Pulmonary Embolism (PE)

Question 1

What is a Pulmonary Embolism?

Answer 1

when an embolus gets trapped in the pulmonary arteries and blocks blood flow to the lung tissue. This puts a strain on the right side of the heart. This can lead to severe cardiorespiratory failure.
* embolus= a blood clot (thrombus), air bubble, fatty deposit, or other material.
* embolism= when an embolus has been carried in bloodstream to block a vessel, at a location different to where it was formed.

Question 2

PE: Aetiology

Answer 2

• Caused by any form of embolism
• PEs are usually caused by a thromboembolism.
• venous thromboembolism (VTE) is when a PE is caused by a DVT.

Question 3

PE: Risk Factors

Answer 3

Risk factors of PEs are mainly associated with the factors that contribute to thrombus formation. The risk factors for thrombus formation PE can be categorised according to Virchow’s triad:
Stasis
* Immobility - Prolonged bed rest, hospitalization, Immobilizer or cast, long-distance travel, or sedentary lifestyle/occupation.
* Malignancy - Solid tumors
* Pregnancy and postpartum period: (Hormonal changes and) venous stasis
Endothelial Injury
* Surgery - Particularly lower limb orthopedic procedures.
* Trauma - Direct injury to blood vessels or immobilization post-injury.
* Chemotherapy
* Central venous catheterization
Hypercoagulability
* Pregnancy and postpartum period - hormonal changes (and venous stasis)
* Hormone therapy particularly with oestrogen - Oral contraceptives, hormone replacement therapy, or selective estrogen receptor modulators. When the liver metabolises oestrogen in tablet form, it releases clotting factors
* Antipsychotics
* Genetic predispositions - Factor V Leiden, prothrombin gene mutation, deficiencies in protein C, protein S, or antithrombin.
* Hypercoagubility disorders - Polycythaemia (raised haemoglobin), Thrombophilia, Systemic lupus erythematosus
* Malignancy - some cancers release more clotting factors than others
* Increasing age (>60 years old)
Medical Comorbidities
* Heart failure, inflammatory bowel disease, nephrotic syndrome, or obesity/hypercholesterolemia

ask about risk factors such as immobility, surgery and long-haul flights

Question 4

PE: Symptoms

Answer 4

Presenting symptoms can range from asymptomatic (discovered incidentally) to sudden death. Presenting features include:
* Dysponea + tachyponea
* Pleuritic chest pain - due to pulmonary infarction
* Cough + Haemoptysis
* Features of DVT (including unilateral leg pain, tenderness and swelling and/or erythema of a leg or an arm)
* syncope/dizziness/stroke - in older patients and severe PE
* Chronic thromboembolic pulmonary hypertension
* Cardiac complications: right heart failure, cardiac arrest
* Low-grade fever (pyrexia) - caused by underlying condition/systemic symtpom

Question 5

PE: Cardiovascular Examination

Answer 5

• Typicalclinical findingsin PE:
  
  • tachyponea - Raised respiratory rate
  • Tachycardia
  • hypoxia
  • Hypotension secondary haemodynamic instability
  • venous distention (elevated JVP)
  • pleural rub
  • gallop rhythm
  • shock

Question 6

PE: Investigations

Answer 6

• Bedside investigations:
  
  • Pulse oximetry
  • Pulmonary embolism rule-out criteria (PERC) - for a low pre-test probability of PE (<15%), but want more reassurance that PE isn’t the diagnosis. Allthe criteria must be absent for a negative PERC. If positive PERC, complete further investigations
  • 2-level PE Wells score - for a high pre-test probability of PE (>15%). Unlikely PE (< 4 points) or likely PE (> 4 points) decides the next investigations
• Unlikely PE (4 points or less): perform ad-dimer, and if positive, perform immediateCT pulmonary angiogram(CTPA)
  
  • Negative d-dimer - stop anticoagulation and consider an alternative diagnosis
  • Offer DOAC if delay in d-dimer
• Likely PE (more than 4 points): perform an immediateCTPA or alternative imaging
  
  • If there is a delay in getting the CTPA, offer DOAC as interim therapeutic anticoagulation.
    
    • NICE 2020 suggest using a direct oral anticoagulant (DOAC) such as apixaban or rivaroxaban instead of low-molecular-weight heparin as interim therapeutic anticoagulation, as it can be continued if the result is positive.
  • Negative CTPA - stop anticoagulation and consider a proximal leg vein ultrasound scan if DVT is suspected

Question 7

Pulmonary Embolism: Prophylaxis

Answer 7

• Assess every patient admitted to hospital for risk ofvenous thromboembolism(VTE).
• prophylactic treatmentis used to reduce the risk of VTE in high-risk patients:
  
  • low molecular weight heparin(e.g.,enoxaparin) unless contraindicated.
    
    • Contraindications include active bleeding or existing anticoagulation withwarfarinor aDOAC.
  • Anti-embolic compression stockingsare also used unless contraindicated
    
    • Contraindications include peripheral arterial disease and T2DM

Question 8

Pulmonary Embolism: Investigations cont.

