Modified Sgarbossa Criteria Calculator

Score an ECG with left bundle branch block or a ventricular paced rhythm on both rules at once — the original weighted Sgarbossa criteria and the Smith modification, which replaces the fixed 5 mm threshold with a proportional ST/S ratio. Specific but not sensitive: a negative result does not exclude infarction.

Last updated 18 Sep 2026

Sgarbossa, original and Smith-modified

Both rules from one ECG

Underlying rhythmBoth rules were derived in left bundle branch block and both have been validated separately in ventricular paced rhythm, where the same problem arises for the same reason: the ventricles depolarise abnormally, so the ST segment and T wave are secondarily abnormal and ordinary ST-elevation criteria cannot be applied. Selecting a paced rhythm changes the performance figures quoted in the answer, not the criteria themselves.

Concordant ST elevation of 1 mm or more, in any lead with a positive (upright) QRSCriterion 1, and it is unchanged between the two rules. Worth 5 points in the original weighted score, so on its own it makes the original rule positive. Concordance means the ST segment is deflected the SAME way as the main QRS deflection — the opposite of what conduction delay alone produces, which is why it is so specific.

Concordant ST depression of 1 mm or more in lead V1, V2 or V3Criterion 2, also unchanged between the two rules, and worth 3 points — enough on its own to make the original rule positive. It is restricted to V1 to V3 in both rules as published. Concordant ST depression elsewhere is not part of either rule, although adding V4 to V6 has been proposed and tested; see the answer.

ST elevation in the lead with the most DISCORDANT ST elevation (mm)Discordant means the ST segment is deflected OPPOSITE to the main QRS deflection, which is the normal appearance in left bundle branch block and in a paced rhythm — some discordance is expected, and the question is only ever whether there is too much. Measure at the J point relative to the PR or TP baseline, in the single lead where discordant elevation is greatest, and measure the S wave in that same lead.

Depth of the S wave in that same lead (mm)The amplitude of the S wave in the SAME lead you measured the ST elevation in — this is the whole point of the modification. The original rule asked only whether the ST elevation reached 5 mm, which a small-amplitude QRS can never produce however proportionally extreme the elevation is. Smith’s rule asks what fraction of the S wave the elevation represents, with 25% as the cut-off.

0of 10 pointsExample

Left bundle branch block. No concordant ST elevation and no concordant ST depression in V1–V3. In the lead with the most discordant ST elevation there is 3 mm of elevation over a 6 mm S wave

Two rules, one ECG

Original (Sgarbossa 1996), weighted: concordant ST elevation ≥1 mm = 5; concordant ST depression ≥1 mm in V1–V3 = 3; discordant ST elevation ≥5 mm = 2. Positive at 3 or more of a possible 10.
Modified (Smith 2012), unweighted: the first two criteria unchanged; the third becomes discordant ST elevation ≥1 mm with an ST/S ratio ≤ −0.25 — the elevation is at least 25% of the depth of the S wave in the same lead. Positive if any one criterion is met.

Concordant: the ST segment deflects the same way as the main QRS deflection. Conduction delay alone does not do this, which is why concordance is the specific finding and why it carries the two heaviest weights
Discordant: the ST segment deflects opposite to the main QRS deflection. This is the expected appearance in left bundle branch block and in a paced rhythm, so the question is never whether discordance is present but whether there is too much of it
The 5 mm problem: the original third criterion is a fixed voltage, and a lead whose S wave is only 6 mm deep can be almost completely obliterated by ischaemic ST elevation and still never reach 5 mm. StatPearls records that this threshold “was selected rather arbitrarily”. The modification makes the criterion proportional, which is why it recovers the small-amplitude QRS complexes the original missed
The maximum: 5 + 3 + 2 = 10, and the attainable scores are 0, 2, 3, 5, 7, 8 and 10. Exactly one attainable score — 2 — sits below the 3-point threshold, and it is the discordant criterion on its own, so that criterion could never make the original rule positive by itself

