Abstract: An implantable medical device, such as a cardiac stimulator, has a noise cancelling circuit which cancels noise signals relating to body movements which originate outside of the heart, and which are sensed between a noise sensing electrode located outside of the heart and the indifferent electrode of the stimulator housing. The noise cancelling circuit cancels these noise signals from the electrical signals which originate within the heart and which are sensed between the tip electrode of a stimulator lead and the indifferent electrode of the stimulator housing.

Abstract: An apparatus and method for enabling radio-frequency communications with an implantable medical device utilizing far-field electromagnetic radiation. Such radio-frequency communications can take place over much greater distances than with inductively coupled antennas.

Abstract: There is disclosed an apparatus and method for reducing power consumption in physiological condition monitors that use a memory data storage device that operates in a high power mode when data is being written to the memory data storage device and operates in a low power mode when inactive. The apparatus comprises: 1) a controller for receiving incoming data to be written to the memory data storage device; and 2) a first low power buffer coupled to the controller. The controller stores the incoming data in the first low power buffer until a predetermined amount of incoming data has been accumulated in the first low power buffer and transfers the accumulated predetermined amount of incoming data to the memory data storage device in a single data transfer.

Abstract: A system and method for receiving telemetry data from implantable medical devices such as cardiac pacemakers with improved noise immunity is disclosed. Ambient noise levels and signal strength are monitored and used to adaptively adjust the detection sensitivity of the receiver. Filtering of the received signal is performed to remove both broadband and narrowband noise. Removal of narrowband noise is accomplished with notch filters that are dynamically adjusted in accordance with a detected noise spectrum.

Abstract: A low pass filter especially adapted for use with ECG equipment designed to negate any noise energy that may be superimposed upon the ECG signal itself. A plurality of low-pass FIR filter stages are connected in tandem between a signal input point and a signal output point where each of the stages has a distinct cut-off frequency characteristic. A device is provided for selectively turning ones of the plurality of stages on or off.

Abstract: An implantable cardiac stimulation device discriminates between noise and an arrhythmia sensed in a heart. A first sensing circuit generates a first signal representing electrical activity sensed in a first location of the heart and a second sensing circuit generates a second signal representing electrical activity sensed in a second location of the heart. The first and second locations are spaced apart and located in respective different corresponding chambers or the same chambers of the heart. A comparison circuit then compares the first and second signals to provide a comparison factor. A control circuit then determines from the comparison factor if noise is sensed or if an arrhythmia is being sensed.

Abstract: An implantable cardiac rhythm management device capable of automatically detecting intrinsic and evoked response of a patient's heart and suitable for use during capture verification. The device of the present invention may operate in an automatic capture verification mode, wherein an electrocardiogram signal of a patient's heart is received and used by the device to determine whether a stimulation pulse evokes a response by the patient's heart. The device suspends the automatic capture verification mode and/or adjust the detection threshold dependent upon detected and/or measured noise, a determined amplitude of evoked response, a determined modulation in the evoked response, or detected and/or measured artifact. Further, the sensing circuit of the rhythm management device of the present invention reduces afterpotentials that result due to delivery of the stimulation pulses.

Abstract: A voltage sensing system includes input impedance balancing for electrocardiogram (ECG) sensing or other applications, providing immunity to common-mode noise signals while capable of use with two electrodes. Signals are received at first and second electrodes having associated impedances. An impedance circuit includes a feedback controller that adjusts an effective impedance associated with the second electrode based on a difference signal, a common mode signal, a phase-shifted (e.g., quadrature common mode) signal, and an impedance associated with the first electrode. As a result, signals associated with each electrode undergo a similar degree of gain/attenuation and/or phase-shift. This reduces common mode noise and enhances the signal-to-noise characteristics of a desired ECG or other output signal, without requiring the use of more than two electrodes.

Abstract: A method for determining a representative noise floor in a cardiac pacing system from which future events are measured is provided. An event amplitude is determined. Pluralities of noise levels are recorded, when each of the plurality of noise levels is less than a predetermined percentage of the event amplitude. The noise floor is determined as an absolute maximum value of the plurality of recorded noise levels.

