Outside of the standard ECG findings which are diagnostic of a STEMI previously mentioned, there is currently only one universally recognized “STEMI equivalent,” which is a left bundle branch block (LBBB) meeting the Sgarbossa’s criteria.19

There are other highly concerning ECG patterns that include the de Winter pattern, the left main pattern, hyperacute T waves, Wellen’s syndrome and posterior MI. These patterns are not considered a STEMI equivalent but emergent/urgent revascularization with PCI that should be considered.24 ECG interpretation may be complex and urgent teleconsultation with a cardiologist should be considered. ECG changes that should also raise concern for ischemia include ST depressions ≥ 0.5 mm (in ≥ 2 contiguous leads) or T-wave inversion.

1. LBBB with Sgarbossa’s criteria – Sgarbossa’s criteria was developed to identify an acute MI in the setting of a LBBB since this pattern can cause ST- and T-wave changes that make it difficult to identify an MI. The ECG is considered consistent with MI if any of the following three criteria are met and combine to equal ≥ 3 points:25

- ≥ 1 lead with ≥ 1 mm of concordant ST-elevation with the QRS complex (5 points)
- ≥ 1 lead of V1-V3 with ≥ 1 mm of concordant ST-depression with the QRS complex (3 points)
- ST- elevation of ≥ 5 mm that is discordant with the QRS complex (2 points)

2. Modified Sgarbossa criteria (listed below) may outperform the original proposed criteria.26 Any of the changes listed below are diagnostic of MI in the modified criteria.

- ≥ 1 lead with ≥ 1 mm of concordant ST elevation with QRS
- ≥ 1 lead of V1-V3 with ≥ 1 mm of concordant ST depression with QRS
- ≥ 1 lead anywhere with ≥ 1 mm ST-elevation and proportionally excessive discordant ST-elevation, as defined by ≥ 25% of the depth of the preceding S-wave (an ST:S ratio of ≤ -0.25)