Abstract: An object information acquiring apparatus that acquires information inside an object by receiving an acoustic wave that has arrived from inside the object through a layer having an acoustic impedance that is different from that of the object, and analyzing the acoustic wave, the object information acquiring apparatus comprises an acoustic wave probe that receives an acoustic wave and converts the acoustic wave into an electric signal; a whole image generation unit that generates a whole image, which is an image indicating information inside the object, based on the electric signal after the conversion; a partial image generation unit that extracts a partial image, which is a part of the whole image, from the whole image; and a similar image search unit that searches an area similar to the partial image, from the whole image.

Abstract: A system includes (i) a needle for insertion into a port of an implantable infusion device, and (ii) a receiver apparatus having a port location signal receiver module capable of receiving a signal from the implantable infusion device regarding spatial orientation of the port. The system further includes a processor operably coupled to the receiver apparatus and capable of determining the orientation of the needle relative to the port based on the received signal. The system also includes a display operably coupled to the processor. The processor is configured to cause the display to graphically render trajectory of the needle relative to the port. The port is graphically rendered as a target structure having a reference area. The needle is graphically rendered as an object moveable relative to the target structure. Occupation of the reference area by the object indicates trajectory alignment of the port and the needle.

Abstract: A method for determining the signal quality of samples in a physiological signal, in particular an electrocardiogram (ECG) signal, is provided. A supra-threshold sample sum, a noise threshold crossing sum, or both are calculated in a noise detection window including the sample to be evaluated, and low signal quality is indicated if either or both of the sums exceed respective values. ECG beat detections can then be labeled as unreliable based on the determination of low signal quality for one or more samples between the detections.

Abstract: One embodiment of the present invention relates to an implantable medical device (“IMD”) that can be programmed from one operational mode to another operational mode when in the presence of electro-magnetic interference (“EMI”). In accordance with this particular embodiment, the IMD includes a communication interface for receiving communication signals from an external device, such as a command to switch the IMD from a first operation mode to a second operation mode. The IMD further includes a processor in electrical communication with the communication interface, which is operable to switch or reprogram the IMD from the first operation mode to the second operation mode upon receiving a command to do so. In addition, the IMD includes a timer operable to measure a time period from when the processor switches the IMD to the second operation mode.

Abstract: Provided is a method and apparatuses for measuring a biological signal, in which a biological signal of an examinee is detected via at least one interface that touches skin of the examinee, and a dummy signal is detected via a dummy interface Noise that is generated by a fluctuation in the electrical characteristics of the at least one interface is removed from the biological signal using the biological signal and the dummy signal.

Abstract: Electrocardiogram wave data in which a component of cardiac massage is removed from the electrocardiogram wave data is generated, so that the electrocardiogram wave at the time of cardiopulmonary resuscitation is identified. An electrocardiogram wave processing system of obtaining and processing the electrocardiogram wave data includes a wave identification unit that identifies an electrocardiogram wave from the obtained electrocardiogram wave data, a feature selection unit that selects a feature pattern including a feature when a cardiac massage has been performed with respect to the electrocardiogram wave data identified by the wave identification unit, a generation unit that generates a component of the cardiac massage using the feature pattern selected by the feature selection unit, and a removal unit that removes, from the obtained electrocardiogram wave data, the component of the cardiac massage generated by the generation unit.

Abstract: A system denoises and rejects artifacts from cardiac signals, by accepting a cardiac signal from a patient, processing the cardiac signal from the patient using a frequency band width controllable choke to separate the cardiac signal into predefined frequencies, filtering each of the predefined frequencies to remove dynamic common noise, joining each of the predefined frequencies into a cardiac signal without the dynamic common noise, and providing feedback control of the filtering of each of the predefined frequencies.

Abstract: A system includes (i) a needle for insertion into a port of an implantable infusion device, and (ii) a receiver apparatus having a port location signal receiver module capable of receiving a signal from the implantable infusion device regarding spatial orientation of the port. The system further includes a processor operably coupled to the receiver apparatus and capable of determining the orientation of the needle relative to the port based on the received signal. The system also includes a display operably coupled to the processor. The processor is configured to cause the display to graphically render trajectory of the needle relative to the port. The port is graphically rendered as a target structure having a reference area. The needle is graphically rendered as an object moveable relative to the target structure. Occupation of the reference area by the object indicates trajectory alignment of the port and the needle.

