My dual-chamber pacemaker was implanted five years ago and is still
working fine.
Days ago I was walking on a stress test treadmill in a hospital while
connected to an ECG machine, and a cardiologist reviewed the ECG
tracing and checked blood pressure periodically.
While the level of exercise was progressively increasing and my heart
got beating faster and faster, from time to time I gave a look to the
monitor and specially to the first track to top.
Well, I noticed that that track apparently maintained its shape (i.e.
the typical pacemaker-driven heart shape) even when approaching the
maximum heart frequency. In other words, it seemed to me like the
pacemaker kept active thru all the test.
Is that normal? I mean, shouldn't pacemaker action switch off when the
heart beat exceeds the normal resting value?

Thanks in advance        
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Uplbet