How it's calculated
Three ECG criteria are weighted by their diagnostic value and summed — concordant ST elevation (+5), concordant ST depression in V1-V3 (+3), and excessively discordant ST elevation (+2). A total of 3 or more is considered positive.
Interpretation
| Score | Interpretation |
|---|---|
| ≥ 3 | Positive — highly specific for acute MI |
| < 3 | Negative — does not rule out MI (limited sensitivity) |
Clinical use
- Applied specifically to patients with baseline LBBB or a ventricular paced rhythm and a clinical presentation concerning for acute coronary syndrome, where the underlying conduction abnormality normally masks standard STEMI ECG criteria.
- A positive result (score ≥3) is highly specific for acute MI and supports urgent reperfusion therapy alongside the clinical picture.
- A negative result does not exclude MI — sensitivity is limited, so ongoing clinical suspicion should still prompt serial ECGs, troponin measurement, and cardiology involvement.
Frequently asked questions
Why can't standard STEMI criteria be used with LBBB?
LBBB itself causes secondary ST-segment and T-wave changes (appropriately discordant from the QRS direction) that can mimic or mask genuine ischaemic ST changes, making the usual ST-elevation criteria unreliable.
What does 'concordant' mean in this context?
Concordant means the ST segment moves in the same direction as the main QRS deflection in that lead — normally in LBBB the ST segment is expected to be discordant (opposite direction), so a concordant change is abnormal and suggestive of ischaemia.
Is there a more sensitive version of these criteria?
Yes — the Smith-modified Sgarbossa criteria replace the fixed discordant ST-elevation threshold with a proportional (ST/S-wave ratio) criterion, improving sensitivity; the original weighted-score version shown here remains widely taught and used.
References
- Sgarbossa EB, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. N Engl J Med. 1996;334(8):481-487.
- Smith SW, et al. Diagnosis of ST-elevation myocardial infarction in the presence of left bundle branch block with the ST-elevation to S-wave ratio. Ann Emerg Med. 2012.