Bundle branch block is a condition that affects the electrical conduction system of the heart. It occurs when there is a delay or blockage in one of the two bundle branches, which are pathways that carry electrical signals to the heart's ventricles. This can lead to an abnormal heart rhythm and may affect how efficiently the heart pumps blood. There are two main types of bundle branch block: right bundle branch block (RBBB) and left bundle branch block (LBBB). Symptoms can vary, and some individuals may not experience any noticeable issues. Diagnosis is typically made through an electrocardiogram (ECG), which records the heart's electrical activity.