Worked example

Left bundle branch block. No concordant ST elevation and no concordant ST depression in V1–V3. In the lead with the most discordant ST elevation there is 3 mm of elevation over a 6 mm S wave
Concordant ST elevation ≥1 mm: no → 0 points
Concordant ST depression ≥1 mm in V1–V3: no → 0 points
Discordant ST elevation ≥5 mm: the elevation is 3 mm, so no → 0 points
Original weighted Sgarbossa score = 0 of 10. Negative. It would still have been negative at 4.9 mm of elevation, and it would have scored only 2 — still below the threshold of 3 — even at 5 mm
Now the modification. ST/S = 3 ÷ 6 = 0.50, which is 50% — twice the 25% cut-off, so the ST/S ratio criterion is met
Modified (Smith) criteria met: 1 of 3. The rule is unweighted and one criterion is enough, so the modified rule is positive
One ECG, two rules, opposite answers. The reason is entirely the S-wave amplitude: at a 6 mm S wave the original rule's fixed 5 mm threshold demands an ST elevation of 83% of the S wave before it will fire, which is why small-amplitude QRS complexes were the ones it missed

The two rules side by side

The first two criteria are identical in both rules. Everything that differs is in the third row and the two rows beneath it, and that is the whole substance of the modification: a fixed voltage becomes a proportion, and the weighting is abandoned so that the proportional criterion can stand on its own. Note the last row — under the original rule, the criterion that the modification exists to fix could never make the rule positive by itself, because it was worth 2 points against a threshold of 3.
Criterion	Original (Sgarbossa 1996)	Modified (Smith 2012)
Concordant ST elevation ≥1 mm in a lead with a positive QRS	5 points	Met / not met
Concordant ST depression ≥1 mm in V1, V2 or V3	3 points	Met / not met
Excessively discordant ST elevation	≥5 mm — 2 points	≥1 mm and ST/S ratio ≤ −0.25 (elevation ≥25% of the S wave)
Scoring	Weighted; maximum 10; positive at 3 or more	Unweighted; positive if any one criterion is met
Can the third criterion alone make the rule positive?	No — 2 points is below the threshold of 3	Yes

How the two rules perform, by study and by setting

Read the last row before the others. In an unselected consecutive cohort — rather than a case-control design enriched with confirmed occlusions — both rules perform far worse than their derivation figures, and the modified rule’s sensitivity falls from 91% to 54%. The direction of the effect is consistent everywhere: the modification roughly doubles to triples sensitivity for almost no specificity cost. The size of the effect is not. The 49% and 80% pair quoted in most secondary sources is Meyers 2015, so a textbook citing both StatPearls and Meyers is citing one study twice.
Study and setting	Original criteria	Modified criteria
Tabas 2008, meta-analysis of 10 studies, 1,614 patients, LBBB — score ≥3	Sensitivity 20% (18–23), specificity 98% (97–99), LR+ 7.9, LR− 0.8	Not assessed — predates the modification
Smith 2012, derivation, LBBB	Sensitivity 52%, specificity 98% (weighted ≥3); 67% and 90% unweighted	Sensitivity 91%, specificity 90%
Meyers 2015, validation, LBBB, 45 occlusions and 249 controls	Sensitivity 49%, specificity 100%	Sensitivity 80%, specificity 99%
Dodd 2021, ventricular paced rhythm	Sensitivity 56% (42–69), specificity 97% (92–99)	Sensitivity 81% (69–90), specificity 96% (90–99)
Lindow 2024, consecutive real-world cohort, LBBB only (441 patients, 13 occlusions)	Sensitivity 15.4%, specificity 91.4%	Sensitivity 53.9%, specificity 92.1%

Why an ordinary ST criterion fails, and what a proportion fixes

Left bundle branch block and ventricular pacing both make the ventricles depolarise through myocardium rather than through the conduction system. Depolarisation is therefore slow and abnormal, and because repolarisation follows depolarisation, the ST segment and T wave are secondarily abnormal too. The rule that describes the normal appearance is appropriate discordance: the ST segment and T wave point away from the main QRS deflection, so a lead with a deep S wave normally shows ST elevation, and a lead with a tall R wave normally shows ST depression. That is why the ordinary STEMI criteria cannot simply be applied — in these rhythms, ST elevation in the right leads is the expected finding, not the abnormal one, and for years that produced two opposite errors at once: patients with left bundle branch block were taken to the catheter laboratory for ST elevation that meant nothing, and patients with real coronary occlusion were left because their ECG was declared uninterpretable.

