[Assessment of sensing parameters in the rate responsive cardiac pacemaker].

Rate responsive cardiac pacemakers in which pacing rate is adjusted by hemodynamic and metabolic demands have been developed in recent years. Although different parameters such as body activity, QT interval, respiration rate, body temperature are used to presume metabolic demand, it is suspected that no single parameter can provide accurate estimate of metabolic demand, and hence rate responsive pacemaker by combined parameters is proposed. This study is aimed to investigate physiological parameters during exercise so as to obtain reliable pacing control algorithm. Twenty healthy volunteers were assessed by a traded treadmill exercise according to the Bruce protocol, and hart rate, QT interval, body temperatures (forehead deep body temperature, rectal, tympanic, oral and axillary temperatures) and respiration rate were monitored. The results showed that correlation coefficient between heart rate and QT interval was 0.979, and that between hart rate and respiration rate was 0.969. Hysteresis was observed when these parameters were plotted against hart rate through a whole exercise protocol.