What is Occlusion Myocardial Infarction (OMI)

Occlusion Myocardial Infarction (OMI) refers to an acute coronary occlusion or near occlusion of a culprit artery with insufficient collateral circulation, resulting in transmural myocardial infarction and cardiac tissue death.

OMI is not an exclusively electrocardiographic (ECG) pattern. Thus it is important to determine OMI on the basis of more clinical investigations, including clinical presentation, cardiac troponin and coronary angiography vessel stenosis and perfusion.

The primary OMI endpoint is defined as an acute culprit vessel identified angiographically with:

1. Thrombolysis In Myocardial Infarction (TIMI) 0-2 Flow
2. TIMI 3 Flow and very high Biomarker elevation (indicating that the vessel was occluded causing a large infarction)

Time is muscle: need for accurate and early diagnosis

Chest discomfort is the most common symptom in patients presenting to the emergency department (ED), accounting for 15-20% of all visits¹. In these, it is essential to accurately and rapidly identify patients with OMI, as they require an emergent invasive strategy with percutaneous coronary intervention (PCI), in order to salvage heart tissue.

Due to its widespread availability and rapid acquisition, the ECG stands as the gold standard for early stratification of patients with chest pain. For the past 15 years, international cardiology guidelines² have identified patients who require emergent invasive management based on the presence of ST elevation myocardial infarction (STEMI) millimeter criteria.

Increasing evidence shows that relying on STEMI criteria frequently fails to identify patients who require immediate invasive management accurately. The 2022 American College of Cardiology Chest Pain Expert Consensus³ has recently acknowledged the limitations of STEMI criteria and defined new STEMI equivalents.

STEMI Equivalents: Navigating Hidden Indicators of Myocardial Infarction

So what’s the problem with STEMI?

Acute coronary syndrome represents a dynamic condition characterized by variable ECG changes. Occlusion myocardial infarction is the underlying pathophysiology for which STEMI criteria serve as an inadequate surrogate indicator.

One-third of myocardial infarction patients presenting without typical ST elevation have acute coronary occlusion (OMI) discovered on delayed angiography. This delay causes a twofold increase in short and long-term mortality⁴.

Furthermore, approximately 25% of emergency cath lab activations due to perceived STEMI turn out to be false positives without a culprit vessel or biomarker elevation⁵. These unnecessary activations contribute to healthcare provider fatigue and result in costs exceeding $10 thousand per activation⁶.

From STEMI to OMI: The Paradigm Shift

The absence of STEMI criteria in an ECG does not rule out a potentially occluded or flow-limiting culprit vessel. Under the new paradigm, we do not dichotomize acute coronary syndrome patients based on the ECG at presentation but rather consider objective parameters such as clinical presentation, biomarkers and invasive angiographic findings.

The OMI paradigm classifies patients with acute myocardial infarction based on their angiographic findings into:

• Occlusion myocardial infarction (OMI): Near or total culprit vessel occlusion with insufficient collateral circulation causing active infarction.
• Non-occlusion myocardial infarction (NOMI): No occlusion or sufficient collateral circulation of a culprit vessel, avoiding active infarction. (includes MINOCA, but not exclusively)

Unlike the previous paradigm, we can now accurately identify patients without typical ST-elevation on their initial ECG but with thrombotic occlusion of the mid-left circumflex artery (mLCx), causing subtle ST depression in V3 as OMI.

OMI ECG criteria

Notably, a patient’s lack of ST-elevation on the initial ECG does not necessarily preclude the presence of OMI. Approximately half of OMI patients may never exhibit ST elevation. Under the OMI paradigm, there are no ECG millimeter criteria. Instead, it requires a thorough examination of the ECG, a comprehensive evaluation of the clinical context, and diligent scrutiny of laboratory findings.

Emre Aslanger has created an excellent flowchart that effectively illustrates the process of identifying OMI ECG criteria. It includes:

• Recognition of patterns with ST elevation only in one lead
• Subtle ST elevation with minimal reciprocal changes
• Exclusively identifying ST depression
• Bulky (hyper-acute) T-waves

Accuracy of OMI ECG criteria

In a substantial cohort of 808 patients suspected of acute coronary syndrome (ACS) and confirmed angiographic outcomes, trained ECG experts have rigorously tested this novel ECG interpretation approach. The results of their study revealed a remarkable two-fold increase in sensitivity compared to STEMI criteria (86% vs. 41%) while maintaining statistically equivalent specificity (91% vs. 94%)⁸.

These findings strongly indicate that these refined criteria are remarkably more effective in precisely identifying patients with OMI (occlusion myocardial infarction). The study’s results emphasize the importance of adopting these more sophisticated ECG criteria to enhance the diagnostic accuracy of OMI cases and improve patient management and outcomes.

The Role of AI in OMI Detection

Recognizing OMI on a 12-lead ECG largely relies on pattern recognition, a process that experts have honed through examining thousands of past cases. The ever-changing attributes of acute coronary syndromes necessitate many years of training to understand intricate ECG patterns. 

Effectively training first responders to recognize these complex patterns remains challenging. Therefore, overcoming these constraints to widespread adoption of this paradigm could be aided by artificial intelligence (AI) models deployed to augment current clinical workflows. 

The potential of AI in analyzing ECG waveforms has been demonstrated in various patient groups, showcasing significant progress in diagnosing conditions such as heart failure, hypertrophic cardiomyopathy, and sudden cardiac arrest.

We have introduced our developed Queen of Hearts (PMcardio OMI AI Model), detecting angiographically confirmed occlusion myocardial infarction in later blogs.

European Heart Journal: Clinical Validation Study of the PMcardio OMI AI Model