Catheter Recording and Validation of Left Bundle-Branch Potentials in Intact Dogs

The left bundle-branch potential (LB), as well as His bundle (H) and atrioventricular nodal (N) potentials, were recorded in intact dogs by using a tripolar electrode catheter positioned in the left ventricle. Simultaneous recordings of H and right bundle-branch (RB) activity from the right endocardial surface were also made. The LB potential was less rapid than the RB potential, but both occurred almost simultaneously after the H potential. Atrial premature stimulation was used to induce aberrant ventricular conduction (right or left bundle-branch block) and to verify the recorded bundle-branch potentials. During LBBB the LB potential became absent, while during RBBB the RB potential became absent, indicating blockade or delay of conduction. Incomplete LBBB showed a delay in the LB potential. Initial spontaneous activity in the left bundle branch or its Purkinje system was manifested by a premature beat which resembled a RBBB pattern electrocardiographically. Spontaneous activity in the right bundle branch or its terminal Purkinje system manifested as a LBBB pattern. The recording of bundle-branch potentials by this technic may enable investigators to study further the cardiac electrical phenomena in intact animals or in man.