Pulmonary Embolism

Question 1

Define PE

Answer 1

Obstruction of one or more pulmonary arteries by a solid, liquid or gaseous mass

Question 2

Epidemiology PE

Answer 2

• Accounts for many deaths per year
• Incidence increases with age
• M > F
• Deaths due to VT = 34% attributable to sudden fatal PE
• Increasing incidence of PE

Question 3

Broad categories of PE aetiologies

Answer 3

• Deep vein thrombosis (most common)
• Fat embolism
• Air embolism
• Amniotic fluid embolism
• Tissue embolism

Question 4

Risk factors for a DVT

Answer 4

• Obesity
• Hypomobility
• Malignancy
• Pregnancy
• Dehydration
• OCP
• Previous DVT

Question 5

When are fat embolisms most common

Answer 5

During major surgical interventions

Question 6

Pathophysiology behind PE

Answer 6

• Thrombus formation that embolises to pulmonary arteries via the IVC (rarely SVC)
• Leads to a partial or complete blockage of the pulmonary arteries
• Thrombi rarely develop de novo in the pulmonary vasculature

Question 7

Problems associated with lung and arterial obstruction

Answer 7

• Infarction and inflammation
• Impaired gas exchange
• Cardiac compromise

Question 8

Describe what happens when infarction and inflammation result from PE

Answer 8

• Occurs in lung and pleura
• Pleuritic chest pain and haemoptysis
• Surfactant dysfunction leads to atelectasis and decreased paO2
• Leads to respiratory alkalosis and hypocapnia (as respiratory drive triggered)

Question 9

Describe what happens with impaired gas exchange in PE

Answer 9

• Ventilation-perfusion mismatch

- Arterial hypoxaemia

Question 10

Describe what happens with cardiac compromise with PE

Answer 10

• Elevated pulmonary artery pressure leads to right ventricular pressure overload
• Forward failure
• Decreased cardiac output
• Hypotension and tachycardia

Question 11

Clinical features of PE

Answer 11

• Acute onset of symptoms
• Often triggered by a specific event (waking up, exercise etc)
• Dyspnoea
• Tachypnoea
• Sudden chest pain - worse on inspiration
• Cough and haemoptysis
• Dullness on percussion
• Decreased breath sounds
• Tachycardia
• Hypotension
• Jugular vein distension
• Low-grade fever
• Syncope/shock/circulatory collapse with major PE
• Possible symptoms of DVT

Question 12

DDx for PE

Answer 12

• Unstable angina
• NSTEMI/STEMI
• CAP
• CHF
• Acute bronchitis
• Acute exacerbation of COPD or asthma
• Pericarditis

Question 13

What does Wells criteria measure

Answer 13

• Score in stable patients - access probability of PE

also a Wells criteria for DVT

Question 14

7 components of Wells

Answer 14

• Clinical signs of DVT
• Alternative diagnosis less likely than a PE
• Previous PE or DVT
• HR >100bpm
• Surgery or immobilisation within 4 weeks
• Haemoptysis
• Active malignancy (treating/palliative/diagnosed <6months ago)

Question 15

Score for a high chance of PE

Answer 15

> 4

Question 16

Score for a low change of PE

Answer 16

<=4

Question 17

If patient is haemodynamically stable (SBP >90) and at high risk of PE, what is initial management on presentation

Answer 17

• CTA/CTPA

- If contraindicated - immediate anticoagulant - unfractionated heparin

Question 18

If a patient is too unstable for CTA - what is first line management

Answer 18

• Bedside echocardiogram - look for RV enlargement and visualise clot)
• Done prior to empiric thrombolysis

Question 19

Management in someone at low probability of PE

Answer 19

• Measure D-dimer, ABG and CXR

Question 20

Positive D-dimer

Answer 20

• Not diagnostic for PE

- Progress to CTA

Question 21

Negative D-dimer

Answer 21

• High probability no PE

- DDx

Question 22

What is the D-dimer test

Answer 22

• D-dimers are fibrin degradation products detected in the blood after thrombus resolution via fibrinolysis

Question 23

Normal D-dimer level

Answer 23

<500ng/mL

Question 24

D-dimer test has high…..

Answer 24

Sensitivity and NPV = negative test can rule our PE

Question 25

D-dimer test has low….

Answer 25

Specificity = poor confirmatory test

Question 26

ABG and PE

Answer 26

Respiratory acidosis - decreased pO2, pCO2 and increased pH

Question 27

What is a CTPA

Answer 27

CT pulmonary angiogram - contrast enhanced imaging of pulmonary arteries

Question 28

Positives about CTPA

Answer 28

• High sensitivity and specificity

- Visible intraluminal filling defects

Question 29

Why is a CXR done on PE management

Answer 29

• Rule OUT other cuases
• Check for atelectasis
• Signs of PE on a CXR are rare

Question 30

Why is an echo done on PE management

Answer 30

• Detect RA pressure signs

Question 31

Why is a VQ test done on PE management

Answer 31

• Use as an alternative to CTPA in patients with severe renal insufficiency or contrast allergy

Question 32

Acute general treatment for suspected PE

Answer 32

• Seated at 45 degrees
• O2 supplementation and intubation
• IV fluids and and vasopressors if hypotensive
• Analgesics

Question 33

PE and empiric anticoagulation - contraindication

Answer 33

Bleeding risk

Question 34

Empiric anticoagulation - 0-10 days

Answer 34

• LMWH (use unfractionated if renally compromised)

Question 35

Empiric anticoagulation - 3-6 months

Answer 35

• Long term treatment and prophylaxis

- Warfarin, LMWH, direct oral anticoagulants

Question 36

Recanalisation and PE

Answer 36

• Thrombolytic therapy = massive PE or haemodynamically unstable = use tPA (fibrinolysis)
• Embolectomy = last resort = surgical or catheter based thrombus removal

Question 37

Interventional surgery prevention for PE

Answer 37

IVC filter

- Mechanical device implanted into IVC

Question 38

Medication prevention of PE

Answer 38

DVT prophylaxis

Question 39

PE complications

Answer 39

• High risk of recurrence without treatment (5-10%)
• RV failure
• Atelectasis (20%)
• Pulmonary effusion
• Pulmonary infarction (10%)
• Pneumonia (from infarction)