Sorry, but I think your question is too general and technical (absent the data) to get much help here. What did the doctor or technician say?
An ECG that lasts 1 hour is unusual in my experience, doctors always run about a 10 second "strip" or recording when the procedure is done on me.
Perhaps it is normal to see variations when an ECG is run for such a long period of time.
It is.
Heart rhythm will vary, the "spikes" will vary with adrenaline, axis will vary with breathing and positioning, and everyone get an occational PAC or PVC.
The ECG was not run for One Hour..
It was run for about a minute. As some variations were noticed, the technician suggested (after a discussion with a physician ) after a gap of an hour he will do another ECG.
As per the instruction, the technician took my husbands ECG after the Gap and the variation was again noticed.