Abstract: An accelerometer has a cantilever beam supported at one end and having an opposite free end with a longitudinal direction between the supported end and the free end, the beam being formed of a piezoelectric layer and a supporting layer. An inertial, sensing mass is mounted at the free end of the beam, and is located eccentrically relative to the longitudinal direction of the beam. The accelerometer has a primary direction of sensitivity to acceleration forces, and a secondary direction of sensitivity, which is orthogonal to the primary direction and in which the sensitivity is negligible. The secondary direction forms an angle relative to the longitudinal direction of the beam such that a line coinciding with a force proceeding through the center of gravity of the inertial mass, and which is directed in the secondary direction, also intersects the beam.

Abstract: A heart stimulator has a stimulation energy delivering assembly, including at least one lead adapted for implantation in contact with cardiac tissue, and an atrial arrhythmia detector, and a control unit connected to the stimulation energy delivering assembly and to the detector. The control unit controls the stimulation energy delivering assembly to deliver at least one atrial arrhythmia abolishing therapy and, if continued atrial arrhythmia is detected, to deliver antithrombus stimulation energy pulses of lower energy than a defibrillation shock, but with different timing and with sufficient energy for producing atrial contraction for increasing hemodynamic blood transportation away from the atrium and for preventing thrombi formation in the atrium. For a patient suffering from a chronic or paroxysmal non-curable atrial arrhythmia, the control unit controls the stimulation energy delivering assembly to deliver the antithrombus energy without any preceding arrhythmia abolishing therapy.

Abstract: A medical electrode cable has an exterior, tubular insulating sheath containing a number of side-by-side wires arranged substantially parallel to the sheath and helically proceeding around and,along a longitudinal axis. At least one of the wires is a low-resistivity conductor, and at least two of the wires are high-resistivity conductors. All of the wires have equal diameters. The low-resistivity conductor is a wire having a core of a low-resistivity material encased in an exterior jacket of the same high-resistivity material which forms the high-resistivity conductors.

Abstract: A sensor arrangement, and a heart stimulator employing such a sensor arrangement, identify bending of an electrode lead. A lead which is implantable in a patient is subjected to bending due to movement of the surrounding tissue, and the lead has a deformation sensor therein which emits an electrical signal dependent on the magnitude and orientation of the bending. The deformation sensor can be formed by two parallel channels extending from the tip of the lead within an insulating sleeve of the lead which encloses a conductor element. The channels are filled with an electrically conductive fluid and are connected at their opposite ends to a resistance measuring unit. Bending of the lead causes the resistance of the fluid to change, which is measured by the resistance measuring unit. The channels can be disposed asymmetrically relative to a longitudinal axis of the lead, so that orientation of the bending can also be identified by comparing signals from the respective channels to each other.

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: A medical implant such as a heart stimulator has a detector which detects an extracorporeally generated interrogation signal for at least one predetermined working parameter of the medical implant. The interrogation signal is generated by an interrogation signal device capable of only unidirectional communication to the medical implant. The implant includes a response signal generator which generates an extracorporeal detectable response signal, detectable, for example, by a stethoscope, which indicates only if the interrogated working parameter has a satisfactory value or a non-satisfactory value.

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: An adaptive delta modulator has an A/D-converter controlled by a digital control signal, which is also supplied to a drift compensation logic circuit, which generates a drift compensated digital output signal by an appropriate shift operation of the applied control signal, dependent on an initially detected shift in the A/D converter.

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: An implantable cardiac monitoring device as an A-mode ultrasound probe which is adapted to be positioned in the right ventricle of a heart, and which emits an ultrasound signal which is reflected from one cardiac segment of the left ventricle of the heart, and the ultrasound probe receives the resulting echo signal. The delay between the emission of the ultrasound signal and the reception of the resulting echo is measured, and from this delay a position of the cardiac segment is determined. The position of this cardiac segment, at least one reflecting the signal, is related to cardiac performance, and thus the monitoring device determines, from the detected position of the cardiac segment, the cardiac performance.

