going out of rhythm and running fast are two different things. When surgery is finished, there is a wire protruding from the chest, attached to the heart, so a temporary pacemaker can be fitted if necessary. This is normally removed 2 to 3 days later.
I do remember after my bypass, my heart rate was 85-90 for a few days. Before surgery it was 50-60. After a few weeks it did settle down again and was 60-70. Since my stenting my resting rate has been 70-80. I did look around the ward after my bypass at everyone elses monitors, there's not much else to do. Some seemed to be quite low, 50-55 while others where like mine. So I assume it is an individual thing, some rates increase, some slow down, some stay the same. There is some swelling for a couple of weeks around the grafting vessels and so I assume the changes occur when this recovers. During exercise after my bypass my heart rate jumped to 186 which I have to say felt great. Cardiac rehab staff were very worried but the surgeon said it was nothing to worry about.