A nurse is caring for a client who has angina and reports a feeling of heaviness in the chest while ambulating in the hall. Which of the following actions should the nurse take first?

Rationale: A. Obtain a 12-lead ECG for the client: An ECG is important for diagnosing myocardial ischemia or infarction, but it is not the immediate first step. The priority is to stop activity and reduce myocardial oxygen demand before further diagnostics. B. Have the client stop walking and sit down: Angina is often triggered by physical exertion. Stopping activity and sitting down reduces oxygen demand on the heart, alleviates symptoms, and prevents further ischemia. This is the most immediate and essential first action. C. Administer sublingual nitroglycerin to the client: Nitroglycerin helps relieve anginal pain by dilating coronary arteries, but it should be given after the client has stopped activity and rested. Administering it while the client is still active may not be effective or safe. D. Measure the client's vital signs: While vital signs are important for assessing the client’s current status, the priority is to stop exertion, which is likely contributing to myocardial oxygen imbalance. Assessment follows immediate symptom relief measures.