whereas no death due to PE occurred in the intravenous heparin group
• IV heparin now superseded by SC Low Molecular Weight Heparin
— when treated earlier, reduces mortality