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 bundlebranch (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 bundlebranch 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.