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| Diagnosis of acute myocardial infarction in the presence of left bundle branch block |
| SHI Xiangmin |
| (Department of Cardiovascular Medicine, the Sixth Medical Center of PLA General Hospital, Beijing 100142, China) |
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Abstract Left bundle branch block (LBBB) results in left ventricular depolarization appearing in the latter half of QRS complex due to altered ventricular activation sequence. Therefore, it could be challenging to make electrocardiographic diagnosis of acute myocardial infarction (AMI) in the presence of LBBB. This paper introduces Sgarbossa’s rule, Smith’s criteria and Barcelona diagnostic criteria, and compares their diagnostic sensitivity and specificity. According to the Sgarbossa’s rule proposed in 1996, LBBB complicating AMI can be diagnosed based on concordant ST alteration, excessive reverse elevation of ST segment and other indexes with high specificity and low sensitivity. Smith’s criteria replaced “excessive discordant ST elevation≥0.5 mV” in Sgarbossa’s rule with ST/S or ST/R ratio, which improves diagnostic sensitivity. The Barcelona criteria propose that in the presence of LBBB, AMI can be diagnosed based on the ECG features, including concordant ST deviation≥0.1 mV in any lead or discordant ST deviation ≥0.1 mV in low-voltage lead. The criteria significantly elevate the diagnostic sensitivity and specificity. Cabrera’s sign and Chapman’s sign also play auxiliary roles in diagnosing concomitant AMI and LBBB.
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