Sulzer Intermedics, Inc.

Drury L Woodson, Iii

Andre G Routh

Joseph W Vandegriff

Yves Verboven

Annette Bruls

Parick J Paul

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 device which acquires physiological data and status information. The physiological data is compressed, reducing the memory requirement of the implantable device and/or increasing the amount of data that can be stored. The compression technique uses variable resolution while maintaining desired accuracy. The physiological data, such as heart beat interval time, is converted into a digital value. The digital representation then is divided into sub-ranges, and various resolution values are assigned to each sub-range. Each resolution is selected to stay within the desired accuracy. The interval time is divided by the particular resolution to obtain a digital value for the interval time within that range. The digital value then is corrected based upon the sub-range to obtain the compressed encoded digital value, which can then be stored in memory together with other desired data.

Growing community of inventors

Alvin, TX, United States of America

Drury L Woodson, Iii