Abstract: An implantable medical device system for regulating a heart of a patient. The system includes a first sensor, a second sensor, a processor, and a medical device. The first sensor is capable of sensing activity of a heart atrium. The second sensor is capable of sensing activity of a heart ventricle. The processor is coupled to the first and second sensors and is capable of determining an atrial cycle time and a ventricular cycle time based upon signals from the first and second sensors. The processor is further capable of generating a hemodynamic baseline ratio based upon an atrial cycle time and a ventricular cycle time of a hemodynamic heartbeat, as well as an active ratio based upon an atrial cycle time and a ventricular cycle time of an active heartbeat. The processor is further capable of comparing the hemodynamic baseline ratio and the active ratio, and determining a corrective action based upon this comparison.

Abstract: The present invention discloses a method of and a system for preventing unwanted alternating current magnetic fields transmitted from an external source from disrupting electrical circuitry within an implantable medical device, while permitting desired communications between the implantable medical device and a programmer detected in proximity to the implantable medical device. The implantable medical device is capable of communication with at least one implantable lead position within a heart of a patient. The method includes activating an electrical device to create a short circuit in parallel with an inductive transreceiver coil of the implantable medical device, thereby shorting out the inductor transreceiver coil. In this mode, alternating current magnetic fields do not effect electrical circuitry within the implantable medical device. The method further includes detecting a direct current magnetic field indicating the presence of a programmer located in proximity to the implantable medical device.

Abstract: An implantable medical device and method of pacing provide for switching from a first pacing mode to second pacing mode upon detection of a period of accelerated atrial arrhythmia. Generally, the second pacing mode has an associated predetermined lower pacing rate. At least initially, upon switching from the first pacing mode to the second pacing mode, the predetermined lower pacing rate is adjusted to an elevated adjusted lower rate. Further, this elevated adjusted lower rate may then be decelerated towards a programmed basic pacing rate during a deceleration period. Generally, the programmed basic pacing rate is elevated relative to the predetermined lower pacing rate.