Abstract 12220: Right Bundle Branch and Bifascicular Blocks: Insensitive Prognostic Indicators for Acute Myocardial Infarction

Abstract

Introduction: The clinical significance of right bundle branch block (RBBB) or bifascicular block (BFB) in the setting of ST-elevation myocardial infarction (STEMI) is uncertain. Informed by studies demonstrating higher rates of complete occlusion of the infarct-related artery in patients presenting with RBBB, the latest guidelines on STEMI management suggest patients with persistent ischemic symptoms and RBBB be considered for emergent coronary angiography. However, there has been little study of the prognostic implication of either RBBB or BFB in the setting of undifferentiated acute chest pain, and even less of the degree of ST-elevation in concomitant RBBB. Methods and Results: A total of 7626 patient encounters presenting to the Baylor St. Luke’s Medical Center between July 2018 and July 2020 with a chief complaint of “chest pain” were identified via electronic health record query. Of these encounters, 211 (2.8%) patients were found to have RBBB. Of that cohort, 18 (8.5%) presented with acute coronary syndrome, with STEMI accounting for 6 (2.8%), non-STEMI 9 (4.3%), and unstable angina 3 (1.4%). New or presumed new RBBBs were found in 59 (28%) of total RBBB patients, of which only 5 (8.5%) were found to have acute coronary syndrome and only 2 (3.4%) STEMI specifically. Similarly, 90 (42.7%) patients with chest pain and RBBB were found to have a BFB. New or presumed new BFBs were found in 40 (19%) patients, of which only 4 (10%) were also found to have acute coronary syndrome. No patients with new-onset BFB had STEMI. Furthermore, real-time diagnosis of anterior STEMI was complicated in two patients presenting with acute coronary syndrome by the masking of ST elevation in leads V1-3 by concomitant RBBB. Conclusions: In a large cohort of undifferentiated patients who presented with chest pain and RBBB or BFB (regardless if new or presumed new), only a small fraction had acute coronary syndrome, and even fewer STEMI. These data suggest patients with undifferentiated chest pain and RBBB on ECG with clinical suspicion for acute myocardial infarction and any degree of ST-elevation in leads V1-3 be considered for emergent coronary angiography rather than RBBB or BFB without ST-segment elevation.