A client presents with crushing chest pain radiating to the left arm. ECG shows ST elevation. What is the priority intervention?

ST-elevation myocardial infarction (STEMI) is a medical emergency where coronary occlusion is causing actively-progressing myocardial damage. 'Time is muscle' — delays in reperfusion increase infarct size and worsen outcomes. Standard initial management (often remembered as MONA-BASH or similar mnemonics, though MONA is no longer routine): (1) Oxygen if SpO2 below 90% (no longer routine for everyone — supplemental O2 may worsen outcomes in non-hypoxic patients); (2) Aspirin 325 mg chewed (decreases platelet aggregation, reduces mortality); (3) Nitroglycerin sublingual (vasodilation, reduces preload and afterload, relieves ischemia — contraindicated in inferior MI with right ventricular involvement, sildenafil use in 24 hrs, severe hypotension); (4) Morphine for pain not relieved by nitrates (use cautiously); (5) IV access and continuous monitoring; (6) Reperfusion: PCI (percutaneous coronary intervention) within 90 minutes from first medical contact is gold standard; thrombolytics if PCI unavailable within timeframe. Other meds: beta-blocker, statin, ACE inhibitor.