Intermedics Inc.

Sulzer Intermedics, Inc.

Joseph W Vandegriff

Andre G Routh

Yves Verboven

Annette Bruls

Drury L Woodson, Iii

Drury L Woodson

Randolph K Armstrong

Ross G Baker, Jr

Eckhard U Alt

Lawrence J Stotts

Douglas Jason Cook

Douglas J Cook

Denise R Brown

Michael Lee

Parick J Paul

Craig Housworth

Bryan J Thome

It has been determined that certain cardiac stimulators may operate in a manner in which the ventricular pace refractory period (VPRP) may be greater than the post-ventricular atrial refractory period (PVARP). Various exemplary techniques may be used to improve the ability of cardiac stimulators to lengthen the PVARP. In accordance with one technique, the VPRP is adjusted with the pacing rate so that as the pacing rate becomes slower the VPRP increases. The VPRP is compared with the PVARP. The PVARP remains constant until the VPRP becomes greater than the PVARP. Then, the PVARP is adjusted to make it greater than or equal to the VPRP. In accordance with another technique, the VPRP and the PVARP are adjusted with the pacing rate, with the PVARP remaining greater than or equal to the VPRP.

Cardiac stimulator with rate-adaptive PVARP

An implantable medical device electrically stimulates the heart to beat and senses electrical activity in the heart. The medical device generally includes a processor, a plurality of electrodes, and a sense amplifier. The medical device is capable of performing a variety of diagnostic tests, such as a sensing test in which a suitable sensitivity setting is computed for the sense amplifier. An external programmer is also provided to initiate the diagnostic tests. The programmer transmits a start signal to the implantable medical device and the medical device's processor initiates the diagnostic test specified by the programmer via the start signal. The implantable device is capable of completing the diagnostic test without further communication from the programmer or may initiate communication with the programmer during a refractory period in which signals from the programmer will not interfere with the diagnostic test. In the latter case, the programmer responds before the refractory period ends.

Diagnostic test protocol in an implantable medical device

An implantable device for providing pacing and defibrillating stimuli to a heart, comprises: a power source, at least one electrode electrically connected to said power source, a sensor capable of providing data that can be used to determine a physiological pacing demand, and a control device. The control device controls the application of electrical stimuli to the heart. The control device calculates an adjusted pacing interval based on said demand, calculates an adjusted ventricular pace refractory period (VPRP.sub.current) that is a function of said pacing interval, and calculates a T-wave monitoring window. The end time, and optionally the start time also, of the T-wave window is a function of the pacing interval. The control device is also capable of adjusting the sensitivity of an amplifier based on signals received during the T-wave window.

Implantable cardiac stimulator with rate-adaptive T-wave detection

An implantable medical device for electrically stimulating the heart to beat includes a sense circuit for detecting cardiac electrical activity. The sense circuit includes a band pass filter with an adjustable frequency response. The frequency response can be repeatedly adjusted after implantation of the medical device and preferably is adjusted upon detection of the loss of normal sinus rhythm (NSR) in the heart's atria. The loss of NSR often indicates atrial fibrillation (AF), and the filter's frequency response is adjusted to increase the sensitivity of the sense circuit to the cardiac electrical activity typical during AF. The medical device is calibrated during implantation or at subsequent doctor visits with the aid of a calibration device external to the body. Cardiac electrical activity in the form of an electrogram is transmitted from the medical device to the external calibration device. The transmitted electrogram preferably includes both NSR and AF rhythms. The calibration device computes two sets of filter coefficients; one set for increased filter sensitivity during NSR and another set for increased sensitivity during AF. The coefficients are transmitted to the medical device which uses the appropriate set of coefficients to increase the filter's frequency response during both NSR and AF.

Dynamic bandwidth control in an implantable medical cardiac stimulator

An implantable medical device for electrically stimulating the heart to beat includes a sense circuit for detecting cardiac electrical activity. The sense circuit includes an amplifier with a dynamically adjustable gain to provide increased sensitivity to the electrogram during atrial fibrillation. Alternatively, sensitivity control is provided by dynamically adjusting threshold limits associated with a threshold detector included in the sense circuit. The sensitivity level of the medical device to the electrogram can be repeatedly adjusted after implantation and preferably is increased upon detection of the loss of normal sinus rhythm (NSR) in the heart's atria. The medical device is calibrated with the aid of a calibration device external to the body to determine appropriate sensitivity levels. A method for calibrating and operating an implanted medical device with dynamically adjustable sensitivity is also disclosed for improving the medical device's sensitivity to atrial fibrillation.

Dynamic atrial detection sensitivity control in an implantable medical

An implantable medical device for electrically stimulating the heart to beat including a sense circuit for detecting cardiac electrical activity. The sense circuit includes a sense amplifier, band pass filter, and threshold detector. The threshold detector determines whether sensed cardiac electrical activity resulted from a normal heart beat or an ectopic beat such as a premature ventricular contraction. In a preferred embodiment, latches in the threshold detector are activated by output pulses from a pair of comparators. A positive comparator produces an output pulse upon detection of cardiac electrical activity exceeding a positive threshold voltage and a negative comparator produces an output pulse upon detection of cardiac electrical activity more negative than a negative threshold. Threshold logic produces output signals indicative of which comparator first produced an output pulse. A logic and control unit monitors the output signals from the threshold logic and thus determines whether the associated cardiac electrical activity represented a normal heart beat or resulted from an ectopic beat so that appropriate pacing may be provided by the implantable device.

