ACS guidelines 2025 – The OMI has officially arrived!

by Dr Anand Senthi

First published 4/9/25

Drs Stephen Smith and Pendell Myers, Emergency Physicians in the United States spent years researching and developing an alternative to the outdated STEMI (ST Elevation Myocardial Infarction) versus NSTEMI (Non-STEMI) paradigm for approaching Acute Coronary Syndrome (ACS).

The STEMI/NSTEMI distinction was based around a belief that STEMIs reliably diagnosed complete coronary artery occlusion that benefit from mobilising pre-hospital, emergency department and cardiology resources to deliver emergent coronary revascularisation (within 60-90 minutes), while NSTEMIs reliably identified cardiac ischaemia due to only partial coronary artery occlusion, that could wait for less urgent coronary artery evaluation.

The rationale for changing this paradigm was the finding that 25-30% of patients diagnosed with NSTEMI, were found at delayed angiogram to have suffered from complete coronary occlusion, where the lack of emergent revascularisation increased the risk of preventable infarction, arrhythmia and death as well as chronic disability due to congestive heart failure. In addition, the STEMI criteria identified numerous false positives.

The work of Drs Smith and Myers culminated with the seminal online publication in 2018 of the OMI Manifesto (in collaboration with to Dr Scott Weingart founder of EMcrit). They argued for replacement of the inadequate STEMI/NSTEMI classification system with a new OMI/NOMI classification system where OMI is defined as (complete) Occlusion Myocardial Infarction (or near occlusion with insufficient collateral circulation) while NOMI represents Non-Occlusion Myocardial Infarction. The evidence indicates that OMIs include most traditional STEMIs as well as a several other recognisable ECG patterns that do not fulfil traditional STEMI criteria. While the OMI Manifesto is very detailed and references many of the source studies that lead to the paradigm shift, a summary of the OMI paradigm with a few examples was released on Life in the Fast Lane in 2023.

In 2021 they published a key article in a cardiology journal – Accuracy of OMI ECG findings versus STEMI criteria for diagnosis of acute coronary occlusion myocardial infarction)  arguing for the superiority of the paradigm shift from STEMI to OMI. Here the OMI criteria included 8 additional ECG patterns as OMIs that did not meet traditional ECG criteria.

Cardiology Guidelines have taken some time to adapt and move from the STEMI paradigm towards the OMI paradigm.

In 2022 the American College of Cardiology took steps towards the OMI paradigm, without adopting the nomenclature, by clearly describing several “STEMI equivalents” that require the same management as STEMIs:

• Posterior STEMI (isolated)
• Modified or original Sgarbossa Criteria within LBBB or ventricular paced rhythm
• De Winter Sign
• Hyperacute T waves

Now, in 2025, the newly released Australian ACS guidelines take this a step further by adopting the OMI nomenclature instead, with a slight rebranding to ACOMI (Acute Coronary Occlusion MI) recognising the following ECG patterns as ACOMI, in addition to the traditional STEMI criteria:

• High lateral MI
• Posterior MI (isolated)
• Right Ventricular MI
• De Winter T Waves
• Modified Sgarbossa criteria within LBBB or paced rhythm

The guidelines also describe several other High Risk ECG findings for ACS, including 3 patterns they describe as associated with “potential progression to ACOMI” necessitating “prompt and continuous clinical ECG monitoring”:

• A. Wellen’s T waves,
• B. Diffuse ST-segment depression in multiple leads associated with ST Elevation in aVR.
• C. Hyperacute T waves

The OMI paradigm shift that initially emerged in the Emergency Medicine sphere appears now to have entered the cardiology world with both evidentiary and guideline support (at least in Australia).

For more information about the new 2025 ACS Guidelines including tables showing pictures and descriptions of the above ECG patterns, see our Australian ACS Guidelines 2025 page (which also provides a link to the source guideline at the top of the page).