Abstract: An artifact rejector for repetitive physiologic-event-signal data generated from electronically-controlled physiologic-event-measuring equipment includes a physiologic-event-signal averager in communication with such physiologic-event-measuring equipment. The artifact rejector is constructed to generate and store repetitive averaged physiologic-event-signal data based upon a substantially stable time relationship between corresponding physiologic-event-signal data and heart-beat-related-signal data. The repetitive averaged physiologic-event-signal data includes less noise than the repetitive physiologic-event-signal data. The artifact rejector generates and continuously updates an averaged-data template by storing such repetitive averaged physiologic-event-signal data for a preselected number of measured physiologic events.

Abstract: We show how to determine whether there has been an axis shift in an electrocardiogram waveform and how to use this for filtering out bad electrocardiogram information and to modify an adaptive filter that can be used to adapt the filtering of such electrocardiogram information to make it available for determining physiologic conditions even after an axis shift.

Abstract: An economically manufactured, highly sensitive, noise and interference resistant, AC powered, two, four or eight channel intraoperative neuroelectrophysiological monitor includes a mainframe having a touch panel display and a low noise interface cable providing connection via a patient interface box for one or more stimulator probes and one or more EMG signal sensing electrodes.

Abstract: We show how to determine whether there has been an axis shift in an electrocardiogram waveform and how to use this for filtering out bad electrocardiogram information and to modify an adaptive filter that can be used to adapt the filtering of such electrocardiogram information to make it available for determining physiologic conditions even after an axis shift.

Abstract: A patient monitoring system for acquiring a physiological waveform, and a method of detecting the presence of pacemaker pulses in same. The patient monitoring system includes an input circuit for acquiring an analog ECG, an analog pace detection circuit connected to the input amplifier for generating analog pacemaker pulse markers and energy measures from analog ECG, a digital ECG processing circuit for providing a digitized output of the analog ECG, and software for analyzing the digitized output to establish digital pace detection markers, and for comparing the analog pacemaker pulse markers and energy measures to the digital pace detection markers to eliminate erroneously detected pacemaker pulses.

Abstract: An ECG signal measuring system uses low frequency compression/enhancement techniques combined with dither techniques to effectively increase the dynamic range while maintaining resolution. This aspect of the present invention is achieved without increasing the number of bits of the ADC. The system includes a HPF, an ADC, a decimation filter (DF), and a compensation filter (CF). The HPF receives an input signal (i.e., the bias current combined with ECG input signal) and attenuates the low frequency components of the input signal, including a portion of the frequency band within the desired ECG frequency band. The ADC oversamples the output signal of the HPF. The DF receives the output samples of the ADC and generates output samples at rate that is at least twice the maximum frequency of the desired ECG output signal. The CF amplifies the low frequency end of the DF output samples.

Abstract: A shielded conductor path comprising: a first signal conductor having an input end for acquiring a physiological signal and an output end for coupling the physiological signal to a physiological signal input of a patient monitor, and a second signal conductor positioned with respect the first signal conductor for acting as a shield therefore. An inductance connected in series between an output end of the second signal conductor and the reference signal input of the patient monitor forms a filter circuit which attenuates the level of an interference signal in the second signal conductor. In one preferred embodiment of the invention, the inductance is part of an RLC filter circuit contained in a housing which is selectively insertable between an EKG lead set and the EKG signal input of a patient monitor. The selectively insertable filter permits the use of standard EKG lead sets in the presence of RF electrosurgery procedures, without risk of burning the patient at the site of the EKG electrodes.

Abstract: The present invention relates to an apparatus for enhancing signals In ECGs including artefacts, said apparatus comprising a mean value unit (4) for evaluating from an ECG signal the curve shape of a predetermined number of beats from the beginning of a QRS complex to the end of a T wave and forming therefrom a mean value beat. A subtracting unit (3) subtracts the mean value beat from the ECG signal of an actual beat to thereby obtain a residual signal. A FIR filter unit (4) subjects the residual signal to high-low-pass filtering and delays it to provide a filtered signal to which the mean value beat is added in an adding unit.

Abstract: An electrode for measuring a biomedical signal has: thin foil electrodes 11a to 11c which are formed into a square shape; lead wires 12a to 12c which are connected to the electrodes 11a to 11c, respectively; and a support section 13 which is made of a flexible material such as rubber or plastic, formed into a slender thin plate-like shape, and supports the electrodes 11a to 11c in a straight line and at constant intervals. The lead wires 12a to 12c are twisted.

