Unexpected loss of atrial tracking caused by interaction between temporary and permanent right ventricular leads during implantation of a biventricular pacemaker

This report describes a patient who underwent implantation of an atriobiventricular pacemaker following AV junction ablation and insertion of a temporary right ventricular (RV) pacemaker. During implantation, intermittent loss of sinus P wave tracking occurred when the three permanent leads were connected to the generator. Analysis of marker annotation disclosed intermittent abnormal ventricular sensing that reinitiated postventricular atrial blanking and caused failure of P wave tracking. This phenomenon disappeared after removing the temporary RV lead, but not by turning off the temporary pacemaker. We assume that mechanical contact between the temporary and the permanent RV leads is the underlying mechanism.