Respiratory Medicine - Pulmonary embolism: investigation

Question 1

We know from experience that few patients (around 10%) present with the medical student textbook triad of pleuritic chest pain, dyspnoea and haemoptysis. Pulmonary embolism can be difficult to diagnose as it can present with virtually any cardiorespiratory symptom/sign depending on it’s location and size.

So which features make pulmonary embolism more likely?

Answer 1

The PIOPED study1 in 2007 looked at the frequency of different symptoms and signs in patients who were diagnosed with pulmonary embolism.

The relative frequency of common clinical signs is shown below:

• Tachypnea (respiratory rate >16/min) - 96%
• Crackles - 58%
• Tachycardia (heart rate >100/min) - 44%
• Fever (temperature >37.8°C) - 43%

Question 2

What are the 2012 NICE guidelines?:

Answer 2

• All patients with symptoms or signs suggestive of a PE should have a history taken, examination performed and a chest x-ray to exclude other pathology.
• If a PE is still suspected a two-level PE Wells score should be performed:

Clinical probability simplified scores

PE likely - more than 4 points

PE unlikely - 4 points or less

• If a PE is ‘likely’ (more than 4 points) arrange an immediate computed tomography pulmonary angiogram (CTPA). If there is a delay in getting the CTPA then give low-molecular weight heparin until the scan is performed.
• If a PE is ‘unlikely’ (4 points or less) arranged a D-dimer test. If this is positive arrange an immediate computed tomography pulmonary angiogram (CTPA). If there is a delay in getting the CTPA then give low-molecular weight heparin until the scan is performed.
• If the patient has an allergy to contrast media or renal impairment a V/Q scan should be used instead of a CTPA.

Question 3

If a PE is still suspected what critera should be used?

Answer 3

Question 4

What is the consensus view from the British Thoracic Society and NICE guidelines?

Answer 4

• computed tomographic pulmonary angiography (CTPA) is now the recommended initial lung-imaging modality for non-massive PE.
• Advantages compared to V/Q scans include speed, easier to perform out-of-hours, a reduced need for further imaging and the possibility of providing an alternative diagnosis if PE is excluded
• if the CTPA is negative then patients do not need further investigations or treatment for PEventilation-perfusion scanning may be used initially if appropriate facilities exist, the chest x-ray is normal, and there is no significant symptomatic concurrent cardiopulmonary disease

Question 5

What does this image show?

Answer 5

Question 6

What are the classic ECG changes in Pulmonary Embolism?

Answer 6

• The classic ECG changes seen in PE are a large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III - ‘S1Q3T3’. However this change is seen in no more than 20% of patients
• right bundle branch block and right axis deviation are also associated with PE
• sinus tachycardia may also be seen

Question 7

What does the ECG look like?

Answer 7

ECG from a patient with a PE. Shows a sinus tachycardia and a partial S1Q3T3 - the S wave is not particularly convincing.

Question 8

Another patient with an atypical ECG:

Answer 8

ECG of a patient with a PE. It shows some of the ECG features that may be associated with PE (sinus tachycardia, S1, T3 and T wave inversion in the precordial leads). Other features such as the left axis deviation are atypical.