Abstract: An implantable medical device operates to promote intrinsic ventricular depolarization according to a pacing protocol. The medical device determines a course of action based upon the presence or absence of sensed ventricular activity. The device further determines whether that activity is properly conducted or the result of a PVC or nodal rhythm.

Abstract: A system for a method of classifying distinct signals sensed from an electrode of an implantable cardiac pacing system positioned within an atrium of a heart of a patient is disclosed. The cardiac pacing system includes a pulse generator for generating pacing pulses and a controller for controlling the operation of a pacemaker. The method includes collecting atrial event signals consisting of P-wave signals and far field R-wave signals. An interim form factor histogram is generated based upon a form of collected atrial event signals. The interim form factor histogram includes an interim P-wave form factor histogram and an interim far field R-wave form factor histogram, each having bins of atrial event signals. A previously generated form factor histogram is weighted and combined with the interim form factor histogram to create a representative form factor histogram.

Abstract: A VDD-type pacing system which may have a floating atrial electrode analyzes P-wave events and absences of P-waves to determine data indicative of the likelihood of P-wave undersensing. The pacemaker logic chooses a reaction algorithm to respond to atrial events in accordance with whether an absence of a P-wave is more likely to have been an undersense or an incidence of bradycardia. Specific algorithms are presented which illustrate pacemaker reactions to probable undersense and brady occurrences. The pacemaker also incorporates a subsystem for detection of undersense events.

Abstract: There is disclosed a pacemaker, a dual chamber VDD(R) or DDD(R) pacemaker, having improved features for avoiding undesired sensor-sinus competition and providing blended sensor and sinus (atrial) control. The pacemaker employs atrial hysteresis which is used during sensing of natural atrial beats in order to enable tracking the sinus signals that occur at rates below the current pacing limit; and sensor hysteresis which prevents early takeover by sensor control and, in a DDDR pacer, controls when the sensor rate controls over a sensed sinus rate and also enables dropping the pacing rate during sensor control so as to enable finding and tracking of underlying lower rate sinus signals. The sensor hysteresis function is automatically adapted by obtaining and processing scattergram data representative of the sensor rate compared to the average of the natural sinus rate, and adjusting the sensor hysteresis function to optimally match the data.

Abstract: A rate adaptive pacemaker and method of operation, where the sensor-indicated rate is adjusted as a function of sensed sinus rate. The pacemaker is particularly adapted for VDDR operation. The natural sinus rate is compared to the sensor-indicated rate at one or more rates, and the sensor response function is adjusted, or adapted as a function of such comparisons, so as to optimize sensing of the atrial rate and maintenance of synchronous operation. The rate response function may be adjusted specifically at upper pacing limit, and may also be adjusted as a function of comparisons made at other rates.