Incomplete Right Bundle Branch Block: A Narrative Review of Clinical Relevance, Diagnostic Pitfalls, and Prognostic Implications

Abstract

Introduction: Incomplete right bundle branch block (iRBBB) is a frequent electrocardiographic (ECG) finding, often considered benign. However, recent evidence suggests it may be associated with underlying structural or electrical abnormalities, particularly in selected populations. Methods: We conducted a narrative review of population-based cohorts, mechanistic studies, and clinical trials focused on the prevalence, pathophysiological mechanisms, differential diagnosis, and prognostic implications of iRBBB. Results: iRBBB is common in athletes and individuals with pulmonary or structural heart diseases. Although frequently asymptomatic, it may reflect right ventricular strain, pulmonary hypertension, or a predisposition to arrhythmias such as atrial fibrillation. Specific ECG features, comorbidities, and clinical context help to differentiate benign from pathologic iRBBB. Conclusions: iRBBB should not be routinely regarded as a harmless variant. In high-risk individuals, it may carry clinical and prognostic significance, warranting further evaluation. Standardized criteria and additional prospective studies are needed to better understand its implications. Infographic available for this article.