Abstract: An implantable medical device for electrically stimulating the heart to beat generally includes a processor, a plurality of electrodes, a sense amplifier, a pulse generator, and a heart status monitor. The processor can determine when the patient has entered an environment of high electromagnetic interference. When this occurs, the processor forces the implantable device into a safe noise mode. While in the same noise mode (which preferably continues while the patient is experiencing the electromagnetic interference), the implantable device paces the heart on demand and inhibits pacing during the vulnerable period. The processor determines when the vulnerable period is occurring and when the heart needs to be paced by monitoring a status signal from the heart status monitor.

Abstract: A method and apparatus for monitoring an electrocardiograph waveform, and for returning an electrocardiograph trace to the middle of a display, such as a chart recorder strip. The monitoring circuit includes an amplifier and a switch for switching the frequency response curve of the monitoring circuit. In a first position, the switch causes the monitoring circuit to have a slow frequency response curve, which allows for accurate monitoring of ECG waveforms. In a second position, the switch causes the monitoring circuit to have a fast frequency response curve, which allows the amplifier of the monitoring circuit to quickly be brought out of saturation. The amplifier of the monitoring circuit becomes saturated when a defibrillation or pace pulse has been applied to a patient who is being monitored. The switch is controlled by a pulse waveform control signal that is provided by a microprocessor.

Abstract: A cardiac rhythm management system provides cross-chamber “soft blanking.” It senses desired electrical heart activity signals associated with a first chamber electrode while reducing unwanted signals (paces and depolarizations) associated with a second chamber of the heart. Detection of a cross-chamber event associated with the second chamber increase a time-varying first chamber sensing threshold, but does not result in completely ignoring signals associated with the first chamber for an appreciable amount of time. As a result, actual first chamber events are less likely to escape detection, such that critically important therapy is properly delivered to the patient.

Abstract: A device for providing natal support and alleviating pain in a pregnant woman includes a support member, an apron, and a strap, with the strap removably attached to the apron. The strap may be removed after installation and adjustment of the natal support on the pregnant woman. The natal support alleviates pain by providing support to the lower abdomen and distributing the weight of the fetus and enlarged uterus over a large portion of the lower back. Additionally, the strap facilitates installation and proper positioning of the natal support on the human body by holding the apron in place on the back while it is being adjusted.

Abstract: A system for monitoring an ECG during an MRI examination which permits the monitoring system to be located near the patient and which eliminates artifacts affecting the accurate reading of the ECG. The system allows for control of lead select and battery on stand by mode and can monitor battery state and lead off conditions.

Abstract: A multiple channel stimulator for applying electrical impulses to nerves of a mammal using a single power supply to drive a plurality of channels which are selectively activated to apply electrical impulses to nerve trunks through cuff electrodes. As a channel is activated, an isolation resistor in that channel is shorted out, providing a path of low resistance in that channel compared to the other channels, insuring that any leakage current or cross currents between channels is minimized, whereby improving the performance of the stimulator.

Abstract: There is provided an implantable cardiac pacing system or other cardiac monitoring system, having an enhanced capability of classifying intracardiac signals through a combination of DSP techniques and software algorithms. The implantable device has one or more DSP channels corresponding to different signals which are being monitored. Each DSP channel provides for amplification of the incoming signal; conversion from analog to digital form; digital filtering of the converted signals to provide filtered signals; operating on the filtered signals to provide slope signals; determining from the filtered and slope signals whenever an intracardiac event has been detected, e.g., R wave, P wave, etc.; and signal processing of the filtered and slope signals for a predetermined analysis interval after threshold crossing, for generating a plurality of signal parameters.

Abstract: A filter system for detecting and removing small amplitude, high frequency signals such as muscle artifact signals is provided. One form of the system includes a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors to identify, signal and remove muscle artifact or loose electrode signal contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal, such as the QRS portion of the ECG signal, prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal and while further providing the operator with the ability to manually or automatically activate the filters and to indicate the status of the filters on a printout or display.

Abstract: A noise detection system having a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors is provided to identify, signal and remove contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal.

Abstract: There is provided a vital information processing apparatus capable of effectively reducing small-amplitude noise and isolated noise without degrading an abrupt change portion in a processing target vital signal. A vital signal detected by a vital signal detector (10) is input from a vital signal input unit (20). A sync signal extractor (25) extracts, e.g., the QRS wave form of an electrocardiogram signal of the input signal and outputs the extracted wave as a sync signal (26). A preprocessor (30) performs predetermined preprocessing for the processing target vital signal, e.g., a K sound signal and outputs the preprocessed signal to median filters (40, 45). Each of the median filters (40, 45) filters the Korotkoff sounds using the QRS signal (26) as the index value and outputs the resultant signal.

