A patient in the dental chair with known angina pectoris develops chest pain. You administer sublingual nitroglycerin, but the pain does not resolve after 5 minutes. What should be the NEXT step?

The standard protocol for unresolved angina in the dental office follows the AHA emergency protocol: (1) Stop dental treatment, (2) Administer sublingual nitroglycerin 0.4 mg, (3) If no relief after 5 minutes, repeat nitroglycerin (up to 3 doses total at 5-minute intervals), and (4) If no relief after the first nitroglycerin dose or if pain worsens, ACTIVATE EMS IMMEDIATELY (suspected myocardial infarction). If MI is suspected, administer aspirin 325 mg (if not contraindicated) and supplemental oxygen. A nitroglycerin-unresponsive anginal episode must be treated as an acute MI until proven otherwise. Waiting for a third nitroglycerin dose without calling EMS delays critical intervention.