This is a cardiogram from a middle aged man with palpitations. The patient had a dual chamber pacemaker (Vista) set at a lower rate of 60/min, and upper rate of 100/min. The patient had developed atrial flutter, and the pacemaker was following this with a 3:1 block. The flutter is seen in the second panel where the pacemaker was set to a VVI mode and a rate of 30/min. Note that in the first tracing the pacer spikes are not well seen as the pacemaker is pacing in a bipolar mode.