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Criteria for Acute Myocardial Infarction in the Left Bundle Branch Block

In the Emergency Department, the diagnosis of acute myocardial infarction (AMI) relies initially on a patient’s history and the 12-lead electrocardiogram (ECG). Establishing the diagnosis of AMI in the left bundle branch block (LBBB) is difficult and can result in delay of definitive treatment. In 1996, Sgarbossa found 3 ECG criteria to evaluate for AMI in patients with LBBB.

Sgarbossa Criteria for Acute Myocardial Infarction in the Left Bundle Branch Block

Three criteria are included in Sgarbossa’s criteria:

Criteria Points
Concordant ST elevation ≥1 mm in a lead with a positive QRS complex 5 points
Concordant ST depression ≥1 mm in lead V1, V2, or V3 3 points
Discordant ST elevation ≥5 mm in a lead with a negative QRS complex 2 points

≥3 points = 90% specificity of STEMI (sensitivity of 36%)

Smith-modified Sgarbossa Criteria for Acute Myocardial Infarction in the Left Bundle Branch Block

Patients with LBBB of unknown onset presenting with chest pain can pose a diagnostic challenge in the ED while Smith-Modified-Sgarbossa (SMS) ECG criteria might facilitate AMI diagnosis.

The use of a 5 mm cutoff for excessive discordance was arbitrary and non-specific — for example, patients with LBBB and large voltages will commonly have ST deviations > 5 mm in the absence of ischaemia. The modified rule is positive for “STEMI” if there is discordant ST elevation with amplitude > 25% of the depth of the preceding S-wave.

  • Concordant ST elevation ≥ 1 mm in ≥ 1 lead
  • Concordant ST depression ≥ 1 mm in ≥ 1 lead of V1-V3
  • Proportionally excessive discordant ST elevation (STE) in ≥ 1 lead anywhere with ≥ 1 mm STE, as defined by ≥ 25% of the depth of the preceding S-wave

Patients with LBBB of unknown onset presenting with chest pain can pose a diagnostic challenge in the ED while Smith-Modified-Sgarbossa (SMS) ECG criteria might facilitate AMI diagnosis.

 

References:

  1. Di Marco A, Rodriguez M, Cinca J, Bayes-Genis A, Ortiz-Perez JT, Ariza-Solé A, Sanchez-Salado JC, Sionis A, Rodriguez J, Toledano B, Codina P, Solé-González E, Masotti M, Gómez-Hospital JA, Cequier Á, Anguera I. New Electrocardiographic Algorithm for the Diagnosis of Acute Myocardial Infarction in Patients With Left Bundle Branch Block. J Am Heart Assoc. 2020 Jul 21;9(14):e015573. [Medline]
  2. Macfarlane PW. New ECG Criteria for Acute Myocardial Infarction in Patients With Left Bundle Branch Block. J Am Heart Assoc. 2020 Jul 21;9(14):e017119. [Medline]
  3. Sgarbossa EB, Pinski SL, Barbagelata A, Underwood DA, Gates KB, Topol EJ, Califf RM, Wagner GS. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators. N Engl J Med. 1996 Feb 22;334(8):481-7. [Medline]
  4. Borovac JA, Orsolic A, Miric D, Glavas D. The use of Smith-modified Sgarbossa criteria to diagnose an extensive anterior acute myocardial infarction in a patient presenting with a left bundle branch block. J Electrocardiol. 2021 Jan-Feb;64:80-84. [Medline]

Created: Apr 09, 2021.

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