MI Diagnosis in LBBB or paced rhythm: Difference between revisions
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In case of a [[Intraventricular Conduction|left bundelbranch block (LBBB)]], infarct diagnostics based on the ECG is difficult. The ST segments | In case of a [[Intraventricular Conduction|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 <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) | ||
*ST depression > 1 mm in V1-V3 ( | *ST depression > 1 mm in V1-V3 (concordance in ST deviation) (score 3) | ||
*ST elevation > 5 mm in leads with a negative QRS complex (discordance in ST deviation) (score 2) | *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. | At a score-sum of 3, these criteria have a specificity of 90% for detecting a myocardial infarction. | ||
Revision as of 21:33, 24 August 2007
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
Acute myocardial infarction in in a patient with a pacemaker and LBBB. Concordant ST elevation in V5-V6 are clearly visible.
The same patient as in the first example 2 months before the myocardial infarction. Normal LBBB pattern.
