C. CT pulmonary angiogram (CTPA) – Explanation

Prolonged plane journey is a recognized risk factor for thromboembolism and
hencepulmonary embolism as well. Sharp chest pain and breathlessness after 3
days of planejourney is highly suggestive of pulmonary embolism. CTPA is the
answer here as it is thebest test among the other options which provide a
definitive diagnosis of pulmonaryembolism.

TWO-LEVEL PE WELLS SCORE

Clinical probability simplified scores
– PE likely – more than 4 points
– PE unlikely – 4 points or less

More than 4 points → Arrange an immediate computed tomography
pulmonaryangiogram (CTPA)

4 points or less → Arranged a D-dimer test. If this is positive arrange an
immediatecomputed tomography pulmonary angiogram (CTPA)

If anytime there is a delay in getting the CTPA → Give low-molecular weight
heparinuntil the scan is performed

If the patient has an allergy to contrast media or renal impairment → A V/Q
scanshould be used instead of a CTPA
Occasionally, questions will have a question with a patient with typical signs and
symptoms of pulmonary embolism and options of a CTPA and V/Q scans would
be in the
mix. Which one would you perform?

• Pick the CTPA over the V/Q scans

The consensus view from the British Thoracic Society and NICE guidelines
is as follows:

• Computed tomographic pulmonary angiography (CTPA) is now
  therecommended initial lung-imaging modality for non-massive PE.Advantagescompared to V/Q scans include speed, easier to perform out-of-
  hours, a reduceneed for further imaging and the possibility of providing analternative diagnosisif PE is excluded
• If the CTPA is negative then patients do not need further investigations
  ortreatment for PE

MORE ON PULMONARY EMBOLISM AND PREGNANCY
What should you pick if you suspect PE in a pregnant woman? CTPA or V/Q
scans?

The Royal College of Obstetricians and Gynaecologists (RCOG) recommends
that a chest x-ray should be ordered before deciding whether a V/Q scan or
CTPA should be done. The reason that RCOG recommends a chest X-ray first
is that it may identify other pulmonary disease such as pneumonia,
pneumothorax or lobar collapse and the radiation dose to the fetus from a chest
X-ray is so low it is negligible.

The choice of an imaging modality for definitive diagnosis (CTPA or V/Q scan)
will usually depend on local availability and individual hospital protocols.

So what should we pick if given such a question?

• Pick CTPA if chest X-ray is abnormal and there is a clinical suspicion of
  pulmonary embolism
• Pick V/Q if chest X-ray is normal and there is a clinical suspicion of
  pulmonary embolism

Note in both CTPA and V/Q scans, the absolute risk for the above is very small.