A client presents to the emergency department with crushing substernal chest pain radiating to the left arm, diaphoresis, and dyspnea. Which nursing action is the *priority*?

✓ Correct Answer: Option B

Obtaining a 12-lead ECG within 10 minutes of arrival is critical to diagnose ST-elevation myocardial infarction (STEMI) or non-STEMI, guiding immediate reperfusion therapy decisions. While other options are important, the ECG dictates the most urgent treatment path.