Right bundle branch block in suspected acute coronary syndromes: Diagnostic challenges, treatment and prognosis.

Background: There is still conflicting evidence regarding the prognostic implications of right bundle branch block (RBBB) in the general population but also in patients with heart diseases like acute coronary syndromes (ACS). In accordance with current guidelines, RBBB in ACS patients is considered as STEMI equivalent. However, recent studies indicate that further differentiation is necessary in this group, as we will outline below.

Methods And Results: A literature search was conducted in PubMed and Google Scholar. In previous studies, RBBB in the general population were mostly considered benign changes of the electrical conduction system. However, recent studies indicate that both complete and incomplete RBBB are associated with increased cardiovascular morbidity and mortality. In addition, among unselected patients with suspected ACS presenting to the emergency department, the prevalence of RBBB was 3 % and it was associated with elevated mortality. The subsequent angiographic identification of a culprit coronary artery stenosis leading to stent implantation was similar at approximately 2 % regardless of the initial ECG presentation with narrow QRS complexes, left bundle branch block (LBBB), or RBBB. Finally, in a group of high-risk patients for ST-elevation myocardial infarction (STEMI), the prevalence of RBBB was 12 %. While RBBB was associated with poor outcome compared to non-BBB and LBBB patients, diagnostic accuracy of STEMI criteria was not affected by the presence of RBBB. However, RBBB patients without distinct STEMI signs in ECG often showed acute STEMI on angiography indicating a potential benefit from immediate transfer to the cardiac catheterization laboratory.

Conclusion: In the general population, patients with RBBB and risk factors may need further evaluation. Regarding ACS patients, recent studies support current guidelines that recommend acute invasive evaluation for high-risk ACS patients with RBBB, regardless of ST-T deviations. However, in an unselected group of ACS patients, differential diagnoses should also be investigated through additional diagnostic procedures.