Abstract: A medical device includes a pulse generator, a lead, and an electrode. The lead includes an electrode and a lead conductor connecting the pulse generator with the electrode via first and second conductive paths. The medical device includes first and second switches. The first switch is disposed along the first conductive path and includes an open state in the presence of a magnetic field and a closed state in the absence of the magnetic field. The second switch is disposed along the second conductive path and includes an open state when a voltage applied across the second switch is at or below a threshold voltage and a closed state when the voltage applied across the second switch exceeds a threshold voltage.

Abstract: Electrical crosstalk between two implantable medical devices or two different therapy modules of a common implantable medical device may be evaluated, and, in some examples, mitigated. In some examples, one of the implantable medical devices or therapy modules delivers electrical stimulation to a nonmyocardial tissue site or a nonvascular cardiac tissue site, and the other implantable medical device or therapy module delivers cardiac rhythm management therapy to a heart of the patient.

Abstract: Implantable medical device having elongated electric line(s) with function conductors, which are respectively multi-stranded and connected to respective function electrode pole(s) to deliver treatment/record diagnostic signals, wherein a first function conductor has a first strand, which, in the course of the longitudinal extension of the first function conductor in first longitudinal section(s) has a first coupling with a second function conductor suitable for coupling electromagnetic radio-frequency waves guided in the second function conductor at least in part in the first strand(s) of the first function conductor, and wherein the first strand(s) in the course of the longitudinal extension of the first function conductor in second longitudinal section(s) has a second coupling with second strand(s) of the first function conductor, suitable for coupling electromagnetic radio-frequency waves guided in the at least one first strand at least in part in the at least one second strand of the first function conduc

Abstract: Techniques are described for controlling effects caused when an implantable medical device (IMD) is subject to a disruptive energy field. The IMD may include an implantable lead that includes one or more electrodes. The IMD may further include a first component having a parasitic inductance. The IMD may further include a second component having a reactance. In some examples, the reactance of the second component may be selected based on the parasitic inductance of the first component such that an amount of energy reflected along the lead in response to energy produced by an electromagnetic energy source is below a selected threshold. In additional examples, the parasitic inductance of the first component and the reactance of the second component are configured such that an amount of energy reflected along the lead in response to a frequency of electromagnetic energy is below a selected threshold.

Abstract: There is provided an implantable cardiac pacing system or other cardiac monitoring system having an enhanced capability to classify 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 most preferably amplifies the incoming signal, converts the signal from analog to digital form, digitally filters the converted signals to provide a filtered signal, operates on the filtered signal to provide a slope signal, determines from the filtered and slope signals when an intracardiac event has been detected, signal processes the filtered and slope signals for a predetermined analysis interval after threshold crossing, and generates a plurality of wave parameters corresponding to the signal.

Abstract: Implantable medical leads with magnetic shielding and methods of shielding implantable leads from magnetic fields during medical procedures such as magnetic resonance imaging (MRI) are disclosed. An exemplary implantable medical lead includes a helically coiled inner electrode conductor wire, a helically coiled outer electrode conductor wire disposed radially about the inner electrode conductor wire, and at least one layer of insulation that electrically isolates the inner and outer electrode conductor wires. The inner electrode conductor wire can have a hollowed, multifilar configuration including six or more co-radially wound wire filars. The outer electrode conductor wire is electrically isolated from the inner electrode conductor wire, and may have either a single or double filar configuration.

Abstract: Electrocardiogram wave data in which a component of cardiac massage is removed from the electrocardiogram wave data is generated, so that the electrocardiogram wave at the time of cardiopulmonary resuscitation is identified. An electrocardiogram wave processing system of obtaining and processing the electrocardiogram wave data includes a wave identification unit that identifies an electrocardiogram wave from the obtained electrocardiogram wave data, a feature selection unit that selects a feature pattern including a feature when a cardiac massage has been performed with respect to the electrocardiogram wave data identified by the wave identification unit, a generation unit that generates a component of the cardiac massage using the feature pattern selected by the feature selection unit, and a removal unit that removes, from the obtained electrocardiogram wave data, the component of the cardiac massage generated by the generation unit.

