What is the initial diagnostic test of choice for suspected PE?

• A. Chest X-ray.
• B. Transthoracic echocardiography.
• C. CT pulmonary angiography (CTPA) or V/Q scan if contraindications.
• D. Carotid ultrasound.

Answer: (C)

In suspected pulmonary embolism, the first-line imaging test in a stable patient is CT pulmonary angiography. It directly visualizes the pulmonary arteries, allowing you to see filling defects caused by emboli, so you can confirm or exclude PE quickly. This modality also provides a clear overall chest assessment, helping spot alternative conditions that could mimic PE. If iodinated contrast cannot be used—such as with a severe contrast allergy or significant renal dysfunction—or in pregnancy, a ventilation-perfusion scan is the alternative choice, since it assesses the match between ventilation and perfusion without relying on iodinated contrast. Chest X-ray isn’t sufficient to diagnose PE, and while transthoracic echocardiography can show signs of right heart strain in massive PE, it doesn’t reliably confirm emboli in most patients. Carotid ultrasound isn’t relevant to diagnosing PE.