Abstract: An adaptive filtering method and apparatus for reducing the level of an undesired noise component in an acquired physiological signal having a desired signal component. The acquired physiological signal is applied to one input of the adaptive filter, and a synthetic reference signal that is modeled so as to exhibit a correlation with the desired signal component is applied to another input of the adaptive filter. Thereafter, in a feedback manner, the adaptive filter iteratively adjusts the modeled synthetic reference signal so as to progressively generate a more accurate approximation of the desired signal component in the adaptive filter, which approximation becomes a reconstruction of the acquired physiological signal wherein the level of the undesired noise component is reduced.

Abstract: A method of reducing noise in a biological signal, such as an ECG signal, includes acquiring a biological signal, comparing the biological signal to a representative signal, and generating a predicted signal corresponding to the representative signal when the biological signal sufficiently matches the representative signal. The predicted signal is subtracted from the biological signal to produce a second signal, and a filter is applied to the second signal to produce a filtered signal. The predicted signal and the filtered signal then are combined to produce a noise-reduced signal.

Abstract: An implantable cardiac device includes electrodes for sensing and pacing the heart, and optionally, defibrillation electrodes. The IECG with a noise component sensed in the heart is processed to derive raw sense signals indicative of whether the sensed QRS complexe's range is outside a certain range. This range is dynamically adjusted to compensate for the noise component. Preferably this range is defined by a threshold signal generator which generates a threshold signal including a first part which varies dynamically in accordance with a preset criteria and a second part which is at least equal to the peak amplitude of the noise.

Abstract: A signal detector for detecting a biosignal with approximately known morpogy in a complex input signal (ECG), in particular for the detection of QRS complexes in an electrocardiogram. The detector has circuitry for detecting the maximum amplitude (PEAK) of the detected signal complex within a predetermined time window, with a threshold value discriminator, a detector parameter preselection circuit for determining an initial value for the detector parameter characterizing the detector sensitivity, which parameter determines the detector threshold value when responding to a detection signal in dependence on the maximum amplitude and a detector parameter timing circuit for adjusting a predetermined time dependence of the detector parameter and thus the detection threshold value.

Abstract: A sensitivity setting device and an electrocardiograph which includes the sensitivity setting device include a differential amplifier whose amplification factor is changed by a CPU and a CR differentiator connected to the differential amplifier for providing an appropriate electrocardiogram waveform. The CR differentiator includes capacitor and two parallel resistors connected with the capacitor with one of the resistors being connected to an analog switch which is switched on/off by the CPU. If there is an input electrocardiogram waveform from a pair of electrodes attached to a patient's body directly after the measurement of the electrocardiogram waveform, the electrocardiogram waveform is amplified with an initial set amplification factor by the differential amplifier and the resulting signal is inputted to the CR differentiator.

Abstract: In a method and apparatus for removing data outliers in measured signals in an implanted medical apparatus, such as data outliers produced by GSM disturbance picked up by an implanted cardiac stimulator lead and superimposed on the sensed cardiac activity signal, the signal from the implanted lead is subjected to median filtering. The median filtering minimizes, or eliminates, the effect of highly aberrational data points in the incoming signal, without the necessity of actually removing the components in the signal produced by the disturbance from the incoming signal itself. Since no portion of the actual incoming signal is removed by the median filtering, the data integrity of the sensed cardiac signal is preserved.

Abstract: A circuit and process for an active implantable medical device, particularly a cardiac type pacemaker or defibrillator of the "demand" type, for discrimination between parasitic signals and characteristic signals. Such a device includes a detection circuit (10) to collect a cardiac signal (SA), which may be a spontaneous or stimulated cardiac signal, of the bearer of the device. The collected cardiac signal includes a characteristic signal component and undesirable parasitic signal component. The device also includes a discriminating circuit (12-18) and technique for receiving as an input the collected cardiac signal and delivering at an output a signal (ST) desirably corresponding essentially to the characteristic signal, from which any parasitic signals have been removed.

Abstract: A method and system for providing highly accurate characterizations of waveform representations of heart function, such as QRS complexes, where such waveform representations are derived from electrocardiographic measurements. The method and system accomplish their objects via the following. One or more signals indicative of heart function are measured and sampled. One or more signal quality indexes are calculated for each of the measured and sampled one or more signals. The signal quality indexes are calculated by dividing a maximum sample value for each one or more measured and sampled signal by a calculated divisor. One or more weighting factors, dependent upon the calculated signal quality index of each of the one or more measured and sampled signals are calculated. And, a waveform representation composed of each of the one or more measured and sampled signals indicative of heart function multiplied by its calculated weighting factor is created.