Abstract: A method of processing a raw acceleration signal, measured by an accelerometer-based compression monitor, to produce an accurate and precise estimated actual depth of chest compressions. The raw acceleration signal is filtered during integration and then a moving average of past starting points estimates the actual current starting point. An estimated actual peak of the compression is then determined in a similar fashion. The estimated actual starting point is subtracted from the estimated actual peak to calculate the estimated actual depth of chest compressions. In addition, one or more reference sensors (such as an ECG noise sensor) may be used to help establish the starting points of compressions. The reference sensors may be used, either alone or in combination with other signal processing techniques, to enhance the accuracy and precision of the estimated actual depth of compressions.

Abstract: A medical device includes a pulse generator, a lead, and an electrode. The lead includes an electrode and a lead conductor connecting the pulse generator with the electrode via first and second conductive paths. The medical device includes first and second switches. The first switch includes a non-conductive state in the presence of a magnetic field, the non-conductive state preventing formation of the first conductive path between the pulse generator and the electrode. The second switch includes a non-conductive state that prevents formation of the second conductive path between the pulse generator and the electrode. The first switch in the non-conductive state and the second switch in the non-conductive state electrically shields the electrode from electromagnetic radiation and induced voltages during a magnetic resonance imaging procedure.

Abstract: An implantable medical device has a first module for performing telemetry communications with another device and a second module for delivering a high voltage therapy to a patient. The first module is configured to detect a communication error, and the second module is configured to determine a need for the therapy and to charge a capacitor in response to the need for the therapy. The second module is configured to suspend the capacitor charging in response to receiving a notification from the first module corresponding to detecting a communication error.

Abstract: One embodiment of the present invention relates to an implantable medical device (“IMD”) that can be programmed from one operational mode to another operational mode when in the presence of electro-magnetic interference (“EMI”). In accordance with this particular embodiment, the IMD includes a communication interface for receiving communication signals from an external device, such as a command to switch the IMD from a first operation mode to a second operation mode. The IMD further includes a processor in electrical communication with the communication interface, which is operable to switch or reprogram the IMD from the first operation mode to the second operation mode upon receiving a command to do so. In addition, the IMD includes a timer operable to measure a time period from when the processor switches the IMD to the second operation mode.

Abstract: The present invention relates to a method for recognizing and measuring heartbeat in physical training, in which method individual heartbeats are recognized and measured from the electrical signal of the heart, the EKG signal, on the area of waist and/or on the body area below the waist by means of two or more electrodes (2, 3) integrated to an outfit (1) or to a part of an outfit, and/or by means of two or more electrodes integrated to one or several wearable sensors, and for calculating various quantities describing the function of the heart. In the method in accordance with the invention, for recognizing and measuring heartbeat, the signals received from the heart are processed and examined with two or more different ways for improving the reliability of calculation and for decreasing the impact of noises.

Abstract: A method of detecting a cardiac event in a medical device that includes sensing a cardiac signal from a plurality of electrodes, determining amplitudes of the sensed cardiac signal during a predetermined sensing window, determining a noise to signal ratio corresponding to the determined amplitudes, and determining the sensed cardiac signal during the predetermined sensing window is corrupted by noise in response to the determined noise to signal ratio being greater than a noise to signal ratio threshold.

Abstract: The presence or absence of objects is determined by interrogating or exciting transponders coupled to the objects using pulsed wide band frequency signals. Ambient or background noise is evaluated and a threshold adjusted based on the level of noise. Adjustment may be based on multiple noise measurements or samples. Noise detection may be limited, with emphasis placed on interrogation to increase the signal to noise ratio. Match filtering may be employed. Appropriate acts may be taken if detected noise is out of defined limits of operation, for example shutting down interrogation and/or providing an appropriate indication.

