Interference recognition circuit in a heart pacemaker
First Claim
1. A synchronizable heart pacemakercomprising in combinationa timing circuit for generating a stimulating impulse after an expected time interval,differentiating means for receiving signals,interference recognition means connected to the output of said differentiating means, and includinga testing stage for each signal, an output signal normally appearing on an output of said testing stage, said testing stage including a peak detector circuit storing a positive maximum value and a negative maximum value of each signal differentiated by an adder which further acts as an amplifier and which forms the difference of both positive and negative maximum values, and a comparator postcoupled with one input thereof to said adder and with another input thereof to a reference voltage,a discriminator postcoupled to the testing stage, said discriminator stage generating a time interval corresponding approximately to a time duration of the QRS complex of a heart-action signal, and includingchecking means for checking for the presence or absence of said output signal after said time interval, anddecision means for recognizing said output signal in the presence thereof within said time interval either as an interfering signal, and thereafter rendering said interfering signal ineffective, or recognizing said output signal as said heart-action signal and passing said heart-action signal to said timing circuit.
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Abstract
A synchronizable heart pacemaker includes a timing circuit, a differentiating circuit for receiving signals, and an interference recognition circuit connected to the output of the differentiating circuit. The interference recognition circuit includes a testing stage for each signal. An output signal normally appears on an output of the testing stage, and the testing stage includes a peak detector circuit which stores a positive maximum value and a negative maximum value of each signal differentiated by the differentiating stage, and an adder forming the sum of said maximum values. A discriminator stage is postcoupled to the testing stage. The discriminator stage generates a time interval corresponding approximately to a time duration of the QRS-complex of a heart-action signal, and includes a checking circuit for checking the presence or absence of the output signal of the testing stage after said time interval, and a decision circuit for recognizing the output signal either as an interfering signal, and thereafter rendering the interfering signal ineffective, or recognizing the output signal as the heart-action signal, and passing the heart-action signal to the timing circuit.
79 Citations
20 Claims
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1. A synchronizable heart pacemaker
comprising in combination a timing circuit for generating a stimulating impulse after an expected time interval, differentiating means for receiving signals, interference recognition means connected to the output of said differentiating means, and including a testing stage for each signal, an output signal normally appearing on an output of said testing stage, said testing stage including a peak detector circuit storing a positive maximum value and a negative maximum value of each signal differentiated by an adder which further acts as an amplifier and which forms the difference of both positive and negative maximum values, and a comparator postcoupled with one input thereof to said adder and with another input thereof to a reference voltage, a discriminator postcoupled to the testing stage, said discriminator stage generating a time interval corresponding approximately to a time duration of the QRS complex of a heart-action signal, and including checking means for checking for the presence or absence of said output signal after said time interval, and decision means for recognizing said output signal in the presence thereof within said time interval either as an interfering signal, and thereafter rendering said interfering signal ineffective, or recognizing said output signal as said heart-action signal and passing said heart-action signal to said timing circuit.
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5. A synchronizable heart pacemaker for generating a current impulse after an expected time interval, said expected time interval being normally started by a heart-action signal, said heart-action signal including a QRS complex appearing within a predetermined time interval, starting with a positive-going spike, followed by a negative-going spike of a predetermined absolute magnitude and steepness followed by a positive-going spike of reduced steepness, followed in turn by a relatively broad excursion of a smaller absolute steepness than said predetermined absolute steepness, said broad excursion having a relatively low-frequency content, each of said spikes having a relatively high-frequency content,
comprising in combination a timing circuit for generating said current impulse after said expected time interval, differentiating means for receiving signals, interference recognition means connected to the output of said differentiating means, and including a testing stage for each signal, an output signal normally appearing on an output of said testing stage a discriminator stage postcoupled to the testing stage, said discriminator stage including decision means for checking the presence or absence of said output signal within said expected time interval, and heart action signal recognition means for recognizing said output signal either as an interfering signal, and thereafter rendering said interfering signal ineffective, or recognizing said output signal as said heart-action signal and passing said heart-action signal to said timing circuit in the event of the presence of said output signal within said time interval, said timing circuit being adapted to only cause generation of a current impulse passed to a stimulation electrode for stimulating the failing heart of a patient, provided no other heart-action signal occurs within said expected time interval.
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11. A synchronizable heart pacemaker for generating a current impulse after an expected time interval, said expected time interval being normally started by a heart-action signal, said heart-action signal including a QRS complex appearing within a predetermined time interval, starting with an initial positive-going spike, followed by a negative-going spike of a predetermined absolute magnitude and steepness, followed by a positive-going spike of reduced steepness, followed in turn by a relatively broad excursion of a smaller absolute steepness than said predetermined absolute steepness, said broad excursion having a relatively low-frequency content, each of said spikes having a relatively high-frequency content,
comprising in combination a timing circuit for generating said current impulse after said expected time interval, differentiating means for receiving signals, each differentiated signal having a positive peak value, and a negative peak value, a testing stage connected to the output of said differentiating means, and including a preamplifier, peak-value storage means postcoupled to said preamplifier for storing said positive and said negative values of each signal differentiated by said differentiating means, and a signal conditioner including an adder postcoupled to said peak-value storage means, an output signal normally appearing on an output of said testing stage, said adder forming a sum from said positive and negative values, and a discriminator stage postcoupled to the testing stage, said discriminator stage including heart-action signal recognition means, including polarity-sensing means for sensing the polarity of said sum formed by said adder, and passing said output signal to said timing circuit only when said sum is negative and exceeds a predetermined absolute value, interference recognition means for recognizing any non-recurring signal having a predominantly positive rise time, and substantially any periodic pulsed or amplitude-modulated signals as interference signals, and interference suppression means for preventing said interference signals from being passed to said timing circuit, said timing circuit being adapted to only cause generation of a current impulse passed to a stimulation electrode for stimulating the failing heart of a patient, provided no other heart-action signal occurs within said expected time duration.
Specification