A 44 year old male presents with dyspnoea  and is diagnosed  as having multiple pulmonary emboli on Computerised tomography pulmonary angiogram (CTPA). He is commenced  on 1000 units of heparin per hour after a 5000 unit bolus.  During the night his heparin has steadily increased to 1500 units per hour.
These blood results are from the next morning.

Test

Value

Normal range

PT

12 sec

12-16

APTT

*38.3sec

25.0-37.0

Fibrinogen

3.8 g/ L

2.20-4.30

D-DIM LIA

*>20.0 mcg/ml

<0.5

a) Give 2 reasons for the relatively low APTT despite heparin therapy

b) List 4 causes for an increased predisposition to venous thromboembolic disease

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College Answer

a) Give 2 reasons for the relatively low APTT despite heparin therapy

1 – Inadequate heparinisation
2.  ATIII deficiency
3.  Increased heparin clearance
4. Increased heparin binding proteins
(1.5 marks)

b) List 4 causes for an increased predisposition to venous thromboembolic disease

Protein C def Protein S def AT III def Malignancy
Factor V Leiden
Lupus anticoagulant

Discussion

This question is identical to Question 13.2 from the second paper of 2013.