Clinical study of a new activity sensor for rate adaptive pacing controlled by electrical signals generated by the kinetic energy of a moving magnetic ball

Rate Adaptive Pacing: Memories From a Bygone Era

With the recognised physiologic value of dual chamber pacing, there was, at the commencement of the 1980s, an intense search for sensors to enable ventricular pacemakers to alter the pulse repetition rate in response to physiologic demand. Manufacturers fell into two main groups; those who chose highly physiologic sensors often requiring special pacing leads and those whose sensors allowed a standard pacing lead. Thirteen (13) sensors for rate adaptive pacing progressed at least to human investigational studies. Eventually the activity sensor, which responded quickly to exercise, but not to emotional stimuli or pyrexia and used a standard lead would predominate, with all manufacturers eventually accepting what was the least physiologic sensor investigated. The activity-based rate response was not dependent on cardiac or pulmonary disease, which could nullify the response with many of the other sensors. Three (3) other sensors survived that period and are still available today; minute ventilation, closed loop stimulation and central venous temperature, with the first two incorporated with activity as dual sensor systems. This review will outline the development of all the sensors used for rate adaptive pacing.

Vibration, acceleration, gravitation, and movement: activity controlled rate adaptive pacing during treadmill exercise testing and daily life activities

Activity-based sensors for rate adaptive pacing have been available for several years and now include several different types: vibration; acceleration; gravitation; and movement. However, a systematic comparison evaluating the relative advantages and disadvantages of these various sensors has received little study. The purpose of the present study was to compare these sensor subtypes using treadmill testing and an outdoor test circuit, which simulated daily life activities and included both uphill and downhill walking. Pacemakers were strapped on the chest of healthy volunteers and connected to one channel of an ambulatory recording device, which also recorded the subject's intrinsic heart rate. The pacemakers were programmed using an initial treadmill test to standardize the rate responsive parameters for each device. Nine different pacemaker models were studied including 3 vibration-based (Elite, Synchrony, Metros), 4 acceleration-based (Relay, Excel, Ergos, Trilogy), 1 gravitational-based (Swing), and 1 movement-based (Sensorithm) device. All devices demonstrated a prompt rate response with casual walking on flat ground. The vibration-, gravitational-, and movement-based pacemakers showed a pronounced rate decline during more strenuous work, e.g., walking uphill. This phenomenon was absent in the accelerometer-based units. In particular, the vibration- and movement-based units showed a higher rate with walking downhill compared to uphill. An optimally tuned rate behavior on the treadmill usually did not provide an optimal rate behavior during daily activities and there was a tendency to overstimulation during low workload. The development of the two newest sensors (gravitational and movement) did not result in an improved performance of rate response behavior. Overall, the accelerometer-based pacemakers simulated or paralleled sinus rate behavior the most closely.