Abstract: An implantable defibrillator, which may include cardioversion and pacemaker capabilities, which has EMI filters which are not susceptible to defibrillation shocks and which reduce or eliminate the effects of charging noise on sensing circuits used for continuous confirmation. A first filter capacitor is provided between a sense electrode, which may include pacing capabilities, and a ground reference within a hermetically sealed can containing a pulse/shock generator. A second filter capacitor is provided between a sensing/pacing reference electrode, which may also be a high voltage or shock electrode, and the ground reference. In addition, there is a third filter capacitor between the ground reference and the can. Preferably, the connections of the first, second and third filter capacitors are physically as well as electrically adjacent to each other. The filter capacitors are housed in the can and in or adjacent to a feedthrough assembly which passes through the can.

Abstract: The present invention provides an improved extracardiac indifferent electrode configuration for implantable medical devices that overcomes the deficiencies of known unipolar and bipolar cardiac sensing and pacing systems. In particular, the present invention provides an indifferent electrode configuration wherein a subcutaneous extracardiac electrode is advantageously positioned so as to provide a truly indifferent return or reference electrode that does not inadvertently stimulate torso muscle and is not subject to detecting myopotentials generated by adjacent torso muscle. In addition, by being placed outside the heart, the indifferent electrode allows the intracardiac catheter to maintain a low profile, i.e., allows the catheter to be as small as possible, and does not generate metallic ions or cause degradation of catheter materials by generating such ions.

Abstract: An intramyocardial activity detector for detecting repeating patterns of irregular intramyocardial Wenckebach activity in the heart of a patient is provided. The apparatus includes a mechanism measuring electrocardiogram (ECG) signals from the body, a mechanism for measuring respiratory signals from the body, and a processor electrically associated with the two mechanisms means for measuring to determine the presence of intramyocardial Wenckebach activity of two or more phases. The processor calculates Wenckebach basis function strengths that indicate the presence of voltage in the measured ECG signals caused by repeating patterns of irregular intramyocardial Wenckebach activity via a relationship that describes the measured ECG signals as comprising Wenckebach input being additive to respiratory interference.

Abstract: A heartrate monitor of the invention includes a signal receiver adapted for being coupled to at least one sensor coupled to a medical patient, for providing an ECG signal and a pacemaker detection signal. A pacemaker activity checker, responsive to the pacemaker detection signal and the ECG signal provides first and second output signals, the first output signal indicating the occurrence of a QRS complex in the vicinity of the pacemaker detection signal, and the second output signal indicating the occurrence of an overshoot in the vicinity of the pacemaker detection signal. An overshoot validator, responsive to the ECG signals and the second output signal indicates the validity of the indicated overshoot. A QRS detector, responsive to the ECG signal, indicates the occurrence of a QRS complex in the ECG signal.

Abstract: A linear phase high pass filter is disclosed using a slew rate limiter and a linear phase low pass filter in parallel with a delay for removing baseline wander from an ECG signal. The linear phase low pass filter is preferably a digital Infinite Impulse Response (IIR) filter. The slew rate limiter preferably includes a clipper and a unit delay. An input ECG signal is simultaneously presented to a slew rate limiter and IIR low pass filter combination and an electronic delay. Thereafter, the outputs from the slew rate limiter and IIR low pass filter combination and the delay are passed to a summer where the output from the slew rate limiter and the low pass filter is subtracted from the output of the delay to produce the output ECG signal representation. The combination of the output from the slew rate limiter and the low pass filter being subtracted from a delayed input signal produces a high pass filter. The resulting high pass filter has a relatively high -3 dB cutoff frequency of about 0.

Abstract: A plurality of magnetic field measurement units are arranged near a patient, a current source distribution and/or a current dipole in the patient are estimated on the basis of plurality of magnetic field distribution data measured by the magnetic field measurement units within a predetermined period of time. In particular, the current distribution and the current dipole at the desired time within the predetermined period of time are estimated by using spatiotemporal magnetic field distribution data measured by the plurality of magnetic field measurement units within the predetermined period of time and correlation information of the spatiotemporal magnetic distribution data. The current distribution and the current dipole are estimated by using cross-correlation information of noise data measured by the plurality of magnetic field measurement units.

