Experimental bilateral bundle branch block^*

Surgical production of bilateral bundle branch block resulted in complete heart block in fourteen dogs. In eight dogs, left bundle branch block resulted from the initial bundle branch section. In six animals, right bundle branch block was produced at first. In either circumstance, section of the opposite bundle branch resulted in complete heart block. Limited correlation between the electrical and mechanical events of the cardiac cycle under these circumstances was demonstrated. The data indicate that complete right and complete left bundle branch block were produced by surgical section of the respective bundle branches.