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 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 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: 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 heart stimulator has a pulse generator for producing stimulation pulses of varying amplitudes and varying durations for stimulating the heart of a patient, and an evoked response detector. The evoked response detector includes measuring and memory circuitry for measuring the charge delivered by a stimulation pulse. The measuring and memory circuitry determine and store, as a reference voltage, a charged voltage value related to the measured charge. Monitoring circuitry monitors the combined polarization and possible evoked response signal picked up from the patient's heart after the delivery of a stimulation pulse and derive a corresponding monitoring voltage value therefrom. A comparator compares the monitoring voltage value to the charged voltage value for determining, from the result of the comparison, the presence or absence of an evoked response.

Abstract: An implantable electrode for stimulating tissue has a piezoelectric electrode for electrically and mechanically stimulating tissue and for detecting electrical and mechanical evoked response of the stimulated tissue. An implantable lead and an implantable stimulation device employing such an electrode are described including diagnostic circuitry for making a diagnosis of the heart condition using such an electrode.

Abstract: A back-up pulse generator for a pacemaker having a first energy storing component for storing energy to be delivered in a stimulation pulse and connectable to means for conducting the stimulation pulse to the heart, the back-up pulse generator including a back-up pulse energy storing component for emitting a back-up pulse after a failure to sense an evoked response from a preceding stimulation pulse. The back-up pulse energy storing component substantially permanently stores energy at a higher voltage than the energy stored in the first energy storing component.

Abstract: A pacemaker system includes an electrode lead having a distal tip electrode for supplying stimulation pulses to cardiac tissue and a ring electrode, the electrode lead being connected to a cardiac stimulator. A detector is contained in a stimulator housing and is connected to the electrode lead for detecting electrical cardiac activity between said ring electrode and said tip electrode.

Abstract: An implantable medical device for in vivo electrochemical measurements of blood properties, such as measurements of, inter alia, oxygen pressure, glucose and pH, avoids the problem with the reference electrodes currently in use which cause inflammatory reactions of tissue, by forming the reference electrode of carbon, preferably activated pyrolytic carbon.

Abstract: A device for heart therapy has a tacharrythmia detector unit, a control unit and a current generator. The current generator controlled by the control unit emits via an electrode system a first, pulsed current to a physiological representative of the parasympathetic nervous system in order to activate same in response to detection of an impending or established arrhythmia. The current generator is further caused by the control unit, in the event of tachyarrythmia detection to emit, via the electrode system, a second current to a physiological representative of the sympathetic nervous system in order to block same.

Abstract: In a device for tissue stimulation, the stimulation energy is matched to the stimulation sensitivity of the tissue by altering the stimulation energy in steps upwardly until a tissue reaction is detected, or in steps downwardly until a tissue reaction fails to occur. In order to obtain a safety factor which is expressible in volts with the lowest possible current consumption, stimulation pulses are generated in the determination of the stimulation sensitivity having an amplitude at a voltage which is below the available voltage of a voltage source by a voltage value which corresponds to the safety factor, and the pulse duration is altered in the aforementioned steps. Stimulation subsequently takes place using the pulse duration found in this manner and at a pulse amplitude corresponding to the available voltage.

Abstract: An appliance for electrically stimulating tissue contractions of a living organism has circuitry for applying a stimulation potential to the tissue region to be stimulated and for applying a reference potential circuitry for detecting to the body of the living organism, stimulated tissue contractions. Following stimulation the stimulated tissue contraction is measured by a bipolar electrode between two adjacent tissue regions, the stimulation potential applied being to at least one of these tissue regions for the purpose of stimulating a tissue contraction.