A 54-year-old man presents with acute shortness of breath and pleuritic chest pain 2 days after a long-haul flight. He is tachycardic at 112 beats/min and mildly hypoxic (SaO2 92% on room air). Wells score is 7.5, indicating high pre-test probability for pulmonary embolism. According to evidence-informed practice, which is the most appropriate next step?