Abstract: A heart monitoring device has a control circuit, the control circuit being adapted to be electrically connected to electrode surfaces arranged at two different positions of the heart. The control circuit derives an impedance value indicative of the impedance between the electrode surfaces. Furthermore, the control circuit is arranged to determine and monitor a relationship between a positive rate of change and a negative rate of change of the impedance value. The device can, in particular, be used to detect and treat a systolic dysfunction of a heart.

Abstract: A multi-chamber pacing system has a pulse generator for successively delivering pacing pulses to chambers of a patient's heart. Evoked response detectors having blanking intervals following the delivery of pacing pulses include sensing elements for sensing IEGM-signals from each of the heart chambers and an integrating unit that integrates the IEGM-signal within evoked response detection time windows after delivery of pacing pulses for detecting evoked response. The evoked response detection time window for a heart chamber contain at least one blanking interval resulting from delivery of a pacing pulse to another chamber and each of the sensed IEGM signals having a generally known morphology. An integral reconstructing unit reconstructs the time integral of the IEGM signal from one of the heart chambers in the blanking interval following delivery of a pacing pulse to another heart chamber.

Abstract: An implantable bi-ventricular heart stimulating device (10) has a control circuit with first and second sensing circuits for respectively sensing in the two ventricles and first and second stimulation circuits for respectively stimulating the two ventricles. The control circuit determines whether a signal, sensed by said second sensing circuit, occurs essentially simultaneously with a signal sensed by the first sensing circuit. Furthermore, the control circuit determines whether a further signal is sensed by said second sensing circuit within a predetermined time interval which follows after the signal sensed by the second sensing circuit but within the same time cycle as that signal. If this occurs, the control circuit determines whether the sensed signals represent actual cardiac events, or are likely the result of far field detection.

Abstract: A multi-chamber pacing system has a pulse generator for successively delivering pacing pulses to chambers of a patient's heart, and IEGM signal detectors, having blanking intervals following the delivery of pacing pulses, including sensing circuits for sensing IEGM-signals from each of the heart chambers. Each of said sensed IEGM signals has a generally known morphology. A signal-reconstructing unit reconstructs the IEGM signal from one of the heart chambers in the blanking interval following delivery of a pacing pulse to another heart chamber.

Abstract: A pacemaker has a pulse generator for delivering stimulation pulses to a patient's heart, a sensor for measuring a parameter related to cardiac output, and a control unit for controlling the delivery of stimulation pulses from the pulse generator. The control unit includes an altering unit for altering at least one of the VV delay between consecutive stimulation pulses to the right and left ventricles and the AA delay between consecutive stimulation pulses to the right and left atria. The sensor measures the parameter in various time windows within a time of operation of predetermined VV- or AA-delay values. A determining unit includes a calculation unit for calculating an average value of the measured parameter during each of said time windows and the determining unit uses these average values to determine which one of the VV- and/or AA-delay values results in a higher cardiac output.

Abstract: An implantable bi-ventricular heart stimulating device has a control circuit that within a time cycle, delivers pacing pulses with both first and second pacing circuits with a time gap between a pacing pulse delivered by these pacing circuits. The time gap can be such that a pacing pulse delivered by the second pacing circuits falls substantially within a first time interval in which an evoked response can be expected to a pacing pulse delivered by the first pacing circuit. The control circuit performs a temporary modification of the operation of the device such that during at least one time cycle no pacing pulse is delivered by the second pacing circuit during the first time interval.

Abstract: A cardiac pacemaker has a pulse generator for delivering stimulation pulses to a patient's heart and a control unit for controlling the delivery of the stimulation pulses from the pulse generator. The control unit includes an altering unit for altering the AV-delay value from a predetermined first AV-delay value to a predetermined second AV-delay value, and back to the first AV-delay value. A sensor measures a parameter related to cardiac output of the patient, the sensor measuring this parameter in a time window within a time of operation with the first AV-delay value, and in a time window within the time of operation with said second AV-delay value, and in a time window within the time of operation after the return back to the first AV-delay value. A calculation unit calculates respective average values of the parameter during each of the time windows, and a determining unit determines from these average values which of the AV-delay values results in a higher cardiac output.

Abstract: In a method and an apparatus for verifying the occurrence of an evoked response in the atrium, following emission of a stimulation pulse to the atrium, an impedance signal is measured in a time window following the emission of the stimulation pulse. The impedance signal is high pass filtered and a characteristic of the high pass filtered impedance signal, such as its amplitude or its morphology, is compared to a predetermined criterion in a comparison unit. The occurrence of an evoked response is verified if the characteristic equals or exceeds the predetermined criterion. The occurrence of an evoked response can therefore be monitored on a beat-to-beat or pulse-to-pulse basis.

