Difference between revisions of "MI Diagnosis in LBBB or paced rhythm"

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[[File:MI_LBBB.png|thumb|Changes in LBBB during ischemia]]
 
In case of a [[Intraventricular Conduction|left bundle branch block (LBBB)]], infarct diagnosis 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 pathological and can be a sign of myocardial infarction. The criteria (Sgarbossa <cite>LBTB</cite>) that can be used in case of a LBBB and suspicion of infarction are:  
 
In case of a [[Intraventricular Conduction|left bundle branch block (LBBB)]], infarct diagnosis 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 pathological and can be a sign of myocardial infarction. The criteria (Sgarbossa <cite>LBTB</cite>) 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 elevation > 1mm in leads with a positive QRS complex (concordance in ST deviation) (score 5)

Revision as of 23:34, 8 May 2009

Changes in LBBB during ischemia

In case of a left bundle branch block (LBBB), infarct diagnosis 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 pathological 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]