When we sleep, our bodies - including our hearts - rest. But the hearts of people with pacemakers may not get the rest they need, an important point since the hearts of those with heart disease may particularly benefit from periods of natural slowing of the heartbeat.
While science is still experimenting with variable-rate pacemakers, the weight of the evidence suggests that, even if these devices can be made to beat at one rate during the day and one rate at night, it may be more difficult than anticipated to programme them for all eventualities. This was recently well illustrated by the case study of a man living in the US with a variable rate pacemaker programmed to work on Eastern Standard time. When the man travelled to the UK, he found that his pacemaker was slowing down during the day and causing him to have mild feelings of light-headedness and dizziness (J Invas Cardiol, 1998; 10: 409).
People with pacemakers using a circadian rhythm feature should make sure they are reprogrammed before going abroad.