MI Diagnosis in LBBB or paced rhythm: Difference between revisions
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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. | ||
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.<cite>3</cite><cite>4</cite> | |||
{{clr}} | {{clr}} | ||
==Examples== | ==Examples== | ||
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#LBTB pmid=8559200 | #LBTB pmid=8559200 | ||
#Wong pmid=15992631 | #Wong pmid=15992631 | ||
#3 pmid=18651461 | |||
#4 pmid=15127382 | |||
</biblio> | </biblio> | ||
Revision as of 14:18, 28 February 2011
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 LBTB) 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). 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.Wong
At a score-sum of 3, these criteria have a specificity of 90% for detecting a 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.34
Examples
-
Case 1: Acute myocardial infarction in in a patient with a pacemaker and LBBB. Concordant ST elevation in V5-V6 are clearly visible. There is discordant ST segment elevation > 5 mm in lead V3. -
Case 1: The same patient as in the first example 2 months before the myocardial infarction. Normal LBBB pattern. -
Case 2: Acute MI in a patient with LBBB -
Case 3: Acute MI in a patient with LBBB -
Case 3: Non-ischemic ECG in this patient -
Myocardial infarction in a pacemaker patient. The ECG shows LBBB as expected during pacing, however overt repolarization abnormalities are present. -
Myocardial infarction post primary PCI in a pacemaker patient
References
<biblio>
- LBTB pmid=8559200
- Wong pmid=15992631
- 3 pmid=18651461
- 4 pmid=15127382
</biblio>