Obstetrics and Gynaecologymiddle twist
A 29-year-old woman at 10 weeks of pregnancy presents with sudden pleuritic chest pain and breathlessness. Her heart rate is 108/min, oxygen saturation is 98% on room air, and there is no leg swelling or tenderness. Electrocardiography is normal, and a chest radiograph shows no abnormality. Which one of the following is the most appropriate next investigation?