This is a rhythm strip recorded from a man attending the pacemaker follow-up clinic.

The Patient had been implanted with a ventricular pacemaker one week before.

In about the middle of the tracing a magnet was placed over the pacemaker.

• Why are there so many spikes on the first half of the tracing?
• Can you identify the manufacturer of and the type of the pacemaker ?
• Do you think the pacer is working?