Rate-responsive pacemakers and anaesthesia. A consideration of possible implications.

A new generation of pacemakers has been developed in recent years which adjust the pacing rate according to changes in physiological variables. The selected parameters are affected during physical activity that involves an increased heart rate in healthy humans. The variables include body movements, QT interval, breathing, temperature, myocardial contractility, oxygen saturation and changes in blood pH which may be influenced during general anaesthesia, and can lead to unphysiological, high, pacing rates. It is important to be familiar with the pacemaker and its functions before administration of anaesthesia in order to prevent complications. Rate-responsive pacemakers in such situations should be programmed to exclude the rate-responsive function.