New Onset Right Bundle Branch Block In Acute Coronary Syndrome and High-Grade Stenosis: A Case Series.

Despite advances in diagnostic and therapeutic interventions, coronary heart disease remains as one of the leading causes of death in developed countries. ST-segment elevation myocardial infarction is associated with the highest mortality and is an indication for emergent reperfusion therapy. Current guidelines for emergent reperfusion not only include ST segment elevations but also consider evidence of a new onset Left Bundle Branch Block (LBBB). However, accumulating evidence indicates that RBBB is also associated with poor outcome in coronary artery disease. To-date, guidelines do not comment on the urgency of reperfusion therapy with sole evidence of a new onset Right Bundle Branch Block (RBBB). Particularly we question whether clinicians should focus on new-onset RBBB as a ST-segment elevation equivalent. If so, appropriate management of patients with the new onset RBBB during cardiac ischemia can have a significant impact on cardiac function and outcomes. In this series, we present four cases of new-onset acute RBBB associated with chest pain in the setting of acute myocardial infarction with critical lesions of the left anterior descending artery. We also highlight the need to consider new RBBB as an additional indication for acute reperfusion therapy in acute myocardial infarction. This will call for revision in the current guidelines by American Heart Association following the initiative recently implemented by the European Society of Cardiology 2018.