Sgarbossa Criteria

Background

  • In patients with left bundle branch block (LBBB) or ventricular paced rhythm, infarct diagnosis based on the ECG is difficult.
  • The baseline ST segments and T waves tend to be shifted in a discordant direction (“appropriate discordance”), which can mask or mimic acute myocardial infarction.
  • However, serial ECGs may show dynamic ST segment changes during ischemia.
  • A new LBBB is always pathological and can be a sign of myocardial infarction.

Electrocardiographic Criteria

The three criteria used to diagnose infarction in patients with LBBB are:

  • 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). This criterium is sensitive, but not specific for ischemia in LBBB. It is however associated with a worse prognosis, when present in LBBB during ischemia.

A total score of  ≥ 3 has a specificity of 90% for diagnosing myocardial infarction.

During right ventricular pacing the ECG also shows left bundle brach block and the above rules also apply for the diagnosis of myocardial infarction during pacing, however they are less specific.

In the GUSTO-1 trial the ECG criterion with a high specificity and statistical significance for the diagnosis of an acute MI was:

  • Excessively discordant ST segment elevation ≥5 mm (in leads with a negative QRS complex).

Two other criteria with acceptable specificity were:

  • Concordant ST elevation ≥1 mm in leads with positive QRS
  • Concordant ST depression ≥1 mm in leads V1, V2, or, V3

ECG  Example

Positive Sgarbossa criteria in a patient with LBBB and troponin-positive myocardial infarction:

  • This patient presented with chest pain and had elevated cardiac enzymes.
  • Baseline ECG showed typical LBBB.
  • There is 1mm concordant ST elevation in aVL (= 5 points).
  • Other features on this ECG that are abnormal in the context of LBBB (but not considered “positive” Sgarbossa criteria) are the pathological Q wave in lead I and the concordant ST depression in the inferior leads III and aVF.
  • This constellation of abnormalities suggests to me that the patient was having a high lateral infarction.

 Video

Amal Mattu presents a case of acute myocardial infarction in the presence of left bundle branch block.

Related Topics

Further Reading

Author Credits

References

  • Sgarbossa EB, Pinski SL, Barbagelata A, Underwood DA, Gates KB, Topol EJ, Califf RM, and 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. doi:10.1056/NEJM199602223340801 pmid:8559200. PubMed HubMed [LBTB]
  • Wong CK, French JK, Aylward PE, Stewart RA, Gao W, Armstrong PW, Van De Werf FJ, Simes RJ, Raffel OC, Granger CB, Califf RM, and White HD. Patients with prolonged ischemic chest pain and presumed-new left bundle branch block have heterogeneous outcomes depending on the presence of ST-segment changes. J Am Coll Cardiol 2005 Jul 5; 46(1) 29-38. doi:10.1016/j.jacc.2005.02.084 pmid:15992631. PubMed HubMed [Wong]
  • Klimczak A, Wranicz JK, Cygankiewicz I, Chudzik M, Goch JH, and Baranowski R. Electrocardiographic diagnosis of acute coronary syndromes in patients with left bundle branch block or paced rhythm. Cardiol J 2007; 14(2) 207-13. pmid:18651461. PubMed HubMed [3]
  • Madias JE. The nonspecificity of ST-segment elevation > or =5.0 mm in V1-V3 in the diagnosis of acute myocardial infarction in the presence of ventricular paced rhythm. J Electrocardiol 2004 Apr; 37(2) 135-9. pmid:15127382. PubMed HubMed [4]
  • Sgarbossa EB, Pinski SL, Gates KB, and Wagner GS. Early electrocardiographic diagnosis of acute myocardial infarction in the presence of ventricular paced rhythm. GUSTO-I investigators. Am J Cardiol 1996 Feb 15; 77(5) 423-4. pmid:8602576. PubMed HubMed [Gusto]
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Comments

  1. austin payor says

    Great summation of Sgarbossa’s criteria. I believe there is an error. You stated “This criterium is sensitive, but not specific for ischemia in LBBB”
    From what I have read it is the opposite, IS specific -- NOT sensitive.
    Thank you.

  2. says

    Austin is correct by my reading of the literature as well.
    Sgarbossa Criteria A = Concordant ST-seg elevation of >/= 1mm — Most specific but least sensitive
    Sgarbossa Criteria B = Concordant ST-seg depression of >/= 1mm in lead V1,2 or 3
    Sgarbossa Criteria C = Disconcordant ST-seg elevation of >/= 5mm — Least specific but most sensitive

    According to data from Tabas et.al. “ECG Criteria for detecting AMI in patients with LBBB: A meta-analysis” in Ann Emerg Med 2008; 52:329-361
    Criteria A and B -- Sensitivity = 20%; Specificity = 98%; +ve Likelyhood Ratio = 7.9; -ve Likelyhood Ratio = 0.81
    Criteria C -- Sensitivity = 40%; Specificity = 85%; +ve Likelyhood Ratio = 2.0; -ve Likelyhood Ratio = 0.81

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