Some atrial under sensing is observed (circled in red). The P waves that are not being sensed are followed by a native R wave that is therefore being counted as a PVC. The P wave measurement was < 0.2mV, and the atrial impedance was within range and stable.

The threshold testing was causing visible stim, and the patient was uncomfortable. It was determined that the atrial lead was dislodged, and the patient was sent for a revision. Notice the surface electrogram compared to the atrial bipolar channel. The intracardiac signals are great, but surface never lies!