Abstract: A pacemaker has a stimulation threshold measuring unit which measures a stimulation threshold voltage value of a heart and a pulse generator for deliverying stimulation pulses of variable amplitudes and durations to the heart. The pulse generator is controlled by a control unit to deliver the stimulation pulses with respective amplitudes related to the measured threshold value and a safety margin. The control unit automatically changes the safety margin in accordance with a predetermined relationship between the safety margin and the measured threshold value, so that the safety margin is progressively increased as the measured threshold value increases.

Abstract: In an implantable electrode for an electrode lead for a stimulation device for stimulating tissue, the electrode is formed as a biocompatible piezoelectric electrode which is adapted to be in direct electrical contact with tissue for electrically and mechanically stimulating the tissue and for detecting electrical and mechanical evoked response of the stimulated tissue. The stimulation device can include circuitry for making a diagnosis of a heart condition using signals received from the implantable electrode.

Abstract: In a method and an apparatus for measuring a concentration of at least one dissolved chemical entity in a liquid medium, employing a counter electrode, a working electrode and a reference electrode immersed in the liquid medium, at least one measurement potential is applied to the working electrode relative to the reference electrode, corresponding to a measurement voltage during at least a part of a measurement period, thereby causing the dissolved chemical entity to participate in an electrochemical reaction at the working electrode, the chemical reaction resulting in a measurement evoked current. Compensation for potential drift at the reference electrode is achieved by comparing the measurement evoked current with a predetermined value, and decreasing or increasing the measurement voltage by an incremental value, in a negative or a positive incremental step, so that the measurement current approaches a predetermined value.

Abstract: In a method and a device for electrochemical determination of the concentration of at least one dissolved chemical entity in a liquid medium, a measurement voltage U is impressed on a working electrode, in contact with the liquid medium, relative to a counter electrode, thereby causing the dissolved chemical entity to react by oxidation or reduction at the working electrode, producing a measurement evoked current. The measurement evoked current is compared to a predetermined value, and the measurement voltage U is adjusted so that the measurement evoked current is substantially equal to the predetermined value, and thus remains substantially constant during measurements. A difference &Dgr;U=U−Umin is formed, which corresponds to an oxidation/reduction reaction at the working electrode, with Umin being a minimum voltage selected as a reference level. This difference is used to calculate concentration variations of the chemical entity in the liquid.

Abstract: In a method and apparatus for eliminating the influence of double-layer capacitance in electrochemical measurements of the concentration of oxygen in blood using a working electrode, a reference electrode and a counter-electrode in contact with blood, a first potential is applied to the working electrode during a first measurement period and a second potential is applied to the working electrode during a second measurement period, the second potential being equal to a floating potential of the working electrode measured while the working electrode is in an electrically floating state. Charge generated by an output current from the working electrode respectively in the first and second measurement periods is accumulated, and the accumulated charge is used as a proportional representation of the amount of oxygen in the blood.

Abstract: An implantable lead for an implantable active device, such as a pacemaker, has at least two electrodes, and a proximal end adapted for electrical and mechanical connection to the active device and a distal end opposite the proximal end. A ventricular electrode is carried at the distal end of the lead for sensing and/or electrical interaction with the ventricle, and an atrial electrode is carried on the lead for sensing and/or electrical interaction with the atrium, the atrial electrode being disposed between the proximal end and the ventricular electrode. The lead at its distal end has a first part with a first predetermined length, which is between 9 and 13 cm, and which exhibits a first stiffness. Adjacent to this first part is a second part, having a second predetermined length, which exceeds 15 cm, and which exhibits a second stiffness.

Abstract: A pressure and heart movement sensor for a heart stimulator, includes an electrode system for implantation with an electrode cable containing at least two electrical conductors leading to electrode poles. A measurement device is arranged to measure an electrical quantity between the electrical conductors, which quantity varying according to the pressure applied to the electrode cable. Alternately, the electrode cable contains at least one electrical conductor, and the measurement device is arranged to measure the impedance between the conductor and ambient medium and to deliver an output signal, which varies according to the impedance measured, when the electrode cable is subjected to pressure.

Abstract: For detecting tachyarrhythmia of the heart, the partial pressure of gases physically dissolved in the blood is measured, preferably the partial oxygen pressure pO.sub.2, and a fast variation and/or a variation of the measured partial pressure pO.sub.2 that exceeds a prescribed degree is utilized as a criterion for the detection of a tachyarrhythmia. An apparatus for treating tachyarrhythmia of the heart operating according to the above method includes a sensor for identifying the partial pressure of gases dissolved in the blood, an evaluation unit supplied with the sensor output for recognizing rapid changes of the partial pressure or changes of the partial pressure that exceed a prescribed degree, the output of the evaluation unit being connected to circuitry for triggering the tachyarrhythmia treatment.