What is the Smith modification?

The original Sgarbossa criterion 3 required ≥5 mm absolute ST elevation discordant to the QRS. Smith's modification replaces this with an ST/S ratio ≥ 0.25 (ST elevation divided by the absolute depth of the S wave), which is more sensitive, especially for patients with low-voltage complexes.

What score is considered positive for STEMI?

A total score ≥3 points carries approximately 98% specificity for STEMI, though sensitivity is modest (~36% for the original criteria). Any concordant change (criteria 1 or 2 alone, 3+ points) is highly specific. The modified criteria improve sensitivity without sacrificing much specificity.

Does a negative result rule out STEMI?

No. A score below 3 does not exclude STEMI. Clinical context, serial ECGs, and troponin measurements are essential. The Sgarbossa criteria are a decision-support tool, not a standalone rule-out.

Which leads are checked for criterion 1?

All 12 leads. Any lead with an upright (positive) QRS that shows ≥1 mm of ST elevation in the same direction (concordant) qualifies.

What counts as a positive QRS for criterion 1?

A QRS complex whose terminal deflection is net positive — the R wave is taller than the S wave is deep, so the overall vector is upward.

Modified Sgarbossa Criteria

Name: Modified Sgarbossa Criteria
Availability: InStock
Author: Nham Vu

Score modified Sgarbossa criteria (with Smith's ST/S ratio) to detect STEMI in LBBB or paced rhythm.

ECG Findings

Evaluate each criterion based on the 12-lead ECG.

1 Concordant ST elevation +5 pts

≥1 mm ST elevation in the same direction as the QRS (positive QRS + upward ST) in ≥1 lead.

Present Absent

2 Concordant ST depression in V1–V3 +3 pts

≥1 mm ST depression in V1, V2, or V3 in the same direction as an overall negative QRS in those leads.

Present Absent

3 Excessively discordant ST elevation +2 pts

Smith's modification: ST elevation / S-wave amplitude ratio ≥ 0.25 in the lead with the most discordant ST elevation (negative QRS + upward ST).

ST elevation (mm)

S-wave depth (mm, positive)

Leave blank if no discordant ST elevation is visible.

Enter ECG findings and press Calculate Score to see results.

Summary

Score modified Sgarbossa criteria (with Smith's ST/S ratio) to detect STEMI in LBBB or paced rhythm.

How it works

Enter whether concordant ST elevation ≥1 mm is present in any lead with a positive QRS complex.
Enter whether concordant ST depression ≥1 mm is present in leads V1–V3.
Enter the ST elevation amount (mm) and S-wave amplitude (mm) for the most discordant lead to calculate Smith's ST/S ratio.
The tool sums the weighted points and classifies the result as positive, indeterminate, or negative for STEMI.
Review the per-criterion breakdown and clinical pearls before making a clinical decision.

Use cases

Emergency physician evaluating a patient with chest pain and LBBB on ECG.
Cardiologist reviewing an ECG from a patient with a ventricular pacemaker.
Medical student or resident learning the original versus modified Sgarbossa criteria.
Telemedicine provider assessing a remotely transmitted ECG for STEMI equivalence.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu