A 58-year-old client arrives at the emergency department with crushing substernal chest pain that started 30 minutes ago. The 12-lead ECG shows 3 mm ST-segment elevation in leads II, III, and aVF, and the troponin level is elevated. Which intervention should the nurse anticipate as the priority?

ST elevation in leads II, III, and aVF with elevated troponin indicates an inferior STEMI. AHA/ACC guidelines mandate primary percutaneous coronary intervention within 90 minutes of first medical contact (door-to-balloon goal). Activating the cardiac catheterization laboratory is the priority. Nitroglycerin and aspirin are still given but reperfusion is the time-critical action. A chest X-ray and morphine are adjuncts and do not change reperfusion timing.

In-depth explanation

<span class="merci-scenario-label">Clinical Judgment</span><br>Inferior STEMI = <span class="merci-kw">ST elevation in II, III, aVF</span>. Time is muscle. <span class="merci-kw">Door-to-balloon goal: 90 minutes</span> from first medical contact. The single most outcome-determining action is <span class="merci-kw">activating the cath lab</span>. MONA-B (morphine, O2, nitro, aspirin, beta-blocker) supports but does not replace reperfusion.<br><br><span class="merci-scenario-label">Memory Tip</span><br><span class="merci-kw-mark">STEMI = Time + Reperfusion. Door-to-balloon &lt;90 min</span><br><br><span class="merci-scenario-label">KR vs US</span><br>US AHA standard: PCI within 90 min, transfer-PCI within 120 min if no PCI center on site. Korea uses identical timeframes; major regional cardiac centers operate 24/7 cath labs and adopt the same Code STEMI workflow.

Clinical scenario

<span class="merci-scenario-label">Clinical Practice Guide</span><br>2022 AHA/ACC STEMI Guidelines: <span class="merci-value">Door-to-balloon ≤90 minutes</span> for PCI-capable hospitals; <span class="merci-value">door-in-door-out ≤30 minutes</span> for transfer to PCI center. Initial therapy: <span class="merci-kw">aspirin 162-325 mg chewed</span>, P2Y12 inhibitor, anticoagulation, oxygen if SpO2 &lt;90%. Avoid routine morphine.<br><br><span class="merci-scenario-label">Caution</span><br>Inferior STEMI with right-ventricular involvement is preload-dependent. <span class="merci-value-abnormal">Avoid nitrates and diuretics</span> in this subset; they can cause profound hypotension. Get a right-sided ECG (V4R) to confirm before nitrates.

Key concepts

• STEMI — ST-elevation myocardial infarction. Defined by ≥1 mm ST elevation in 2 contiguous leads or new LBBB with positive troponin. Inferior STEMI: II, III, aVF (right coronary artery). Anterior: V1-V4 (LAD). Lateral: I, aVL, V5-V6.
• Door-to-balloon time — Time interval from arrival at the hospital to balloon inflation in the culprit coronary artery during PCI. AHA goal: 90 minutes or less. Strongly correlated with mortality reduction in STEMI.
• Troponin — Cardiac-specific protein released from injured myocytes. Elevation begins 3-6 hours after ischemia, peaks 12-24 hours, returns to baseline 7-14 days. High-sensitivity troponin allows earlier rule-in/rule-out.