Right Bundle Branch Block without Anterior ST-Segment Depression: Should It Be Automatically Flagged as Anterior STEMI Equivalent?

Abstract

Introduction: In patients with right bundle branch block (RBBB), the utility of ST-segment abnormalities in assessing for acute myocardial infarction remains a topic of ongoing discussion. We studied whether lack of ST depression in V1-V3 should be added to the computerized algorithms of interpretation as an equivalent of ST elevation in patients with acute myocardial infarction due to LAD occlusion.

Methods: A total of 99 patients were selected from a single center based on evaluation of routine electrocardiography (ECG) showing RBBB and an ST-segment which was at or above the isoelectric line in leads V1-V3. A retrospective chart review was then performed to evaluate for diagnosis of acute myocardial infarction (MI), as well as need for revascularization via PCI or CABG. Additional data were collected for this population, including symptomatology at the time of ECG, past medical history, and frequency of additional cardiac workup including stress test and catheterization.

Results: In total, 9 of 99 (9.1%) patients were found to have a diagnosis of acute MI based on cardiac catheterization findings and/or troponin elevation from baseline. Of the 9 patients with acute MI, two were referred for possible CABG with revascularization performed on one. No patients with acute MI underwent emergent PCI. PCI and CABG were subsequently performed for 3 (3%) and 5 (5.1%) of all patients, respectively. Only 1 of these revascularized patients received a diagnosis of acute MI.

Conclusion: In patients with RBBB lacking ST depression in the anterior leads, the frequency of emergent revascularization was low. These findings demonstrate that while acute occlusion is a possible etiology for ST-segment at or above the isoelectric line in patients with RBBB, these changes are a poor indicator of occlusion in isolation. ECG should be considered in clinical context when deciding whether or not to activate primary percutaneous coronary intervention protocol.