Written by Catherine Burger
Patients presenting with anginal symptoms and a new right bundle branch block (RBBB) on ECG or RBBB-specific high-risk features should prompt emergent evaluation for reperfusion therapy.
Signs of a deadly RBBB
This narrative review focuses primarily on the cautious evaluation and treatment of patients with RBBB on ECG. Concerningly, new RBBB with anginal symptoms is associated with proximal LAD involvement, larger infarct size, higher rates of cardiogenic shock, and increased mortality. Furthermore, patients presenting with anginal symptoms with either confirmed or suspected new RBBB should be strongly considered for emergent reperfusion therapy (supported by AHA 2021 ACS guidelines and ESC 2017 STEMI guidelines).
Although RBBB can be a benign finding, authors note that the key additional ECG features concerning for acute ischemia include:
- concordant ST elevation in the precordial leads (V1-V2)
- excessive discordant ST depression (>25% of the QRS amplitude) in the precordial leads
- reciprocal changes
- presence of bifascicular block (left axis deviation in the setting of RBBB)
Non-ischemic RBBB can be considered in asymptomatic patients with low-risk ECG findings including rsR’ in the precordial leads (V1-V2), slurred S wave in the lateral leads (I, aVL, V5-V6), as well as expected discordant ST depression (less than 25% of the QRS) and T wave inversion in the precordial leads. Some notable additional causes of RBBB include right-sided volume overload (pulmonary embolism), congenital heart disease, cardiomyopathy, myocarditis, hyperkalemia, and age-related calcification of the conducting system.
How will this change my practice?
Since the ECG findings of RBBB-related ischemia can be subtle and the risk to patients is so high, I will carefully dissect RBBB ECGs for high-risk features and emergently engage interventional cardiology for any concerning findings.
Source
Right bundle-branch block (RBBB) and acute coronary syndrome (ACS) a narrative review. Am J Emerg Med. 2026 Jan;99:325-334. doi: 10.1016/j.ajem.2025.10.037. Epub 2025 Oct 17. PMID: 41429745.
