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 to assess for myocardial ischemia or infarction, but it should be done after immediate measures are taken to reduce myocardial oxygen demand. B. Administer sublingual nitroglycerin to the client: Nitroglycerin helps relieve chest pain by dilating coronary arteries, but it should be given only after the client is safely seated or resting to prevent hypotension or injury. C. Measure the client's vital signs: Vital signs provide valuable baseline data, but addressing the client’s immediate safety and reducing cardiac workload takes priority. D. Have the client stop walking and sit down: Stopping activity decreases oxygen demand on the heart and prevents worsening ischemia or collapse, making it the first and most critical action.