Answer 8

Bedside investigations:
* Pulse oximetry
* Pulmonary embolism rule-out criteria (PERC) - for a low pre-test probability of PE (<15%), but want more reassurance that PE isn’t the diagnosis. Allthe criteria must be absent for a negative PERC. If positive PERC, complete further investigations
* 2-level PE Wells score - for a high pre-test probability of PE (>15%). Unlikely PE (< 4 points) or likely PE (> 4 points) decides the next investigations

Laboratory investigations:
* D-dimer: D-dimeris asensitive(95%) butnot a specificblood test for VTE. It helps excludeVTEwhere there is a low suspicion. It is almost always raised if there is a DVT. However, other conditions can cause a raised d-dimer:
- Pneumonia
- Heart failure
- Pregnancy
- Surgery
- Malignancy
- age-adjusted D-dimer levels should be considered for patients > 50 years
- FBC: important in trauma cases, as the patient may need ablood transfusion
- Clotting screen: may need to correct coagulopathy (such as INR >1.5 or platelets <50), and may alter choice of anticoagulant
- International normalised ratio (INR) blood test: (measures how long it takes for your blood to clot). If prescribing warfarin as an anticoagulant. INR has a critical role in maintaining the warfarin response within a therapeutic range,to provide the benefits of anticoagulation, while avoiding the risks of haemorrhage
- ABG: the most common finding isrespiratory alkalosissecondary to hyperventilation, but it may demonstrate type 1 respiratory failure in severe cases.

    ***TOM TIP: Patients with a pulmonary embolism often have respiratory alkalosis on an ABG. Hypoxia causes a raised respiratory rate. Breathing fast means they “blow off” extra CO2. A low CO2means the blood becomes alkalotic. The other main cause of respiratory alkalosis is hyperventilation syndrome. Patients with PE will have a low pO2, whereas patients with hyperventilation syndrome will have a high pO2.***
    
- U&Es
- CRP
- ECGs - classic ECG changes seen in PE incl. S1Q3T3, RBBB and right axis deviation, sinus tachycardia (most common)

Imaging investigations
- CT pulmonary angiogram (CTPA)(the usual first-line)
- chest CT scan with anintravenous contrastthat highlights the pulmonary arteries to demonstrate any blood clots and can give information about alternative diagnoses, such as pneumonia or malignancy.
- Not suitable for patients with renal impairment, contrast allergy or at risk from radiation.
- Ventilation-perfusion (VQ)scan
- involves inhaling radioactive isotopesto fill the lungs and injecting a contrast with radioactive isotopes into… Agamma camerais used to get a picture of and compareventilationandperfusionof the lungs. With a pulmonary embolism, the lung tissue will be ventilated but not perfused.
- may be used if unsuitable for CTPA due to renal impairment (creatinine clearance less than 30 ml/min), contrast allergy or radiation exposure.
- other causes of mismatch in V/Q include old pulmonary embolisms, AV malformations, vasculitis, previous radiotherapy. COPD gives matched defects
- Chest x-rayfor all patients to exclude other pathology. Usually normal in a pulmonary embolism, but possible findings include a wedge-shaped opacification

Question 9

Pulmonary Embolism: Investigations Passmed

Answer 9

• CXR - prior to CTPA or V/Q
  PE unlikely
• D-dimer (negative) + stop anticoagulation + alternative diagnosis
• D-dimer (positive) + CTPA/V/Q
  PE likely
• CTPA/V/Q (negative) + stop anticoagulation + proximal leg ultrasound
• CTPA/V/Q (positive)

CTPA or V/Q?? - renal impairment (creatinine clearance less than 30 ml/min), contrast allergy, radiation exposure

Question 10

Pulmonary Embolism: Management Passmed

Answer 10

1. Is the patient haemodynamic unstable (ie. hypotension)? - thrombolysis with alteplase
2. PESI Score to determine low risk (outpatient) or high risk (inpatient)
3. DOAC/LMWH, Unfractionated heparin, or LMWH + VKA - severe renal impairment (creatinine clearance <15ml/min), pregnant (no VKA), antiphospholipid syndrome
4. Recurrent PE - Inferior vena cava filters

Question 11

Pulmonary Embolism: Prophylaxis for all inpatients

Answer 11

All patients should have VTE risk assessed against bleeding risk (HAS-BLED Score) to determine prophylactic treatment

• The following inpatients would be deemed at increased risk of VTE:
  
  • anticipated or current significant reduction in mobility for ≥ 3 days while admitted
  • lower limb orthopaedic surgery/trauma
  • inflammatory/intra-abdominal surgical admission
  • general anaesthetic and a surgical duration of over 90 minutes
  • risk factors mentioned

Types of VTE prophylaxis

Mechanical:

• Correctly fitted anti-embolism (aka compression) stockings (thigh or knee height)
• An Intermittent pneumatic compression device
• First-line for low risk surgical patients, for high-risk add pharmacological management

Pharmacological:

• Fondaparinux sodium (SC injection)
• Low molecular weight heparin (LMWH) - enoxaparin, dalteparin sodium
  
  • reduced doses should be used in patients with severe renal impairment (creatinine clearance ≤ 15 mol/min)
• Unfractionated heparin (UFH)
  
  • used as an alternative to LWMH in patients with chronic kidney disease (??)
• First-line for low risk medical patients, for high-risk add mechanical management

Advice for patients

Pre-surgical interventions:

• Advise women to stop taking their combined oral contraceptive pill/hormone replacement therapy 4 weeks before surgery
• withhold anticoag before major surgery due to bleeding risk (assess risk) and use mechanical prophylaxis instead
  
  • severe risk of VTE use short acting anticoag eg. LMWH and withold evening before

Post-surgical interventions:

• Try to mobilise patients as soon as possible after surgery
• Ensure the patient is hydrated