On the nonpathological nature of ST-segment elevation in lateral leads in patients with CRBBB

Stable ST-segment elevation (STSE) in the lateral electrocardiogram (ECG) leads (i.e., I, II, aVL, V5, and V6) are frequently encountered in association with stable and transient complete right bundle branch block (CRBBB). These STSE in the lateral ECG leads in patients with CRBBB, represent parallel changes to the ST-segment depression seen in the V1-V3 leads, and both represent secondary ECG changes expected in patients with intraventricular conduction delays, and they are opposite in polarity to the latter part of the QRS complexes. Proprietary automated ECG interpretation algorithms provided by the different electrocardiographs associate such ECG changes in the lateral leads in the presence of CBBB to “lateral myocardial infarction, ischemia, or injury,” “pericarditis,” or “early repolarization,” which results in inappropriate concern among clinicians, and leads to costly unnecessary diagnostic testing. This piece strives to reassure clinicians about the nonpathological nature of lateral STSE in ECGs with CRBBB.