The investigations required are outlined below.
A chest radiograph should be requested for all patients with a suspected PE. It is usually normal or may reveal non-specific changes such as small pleural effusion. Rarely, a wedge shaped pulmonary infarction or regional oligaemia (Westermark sign) may be seen.
Click on the x-ray to enlarge.
The main purpose of the chest radiograph is to exclude alternative diagnosis, for example, pneumothorax or infection which may give rise to the same presenting symptoms.
An ECG should be obtained to look for signs supportive of right heart strain such as right axis deviation, and to rule out an acute coronary syndrome. The most common ECG finding is a sinus tachycardia. Atrial fibrillation is present in approximately 20% of cases.
Click on the ECG to enlarge.
The classical S1 Q3 T3 pattern (right) is present in only ~10% of patients with PE.
Neither a chest radiograph nor any of the tests listed above are sensitive or specific enough to rule in or exclude a diagnosis of PE.