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. INFOGRAPHIC.

Department of Internal Medicine and Cardiology University Hospital Ostrava 17 listopadu 1790 5 70800 Ostrava Czech Republic

Research Center for Internal and Cardiovascular Diseases Faculty of Medicine University of Ostrava 70300 Ostrava Czech Republic

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