Clinical Module · Cardiology
OMI / NOMI
OMI / NOMI
Occlusion Myocardial Infarction.
The OMI/NOMI paradigm reframes acute MI by coronary artery patency, not just ST elevation. Recognise the patterns that demand immediate reperfusion even when the 12-lead ECG does not show classic STEMI criteria.
The Paradigm
Occlusion-Equivalent Patterns
OMI vs NOMI: Why it matters.
The traditional STEMI/NSTEMI classification relies on ST-segment elevation to decide reperfusion urgency. But up to 25–30% of acute coronary occlusions do not produce ST elevation on a standard 12-lead ECG. These patients have an occluded artery (OMI) but may be classified as "NSTEMI" and miss the PPCI window.
The OMI/NOMI paradigm asks a different question: is the artery open or closed? Patterns such as posterior OMI, De Winter, Wellens, and new LBBB with ischaemic symptoms are recognised as occlusion equivalents requiring the same emergency PPCI pathway as classic STEMI.
OMI — Occlusion MI
- Complete or near-complete coronary artery occlusion
- Requires immediate reperfusion (PPCI or thrombolysis)
- Includes classic STEMI and STEMI equivalents
- Time-critical: door-to-balloon target ≤90 min
- May not show ST elevation (posterior, De Winter, Wellens)
NOMI — Non-Occlusion MI
- Partial coronary obstruction, subtotal stenosis
- Troponin-positive but no acute total occlusion
- Managed with dual antiplatelet, anticoagulation, and early invasive strategy
- Angiography within 24–72 hours per ESC guidelines
- Does not require emergent PPCI activation
Clinical Rule
Do not let the absence of ST elevation prevent PPCI activation. If the ECG shows a recognised occlusion-equivalent pattern and the clinical picture fits acute coronary syndrome, activate the PPCI pathway. Posterior OMI, De Winter, and Wellens are not "NSTEMI". They are occlusion emergencies.
Patterns that demand PPCI activation.
Posterior OMI (Occlusion Myocardial Infarction)
ImmediateECG Findings
- ST depression V1–V3 (reciprocal mirror image of posterior STE)
- Tall broad R waves in V1–V2 (mirror Q waves)
- Upright T waves V1–V2 (mirror T inversion)
- ST elevation ≥0.5 mm in posterior leads V7–V9 (when obtained)
ACTIVATE PPCI PATHWAY. Obtain posterior leads V7–V9. Treat as occlusion MI equivalent. Dual antiplatelet + heparin. Do not wait for serial ECGs. This is a STEMI equivalent despite absent anterior ST elevation.
De Winter Pattern (LAD Occlusion Equivalent)
ImmediateECG Findings
- Upsloping ST depression ≥1 mm at J-point in V1–V6
- Tall peaked symmetrical T waves (distinctive ski-slope appearance)
- No ST elevation anywhere (static pattern: does not evolve)
ACTIVATE PPCI PATHWAY IMMEDIATELY. This is an acute LAD occlusion equivalent. Do not wait for evolving changes. Treat identically to anterior STEMI. Dual antiplatelet + heparin.
Wellens Syndrome (Type A & B)
UrgentECG Findings
- Type A (25%): biphasic T waves in V2–V3 (initially positive then negative)
- Type B (75%): deep symmetrical T-wave inversions V2–V3 (±V1–V6)
- Recorded during pain-free interval: the ECG normalises or shows STE during pain
- Minimal or no troponin elevation at time of recording
ADMIT TO CARDIOLOGY IMMEDIATELY. This is a pre-infarction state: critical proximal LAD stenosis with impending occlusion. Do not discharge. Do not stress test. Urgent angiography required. Serial troponin and continuous monitoring.
New LBBB with Ischaemic Symptoms
ImmediateECG Findings
- QRS ≥120 ms with no septal Q waves in lateral leads
- Discordant ST-T changes (ST elevation opposite to major QRS deflection)
- Apply modified Sgarbossa criteria: concordant STE ≥1 mm or discordant STE ≥25% of preceding S wave
ACTIVATE PPCI PATHWAY if new LBBB with ischaemic symptoms (ESC 2023 STEMI equivalent). Apply Sgarbossa criteria. If no prior ECG for comparison, treat as presumed new and activate reperfusion pathway.
Inferior STEMI with Posterior Extension
ImmediateECG Findings
- STE ≥1 mm in leads II, III, aVF with reciprocal STD in I and aVL
- STD V1–V3 suggesting concurrent posterior involvement
- Check V4R: STE ≥0.5 mm indicates RV MI (complicates ~30%)
- 15-lead ECG recommended: V3R, V4R for RV; V7–V9 for posterior
ACTIVATE PPCI per local pathway. A 15-lead ECG is recommended. If RV MI present: consider an IV fluid challenge, and withhold nitrates and morphine (preload-dependent). Up to 30% of inferior MIs present with epigastric pain. Obtain an ECG before attributing epigastric pain to GI causes.
OMI pattern recognition at a glance.
| Pattern | ECG Hallmark | Urgency | Action |
|---|---|---|---|
| Posterior OMI | STD V1–V3 (mirror), tall R V1–V2, STE V7–V9 | Immediate | Activate PPCI + posterior leads |
| De Winter Pattern | Upsloping STD J-point + tall T V1–V6. No STE. | Immediate | Activate PPCI (LAD occlusion equivalent) |
| Wellens Syndrome | Biphasic or deep T inversion V2–V3. Pain-free. | Urgent | Admit cardiology. No discharge. |
| New LBBB + symptoms | QRS ≥120 ms, no septal Q laterally, discordant ST-T | Immediate | Activate PPCI (STEMI equivalent) |
| Inferior STEMI | STE ≥1 mm II/III/aVF, reciprocal STD aVL/I | Immediate | Activate PPCI + right-sided leads |
| Anterior STEMI | STE ≥2 mm V1–V4, hyperacute T, loss of R progression | Immediate | Activate PPCI |
Inferior MI & Epigastric Pain
Get an ECG before attributing epigastric pain to any GI cause. Inferior MI presents as epigastric pain in up to 30% of cases. Avoid performing an upper GI procedure in an undiagnosed MI. The patient who says "indigestion" but looks pale and diaphoretic has a cardiac presentation until the ECG says otherwise.
Sources & References
ESC 2023 Acute Coronary Syndromes Guidelines | NICE CG167 — MI with ST-segment Elevation | RCEM 2019 ECG Interpretation Standards | LITFL — Posterior MI ECG Library (CC BY-NC-SA 4.0) | LITFL — De Winter Pattern | LITFL — Wellens Syndrome | ECG Waves — Posterior MI | ECG Waves — De Winter | RCEMLearning | AHA/ACC 2022
ESC 2023 Acute Coronary Syndromes Guidelines | NICE CG167 — MI with ST-segment Elevation | RCEM 2019 ECG Interpretation Standards | LITFL — Posterior MI ECG Library (CC BY-NC-SA 4.0) | LITFL — De Winter Pattern | LITFL — Wellens Syndrome | ECG Waves — Posterior MI | ECG Waves — De Winter | RCEMLearning | AHA/ACC 2022