How Reliable and Effective Are Hemodynamic Sensors in Correcting Chronotropic Incompetence

Conventional dual chamber rate-responsive pacing is the treatment of choice in patients with severely impaired of chronotropic competence. In currently available DDDR pacemakers, appropriate modulation of the heart rate depends on the degree to which the artificial rate-control algorithm approximates the physiological response, and therefore on the specificity of the signal detected by the sensor [1]. Activity sensors respond to body movements or muscle tremors and are specific for physical exercise only. Other sensors, such as those based on minute ventilation, detect signals more closely correlated to metabolic needs. The time response of activity sensors (rate vs signal variation) is quite fast but often not truly physiological; by contrast, the response of metabolic sensors is more “physiologic” but it is slow; however these latter are claimed to have a more appropriate response to metabolic demand [2]. A device combining activity and metabolic (minute ventilation) sensing could obviate the problems of the faster less, “physiologic” and the slower, more “physiologic” system; cross-checking between the two sensor systems could also eliminate false positive heart rate increases [3,4].