System and method for selecting a mode of operation of a dual-chamber pacemaker
 A system and method for preventing atrial competition during sensor-driven operation of a dual-chamber pacemaker includes means for sensing atrial activity during an atrial refractory period. Atrial competition is avoided by either: (1) generating an atrial competition prevention (ACP) interval upon the detection of any atrial activity during the relative refractory portion of an atrial refractory period, and preventing any atrial stimulation pulses from being generated for the duration of such ACP interval; or (2) shortening the atrial refractory period in the event that the sensor-driven rate of the pacemaker begins to approach a rate that might place atrial stimulation pulses near the end of the unshortened atrial refractory period. Further, the invention includes features that allow monitoring of the intrinsic atrial rate to determine if such is much greater than the sensor-driven rate, and, if so: (1) reducing the maximum tracking rate of the pacemaker, and/or (2) switching the operating mode of the pacemaker from a dual-chamber sensor-driven mode to an single-chamber sensor-driven mode. 
Siemens Pacesetter, Inc.
A A
A61N A61N
inventional inventional
James L.
Duncan