Implantable cardiac stimulator with polarity detection for detecting

An implantable medical device for electrically stimulating the heart to beat including a pulse generator, a logic and control unit, and an atrial sense circuit. The atrial sense circuit processes signals from electrodes implanted in an atrial chamber of the heart. The atrial sense circuit provides an atrial sense signal to the logic and control unit when the magnitude of electrical activity in the atria exceeds a threshold. The medical device preferably paces the ventricles in response to detected electrical activity in the atria indicative of atrial contraction. Immediately following ventricular pacing, the medical device initiates an absolute atrial blanking period followed by an atrial sensing period and a programmable blanking period. During both the absolute atrial blanking period and the programmable blanking period, atrial sensing is disabled, while during the atrial sense period, atrial sensing is enabled. The time durations of the atrial sensing period and the programmable blanking period are programmable and may be programmed noninvasively while the medical device is implanted. The time durations of the atrial sense period and the programmable blanking period are adjusted so that paced far field R-waves resulting from a ventricular pace preferably occur during the programmable blanking period when atrial sensing is disabled. Atrial sensing during the atrial sensing period advantageously allows the medical device to monitor the atrial sense signal for normal atrial contractions.

Variable atrail blanking period in an implantable medical device

A programmable dual-chamber artificial cardiac pacemaker senses atrial activity and normally tracks the sensed atrial activity in pacing the ventricular activity. An accelerometer located in the case of the pulse generator portion senses physical exercise by a patient when the pacemaker is implanted in the patient, and generates a rate control signal indicative of extent of the sensed physical exercise. The pulse generator is programmed for ventricular pacing rate control in multiple rate zones bounded by rate limits including a ventricular tracking limit (VTL) that varies dynamically with sensed physical exercise and a higher mode switch rate. The ventricular pacing rate tracks the sensed atrial activity on a 1:1 basis for atrial rates below the dynamic VTL (DVTL) during a predetermined interval of time for which the DVTL applies, and tracks the sensed atrial activity in Wenckebach behavior for atrial rates above the DVTL up to the mode switch rate with the ventricular pacing rate limited by the DVTL. The mode switch rate is set to effect a switch from dual-chamber to single-chamber mode when the sensed rate of atrial activity exceeds the mode switch rate for a programmed number of cardiac cycles, in which the ventricular pacing rate is controlled solely by sensed spontaneous ventricular activity without regard to the DVTL or sensed physical exercise. The mode switch rate also effects a reversion to the dual-chamber mode when the sensed rate of atrial activity drops below the mode switch rate for a programmed number of cardiac cycles, in which the ventricular pacing rate is controlled according to the respective one of the multiple rate zones in which the atrial activity rate is present.

Control of pacing rate in dual-chamber, rate-adaptive pacemakers

A pacemaker with a variable, asynchronous minimum heart rate and a second variable, synchronous heart rate. The second, variable heart rate has an absolute minimum, lower than the asynchronous minimum heart rate, which is preselected by the attending physician. The minimum heart rates can vary, conditioned upon sensed physiologic need. The cardiac pacemaker attempts to reestablish synchrony in every cycle, even if the intrinsic or natural atrial heart rate is below the asynchronous minimum heart rate in that cycle and can maintain cardiac synchrony at lower rates, thereby increasing cardiac efficiency and minimizing strain on the heart.

Implantable cardiac pacemaker with extended atrial sensing

A state machine for automatic gain control of sensing functions in an implantale cardiac stimulator. The state controls sensing levels based on present sensed conditions and on the prior state of the heart. Different rates of adjustment are selected under varying conditions so that the gain level for sense amplifiers can be adjusted without significant overshoot. The state machine comprises a set of four conditions or states together with interconnections or logical paths from one state to another. The rate of adjustment of sense amplifier gain is based on the path traversed in the state machine so that different effective time constants for the control function may be used for different conditions.

Implantable cardiac stimulator with state machine for automatically

A dual chamber pacemaker with variable V-A delay based on detection of multiple criteria before lengthening the V-A delay period. Before the V-A delay period can be extended, the pacemaker must be stimulating the ventricle at a maximum ventricular rate, and an atrial event must be sensed in a relative atrial refractory period. During this interval the pacemaker would not respond to an atrial event that was sensed, but the occurrence of the event would be detected. To optimize a ventricular blanking period, in each cardiac cycle, the energy level of the atrial output pulse and the sensitivity of the ventricular sense amplifier are sampled. Based on these dynamic parameters, the duration of the ventricle blanking period is adjusted for each cycle so that a minimum ventricular blanking period can be maintained without cross-talk.

Dual chamber pacemaker with adjustable blanking and V-A extension

A series of test signals are generated by a microprocessor of a pacemaker to determine whether a bipolar or unipolar lead is attached to an implanted cardiac pacemaker restricting programming of said pacemaker to only an unipolar pacing mode unless the presence of an operational bipolar lead is detected. Detection is accomplished by generating a series of low frequency high impedance pulses, applying them to lead contacts and sensing a return signal. If a return signal is detected, then that indicates either a unipolar lead is connected to the pacemaker or that the ring conductor of a bipolar lead is open and bipolar pacing must be inhibited.

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Freeport, TX, United States of America

Joseph W Vandegriff