Central venous blood temperature for rate control of physiological pacemakers

In 17 pacemaker patients and 14 volunteers we studied the behaviour of central venous blood temperature and heart rate under different kinds of exercise. Data were recorded by means of 5F catheter placed at the right ventricle. Temperature was measured with a thermistor incorporated in the lead. We found the increase in central venous blood temperature to be dependent on the individual exercise capacity and work load performed. The maximum temperature increase seen was 1.7 degrees Celsius. Subjects with lower physical fitness showed a more pronounced increase in temperature and heart rate compared to more physically fit subjects at the same work load. Due to its close relationship to metabolic and circulatory parameters, central venous blood temperature represents an appropriate signal to control the rate of physiological pacemaker systems. A special algorithm also using the initial dip for rate control has been incorporated into a pacemaker system, that is currently under clinical investigation (Intermedics NOVA MR).