Cardiovascularcommon
A 28-year-old woman presents to the emergency department with two days of right-sided chest pain that is worse on deep inspiration. She takes a combined oral contraceptive pill and is recovering from an upper respiratory tract infection with a persistent cough. She has had no surgery or immobilisation, has not travelled recently, and has no personal or family history of venous thromboembolism. Her temperature is 36.9°C, heart rate 88/min, respiratory rate 16/min and oxygen saturation 98% on room air; both calves are soft and non-tender. Which one of the following is the most appropriate next step in investigation?