Sgarbossa’s contribution in 1996 was to identify the findings that conduction delay cannot produce. Two of them are concordance: ST elevation of at least 1 mm in a lead whose QRS is upright, and ST depression of at least 1 mm in V1, V2 or V3 where the QRS is downward. Both point the wrong way for appropriate discordance, so both demand a second explanation, and both are highly specific. They were weighted 5 and 3 points respectively, against a threshold of 3, which means either one alone makes the rule positive. The third criterion tried to capture the other half of the problem — discordance in the right direction but of the wrong magnitude — and did it with a fixed voltage: ST elevation of 5 mm or more in a lead with a negative QRS, worth 2 points.

That third criterion is the one the modification exists to fix, and the reason is arithmetic rather than physiological. A fixed millimetre threshold ignores the size of the complex it is measured against. In a lead with a 40 mm S wave, 5 mm of discordant elevation is 12% of the complex and close to normal; in a lead with a 6 mm S wave, 5 mm of elevation is 83% of the complex, an extraordinary finding that will essentially never occur, so the criterion can never fire however proportionally extreme the ischaemic change is. Small-amplitude QRS complexes are therefore systematically invisible to it — and StatPearls, reproducing the original rule, records that the 5 mm figure “was selected rather arbitrarily”. Worse, the criterion was worth only 2 points against a threshold of 3, so even when it did fire it could not make the rule positive by itself. Enumerate the attainable scores — 0, 2, 3, 5, 7, 8 and 10 — and exactly one of them, 2, falls below the threshold, and it is this criterion standing alone.

Smith’s 2012 revision replaces the fixed voltage with a proportion. Discordant ST elevation of at least 1 mm counts when the ratio of ST elevation to S-wave depth in the same lead reaches 0.25 — expressed in the paper as an ST/S ratio of −0.25 or less, the sign reflecting that the two deflections point opposite ways. And the revision drops the weights: it is “unweighted, requiring just 1 of 3 criteria”. In the derivation cohort this raised sensitivity from 52% to 91% against the original weighted rule, at a specificity of 90% against 98%. The comparison that matters more is the one against the original rule applied unweighted — 91% against 67%, at identical specificity of 90% — because it shows the gain comes from making the criterion proportional and not simply from lowering the bar. Meyers’ independent validation, in 45 confirmed coronary occlusions and 249 controls across three institutions, found 80% against 49% at 99% against 100% specificity.

Both rules apply to ventricular paced rhythms as well as to left bundle branch block, and this deserves saying plainly because the opposite is still taught. In paced rhythm the modified criteria reached 81% sensitivity against 56% for the original, at specificities of 96% and 97%. The same study found that adding concordant ST depression in V4 to V6 pushed sensitivity to 86%; that is a proposed extension rather than part of either rule, and it is not scored here, but it is worth having in mind while looking at the tracing. A paced rhythm is not a reason to declare an ECG uninterpretable or to withhold reperfusion assessment.

The limitation is the same for both rules and it is the most important thing on this page. They are specific, not sensitive. The pooled meta-analysis of the original rule gives a specificity of 98% and a positive likelihood ratio of 7.9 — a positive result genuinely means something — alongside a sensitivity of 20% and a negative likelihood ratio of 0.8, which moves the probability of infarction almost not at all. The modification improves sensitivity substantially but does not rescue it: in an unselected consecutive cohort rather than a case-control design, sensitivity was 53.9% for the modified rule and 15.4% for the original. A negative result on either rule is not a rule-out. If the story is convincing, the next steps are serial ECGs, serial high-sensitivity troponins read with the delta calculator rather than by eye, bedside echocardiography for a regional wall motion abnormality, and a low threshold for angiography. And once a troponin comes back, read it as what it is: the myocardial injury versus infarction interpreter sets out what a raised troponin does and does not establish.