Abstract: The invention relates to a physiological sensor system for recording electric measuring signals in a magnetic resonance device, comprising at least one measuring electrode, a signal amplifier unit in a shielded housing that is placed in close proximity to a patient and a signal processing unit for preparing the measuring signals. According to the invention, the measuring electrode is connected to the signal amplifier unit via a cable connection. The invention is characterized in that the cable connection comprises a low-ohm conductor, which is connected to the measuring electrode by means of a first electric resistor on a first end and to the signal amplifier unit by means of a resistance between the skin and the measuring electrode. The development of heat caused by an induced current is concentrated on the resistors, so that there is no risk of burning to the patient.

Abstract: An electromagnetic interference (EMI) filter is provided to attenuate potentially damaging high frequency electromagnetic interference from interfering with the operation of a hermetically sealed implantable medical device. In one embodiment, the EMI filter is joined to a bypass unit that is configured to provide an energy path for the delivery of an energy pulse. The bypass unit, in one embodiment, may include a non-linear device in parallel with an impedance component. The non-linear device can be a DIAC, a MOSFET, or any other non-linear semiconductor array. The EMI filter may be located within the header assembly, the feedthrough assembly, or located proximate to a pulse generator along the energy delivery path.

Abstract: An implantable cardiac rhythm management (CRM) device includes a sensing and detection circuit that senses at least one cardiac signal and detects cardiac electrical events from the sensed cardiac signal using a detection threshold that is adjusted based on a dynamic noise estimation. The sensed cardiac signal is filtered to produce a filtered cardiac signal having a signal frequency band and a noise signal having a noise frequency band. The noise frequency band is substantially different from the signal frequency band. A dynamic noise floor is produced based on the noise signal and used as the minimum value for the detection threshold. A cardiac electrical is detected when the amplitude of the filtered cardiac signal exceeds the detection threshold.

Abstract: A system, method, or device determines whether noise is present on a sampled and/or digitized sensed intrinsic cardiac signal based on a moving count of turning/inflection points of the signal. If noise is detected, the manner in which the cardiac signal is acquired, or the manner in which the device operates in response to the acquired cardiac signal (or both) is altered to reduce the risk of erroneously detecting noise as a heart depolarization and, therefore, inappropriately triggering or withholding therapy.

Abstract: A medical device is configured to attenuate emission of electromagnetic radiation and comprises a housing, a circuit assembly mounted in the housing, and a panel coupled to the housing and to the circuit assembly. The panel comprises a first conductive region on an interior surface of the panel that is configured to be capacitively coupled to the ground, an opening substantially adjacent to the first conductive region, a second conductive region on the interior surface that is configured to be coupled to ground, and a non-conductive region on the interior surface between the first conductive region and the second conductive region.

Abstract: A grounding arrangement in a system using the same connector for 5- and 12-lead connection in ECG-measurement. If 5-lead configuration is used, the connector elements of the 12-lead connection are used for grounding of lead wire shields through a current limiting circuit exhibiting non-linear voltage-current characteristics.

Abstract: An implantable cardiac stimulation device, mode switchable between atrial tracking and atrial non-tracking pacing modes includes a threshold control for controlling atrial sensing threshold. The threshold control reduces the sensing threshold from a first threshold used during the atrial tracking pacing mode to a second threshold between the first threshold and the noise for use during the atrial non-tracking pacing mode. The necessity for readjusting the atrial sensing threshold is based upon the ratio of the sensing threshold and atrial amplitudes or upon a diagnostic distribution of atrial amplitudes.

Abstract: A method and device for filtering an input signal containing wanted signal components and unwanted signal components, wherein the signal is modeled as a set of polynomials. Polynomials from the set are identified to model the unwanted signal components. These unwanted signal components are removed from the input signal by removing the polynomials identified as modeling the unwanted signal components from the set of polynomials to thereby leave in the input signal only the wanted signal components. According to an alternative, polynomials from the set are identified to model the wanted signal components, and the polynomials identified as modeling the wanted signal components are outputted as an estimate of the wanted signal components substantially free from the unwanted signal components. According to another aspect, a weighting factor indicative of signal strength is determined for each polynomial and these weighting factors are summed to provide an estimate of the strength of the input signal.

