MI Diagnosis in LBBB or paced rhythm

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In case of a left bundelbranch block (LBBB), infarct diagnostics based on the ECG is difficult. The ST segments are always abnormal in a LBBB, so new ischemia can not be detected. A new LBBB is always pathologocal and can be a sign of myocardial infarction. The criteria (Sgarbossa [1]) that can be used in case of a LBBB and suspicion of infarction are:

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

At a score-sum of 3, these criteria have a specificity of 90% for detecting a myocardial infarction.

Examples

References

  1. Sgarbossa EB. Value of the ECG in suspected acute myocardial infarction with left bundle branch block. J Electrocardiol. 2000;33 Suppl:87-92. DOI:10.1054/jelc.2000.20324 | PubMed ID:11265742 | HubMed [LBTB]