A 70-year-old female with a recent history of knee replacement surgery presents with acute onset shortness of breath and pleuritic chest pain. She is tachycardic (HR 115 bpm) and tachypneic (RR 24/min), but hemodynamically stable (BP 130/85 mmHg, SpO2 94% on room air). Her Wells score for PE is 6. What is the most appropriate immediate diagnostic step?
✓ Correct Answer: Option C
Given the high clinical suspicion for PE (Wells score >4) and hemodynamic stability, CTPA is the gold standard diagnostic test. D-dimer is useful for ruling out PE in low-probability patients, not high-probability ones.