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

The clinical significance of right bundle branch block (RBBB) or bifascicular block (BFB) in the setting of acute myocardial infarction (AMI) is uncertain. RBBB was found in 211 of 7,626 patients (2.8%), presenting to the ED (emergency department) with chest pain, of which 18 (8.5%) also had acute coronary syndrome (ACS). Incidences of ACS were not significantly different between new or presumed new RBBB and prior known RBBB or new or presumed new BFB and prior known BFB. In 2 patients, baseline ST-segment depression in leads V1-3 masked anterior ST-elevation detected on electrocardiogram (ECG). In opposition to the guidelines, the presence of RBBB or BFB does not appear to offer any clinical utility when evaluating patients with suspected AMI. Patients with suspected AMI who present with RBBB and any ST-elevation in leads V1-3 should be considered for emergent coronary angiography rather than RBBB alone.