Sgarbossa's criteria

Sgarbossa's criteria are a set of electrocardiographic findings generally used to identify myocardial infarction (also called acute myocardial infarction) in the presence of a left bundle branch block (LBBB) or a ventricular paced rhythm.^[1]

Myocardial infarction (MI) is often difficult to detect when LBBB is present on ECG. A large clinical trial of thrombolytic therapy for MI (GUSTO-1) evaluated the electrocardiographic diagnosis of evolving MI in the presence of LBBB.^[2] Among 26,003 North American patients who had a myocardial infarction confirmed by enzyme studies, 131 (0.5%) had LBBB. A scoring system, now commonly called Sgarbossa criteria, was developed from the coefficients assigned by a logistic model for each independent criterion, on a scale of 0 to 5. A minimal score of 3 was required for a specificity of 90%.

Sgarbossa's criteria

Three criteria are included in Sgarbossa's criteria:^[2]

• ST elevation ≥1 mm in a lead with a positive QRS complex (ie: concordance) - 5 points
• ST depression ≥1 mm in lead V1, V2, or V3 - 3 points
• ST elevation ≥5 mm in a lead with a negative (discordant) QRS complex - 2 points

≥3 points = 90% specificity of STEMI (sensitivity of 36%)^[2]

Validation and usefulness

A high take-off of the ST segment in leads V1 to V3 is well-described with uncomplicated LBBB, such as in the setting of left ventricular hypertrophy. In a substudy from the ASSENT 2 and 3 trials, the third criteria added little diagnostic or prognostic value.^[3]

A Sgarbossa score of ≥3 was specific but not sensitive (36%) in the validation sample in the original report.^[2] A subsequent meta-analysis of 10 studies consisting of 1614 patients showed that a Sgarbossa score of ≥3 had a specificity of 98% and sensitivity of 20%.^[4] The sensitivity may increase if serial or previous ECGs are available.^[5]

Other methods for detecting AMI in patients with LBBB

Several other studies have evaluated the usefulness of different ECG findings in diagnosing MI when LBBB is present. Smith et al. modified Sgarbossa's original criteria.^[6]

Smith modified Sgarbossa rule:

• at least one lead with concordant STE (Sgarbossa criterion 1) or
• at least one lead of V1-V3 with concordant ST depression (Sgarbossa criterion 2) or
• proportionally excessively discordant ST elevation in V1-V4, as defined by an ST/S ratio of equal to or more than 0.20 and at least 2 mm of STE. (this replaces Sgarbossa criterion 3 which uses an absolute of 5mm)

Wackers et al. correlated ECG changes in LBBB with localization of the infarct by thallium scintigraphy.^[7] The most useful ECG criteria were:

• Serial ECG changes — 67 percent sensitivity
• ST segment elevation — 54 percent sensitivity
• Abnormal Q waves — 31 percent sensitivity
• Cabrera's sign — 27 percent sensitivity, 47 percent for anteroseptal MI
• Initial positivity in V1 with a Q wave in V6 — 20 percent sensitivity but 100 percent specificity for anteroseptal MI

See also

• Electrocardiography in myocardial infarction

References

1. Sgarbossa, Elena B.; Pinski, Sergio L.; Gates, Kathy B.; Wagner, Galen S. (1996). "Early Electrocardiographic Diagnosis of Acute Myocardial Infarction in the Presence of Ventricular Paced Rhythm. GUSTO-I investigators.". American Journal of Cardiology 77 (5): 423–424. doi:10.1016/S0002-9149(97)89377-0. ISSN 1062-1458. PMID 8602576.
2. Sgarbossa, Elena B.; Pinski, Sergio L.; Barbagelata, Alejandro; Underwood, Donald A.; Gates, Kathy B.; Topol, Eric J.; Califf, Robert M.; Wagner, Galen S. (1996). "Electrocardiographic Diagnosis of Evolving Acute Myocardial Infarction in the Presence of Left Bundle-Branch Block". New England Journal of Medicine 334 (8): 481–487. doi:10.1056/NEJM199602223340801. ISSN 0028-4793. PMID 8559200.
3. Al-Faleh, Hussam; Fu, Yuling; Wagner, Galen; Goodman, Shaun; Sgarbossa, Elena; Granger, Christopher; Van de Werf, Frans; Wallentin, Lars; W. Armstrong, Paul; et al. (2006). "Unraveling the spectrum of left bundle branch block in acute myocardial infarction: Insights from the Assessment of the Safety and Efficacy of a New Thrombolytic (ASSENT 2 and 3) trials". American Heart Journal 151 (1): 10–15. doi:10.1016/j.ahj.2005.02.043. ISSN 0002-8703. PMID 16368285.
4. Tabas, Jeffrey A.; Rodriguez, Robert M.; Seligman, Hilary K.; Goldschlager, Nora F. (2008). "Electrocardiographic Criteria for Detecting Acute Myocardial Infarction in Patients With Left Bundle Branch Block: A Meta-analysis". Annals of Emergency Medicine 52 (4): 329–336.e1. doi:10.1016/j.annemergmed.2007.12.006. ISSN 0196-0644. PMID 18342992.
5. E. B. Sgarbossa (2000). "Value of the ECG in suspected acute myocardial infarction with left bundle branch block". Journal of electrocardiology. 33 Suppl: 87–92. doi:10.1054/jelc.2000.20324. PMID 11265742.
6. Smith, Stephen W.; Dodd, Kenneth W.; Henry, Timothy D.; Dvorak, David M.; Pearce, Lesly A. (2012). "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". Annals of Emergency Medicine 60 (6): 766–776. doi:10.1016/j.annemergmed.2012.07.119. ISSN 0196-0644. PMID 22939607.
7. F. J. Wackers (August 1987). "The diagnosis of myocardial infarction in the presence of left bundle branch block". Cardiology clinics 5 (3): 393–401. PMID 3690603.