What are causes of right bundle branch block?

Variety of things: Right bundle branch block is due to a conduction problem within the electrical system of the heart. This can be an isolated electrical problem or a reflection of structural heart disease.

Many: It can be congenital. It is often present with right ventricular or right atrial pressure or volume overload such as occurs with atrial or ventricular septal defect. Hypertension causes many cases. Pulmonary artery hypertension, as occurs in advanced lung disease or pulmonary embolism, can cause it. Finally, it's present in many healthy people for no reason at all.