Abstract: An implantable heart stimulator has a connector for an electrode lead in the form of a self-contained tubular connector, which can be placed as a unit in one-half shell of a stimulator housing, together with a hybrid circuit and a power source. The other half shell of the stimulator housing can then simply be placed over these assembled components and joined thereto by welding, thereby considerably simplifying manufacture and assembly of the stimulator. When an even number of such self-contained connector tubes is employed, the two stimulator housing half shells can be identical.

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: A heart stimulator has a circuit for determining cardiac output and for producing a control signal corresponding to the determined cardiac output, and a controller for controlling cardiac stimulation dependent on the control signal. The circuit for determining cardiac output includes a pressure sensor which measures pressure in the right ventricle and which generates an electrical pressure signal corresponding to the measured pressure, and an integrator supplied with the pressure signal which integrates the pressure signal between a start time and stop time to produce an integration result corresponding to the cardiac output, which is used to form the control signal. The pressure signal is bandpass filtered during a systolic phase to identify opening of a valve at the right ventricle as the start time, and to identify closing of the valve as the stop time.

Abstract: An ischemia detector has a patient workload sensor and a patient breathing sensor which emits a signal representing sensed workload, and a patient breathing sensor which emits a signal representing sensed breathing activity of a patient. These signals are supplied to a detector unit which identifies a state of ischemia upon an occurrence of a predetermined relation between the sensed workload and the sensed breathing activity. This predetermined relation is a sensed low workload and a simultaneously sensed high breathing activity.

Abstract: The above objects are achieved in accordance with the principles of the present invention in a female connector part for cooperation with an elongated male connector part, the female connector part being intended for use in a pacemaker housing and having a longitudinal bore adapted to receive the male connector part. An element carrying resilient tongues, disposed at a small inward angle, i.e. inward from the opening of the female connector part, relative to a plane orthogonal to the longitudinal axis of the bore. The tongues are movable between a first position at which the respective tips of the tongues can engage the male connector part in the bore, and a second position at which the tips of the tongues do not engage the male connector part in the bore. The female connector part also includes a sleeve which is movable between two positions respectively corresponding to the first and second positions of the tongues.

Abstract: An implantable heart stimulator has a control unit which controls the delivery of stimulation pulses to a subject, and an ischemia detector. The control unit is connected to the ischemia detector and reduces the stimulation rate in response to a detection of ischemia.

Abstract: An accelerometer has a cantilevered beam supported at one end and having an opposite free end, with an inertial, sensing mass mounted at the free end of the beam. The beam is formed of a piezoelectric layer and a supporting layer. The ratio of the thickness of the piezoelectric layer relative to the thickness of the supporting layer is in a range between 2 and 4. The ratio of the modulus of elasticity of the material forming the supporting layer relative to the modulus of elasticity of the material forming the piezoelectric layer is in a range between 8 and 12.

Abstract: An implantable stimulating device for electrical stimulation of a heart has a stimulus generator which generates electrical stimuli and at least one lead for delivering the stimuli from the generator to the heart. A measurement unit detects spontaneous intervals between successive intrinsic heartbeats, and forms an average of at least five of these spontaneous intervals. A variation with respect to this average for later spontaneous intervals is then identified, and this variation is then used to control a pacing parameter of the stimulus generator.

Abstract: A heart stimulating device has the capability of detecting fusion and/or pseudofusion heartbeats by measuring electrical impedance encountered by a delivered stimulation pulse. The device has a pulse generator connected to a lead system for emitting and delivering stimulation pulses, and an impedance measuring arrangement for measuring the impedance. A logic circuit determines that a response by the cardiac tissue to a delivered stimulation pulse includes a fusion or pseudofusion heartbeat if the measured electrical impedance is within a predetermined impedance range, and determines that the response does not include a fusion and/or pseudofusion heartbeat if the measured electrical impedance is outside of the predetermined impedance range.

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.