Dynamic bandwidth control in an implantable medical cardiac stimulator
First Claim
1. A medical device for electrically stimulating the heart, comprising:
- a logic and control unit for initiating a pacing pulse to be delivered to the heart;
an output multiplier/regulator coupled to said logic and control unit, said output multiplier/regulator receiving said pacing pulse from said logic and control unit and altering the magnitude of the pacing pulse;
a plurality of electrodes for coupling to the heart, said pacing pulse delivered to the heart through said electrodes; and
a sense circuit including a band pass filter which includes a dynamically adjustable frequency response, said frequency response is dynamically adjustable by an external device, said sense circuit providing to said logic and control unit an electrical signal indicative of electrical activity in a predetermined chamber of the heart;
said logic and control unit provides different modes of pacing and switches modes depending upon predetermined conditions, and wherein said dynamically adjustable frequency response of said band pass filter is adjusted upon a mode switch.
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Accused Products
Abstract
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.
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Citations
24 Claims
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1. A medical device for electrically stimulating the heart, comprising:
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a logic and control unit for initiating a pacing pulse to be delivered to the heart; an output multiplier/regulator coupled to said logic and control unit, said output multiplier/regulator receiving said pacing pulse from said logic and control unit and altering the magnitude of the pacing pulse; a plurality of electrodes for coupling to the heart, said pacing pulse delivered to the heart through said electrodes; and a sense circuit including a band pass filter which includes a dynamically adjustable frequency response, said frequency response is dynamically adjustable by an external device, said sense circuit providing to said logic and control unit an electrical signal indicative of electrical activity in a predetermined chamber of the heart; said logic and control unit provides different modes of pacing and switches modes depending upon predetermined conditions, and wherein said dynamically adjustable frequency response of said band pass filter is adjusted upon a mode switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for calibrating an implantable pacemaker having a dynamically adjustable band pass filter, said method using an external calibration device and comprising the steps of:
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(a) transmitting an electrogram waveform to said calibration device; (b) performing a frequency analysis on said electrogram waveform with said calibration device; (c) determining a frequency response suitably sensitive to said electrogram; (d) determining filter coefficients for implementing said frequency response; and (e) transmitting said filter coefficients from said calibration device to said implantable pacemaker. - View Dependent Claims (11, 12, 13)
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14. A method for calibrating an implantable pacemaker having a dynamically adjustable band pass filter said method using an external calibration device and comprising the steps of:
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(a) detecting atrial fibrillation; (b) storing a sample of an atrial electrogram including said detected atrial fibrillation in a memory device in said pacemaker; (c) determining a first frequency response and a second frequency response for said dynamically adjustable band pass filter wherein said first frequency response is suitably sensitive for normal sinus rhythm and said second frequency response is suitably sensitive for atrial fibrillation. - View Dependent Claims (15, 16)
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17. A method for electrically stimulating a heart using an implantable pacemaker that includes a pacing circuit, a sense circuit including a dynamically adjustable band pass filter, and a logic and control unit, comprising the steps of:
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(a) operating said pacemaker in a first pacing mode with said band pass filter set to a first frequency response; (b) monitoring an electrogram; (c) switching said pacemaker to a second pacing mode upon detection of a first event in the electrogram; and (d) increasing the sensitivity of the sense circuit to said electrogram upon mode switching. - View Dependent Claims (18, 19, 20, 21)
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22. A medical system for monitoring the heart, comprising:
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an implantable medical device including a processor coupling together an atrial sense circuit having a dynamically adjustable band pass filter and a telemetry unit; and an external calibration device adapted to communicate to the implantable medical device; wherein said telemetry unit transmits atrial electrogram data to said calibration device; and
wherein said calibration device determines a set of filter coefficients for dynamically adjusting said dynamically adjustable band pass filter to provide a frequency response that increases the medical device'"'"'s sensitivity to said transmitted atrial electrogram data. - View Dependent Claims (23, 24)
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Specification