From the Guidelines
STEMI equivalents include new or presumably new Left Bundle Branch Block (LBBB) and posterior MI, which can be indicated by ST depression in leads V1-V4 or ST elevation in posterior chest leads V7-V9.
Key Equivalents
- New or presumably new LBBB not documented to be resolved within 20 min 1
- Posterior MI, which can be indicated by ST depression in leads V1-V4 or ST elevation in posterior chest leads V7-V9 1
Diagnostic Criteria
The diagnosis of STEMI equivalents is based on the presence of characteristic symptoms of myocardial ischemia, ECG changes, and biomarker elevation.
- New or presumably new LBBB on the initial ECG is considered a STEMI equivalent 1
- ST depression in leads V1-V4 may indicate transmural posterior injury, and ST elevation in posterior chest leads V7-V9 can confirm posterior MI 1
Clinical Context
In the clinical context, STEMI equivalents require prompt recognition and treatment, similar to STEMI.
- Reperfusion therapy should be initiated as soon as possible in patients with suspected STEMI or STEMI equivalents 1
- Immediate referral for invasive angiography may be necessary to guide therapy in the appropriate clinical context 1
From the Research
STEMI Equivalents
The following are considered equivalents of ST-Elevation Myocardial Infarction (STEMI):
- Wellens' syndrome 2, 3, 4, 5
- De Winter sign 2, 3
- Hyperacute T waves 2, 5
- Left bundle branch block, including paced rhythm 2
- Right bundle branch block 2
- aVR ST elevation 3, 5
- Subtle ST-segment elevations 5
- ST-segment elevation in leads aVR/V1 with concomitant ST-segment depression in ≥ 8 other leads 5
- High R-peak with positive T-waves combined with horizontal ST-segment depression in leads V1/V2 5
Incidence of STEMI Equivalents
The incidence of STEMI equivalents in prehospital patients presenting with chest pain is significant, with studies showing that around 4-5% of patients meet the criteria for STEMI equivalency 3.
Importance of Recognition
Prompt recognition of STEMI equivalent ECG patterns is crucial for every physician or paramedic dealing with acute coronary syndrome patients, as misinterpretation of those high-risk presentations can lead to reperfusion delays and worse outcomes 2, 3.