Frequently asked questions

What are the Sgarbossa criteria?

Three ECG findings for diagnosing acute myocardial infarction in the presence of left bundle branch block, published by Sgarbossa and colleagues in 1996 from the GUSTO-1 population. As reproduced in StatPearls: concordant ST elevation greater than 1 mm in a lead with a positive QRS scores 5 points; concordant ST depression greater than 1 mm in V1 to V3 scores 3 points; discordant ST elevation greater than 5 mm in a lead with a negative QRS scores 2 points. Three or more points is the usual positive threshold, giving a maximum of 10. Because the third criterion is worth only 2 points, a positive score always rests on one of the two concordance criteria.

What is the difference between the Sgarbossa and the modified Sgarbossa criteria?

Two differences, both in how the third criterion is handled. The Smith modification replaces the original’s fixed “ST-segment elevation greater than or equal to 5 mm” with a proportional criterion — discordant ST elevation of at least 1 mm with an ST/S ratio of −0.25 or less, meaning the elevation is at least 25% of the depth of the S wave in the same lead. And the modified rule is unweighted: it is positive if any single criterion is met, rather than requiring 3 points. The first two criteria are identical in both rules. The modification exists because a fixed 5 mm threshold cannot be reached in a lead with a small-amplitude QRS however extreme the proportional ST elevation is.

What is the ST/S ratio cut-off in the modified Sgarbossa criteria?

An ST/S ratio of −0.25 or less, as published by Smith and colleagues in 2012. In practice that means measuring the discordant ST elevation at the J point and the depth of the S wave in the same lead, and asking whether the elevation is at least a quarter of the S wave. Three millimetres of elevation over a 6 mm S wave is a ratio of 0.50 and clearly positive; 3 mm over a 20 mm S wave is 0.15 and negative. The elevation must also be at least 1 mm in absolute terms.

Do the Sgarbossa criteria apply to paced rhythms?

Yes, and both rules have been validated there in their own right. In ventricular paced rhythm the modified criteria reached a sensitivity of 81% (95% CI 69–90) against 56% (95% CI 42–69) for the original criteria, at specificities of 96% and 97% respectively — the same pattern seen in left bundle branch block. Adding concordant ST depression in V4 to V6 raised sensitivity to 86% in the same study, although that is a proposed extension rather than part of either published rule. The older teaching that a paced ECG is uninterpretable for ischaemia is not supported and should not be a reason to withhold reperfusion assessment.

Does a negative Sgarbossa score rule out myocardial infarction?

No, and this is the most important limitation of both rules. In the pooled meta-analysis of 10 studies and 1,614 patients, a Sgarbossa score of 3 or more had a sensitivity of only 20% (95% CI 18% to 23%) and a negative likelihood ratio of 0.8 — which barely shifts the probability of infarction at all. The modification improves sensitivity substantially, to 91% in its derivation cohort and 80% in validation, but in a consecutive real-world cohort of 441 patients with left bundle branch block the modified rule’s sensitivity was 53.9% and the original’s 15.4%. A negative result on either rule means you have not found the diagnosis, not that it is not there.

Why does a small QRS complex matter for the Sgarbossa criteria?

Because the original third criterion is a fixed voltage and the size of the QRS is what the ST elevation should be judged against. In a lead with a 40 mm S wave, 5 mm of discordant ST elevation is 12% of the complex and unremarkable. In a lead with a 6 mm S wave, reaching 5 mm would require the ST elevation to be 83% of the S wave — a finding that essentially never occurs — so the criterion can never fire in that lead however severe the ischaemia. Patients with small-amplitude QRS complexes were therefore systematically missed, and making the criterion proportional is precisely what recovers them.

