Abstract: A capture detection algorithm in which atrial capture is detected and distinguished. Further, an immediate measurement of the capture threshold is implemented when a pacemaker switches a lead's polarity from bipolar to unipolar in response to a detected lead failure, in either one or both chambers. Atrial chamber reset (ACR) and AV conduction (AVC), implemented to measure an atrial pacing threshold, are comparatively measured to enable measurement of the atrial pacing threshold. The data that is used to choose between ACR and AVC methods is used to determine the progression of the patient's disease state. Some of the significant aspects of the invention include enablement of accurate threshold measurements, including calculation of stability criteria, precise interval measurements and the use of reference interval to determine capture and loss of capture.

Abstract: There is provided a system and method applicable for use with a dual chamber pacemaker for determining whether long atrial intervals are due to atrial undersensing or to sick sinus syndrome. The determination of undersensing is based upon an algorithm which statistically analyzes a long atrial interval in terms of the patient's prior atrial rate history, and compares a calculated statistical probability measure with an empirically determined undersense threshold factor. The pacemaker can respond to a determination of undersensing by correcting already collected diagnostic data, adjusting one or more pacemaker operating parameters, adjusting synchronous tracking and/or providing an annotated marker channel for indicating undersense events.

Abstract: There is provided an improved pacing system and method which monitors when the ventricle has become appropriately filled with blood and controls the delivery of each ventricular pace pulse to substantially coincide with desired ventricular filling, e.g., when the chamber has substantially filled. By this technique, the desired time for delivering the ventricular pace pulse is determined on a beat-by-beat basis, providing an improved physiologically optimum mode of pacing. The physiologically ventricular pacing technique of this invention is applicable either to a single chamber pacemaker, or to a dual chamber pacemaker, and in either case enables the important improvement of delivering the pace pulse at the most physiologically appropriate time.

Abstract: There is provided a system and method for increased data transmission from an implanted pacemaker when the pacemaker is in magnet mode. Pacemaker data including, e.g., pacemaker operating conditions, pacing events and patient events, is outputted by changing the asynchronous pacing rate to selected ones of available rates, and with a predetermined sequence, enabling read out of the data on an EKG strip chart. In a preferred embodiment, data-encoded pace pulses with intervals corresponding to selected rates are delivered in a predetermined sequence with fixed rate non-data intervals. For example, four pulses are delivered at 85 ppm followed by one or more data-encoded pulses, each data-encoded pulse being at 90, 95 or 100 ppm, whereafter the sequence is repeated with additional data-encoded intervals. The combination of rates for each of the data-encoded intervals represents the pacemaker data, and can be decoded by observing an EKG strip taken during the pattern of pace pulses.

Abstract: Capture detection and stimulation threshold-measurement methods and apparatus for deriving atrial and ventricular pace pulse (A-pace and V-pace) stimulation energy strength-duration data. In a first atrial and ventricular threshold test regimen for use with patients having intact A-V conduction or first degree AV block, A-pace pulses are delivered at a test escape interval and A-V delay. Atrial loss of capture (ALOC) in response to an A-pace test stimulus is declared by the absence of a detected ventricular depolarization (V-event) in the latter portion of the paced A-V delay interval following the delivery of the A-pace test stimulus. In the ventricular threshold test regimen, a V-pace test stimulus is delivered after a shortened A-V delay. Ventricular loss of capture (VLOC) is declared by the detection of a V-event in the ventricular refractory period of the V-pace test stimulus.

Abstract: A multiple sensor cardiac pacemaker blends the outputs from a fast-reacting Activity sensor and a slower-reacting Minute Ventilation sensor to achieve an optimally desirable pacing rate. The pacemaker conserves battery energy by forcing the Minute Ventilation sensor output to be at its minimum value by disabling the Minute Ventilation algorithm for a predetermined time period when the Activity sensor is at its minimum observed value. Power is conserved because the Minute Ventilation sensor and associated algorithms which normally consume power to operate the circuitry, and to measure impedance are disabled temporarily only during selected periods where the Activity sensor is at its minimum observed value, thereby maintaining optimal blending of the pacemaker sensor outputs in achieving the desired pacing rates.

Abstract: A physiologic cardiac pacer operable in the DVI or A-V sequential pacing mode or the DDD or fully automatic pacing mode senses for the omission of an R-wave from an implantable cardiac pacer during the A-V interval. If the pacer does not sense a R-wave during the A-V interval the V-A interval is timed out immediately following the A-V interval and an atrial pacing pulse is issued at the end of the V-A interval. In the event, however, that an R-wave is sensed during the A-V interval, a flag is set and then the entire A-V interval is to be timed out, at which time the state of the flag is determined. If an R-wave was previously issued, a ventricular pacing pulse is not issued to the pacer at the end of the A-V interval, whereas if the flag is not set it is transmitted to the pacer.

Abstract: A pacing system analyzer is constructed to provide verification that an implantable cardiac pacer operating in a demand mode will not itself produce tachycardia in a patient because of abnormally long patient retrograde conduction time. The analyzer when performing the retrograde conduction test provides an intercardiac electrogram, changes the ventricular sense amplifier to asynchronous and samples to determine the maximum amplitude signals over a sampling period to select an amplifier gain factor. After the gain factor is set additional signal samples are collected, peak-to-peak amplitude is measured and interpolation between data is made to provide waveform "segments" and the best waveform segment to employ for testing for retrograde conduction is selected. The time periods from pacing to these segments are measured and utilized to determine if retrograde conduction is present.

Abstract: A pacing system analyzer as connected to an implantable cardiac pacer and if an atrial pacing pulse is detected only, the analyzer sends a simulated P-wave to the pacer and determines the response of the simulated P-wave to determine if the pacing mode is AAI, AAT, or AOO. In the event a ventricular output pulse only is detected by the analyzer, a simulated R-wave is sent to the pacer and if the pacer responds either by a triggered ventricular pulse or by not changing its response, the analyzer determines that the pacer is in a VVT or VOO mode. On the other hand, if the pacer is inhibited a subsequent simulated P-wave is sent to it and the response of this P-wave determines whether or not the pacer is in a VVI or VDD mode. In the event that both atrial and ventricular pacing pulses are detected by the analyzer, the simulated R-wave is first sent to the pacer and an unchanged response determines that the pacer is in a DOO mode.