Historically, the right atrial appendage (RAA) has been the conventional site for atrial lead placement. This was due to the earliest transvenous leads being tined, passive fixation leads making the RAA an ideal location for atrial lead implantation [1], which has persisted despite the availability of contemporary active fixation leads and lack of physiologic atrial activation. RAA pacing is associated with a P wave which is low amplitude and prolonged compared to sinus rhythm [2]. A prominent negative terminal force in V1 is observed during RAA pacing which, in sinus rhythm, has been linked to an increased incidence of atrial fibrillation (AF) [3]. Furthermore, RAA pacing prolongs interatrial activation time resulting in atrial electromechanical delay [[4], [5], [6]] which may be associated with negative hemodynamic consequences [7]. These problems opened the doors for exploration of alternate atrial pacing sites which included the interatrial septum, coronary sinus, and coronary sinus ostium [1]. Among these, Bachmann's bundle (BB), a specialized band of myocardium connecting the right and left atria in the anterior aspect, allows for rapid interatrial conduction and has favorable effects on the P wave when paced. Compared to RAA pacing, P wave duration in BB pacing is significantly reduced and a larger P wave amplitude is observed. Several studies, including a multi-center randomized trial, have demonstrated that BB pacing reduces atrial fibrillation compared to RAA pacing which may be related to improved interatrial conduction among other factors [8,9]. Although BB pacing has been shown to shorten P wave duration and increase P wave amplitude, a detailed comparison of differences in P wave parameters during sinus rhythm, RAA pacing and BB pacing has not yet been reported. In the present study, we describe within-patient changes in seven P wave parameters (P wave duration, P wave voltage, P wave area, PTFV1, and P wave axis), as well as PR interval and PR segment, during sinus rhythm, RAA pacing, and BB pacing at time of Bachmann's bundle atrial lead implantation.