Sulzer Intermedics, Inc.

Annette Bruls

Andre G Routh

Joseph W Vandegriff

Yves Verboven

Drury L Woodson, Iii

Parick J Paul

Craig Housworth

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.

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Brussels, Belgium

Annette Bruls