Abstract: A telemetry system for radio-frequency communications between an implantable medical device and an external device providing improved noise immunity is disclosed. Multiple communications channels are used to enable establishment and re-establishment of communications between a particular pair of devices in a multiple device environment.

Abstract: In an implantable heart stimulating device, system and method, a control circuit has first and second circuits for sensing and pacing. The first circuit can be connected to a first electrode member suited to be positioned in or at a first ventricle of the heart. The second circuit can be connected to a second electrode member suited to be positioned in or at a second ventricle of the heart. The control circuit is able to detect whether signals sensed by the second circuit are likely to be far field signals. The control circuit performs this detection by at least determining whether, during a predetermined time (length, more signals are sensed by the second circuit than by the first circuit.

Abstract: A method of analysis of medical signals which uses wavelet transform analysis to decompose cardiac signals. Apparatus for carrying out the method, and cardiac apparatus adapted to employ the method are also described.

Abstract: An implantable cardiac rhythm management (CRM) device includes a sensing and detection circuit that senses at least one cardiac signal and detects cardiac electrical events from the sensed cardiac signal using a detection threshold that is adjusted based on a dynamic noise estimation. The sensed cardiac signal is filtered to produce a filtered cardiac signal having a signal frequency band and a noise signal having a noise frequency band. The noise frequency band is substantially different from the signal frequency band. A dynamic noise floor is produced based on the noise signal and used as the minimum value for the detection threshold. A cardiac electrical is detected when the amplitude of the filtered cardiac signal exceeds the detection threshold.

Abstract: System and techniques for distributed monitoring of cardiac activity include selective T wave filtering. In general, in one implementation, a distributed cardiac activity monitoring system includes a monitoring apparatus, with a selectively activated T wave filter, and a monitoring station. The monitoring apparatus can include a communications interface, a real-time QRS detector, a T wave filter, and a selector that activates the T wave filter to preprocess a cardiac signal provided to the real-time QRS detector in response to a message. The monitoring station can communicatively couple with the monitoring apparatus, over a communications channel, via the communications interface and can transmit the message to the monitoring apparatus to activate the T wave filter based at least in part upon a predetermined criteria (e.g., abnormal T waves for an individual, as identified by a system operator).

Abstract: A method is provided, the method comprising detecting a magnetic resonance imaging (MRI) interference signal and enabling at least one preventive measure to protect an implantable medical device from interference by the magnetic resonance imaging (MRI) interference signal. The method also comprises switching from a first sensing mode more affected by the magnetic resonance imaging (MRI) interference signal to a second sensing mode less affected by the magnetic resonance imaging (MRI) interference signal.

Abstract: An apparatus and method is provided for improving the quality of electrocardiogram (ECG) signals obtained from a patient undergoing magnetic resonance imaging (MRI) wherein the ECG signal has relatively high levels of noise or interference voltages induced on it by changing magnetic fields. The apparatus includes the arrangement of a differential amplifier, a prefilter, a signal limiter (SL) circuit and an intermediate amplifier with an integral low pas filter. The prefilter limits the rise time or high frequency component of the noise or interfering voltages induced on the ECG that are presented to the signal limiter.

Abstract: A method and an apparatus for reducing coupled electrical energy resulting from an electromagnetic field. Embodiments of the present invention provide for an elongate body having a proximal end portion, a middle portion, and a distal end portion and at least one coil wound about at least one of the proximal end portion, the middle portion, and the distal end portion, the coil to provide for filtering of radio frequency (RF) signal-coupled electrical energy.

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: An implantable cardiac rhythm management device is configured to estimating the noise level and noise floor in a sensing channel by measuring the magnitude of signal in the sensing channel when noise is determined to be present or absent, respectively. The presence or absence of noise may be determined by computing the density of local peaks or inflection points in an electrogram waveform. The computed local peak density is then used to set or clear a noise flag, which signifies whether noise is present or not. A noise statistic computed from samples of the electrogram signal obtained through a sensing channel may then be used to estimate a noise level or a noise floor.

