Visualization of a septal perforator branch vein and coronary sinus during left bundle pacing implant

Figure 2 Surface electrocardiogram and endocavitary signal sensed by electrode (lower record).First three complexes: left bundle pacing (rsr 0 morphology in V1).Last two complexes: sensed R-wave (from old right ventricular lead).Retrograde left bundle branch potential (red arrows).