MI Diagnosis in LBBB or paced rhythm

From ECGpedia
Revision as of 14:11, 14 December 2007 by Drj (talk | contribs) (→‎Examples)
Jump to navigation Jump to search

In case of a left bundelbranch block (LBBB), infarct diagnostics based on the ECG is difficult. The baseline ST segments and T waves tend to be shifted in a discordant direction with LBBB, which can mask or mimic acute myocardial infarction. However, serial ECGs may show a moving ST segment during ischemia secondary to dynamic supply versus demand characteristics. 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 (concordance in ST deviation) (score 3)
  • ST elevation > 5 mm in leads with a negative QRS complex (inappropriate 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]