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Lesson

STEMI Equivalents: Transmit Anyway

12 min Cardiac & ECG Skip to quiz

Objective: When the tracing is ugly in a territorial or equivalent pattern, transmit and use STEMI-alert language even if classic mm-elevation rules are not met.

Why This Is Hard

Crews wait for “real ST elevation” because they got burned on a mimic. 2025 ACC/AHA ACS: acquire and interpret a 12-lead within 10 minutes of first medical contact when ACS is on the table. Occlusion MI is not only the textbook STEMI millimeter rule. Your job is to transmit a concerning pattern and pick a PCI-capable destination — not to be the cath-lab reader.

On this truck
  • Get the 12-lead early. Serial if symptoms persist. Lead II is not a STEMI call.
  • Transmit. Use your STEMI-alert language: “possible occlusion MI / STEMI equivalent vs mimic — need PCI-capable evaluation.”
  • You do not need to name de Winter perfectly. You need to say “territorial ST depression with hyperacute T / ugly anterior pattern” and move.

Street Sequence

  1. ABCs. If ACS is on the table, 12-lead within 10 minutes of first medical contact without delaying a crashing patient.
  2. Look for a territorial story: hyperacute T waves, ST depression with tall T (de Winter-style), biphasic/deeply inverted precordial T after pain (Wellens-style), isolated posterior (anterior depression, tall posterior R).
  3. LBBB or paced: do not let uncertainty cancel a STEMI-alert conversation. Transmit. Modified Sgarbossa is advanced — “possible equivalent” is enough.
  4. Aspirin and destination per protocol. Serial ECGs if pain continues.

Field Rules (Education)

  • Hyperacute T: broad, fat T waves in a territory with a sick patient can be the first ECG of occlusion. Transmit.
  • de Winter-style: upsloping ST depression at the J point into tall, peaked anterior T waves — treat as an anterior occlusion conversation, not “just strain.”
  • Wellens-style: deep inverted or biphasic T in V2–V3 in a pain-free (or recently painful) ACS patient is a proximal-LAD warning, not “non-specific T-wave changes.”
  • Posterior: anterior ST depression may be a posterior STEMI. Right/posterior leads if protocol includes them. See the right/posterior lesson.
Say out loud
  • ACS on the table — 12-lead now
  • Ugly territorial pattern — transmitting as possible occlusion MI / equivalent
  • LBBB or paced: still a STEMI-alert conversation if the story is ACS
  • PCI-capable destination

Field Pitfalls

  • Waiting for 2 mm in two leads while an anterior de Winter pattern sits on the paper.
  • Calling Wellens “non-specific” and staying on scene for a second set of vitals.
  • Skipping transmission because “they’ll repeat it anyway.”

Practice

60-second drill

Partner holds three one-liners: (1) fat hyperacute T in V2–V4, pain 8/10; (2) biphasic T in V2–V3, pain-free now; (3) LBBB, diaphoretic, pressure. For each, say the radio sentence.

Related: 12-Lead STEMI Recognition, Right-Sided & Posterior MI.

Sources & Further Study

Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.

Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.

Check Your Understanding

Street decisions from this lesson only. After you check, the key is highlighted. Education practice — not a certification exam.

1. A 12-lead with fat hyperacute T waves in V2–V4 in a diaphoretic patient:
2. Anterior ST depression with tall, peaked T waves (de Winter-style) is best treated as:
3. Deep inverted or biphasic T waves in V2–V3 after chest pain (Wellens-style) mean:
4. LBBB or a paced rhythm with an ACS story:
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