Right Bundle Branch Block Without Anterior ST-Segment Depression - Should it be Automatically Flagged as Anterior STEMI Equivalent?

Background 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 ECG showing RBBB and isoelectric or mildly elevated (<2 mm) ST-segment in leads V1-V3. A retrospective chart review was then performed to evaluate for diagnosis of acute myocardial infarction (AMI), as well as need for revascularization via percutaneous coronary intervention (PCI) or bypass surgery (CABG). Additional data were collected, including symptoms at the time of ECG, past medical history, and additional cardiac work up including stress test and catheterization. Results In total, 9 of 99 patients (9.1%) 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 one 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. Lack of ST depression in the anterior leads in RBBB should not be added to the computerized interpretation as an indication of anterior AMI. ECG should be interpreted in clinical context when deciding whether or not to activate primary PCI protocol.