Right bundle branch block

Right bundle branch block (RBBB) is characterised by an RSR’ pattern with the R’ being slurred, producing a QRS duration of 120 msec or more. This delayed right ventricular activation is reflected as a delayed and slurred S wave in leads oriented to the left ventricle, viz. lead I, aVl, V5 and V6. The same pattern if it occurs with a QRS duration of less than 120 msec, it is generally designated as incomplete RBBB. Mild ST segment depression and inverted T waves in anterior leads are associated with RBBB.

Unlike left bundle branch block which often co-exists with structural heart disease, RBBB can occur in the absence of structural heart disease. In a large study involving 67,375 asymptomatic individuals [1], the incidence of RBBB was found to be 0.15% in the age group of 20 to 30 years and 0.29% in those above 40 years .

RBBB may complicate acute myocardial infarction of the anterior wall, in which case it has prognostic significance, usually indicative more extensive myocardial infarction and possibility of left ventricular dysfunction. Incomplete RBBB pattern can occur in atrial septal defect, Ebstein’s anomaly of tricuspid valve and acute pulmonary embolism.

Reference

1. R L Johnson RL, K H Averill, L E Lamb. Electrocardiographic findings in 67,375 asymptomatic subjects. VI. Right bundle branch block. Am J Cardiol. 1960 Jul;6:143-52.