Related calculators

References

Scherbak D, Shams P, Hicks GJ. Left Bundle Branch Block. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 5 October 2024. NCBI Bookshelf NBK482167. Used here as the attributed reproduction of the original 1996 criteria, because the New England Journal of Medicine original could not be retrieved: “Concordant ST elevation greater than 1 mm in leads with a positive QRS complex gets a score of 5 points”; “Concordant ST depression greater than 1 mm in V1 to V3 gets a score of 3 points”; “Discordant ST elevation greater than 5 mm in leads with a negative QRS complex gets a score of 2 points”; “Three or more points indicate AMI”; “Their sensitivity is only 49%, but their specificity is greater than 90%”; “The sensitivity of the modified criteria increases to 80% without affecting specificity”; and that the original third criterion “was selected rather arbitrarily”.
Sgarbossa EB, Pinski SL, Barbagelata A, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 Investigators. N Engl J Med. 1996;334(8):481–487. The original derivation. The full text was not accessible when this page was written, so no figure on this page is attributed to it directly; the criteria and their weights are taken from the StatPearls reproduction above and cross-checked against the four studies below.
Smith SW, Dodd KW, Henry TD, Dvorak DM, Pearce LA. Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule. Ann Emerg Med. 2012;60(6):766–776. “ST-segment elevation with an ST/S ratio less than or equal to −0.25” replaces “ST-segment elevation greater than or equal to 5 mm”; “The revised rule is unweighted, requiring just 1 of 3 criteria”; modified versus original weighted (≥3 points) sensitivity 91% vs 52% (P<.001) and specificity 90% vs 98% (P=.002); modified versus original unweighted sensitivity 91% vs 67% (P=.008) at specificity 90% vs 90% (P=1.0).
Tabas JA, Rodriguez RM, Seligman HK, Goldschlager NF. Electrocardiographic Criteria for Detecting Acute Myocardial Infarction in Patients With Left Bundle Branch Block: A Meta-analysis. Ann Emerg Med. 2008;52(4):329–336.e1. Ten studies, 1,614 patients; for a Sgarbossa score of 3 or more, sensitivity “20% (95% confidence interval [CI] 18% to 23%)”, specificity “98% (95% CI 97% to 99%)”, positive likelihood ratio “7.9 (95% CI 4.5 to 13.8)”, negative likelihood ratio “0.8 (95% CI 0.8 to 0.9)”.
Meyers HP, Limkakeng AT Jr, Jaffa EJ, et al. Validation of the modified Sgarbossa criteria for acute coronary occlusion in the setting of left bundle branch block: a retrospective case-control study. Am Heart J. 2015;170(6):1255–1264. Modified versus original weighted criteria, sensitivity “80% vs 49%, P < .001” and specificity “99% vs 100%, P = .5”; third criterion stated as “at least 1 mm STE and STE/S wave ≤−0.25”; 45 acute coronary occlusions and 249 controls across three institutions. This is the source of the 49% and 80% figures quoted in StatPearls, so the two are not independent.
Dodd KW, Zvosec DL, Hart MA, et al. Electrocardiographic Diagnosis of Acute Coronary Occlusion Myocardial Infarction in Ventricular Paced Rhythm Using the Modified Sgarbossa Criteria. Ann Emerg Med. 2021;78(4):517–529. In ventricular paced rhythm, modified criteria sensitivity 81% (95% CI 69–90) against original 56% (95% CI 42–69), specificity 96% (95% CI 90–99) against 97% (95% CI 92–99); adding concordant ST depression in V4–V6 raised sensitivity to 86% (95% CI 75–94).
Lindow T, et al. Comparison of diagnostic accuracy of current left bundle branch block and ventricular pacing ECG criteria for detection of occlusion myocardial infarction. Int J Cardiol. 2024;395:131569. A consecutive cohort of 623 patients with 15 occlusions; in the 441 patients with left bundle branch block (13 occlusions), original Sgarbossa sensitivity 15.4% and specificity 91.4%, modified Sgarbossa sensitivity 53.9% and specificity 92.1%. The real-world counterweight to the case-control derivation and validation figures.

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