Sgarbossa criteria for AMI with LBBB (Left Bundle Branch Block)

Shadiya Sulthana. S1, S. Aravindakumar2

1PG –Resident, Internal Medicine, Kauvery Hospitals, Trichy

2Senior Interventional Cardiologist, Kauvery Hospital, Heart City, Trichy

Introduction

Accurately diagnosing occlusion myocardial infarction in patients with LBBB or ventricular paced rhythms remains a complex challenge in cardiology. The Sgarbossa criteria, introduced in 1996 by Dr. Elena Sgarbossa, marked a major advancement in addressing diagnostic dilemma. Subsequent modifications by Dr. Stephen Smith have further enhanced their sensitivity and specificity, significantly improving the detection of myocardial infarction in these cases.

Case Presentation

A 78 years’ gentleman known to have hypertension, diabetes mellitus, coronary artery disease presented with sudden onset of severe breathlessness classified as NYHA grade 4 dyspnea. On examination he was tachypnic, dyspneic and noted to have bilateral basal crepitation’s.

ECG done showed excessively discordant ST elevation in lead V3 and concordant ST depression in V5. Modified Sgarbossa criteria applied and he was suspected to have acute myocardial infarction with LBBB. Coronary angiogram done showed 100% occlusion of ostial LAD.

ECG on presentation

Discussion

Patients having LBBB or ventricular paced rhythm, diagnosis of AMI can be difficult.

Appropriate discordance

  • In left bundle branch block (LBBB), delayed activation of the left ventricle causes abnormal depolarization and secondary repolarization changes.
  • This results in discordant ST segments and T waves relative to the QRS complex.
  • In leads with a positive QRS (e.g., I, aVl, V5-V6), the ST segment is typically depressed and the T wave inverted. In leads with a negative QRS (e.g., V1-V3), ST elevation and upright T waves are common.

Sgarbossa criteria

Originally described by Dr. Elena Sgarbossa in 1996, to help clinicians diagnose acute myocardial infarction in patients with LBBB.

The original criteria

  • Concordant ST elevation > 1mm in leads with a positive QRS complex (score 5)
  • Concordant ST depression > 1 mm in V1-V3 (score 3)
  • Excessively discordant ST elevation > 5 mm in leads with a negative QRS complex (score 2)

These criteria are specific, but not sensitive (36%) for myocardial infarction. A total score of ≥ 3 is reported to have a specificity of 90% for diagnosing myocardial infarction.

Modified Sgarbossa criteria

  • The Smith-modified Sgarbossa criteria were developed to improve the accuracy of diagnosing Occlusion Myocardial Infarction (OMI) in the setting of LBBB.
  • This revised the criterion for excessive discordance. The original 5 mm cut off was arbitrary and lacked specificity, as patients with LBBB and high QRS voltage often exhibit ST deviations greater than 5 mm without ischemia.
  • The modified criterion considers discordant ST elevation to be significant if it exceeds 25% of the depth of the preceding S-wave.

Criteria

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

This patient was suspected to have Acute MI by the modified Sgarbossa criteria.

Conclusion

ECG findings should be interpreted with great attention, as even subtle changes can be crucial and potentially life-saving. In complex scenarios such as left bundle branch block, precise interpretation becomes even more critical. A carefully analysed ECG can guide timely and appropriate intervention, highlighting its indispensable role in clinical decision-making.

Kauverian Bookshelf

Applied Medical Statistics

Journals

Kauvery Hospital
Find Doctor
Book Appointment