Pulmonary Thromboembolism Flashcards
What is a pulmonary embolism?
An obstruction of the pulmonary arteries by clot from the veins of the systemic circulation.
- over 90% arrive from a DVT in the leg or pelvis
Very rarely it can be caused by a fat embolus, air, or post-partum amniotic fluid
What are the predisposing risk factors for a pulmonary embolism? - Risk factors are present in over 90% of cases
Surgery less than 12 weeks ago Being immobile for more than 3 days in the last 4 weeks Previous DVT/PTE Positive family history Pregnancy or up to 6 weeks postpartum Long distance travel Oestrogen - including OCP use
What are two of the genetic risk factors of a pulmonary embolism?
Factor V Leiden point mutation - increases oestrogen risk
Prothrombin G20210A point mutation in gene 3’-UTR
What are the signs and symptoms of a pulmonary embolism?
Pleuritic chest pain Dyspnoea Cough Haemoptysis Syncope Tachypnoea Crackles in the lungs Tachycardia (over 100bpm) Fever over 37.8C Signs of peripheral DVT
What are the acute changes in the pathophysiology of a pulmonary embolism?
Anatomical obstruction of the pulmonary vascular bed
- increased pulmonary vascular resistance
Right ventricular strain (with or without dilation)
Reduced mixed venous oxygen content - right to left shunting through the PFO
Increase in the alveolar-arterial gradient (hypoxaemia in large PE cases)
When the body attempts to compensate for a pulmonary clot, what pathophysiology occurs?
Partial lysis of the clot
Recovery of right ventricular function
Vasoconstriction occurs in the less well ventilated parts, which increases the PAP
- increased pulmonary arterial pressure leads to increased perfusion of poorly perfused areas
- can fluctuate between this and decreased perfusion in poorly ventilated areas if the increases PAP is ineffective at shifting the clot
Decreased surfactant in obstructed zones causes atelectasis
- PaO2 remains low
What investigations would you run on someone with a suspected pulmonary embolism?
D-dimer - raised in a PTE (over 230mg/L)
Arterial blood gases
- usually find respiratory alkalosis (decreased PaCO2)
- hypoxaemia only seen with large PTE
Troponin levels
ECG - sinus tachycardia and atrial fibrillation (S1Q3T3)
- S-waves in lead 1, Q-waves in lead 3 and inverted T-waves in lead 3
Echocardiogram- look for RV strain
Radiology - X-Ray, CT-pulmonary angiogram and V/Q scan
What could you expect to see on an X-Ray if someone has a pulmonary embolism?
Sub-segmental atelectasis (small lung collapses)
What could you expect to see on a CT-pulmonary angiography if someone has a pulmonary embolism?
Contrast dye is passed through the main coronary arteries and any pulmonary embolus is lit up
When would a ventilation/perfusion scan be performed?
If the chest X-Ray was normal, or if the patient is pregnant
If the results are negative or positive, it is very specific, but ambiguous answers are difficult to manage
How would a massive pulmonary embolism be defined?
Defined as PE associated with a systolic blood pressure of less than 90mmHG
- or a drop in systolic BP of over 40mmHg in under 15 mins
How would a massive pulmonary embolism be treated?
Unfractioned heparin IV
Fluid resuscitation
Thrombolysis with alteplase in they fail to improve - only considered during a massive PE
How would a sub-massive pulmonary embolism be treated?
Initially treated on low-molecular weight heparin (dalteparin)
- then they are moved onto oral anti-coagulation for 3 months
- factor Xa inhibitors (rivaroxiban or apixaban)
- warfarin
