Measurement of correlation between heart rate and physiological parameters variations

The correlation of variations for different physiological parameters have been investigated to develop the best model of the heart rate based on other physiological parameters or their combinations for rate adaptive pacing. There were three different parameters under examination: QT interval, ventilation volume and physical activity. The problem of the present study is also to determine whether the dynamicity of QT interval, obtained from the standard ECG is comparable with the MAP duration changes. The simultaneous noninvasive measurements of ECG. transthoracic impedance and physical activity for six healthy person during different predetermined exercise tests and normal daily activities have been carried out. In 11 patients undergoing invasive cardiac electrophysiologic study of monophasic action potential from the right ventricular apex was recorded simultaneously with several ECG leads. A special multichannel recording instrument has been developed for signal registration. The calculated for the entire group correlation coefficient between surface QT interval and monophasic action potential duration is r= 0.774. The linear combination of QT and activity gives a relatively simple, but satisfactory model of the Mi for rate adaptive cardiac pacing. This model was tested with group of persons and the relative mean squared error between calculated and natural heart rate for the group turned to be 8.4%.