Current status of dual-sensor pacemaker systems for correction of chronotropic incompetence.

Rate-adaptive pacing has been shown to improve exercise capacity in patients with chronotropic incompetence. However, all sensors used to adapt the pacing rate to meet metabolic demands show typical limitations. To overcome these, concepts using 2 sensors for rate adaptation have been developed, combining an unspecific but fast-reacting sensor with a specific but slower-reacting one. Clinical performance of these dual-sensor pacemaker systems is related to 3 factors: (1) choice of sensors, (2) mode of sensor integration, and (3) algorithms for automatic optimization of the integrated sensor response. Clinical studies using dual-sensor rate-adaptive pacing systems have demonstrated their ability to mimic normal sinus rate during different forms of exercise, avoiding inadequate or delayed rate response. However, to avoid combining the disadvantages of both single sensors, dual-sensor rate-adaptive systems need effective automatic algorithms. Sensor cross-check should be quick and combine fast reactivity and high specificity, particularly so as to prevent overpacing. Programmable rate response-related parameters should continuously be optimized. The pacemaker should provide diagnostic facilities during exercise to simulate short-term sensor performance at different settings and memory functions to evaluate long-term sensor performance. Assessment and eventually deactivation of all automatic functions should be possible. Finally, even with automatic algorithms for sensor optimization, maximal benefit from a dual-sensor system can only be achieved if the physician is able to identify and correct pitfalls of each system.