The Holter system has added markers where it detected pacemaker spikes. The yellow arrow indicates the detection of a ventricular spike and the blue arrow an atrial spike. The recording shows pectoral muscle inhabition of the pacemaker (turquoise arrow). It is characteristic to see muscle artifact on the recording as seen here ( mostly between the two red arrows) Note there is no detection of a ventricular pacing spike, and also there is no native QRS to be sensed! This is a form of inappropriate sensing.