Pulmonary embolism

Question 1

Pulmonary embolism : Pathophysiology

Answer 1

1. Blockage of pulmonary artery secondary to an embolism - blood clot
   i) Blood clot enters via the systemic venous circulation
   ii) into the vena cava - right ventricle,
   iii) then gets trapped within the narrow pulmonary arteries or capillaries surrounding the alveoli.
2. Blockage of any arteries leads to decreased blood flow to tissues down stream
3. Pulmonary arteries are the site of gas exchange of CO2 and O2 with the alveoli

Question 2

Pulmonary embolism : V/Q mismatch

Answer 2

• Blockage of any arteries leads to decreased blood flow to tissues down stream
• Ventilation with a lack of perfusion due to stasis of blood flow caused by the clot
• Impaired gas exchange occurs } Hypoxia

Question 3

Pulmonary embolism : Respiratory alkalosis

Answer 3

• Impaired gas exchange : high CO2 concentration and low O2 in the blood
• Physiological increase in RR to compensate
• Increased exhalation of CO2 causes respiratory alkalosis

Question 4

Pulmonary embolism : Clinical features

Answer 4

• Sudden onset pleuritic chest pain
• Tachyonea > 20RR : 96% of patients
• Tachycardia
• Crackles
• Fever
• Hypoxia

Question 5

Pulmonary embolism : High sus of PE - Ix

Answer 5

Well’s score
1. < 4 : PE unlikely
I) D -dimer if high } CTPA

2. > 4 : PE likely
   I) CTPA
   If negative
   II) Proximal leg US

Question 6

Pulmonary embolism : Low sus of PE - Ix

Answer 6

1. PERC criteria
   * if negative } reduces probability of PE to <2%
   * If positive } Well’s test

Question 7

Pulmonary embolism : V/Q scan indication

Answer 7

V/Q scan - alternative to CT scan
* Renal failure : unable to tolerate contrast
* Pregnancy

Question 8

Pulmonary embolism : ECG

Answer 8

• ECG changes in PE are due to ;
  -Increased RV pressure and ischaemia : evidence of RV dilation

1. SIQIIITIII pattern– deep S wave in lead I, Q wave in III, inverted T wave in III
2. T wave inversion : anterior, inferior and lead III
3. Dominant R wave in V1
4. Right acts deviation

Question 9

Pulmonary embolism : Mx

Answer 9

• Provoked PE
  1. DOAC : Apixaban/Rivoraxaban } continue for 3 months
  eGFR<15 } LMWH
• Unprovoked PE OR 2nd to Cancer
  1. .>6 months following ORBIT score or until cancer tx is done

Question 10

Pulmonary embolism : Emergency management

Answer 10

1. Indication : Haemodynamically unstable
2. Investigation : ECHO if unstable for CTPA

Management:
* Unfractionated heparin prior to thrombolysis
* Thrombolysis
* Switch from unfractionated heparin to DOAC

Question 11

Pulmonary embolism : Mx of recurrent PEs

Answer 11

• Consider alternative coagulation
• IVC filters