Causes of Right Bundle Branch Block (RBBB)

Structural heart disease

Chronically high right ventricular pressure (i.e. cor pulmonale)
Acutely high right ventricular pressure with stretch (i.e. pulmonary embolism)
Myocardial ischemia
Myocardial infarction
Myocardial inflammation (i.e. myocarditis)
Hypertension
Cardiomyopathy
Congenital heart disease (i.e. atrial septal defect)
Lenegre’s disease or Lev’s disease (i.e. idiopathic progressive cardiac conduction disease)
Hyperkalemia, rarely

Iatrogenic

Right heart catheter insertion results in transient RBBB in 5% of cases
Nonsurgical septal reduction therapy with ethanol ablation, used in patients with hypertrophic cardiomyopathy and left ventricular outflow tract obstruction, results in RBBB in about 50% of cases
Functional RBBB, as a result of a long preceding R-R interval following by a short cycle
Idiopathic left ventricular tachycardia with right bundle branch block morphology and left axis deviation (Belhassen type) or in bundle branch reentrant ventricular tachycardia.

Pseudo right bundle branch block