Pulmonary Embolism Flashcards
What is pulmonary embolsim?
- occlusion of pulmonary vessels, most commonly by a thrombus that has travelled to the pulmonary vascular system from another site
- Clots break off and pass through the veins and the right side of the heart before lodging in the pulmonary circulation.
Describe the formation of a thromboembolus
- After tissue injury, primary haemostasis takes place:
- vasoconstriction to limit blood flow to limit blood loss via the site of injury
- Platelets adhere and are activated by tissue factor and collagen, recruit more platetlets and form a plug over injury - Secondary haemostasis occurs only a few minutes later:
- Clotting factors mostly made by the liver become acitvated and activate the next CF in a coagulation cascade
- Until fibrinogen is cleaved to form fibrin, which strengthens the plug forming a hard clot - (Usually clots are broken down by plasmin) As the clot grows, blood flow is reduced and therefore blood pressure increases and can break the clot off, sending it into the blood towards the heart (forming a thromboembolus)
What are 2 consequences can arise from a thromboembolus?
- LUNGS:
- The thromboembolus can enter the deep veins from the superficial veins and enter the heart via the superior/ inferior vena cava
- Here the thromboembolus follows the heart circulation entering the RA then into the pulmonary arteries where it can reach the lungs
- Eventually a pulmonary thromboembolus/ block can decreased ventilation leading to V/Q (perfusion) mismatch, causing the pt to hyperventilate, releasing CO2 leading to resp alkalosis (increasing blood pH) - BRAIN:
- IMPORTANT to check for atrial septal defect in pts: if there is an ASD (hold b/t RA and LA) when the thromboembolus reaches the RA it will travel to the LA
- Here it will enter the LV then the aorta, leading it towards the body/ brain, risking an embolic stroke
What are the causes of a pulmonary embolism/
Thrombus
1. 95% arise from DVT in the lower limbs
2. Rarely arises in the right atrium (in AF patients)
Other causes of embolus:
2. Amniotic fluid
3. Air
4. Fat
5. Tumour
6. Mycotic (infection with a fungus)
7. Parasites
8. Right ventricular thrombus (post MI)
9. Septic emboli (right sided endocarditis)
What are the risk factors for a pulmonary embolism?
o Surgical patients
- age
- DVT
- recent surgery
- bed rest > 5 days
o Immobility
o Obesity
o COCP
o Heart failure
o Malignancy
o Thrombophilia
o Pregnancy
o Previous PE/ FHx
- recent trauma
Summarise the epidemiology of pulmonary embolism
● Relatively COMMON (especially in hospitalised patients)
● Occur in 10-20% of patients with confirmed proximal DVT
What presenting symptoms of pulmonary embolism can be found in the history?
Depends on the SITE and SIZE of the embolus
1. Small:
- may be ASYMPTOMATIC
2. Moderate:
- Dyspnoea
o Sudden-onset SOB
o Cough
- fever
o Haemoptysis
o Sudden Pleuritic chest pain (acute pain aggravated by coughing, swallowing or deep inspiration) → normally localised to one side of the chest)
3. Large (or proximal):
* As above and:
▪ Severe central pleuritic chest pain
▪ Shock
▪ Collapse
▪ Acute right heart failure
▪ Sudden death
4. Multiple Small Recurrent:
o Symptoms of pulmonary hypertension
What signs of a pulmonary embolism that can be found on physical examination?
Severity of PE can be assessed based on associated signs:
1. Small:
- often no clinical signs. There may be some tachycardia and tachypnoea
- Sudden onset
2. Moderate
o Tachypnoea
o Tachycardia
o Pleural rub (raspy breathing sound on ausultation)
o Low O2 saturation (despite O2 supplementation)
o Pyrexia (raised body temperature, fever)
o Hypotension
3. Massive PE
o Shock
o Cyanosis
o Signs of right heart strain
- Raised JVP
- Left parasternal heave
- Accentuated (louder) S2 heart sound
4. Multiple Recurrent PE
o Signs of pulmonary hypertension
o Signs of right heart failure
- signs of DVT: unilateral painful leg swelling
What investigations are used to diagnose/ monitor pulmonary embolism?
- The Well’s Score (based on clinical findings) is used to determine the best investigation for PE: score of 7= PE
- If Well’s 4 or less do D-dimer
* If D-dimer negative: PE excluded
* If D-dimer raised: do CTPA - CT Pulmonary Angiogram – GOLD STANDARD
- can see thrombus in pulmonary artery
- Poor sensitivity for small emboli
- VERY sensitive for medium to large embolism - If CT is contraindicated (e.g. V/Q scan is preferred if the patient has renal impairment, contrast allergy or is pregnant.)
- Identifies areas of ventilation and perfusion mismatch, indicating area of infarcted lung. - Bloods– ABG if pt is acutely unwell (low PaO2 and PaCO2), thrombophilia screen
- ECG:
● May be normal
● May show sinus tachycardia, right axis deviation or RBBB or right ventricular strain (inverted T in V1-V4)
● May show S1Q3T3 pattern (S waves in lead I, Q waves in III, Inverted T waves in III) - CXR: often NORMAL, in acute setting to rule out other causes of chest pain (eg. pneumothorax)
- ABG → hypoxaemia (type 1 respiratory failure)
- Echocardiography → use for haemodynamically unstable patients who can’t have CTPA
- FBC → Thrombocytopenia or Anaemia
Generate a management plan for pulmonary embolism
- Primary Prevention
o Compression stockings
o Heparin prophylaxis for those at risk
o Good mobilisation and adequate hydration - If haemodynamically stable:
o O2
o First offer DOAC (apixaban or rivaroxaban)
*3 months if provoked PE
*6 months if unprovoked PE. Use warfarin if DOAC contraindicated.
o LMWH and warfarin are second-line alternatives
o Switch over to oral warfarin for at least 3 months (Maintain INR 2-3)
o if pt has recurrence of VTE on warfarin, INR should be increased from 2-3 to 3-4
o Analgesia - If haemodynamically UNSTABLE (massive PE):
o Resuscitate
o O2
o IV fluids
o Thrombolysis with tPA may be considered if cardiac arrest is imminent (stronger treatment need if pt has CV compromise) BUT Previous history of haemorrhagic stroke at any time is an absolute contraindication for thrombolysis treatment
- approproate thrombolytic agent: IV Alteplase - Surgical or radiological
o Embolectomy
- pulmonary thombectomy/ thromboendarterectomy
o IVC filters - sometimes used for recurrent PEs despite adequate anticoagulation or when anticoagulation is contraindicated
Identify the possible complications of pulmonary embolism
● Death
● Pulmonary infarction
● Pulmonary hypertension
● Right heart failure
Summarise the prognosis for patients with pulmonary embolism
● 30% mortality in those left untreated
● 8% mortality with treatment
● Increased risk of future thromboembolic disease
What are the factors that lead to deep vein thrombosis?
Virchow’s triad:
1. Slowed blood flow (stasis):
- turbulence- slow or static blood
- inactivity of skeletal muscle pump (muscles compress on vessel helping blood circulate)
- can be due to: bed rest, long flights, car trips, pregnancy
2. Hypercoagulation:
- altered amounts of clotting factors due to:
genetics, surgery (damage to vessels trigger clotting cascade) and medications (e.g. birth control)
3. Damage to blood vessels:
- infections
- chronic inflammation
- toxins: e.g. tobacco smoke
