👤 By the CinnaEMS Content Team🕐 Updated 2026-09-27🏷️ Cardiology & Resuscitation🔖 Free to read, print, and share
Also known as: 12-lead ECG · STEMI · ST elevation · reciprocal changes · right ventricular infarction · posterior MI · pericarditis
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Use this quick-reference guide to recognise, treat and hand over 12-Lead & STEMI Mimics on the NREMT and on the call. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
📌 Locate
Inferior II, III, aVF
Anterior V3–V4 · septal V1–V2
Lateral I, aVL, V5–V6
📌 Extra Leads
Inferior → V4R
ST down V1–V3 → V7–V9
📌 Mimics
BBB · paced · LVH
Early repol · pericarditis
Hyperkalemia
📌 Timing
12-lead within 10 min
Transmit early · repeat it
📚 12-Lead & STEMI Mimics — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what changes the plan, and what to hand over.
The 12-lead is how EMS shortens time to reperfusion, but ST elevation is not always a heart attack. Candidates must localize a STEMI by contiguous leads, look for reciprocal change, and recognize the patterns that imitate it.
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Key points
Understand these first
STEMI: new ST elevation in two or more contiguous leads, ideally with reciprocal ST depression.
Inferior II, III, aVF · septal V1–V2 · anterior V3–V4 · lateral I, aVL, V5–V6.
ST depression in V1–V3 may be a posterior MI — obtain posterior leads V7–V9.
Inferior MI: obtain right-sided V4R; right ventricular involvement is preload-dependent.
Acquire a 12-lead within 10 minutes of contact for suspected ACS.
Transmit or activate early — the goal is to shorten time to reperfusion.
Repeat the 12-lead: a normal first tracing does not rule out ACS.
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Red flags — report now
Escalate immediately
Inferior STEMI with hypotension (right ventricle)
Diffuse ST elevation read as STEMI
Peaked T waves with a wide QRS
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Patient teaching
What patients must know
Pericarditis: diffuse ST elevation, PR depression, pain better leaning forward.
Avoid nitrates when right ventricular infarction or hypotension is present.
❓ 12-Lead & STEMI Mimics: NREMT FAQs
What are the priority actions for 12-Lead & STEMI Mimics in the field?
Acquire a 12-lead within 10 minutes of contact for suspected ACS. Transmit or activate early — the goal is to shorten time to reperfusion. Repeat the 12-lead: a normal first tracing does not rule out ACS.
What findings in 12-Lead & STEMI Mimics change your plan or your transport decision?
Inferior STEMI with hypotension (right ventricle). Diffuse ST elevation read as STEMI. Peaked T waves with a wide QRS.
What do I need to know about 12-Lead & STEMI Mimics for the NREMT?
STEMI: new ST elevation in two or more contiguous leads, ideally with reciprocal ST depression. Inferior II, III, aVF · septal V1–V2 · anterior V3–V4 · lateral I, aVL, V5–V6. ST depression in V1–V3 may be a posterior MI — obtain posterior leads V7–V9. Inferior MI: obtain right-sided V4R; right ventricular involvement is preload-dependent.
What should the crew communicate or document for 12-Lead & STEMI Mimics?
Pericarditis: diffuse ST elevation, PR depression, pain better leaning forward. Avoid nitrates when right ventricular infarction or hypotension is present.
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Quick Tip
STEMI: new ST elevation in two or more contiguous leads, ideally with reciprocal ST depression.