Occlusive Myocardial Infarction (OMI): Definition and Diagnostic Criteria
Occlusive Myocardial Infarction (OMI) is a pathophysiological classification of myocardial infarction characterized by complete or near-complete coronary artery occlusion requiring urgent revascularization, regardless of traditional ECG classification as STEMI or NSTEMI. This paradigm focuses on identifying coronary occlusion rather than relying solely on ST-elevation criteria.
Definition of OMI
OMI represents a shift from the traditional STEMI/NSTEMI classification to a more pathophysiologically-based approach. It is defined as:
- An acute culprit coronary lesion with TIMI 0-2 flow (complete or near-complete occlusion)
- OR an acute culprit lesion with TIMI 3 flow that was intervened upon with highly elevated troponin levels (cTnI > 10.0 ng/mL or hs-cTnI > 5000 ng/L) 1
The key concept is that OMI identifies patients with acute coronary occlusion who need immediate reperfusion therapy, regardless of whether they meet traditional STEMI criteria on ECG.
Diagnostic Criteria for OMI
The diagnostic criteria for OMI include:
Clinical Features
- Symptoms of myocardial ischemia (chest pain, dyspnea, etc.)
- Signs of acute myocardial injury with necrosis
- Evidence of coronary occlusion requiring revascularization
ECG Findings
OMI may present with various ECG patterns, including:
- Traditional STEMI criteria (ST-segment elevation in contiguous leads)
- STEMI-equivalent patterns without meeting formal STEMI criteria:
- Hyperacute T-waves
- De Winter pattern (upsloping ST depression with tall, symmetric T-waves)
- Shark fin pattern (fusion of QRS, ST-segment elevation, and T-wave into a wide triangular waveform) 2
- Posterior MI patterns
- ST depression with ST elevation in lead aVR
- Subtle ST changes not meeting traditional STEMI criteria
Laboratory Findings
- Elevated cardiac troponin levels with a rise and/or fall pattern
- Evidence of myocardial necrosis in a clinical setting consistent with acute myocardial ischemia 3
Angiographic Findings
- TIMI 0-2 flow in the culprit artery (complete or near-complete occlusion)
- Evidence of thrombus formation
- Acute plaque rupture, ulceration, fissuring, erosion, or dissection 3
Clinical Significance of OMI
The OMI concept addresses a critical gap in current practice:
- Approximately 40% of patients with acute coronary occlusion do not present with traditional STEMI criteria 1
- These NSTEMI-OMI patients experience significant delays in catheterization and reperfusion therapy
- Despite these delays, NSTEMI-OMI patients have similar angiographic findings, rates of PCI, and complications compared to STEMI patients 1
- Delayed treatment in OMI leads to increased morbidity and mortality
Diagnostic Challenges
Identifying OMI remains challenging:
- No reliable pre-angiographic characteristics have been identified to distinguish OMI from non-OMI with high accuracy 4
- Point-of-care ultrasound showing wall motion abnormalities may help identify OMI earlier than standard evaluation and expedite management 5
Implications for Management
The OMI paradigm suggests:
- Focusing on identifying all patients with coronary occlusion requiring immediate reperfusion, rather than only those meeting STEMI criteria
- Using additional diagnostic tools like point-of-care ultrasound to identify wall motion abnormalities when OMI is suspected but ECG is non-diagnostic
- Expediting coronary angiography for suspected OMI cases, even without classic STEMI criteria
Conclusion
The OMI concept represents an important evolution in our understanding of acute myocardial infarction, moving beyond the traditional STEMI/NSTEMI dichotomy to a more pathophysiologically-based approach focused on identifying coronary occlusion requiring urgent revascularization. While diagnostic criteria continue to evolve, recognizing OMI patterns beyond traditional STEMI criteria is crucial for reducing treatment delays and improving outcomes in patients with acute coronary occlusion.