Abstract: A method of reducing noise in a signal that represents a physiologic process includes obtaining multiple input signals, measuring a relationship between noise content of the input signals, and combining the input signals in consideration of the measured relationship to produce an output signal having low noise content. The multiple input signals may include, for example, two or more primary physiologic input signals or one or more primary physiologic input signals and two or more secondary input signals that represent noise. The method may further include dividing one or more ECG input signals and secondary input signals into set of segments, where each set of segments represents a beat of the ECG signal, measuring a relationship between noise content of corresponding points from successive sets of segments, and combining the input signals based on the measured relationship.

Abstract: A method and system for use in an EKG system are provided for selecting from a number of different voltage threshold detectors that detector likely to yield the most reliable data to be utilized in determining whether the electrical activity of the heart is normal or abnormal. The method and system work by first specifying a particular window of time during which the outputs of the number of different voltage threshold detectors are to be observed. On the basis of the observation, different detectors are specified as either active or inactive. For those detectors specified as active, the times at which their thresholds were crossed during the specified window of time are recorded, and on the basis of these recorded times, the temporal regularity of threshold crossing for each detector is calculated.

Abstract: A method and apparatus for reducing noise in an output signal produced from a plurality of input signals indicative of a repetitious phenomena exhibited by a signal source.

Abstract: Disclosed are apparatus and method for detecting electromagnetic interference (EMI), or noise, that may disrupt the proper operation of medical devices implantable in patients, such as cardiac stimulators. Circuitry of the detector of the invention is independent of other circuitry of the medical device. EMI is magnetically induced on an antenna that may be within the metal housing of the device in a receiver circuit, and the EMI signals are output to the noise detector. A variety of alert signals may be provided to the medical device circuitry to warn of the presence of EMI so that appropriate responses may be taken to insure the safety of the patient dependent on the device. The detector may share the telemetry antenna of the medical device, or utilize a separate, dedicated antenna to receive EMI. Alternative antennas external to the metal housing of the medical device include leads from the device to the heart of the patient, and a dedicated antenna in the non-metal header of the device.

Abstract: In a method and apparatus for suppressing electrode polarization components in a sensed cardiac signal, the sensed cardiac signal is added to either a differentiated or autocorrelated sensed cardiac signal and a difference is formed between the original sensed cardiac signal and the autocorrelated or differentiated signal, thereby extracting an evoked response component from the sensed cardiac signal, the evoked response component otherwise being overshadowed by the much higher-amplitude polarization component.

Abstract: An apparatus effectively removes after potential occurring after a electrical pulse is delivered in a cardiac rhythm management system such as a pacemaker system or cardioverter/defibrillator system having an electrode used for both sensing electrical activity of the heart and carrying the electrical pulse to the heart and a sense amplifier for detecting the electrical activity from the electrode. The apparatus includes a lowpass filter coupled to the electrode to filter the sensed electrical activity. A highpass filter is coupled between the lowpass filter and the sense amplifier to further filter the electrical activity passed from the lowpass filter. Equilibrium circuitry is included to allow passive filter components of the lowpass filter and the highpass filter to return to an equilibrium state following delivery of the electrical pulse.

Abstract: An apparatus and method for the filtering of signals collected during a period that includes a quiet ("signal-free") epoch and an event epoch is disclosed. The apparatus includes a means for generating electrical digitized signals of the event episode, memory for receiving and storing the digitized signals of the event episode, an event detector for determining the event epoch and the quiet epoch of the event episode in the digitized signals, a spectrum analyzer to analyze the power spectrum of the digitized signals of at least one event episode, an estimator to estimate electromagnetic interference (EMI) based on the digitized signals of the quiet epoch and the frequencies obtained in the spectral analysis; and a subtractor to subtract the estimated EMI from the digitized signals of the event epoch. The resulting signals are signals of the event epoch with reduced EMI.

Abstract: A heart pacemaker with improved detection of electrical signals which are used for triggering pacemaker functions, has a detection circuit for registering intracardial heart signals in which certain noise signals having a generally chromatic spectrum are superimposed on the signals to be detected, the detection circuit undertaking an adaptive, non-linear noise filter of those intracardial heart signals for converting the spectrum of the noise signals into an essentially white spectrum. The signals filtered by the non-linear noise filtering are supplied to a matched filter wherein correlation of these signals with a sought signal pattern takes place.