Cardiac pacer employing discrete frequency changes
First Claim
1. A fully implantable cardiac pacer comprisinga cardiac stimulation generator capable of producing stimulation pulses at at least two controlled and well-defined frequencies, said generator including at least one component having an operating condition which can change,monitor circuitry responsive to the condition of at least one said component of said pacer to provide an output signal indicative of said condition, said output signal characterized by having a plurality of defined states, andsaid generator havingclock means for generating primary clock pulses at a frequency higher than the frequency of said stimulation pulses, andfrequency changing means responsive to said monitor output signal and said primary clock pulses for generating said stimulation pulses at one of said well-defined frequencies depending upon the state of said output signal.
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Accused Products
Abstract
In the implantable cardiac pacer disclosed herein, a drop in battery voltage is signalled by a discrete change in the stimulation frequency of the pacer. Reliably distinct frequencies are obtained by digitally dividing, by two different integer factors, a stable high frequency pulse signal generated by a mechanically controlled oscillator, for example a piezoelectric crystal controlled oscillator.
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Citations
12 Claims
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1. A fully implantable cardiac pacer comprising
a cardiac stimulation generator capable of producing stimulation pulses at at least two controlled and well-defined frequencies, said generator including at least one component having an operating condition which can change, monitor circuitry responsive to the condition of at least one said component of said pacer to provide an output signal indicative of said condition, said output signal characterized by having a plurality of defined states, and said generator having clock means for generating primary clock pulses at a frequency higher than the frequency of said stimulation pulses, and frequency changing means responsive to said monitor output signal and said primary clock pulses for generating said stimulation pulses at one of said well-defined frequencies depending upon the state of said output signal.
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7. The pacer of claim 7 wherein said blocking means includes a one shot circuit for generating a pulse signal in response to a signal derived from at least one of said counter stages for blocking said at least one output pulse from said crystal source.
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10. A fully implantable cardiac pacer comprising:
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batteries for powering said pacer; a crystal controlled oscillator providing a pulse signal of highly stable frequency; digital countdown circuitry for dividing the frequency of said pulse signal and providing an output signal at reduced frequency, said countdown circuitry having a first state in which said stable frequency is divided by a first integer number and a second state in which said stable frequency is divided by a second integer number; at least one component characterized by an operating parameter which can change, a detector responsive to the value of an operating parameter of said pacer for switching said countdown circuitry from one of said states to the other in response to a change in said parameter past a predetermined value; and circuit means for providing stimulation pulses at a rate determined by the output signal frequency.
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11. A fully implantable cardiac pacer comprising:
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batteries for powering said pacer; a crystal controlled oscillator providing a pulse signal of highly stable frequency; digital countdown circuitry for dividing the frequency of said pulse signal and providing an output signal at reduced frequency, said countdown circuitry having a first state in which said stable frequency is divided by N and a second state in which said stable frequency is divided by N+d, where N is substantially larger than d; a threshold detector responsive to the battery voltage for switching said countdown circuitry from one of said states to the other when the battery voltage drops below a predetermined value; and circuit means for providing stimulation pulses at a rate determined by the output signal frequency, the rate being thereby indicative of the state of said battery.
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12. A fully implantable cardiac pacer comprising
a power source for said pacer, a cardiac stimulation generator capable of producing stimulation pulses at two controlled and well-defined frequencies, a monitoring circuit including a threshold detector for providing an output signal having a first and a second state, said first state indicating the power source for said pacer having a voltage output above a predetermined threshold, and said second state for indicating that said power source voltage output is below said predetermined threshold, the generator including a crystal controlled frequency source for providing a basic frequency pulse output for the generator, a first gating circuitry connected to said crystal source, countdown circuitry for dividing the basic frequency pulse output of the crystal source, said countdown circuitry being connected to said crystal source through said first gating circuitry, a second gating circuitry connected to at least one stage of said countdown circuitry and to an output of a monitoring circuit, said second gating circuit responsive to said output of the monitoring circuit and operative to disable for a predetermined time said first gating circuit to block at least one pulse derived from said crystal controlled oscillator.
Specification