What are the diagnostic criteria and management for Occlusion Myocardial Infarction (OMI)?

Diagnostic Criteria and Management for Occlusion Myocardial Infarction (OMI)

Occlusion Myocardial Infarction (OMI) represents acute coronary occlusion requiring immediate reperfusion therapy, regardless of whether traditional ST-elevation criteria are met.

Diagnostic Criteria for OMI

ECG Findings

• Traditional STEMI criteria (measured at J-point) 1:

  • ≥2.5 mm ST-elevation in men <40 years in leads V2-V3
  • ≥2 mm ST-elevation in men ≥40 years in leads V2-V3
  • ≥1.5 mm ST-elevation in women in leads V2-V3
  • ≥1 mm ST-elevation in other leads (in absence of LV hypertrophy or LBBB)

• OMI-specific ECG patterns that may not meet traditional STEMI criteria 2, 3:

  • ST-depression in leads V1-V3 with terminal T-wave positivity (posterior MI equivalent)
  • Isolated ST-elevation in lead III (may indicate inferior OMI) 4
  • "Shark fin" pattern - fusion of QRS, ST-elevation, and T-wave creating a triangular waveform 5
  • Hyperacute T-waves preceding ST-elevation 1
  • ST-depression in multiple leads with ST-elevation in aVR (left main or multivessel disease) 1

Clinical Findings

• Symptoms of myocardial ischemia (chest pain, dyspnea, etc.) 1
• Cardiac biomarker elevation (preferably cardiac troponin) with at least one value above the 99th percentile upper reference limit 1
• New regional wall motion abnormality on imaging 1

Angiographic Criteria

• Acute culprit lesion with TIMI 0-2 flow, or 2
• Acute culprit lesion with TIMI 3 flow with highly elevated troponin (cTnI >10.0 ng/mL, hs-cTnI >5000 ng/L) 2

Management of OMI

Immediate Actions

• Immediate ECG within 10 minutes of arrival for all patients with suspected ACS 1
• Continuous cardiac monitoring with emergency resuscitation equipment available 1
• Oxygen therapy only if SaO₂ <90% or PaO₂ <60 mmHg 1
• Pain relief with titrated IV opioids 1
• Consider mild tranquilizer (benzodiazepine) for anxious patients 1

Reperfusion Strategy

• Primary PCI is the preferred reperfusion strategy for all OMI patients 1:

  • Should be performed as soon as possible, ideally within 90-120 minutes of first medical contact 1
  • Indicated for all patients with OMI, even those without traditional STEMI criteria 2, 3
  • Particularly urgent in patients with hemodynamic instability or electrical instability 1

• Fibrinolytic therapy if PCI cannot be performed in a timely manner 1:

  • Administer as soon as possible after OMI diagnosis, preferably pre-hospital 1
  • Use fibrin-specific agents (tenecteplase, alteplase, or reteplase) 1
  • Transfer to PCI-capable center immediately after fibrinolysis 1

Antithrombotic Therapy

• Aspirin (loading dose 162-325 mg, then 75-100 mg daily) as soon as possible 1
• P2Y₁₂ inhibitor in addition to aspirin 1:
  • Prasugrel or ticagrelor preferred over clopidogrel for primary PCI 1
  • Clopidogrel indicated with fibrinolytic therapy 1
• Anticoagulation until revascularization or for duration of hospital stay 1

Post-Reperfusion Care

• Echocardiography to assess LV/RV function and detect complications 1
• High-intensity statin therapy started as early as possible 1
• Beta-blockers for patients with heart failure and/or LVEF <40% 1
• ACE inhibitors within 24 hours for patients with heart failure, LV dysfunction, diabetes, or anterior infarct 1
• Cardiac rehabilitation program participation 1

Clinical Pitfalls and Caveats

• Current STEMI criteria miss approximately 40% of patients with acute coronary occlusion 2, 3

• Patients with OMI not meeting STEMI criteria (NSTEMI-OMI) experience significant delays in treatment (median door-to-cath time 1712 minutes vs. 103 minutes for recognized STEMI) 3

• NSTEMI-OMI patients have similar rates of complications to STEMI patients despite treatment delays 2

• Special attention needed for high-risk presentations that may not meet traditional STEMI criteria:

  • Left circumflex occlusions often present without ST-elevation 1
  • Left main disease may present with widespread ST-depression and ST-elevation in aVR 1
  • Patients post-cardiac arrest with OMI may have ECG patterns easily misinterpreted as arrhythmias 5

• Machine learning models may help identify OMI patients without classic STEMI criteria in the future 6