Abstract: A system, method, or device determines whether noise is present on a sampled and/or digitized sensed intrinsic cardiac signal based on a moving count of turning/inflection points of the signal. If noise is detected, the manner in which the cardiac signal is acquired, or the manner in which the device operates in response to the acquired cardiac signal (or both) is altered to reduce the risk of erroneously detecting noise as a heart depolarization and, therefore, inappropriately triggering or withholding therapy.

Abstract: A method of obtaining an electrocardiograph (ECG) of a patient located in a turbulent electromagnetic environment. The method includes recovering an ECG signal from a patient. The signal, including added noise, is recovered near the cardiac region as the differential signal resulting from signals delivered by two electrodes forming part of a first measurement loop. The signal further consists of simultaneously recovering from the patient a second measurement signal incorporating at least the noise, as a differential signal resulting from the signals delivered by two electrodes forming part of a second measurement loop distinct from the first measurement loop. Then, the second measurement signal is added or subtracted from the first noisy ECG signal, in real time. The second measurement signal is as a function of the polarity of the noise in the second signal relative to the noise in the first noisy ECG signal.

Abstract: In an apparatus for determining the actual status of a piezoelectric sensor in a medical implant, electrical charges generated in the sensor, in response to changes in acceleration and/or gravitational force or other loads acting on the sensor, are continuously detected and the charges are then removed from the sensor, thereby maintaining the voltage across the sensor at a substantial constant zero level. The detected charges, both negative and positive, are integrated, thereby providing a resulting integrated signal representing the actual status of the sensor. The integrated signal is then evaluated for determining the physical activity and/or the posture of a patient in whom the medical implant is implanted.

Abstract: A method of processing a raw acceleration signal, measured by an accelerometer-based compression monitor, to produce an accurate and precise estimated actual depth of chest compressions. The raw acceleration signal is filtered during integration and then a moving average of past starting points estimates the actual current starting point. An estimated actual peak of the compression is then determined in a similar fashion. The estimated actual starting point is subtracted from the estimated actual peak to calculate the estimated actual depth of chest compressions. In addition, one or more reference sensors (such as an ECG noise sensor) may be used to help establish the starting points of compressions. The reference sensors may be used, either alone or in combination with other signal processing techniques, to enhance the accuracy and precision of the estimated actual depth of compressions.

Abstract: A system and method for reducing the amount of noise causes by inductive elements within an implantable medical device. In particular, the invention provides a system for gradually initiating and terminating the current flow within inductive elements such as transformers that are used to charge energy storage devices such as high-voltage capacitors of an implantable cardio/defibrillator. This more gradual change in the rate of current flow prevents ground shifts and subsequent noise spikes within the device. This, in turn, allows cardiac signals to be sensed more accurately by sensing circuits, preventing oversensing, and minimizing the occurrence of inappropriate shock delivery.

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: 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: A signal evaluation method for detecting QRS complexes in electrocardiogram signals incorporates the following process steps: sampling of the signal (4) and conversion to discrete signal values (x(n)) in chronological order, determining the sign of each signal value (x(n)), continuous checking of the signs of consecutive signal values (x(n)) for the presence of a zero crossing between two consecutive signal values (x(n)), determining the number (D(n)) of zero crossings in a defined segment (N) of the consecutive signal values (x(n)), and comparing the determined number of zero crossings (D(n)) to a defined threshold value, wherein an undershoot of the threshold value signifying the presence of a QRS complex (5, 6, 7) in the defined segment of the signal curve (4).

Abstract: A system and method for removing narrowband noise from an input signal in which notch filters having notch frequencies corresponding to the noise are dynamically adjusted in accordance with a detected noise spectrum. The method may be applied to telemetry systems for implantable medical devices such as cardiac pacemakers to result in improved noise immunity.

Abstract: An apparatus for measuring electrical signals emanating from a body of a patient, and, in particular, from the patient's heart, comprises a catheter having an electrode array, preferably on its distal end. The apparatus of the invention further comprises a first amplifier for measuring a voltage from a first electrode of the array, and a cascade of differential amplifiers, each of which measures a voltage difference between two successive electrodes in the array.