Lecture 22 - PE

Question 1

Pulmonary embolism

Answer 1

Obstruction of a blood vessel by a foreign substance distal to the site of origin

Question 2

Embolus substances

Answer 2

Thrombus
Tumour
Amniotic fluid 
Fat - fracture of long bones 
Air 
Bullet

Question 3

Fat embolism syndrome

Answer 3

Triad of lung, brain and skin

Question 4

How can fat embolism to the brain

Answer 4

Via a patent foramen ovale

Question 5

Where do most PEs arise from

Answer 5

90% arise from DVTs

25% of those have symptoms of DVT

Question 6

Risk factors for PE

Answer 6

Endothelial injury
- surgery

Stasis or turbulent blood flow

• immobile
• long haul flight
• heart failure

Blood hypercoagulabilty

• COCP
• inherited disorders e.g thrombophilia
• cancer (pancreatic)
• obesity
• pregnancy

Question 7

Factor Xa

Answer 7

Factor Xa activates fibrin from fibrinogen to form a clot

Question 8

Hypercoaguable conditions

Answer 8

Antithrombin III deficiency 
Protein C or S deficiency/ resistance (anticoagulants)
Lupus anticoagulant
Homocystinuria 
Occult neoplasm
Chronic inflammation e.g RA

Question 9

How does a PE cause right ventricular overload

Answer 9

1. Pulmonary artery hypertension if more than 30% occlusion
2. High right ventricle afterload
3. Right ventricle hypertrophy
4. Eventually the right ventricle will dilate

Question 10

Inotropes

Answer 10

• Right sided heart failure decreases blood pressure due to decreased venous return.
• inotropes are released to increase blood pressure by causing systemic vasoconstriction
• pulmonary artery vasoconstriction further increases right sided afterload

Question 11

Main cause of death in PE

Answer 11

• cardiogenic shock with circulatory failure

- cardiac arrest secondary to arrhythmias

Question 12

PE with patent foramen ovale

Answer 12

• Due to the increased pressure in the right ventricle, blood flows from right to left
• causes cyanosis and hypoxaemia

Question 13

Paradoxical embolism

Answer 13

Embolus carried from the venous system to the arterial system
Occurs due to patent foramen ovale

Question 14

How does PE cause respiratory failure?

Answer 14

• areas of ventilation perfusion mismatch
• low right ventricle output
• shunt with patent foramen ovale

Question 15

Pulmonary infarct

Answer 15

Not common as lungs have a collateral circulation

• small distal emboli create areas os alveolar haemorrhage
• haemoptysis, pleuritis, small pleural effusion

Question 16

Symptoms of PE

Answer 16

Common:
Dyspnoae
Pleuritic chest pain

Less common:
Cough
Haemoptysis
Syncope

Question 17

Signs of PE

Answer 17

Tachypnoea (16+)
Decreased breath sounds
Accentuated second heart sounds (P2) - pump against resistance
Tachycardia (100+)

Question 18

Investigations

Answer 18

ABG

• hypoxaemia
• hypocapnia - respiratory alkalosis due to hyperventilation

Oxygen saturation

CXR

• NORMAL
• exclude other diagnosis

ECG - not diagnostic

Blood tests
- D-dimer raised - if normal can rule out if low risk for PE

Question 19

ECG

Answer 19

• right ventricle strain (broad complex QRS)
• supraventricular tachycardia
• T wave inversion in lead III
• deep S wave in Lead I
• Q wave in Lead III

Question 20

Imaging for PE

Answer 20

Invasive:
Pulmonary angiogram
Ventilation perfusion lung scintigraphy

Non invasive:
CT pulmonary angiography
- high specificity and sensitivity

Question 21

Saddle pulmonary embolism

Answer 21

Large pulmonary embolism that partially occludes the bifurcation of the pulmonary trunk therefore affects the left and right pulmonary artery

Question 22

Treatment of low risk PE patient

Answer 22

Oxygen
Immediate IV heparinisation
Oral warfarin

Question 23

How does heparin treat PE

Answer 23

Stops propagation of embolism

Allows body’s fibrinolytic system to lose the embolus

Question 24

Risk of heparin use

Answer 24

Heparin induced thrombocytopenia

Question 25

Treatment of high risk patients

Answer 25

Oxygen 
Haemodynamic support 
Exogenous fibrinolytics e.g streptokinase (can only use once)
Thrombectomy 
Embolectomy