Presentation
A 64-year-old woman presents 6 days after total knee arthroplasty with the sudden onset of severe dyspnea and a witnessed syncopal episode. She appears anxious and diaphoretic, with cool extremities and distended neck veins. She has not been taking her prescribed chemoprophylaxis because it "upset her stomach."
Initial observations
- T 37.0 C
- HR 128
- BP 82/54 mmHg
- RR 30
- SpO2 86% on room air
Given her presentation and hemodynamics, what is the most appropriate immediate step to confirm the suspected diagnosis?