Abstract: An ischemia detector has a sensor unit which determines the systolic pressure of a subject, a unit wherein a relation is established between the systolic pressure and the subject's heart rate, as the heart rate is varied over a range, and an analyzer which determines the occurrence of ischemia from this relation.

Abstract: A device for manipulating a stylet unit having a stylet movable within a stylet sleeve, for positioning an electrode cable in a body cavity, has first and second relatively movable parts, with an interface area wherein respective surfaces of the first and second parts are in contact with each other. A groove is disposed in one of these surfaces and receives the stylet unit, with the stylet being connected to one of the first and second parts, and the stylet sleeve being connected to the other of the first and second parts.

Abstract: A pacemaker housing has a socket for receiving a plug of an electrode lead, the socket being located in an opaque part of the housing, and the housing having an exterior marking which indicates a proper insertion depth for the plug into the socket. The plug of the electrode lead can be provided with one or more markings which successively proceed toward the side of the housing having the socket opening therein, with one of the markings coinciding with the edge of the socket when the plug is inserted to a proper depth into the socket.

Abstract: Mathematical functions such as recursive autoregression models which include parameters are used for defining the heart signal and any signals disturbing the heart signal, such as polarization signals. By registering, during a predetermined time interval, the electrode signal for determining the parameters for one or more different mathematical functions, the parameters can be used on their own or in combination to determine the activity of the heart, i.e., whether the registered electrode signal corresponds to a stimulated, spontaneous or absence of heart activity.

Abstract: A pacemaker has an interference detecting circuit, and an evaluating and storing unit for continuously evaluating and storing the heart rate. The evaluating and storing unit stores the rate evaluated from at least one of the most recent cardiac cycles free of interference. A determining unit determines an interference backup rate from the stored rate in response to the detection of the onset of an interference situation. A control unit then adjusts the pacing rate equal to the interference backup rate.

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: An implantable electrode lead has a proximal end intended for connection to, e.g., a pacemaker and has a distal end with an electrode head equipped with an external, tine-type anchoring unit. The anchoring unit has a number of projections which are integrally formed as a one-piece unit together with a ring-shaped carrier. The carrier is made of an elastic material, and is disposed under elastic tension in an annular groove in the exterior of the electrode head, which fixes the position of the anchoring unit relative to the electrode head. The anchoring unit detaches from the electrode head, by the carrier being pulled out of the groove, when a predetermined, minimum pulling force is exerted on the electrode head from the proximal end of the lead.

Abstract: In the determination of an optimal rate for the delivery of stimulation pulses to a heart, the stroke volume (SV) of a heart ventricle is measured as a function of heart rate (HR), e.g. by determination of impedance in individual heart cycles whose duration is varied from the duration corresponding to the prevailing rate or the basic rate regarded as optimal for stimulation. The optimal rate should lie at the knee of this function. A corresponding knee is also found in the curve for cardiac output (CO). This rate is determined by calculation of an auxiliary function, e.g. HF=HR.times.CO, which displays a peak at the heart rate at which the knee is located, and the heart rate is determined which yields this maximum. The heart rate determined in this manner is subsequently employed as a basic rate.

Abstract: A connector assembly for an implantable medical device such as a heart stimulator having a hermetically sealed enclosure containing electrical circuits and a power source, is affixed to the enclosure of the stimulator or is incorporated therein for producing an electrical connection between a proximal end of an electrical cable and the circuits in the enclosure. The connector assembly has a first connector in the form of a female connector part with the electrical contacts embedded in a puncturable membrane disposed inside of the connector assembly. The first connector is placed in electrical contact with a second connector which is arranged on a male connector part on the proximal end of the electrode cable.

Abstract: A device for preventing an anchoring element disposed at the distal end of an implantable electrode cable from coming into contact, during introduction of the cable into a body cavity, with a cavity wall and thereby damaging the cavity wall, as a protection element which either projects beyond the distal tip of the helical anchoring element, or has the distal tip of the helical anchoring element embedded therein. The protection element is composed of a porous, resilient, spongy material which is compressible. The protection element has interstices which are at least partially filled with medication, and the protection element is compressible during affixing of the anchoring element in the heart wall, so as to express the medication from the interstices.

Abstract: An electrical female connector for affixing a contact pin of an electrode cable in a connector part of a heart stimulator has a sleeve which is elastic and which has a curved shape in a relaxed condition. The sleeve is straightened to a substantially straight configuration when the contact pin is inserted into the sleeve, and thereupon rebounds back to a partially curved configuration so as to clamp the contact pin inside the sleeve.

Abstract: A cardiac event detecting system for an implantable heart stimulator intended to be connected to the heart of a patient through at least two unipolar electrode leads or at least one bipolar electrode lead having one electrode pole in the atrium and one electrode pole in the ventricle for sensing heart signals, has at least two signal channels for signals sensed between the two electrode poles and between one of the electrode poles and the stimulator capsule, respectively. Each signal channel has a signal processing stage. Decision logic compares the signals from the two signal channels with signal criteria for detecting the occurrence of a cardiac event. An A/D-convertor converts sampled values of the sensed heart signals into digital words for each signal channel. The decision logic is adapted for comparing the digital words and their differences with the criteria for determining the occurrence of a cardiac event.

Abstract: An implantable cardiac stimulator has a connector with at least two terminals, each terminal being connectible to an implantable electrode for delivering stimulation pulses to a heart and/or for sensing cardiac activity signals. The stimulator also has a switch and a control unit which operates the switch, so that one or both terminals are connectible to the pulse generator and/or to an input stage. The control unit identifies a position status for at least one of the electrodes in response to a signal received by the input stage at the time of implantation of the stimulator. The control unit also can select a terminal to be connected to the pulse generator, dependent on the established position status.

Abstract: A pacemaker has control circuits contained in an enclosure and a lead containing an electrical conductor connected to an electrode for delivering electrical stimulation pulses to a heart. The stretching of a wall in the ventricle, corresponding to adequate filling of the ventricle in the heart, is determined in order to identify a time of emitting the stimulation pulses. This stretching is measured indirectly by measurement of pressure in the ventricle using a pressure sensor disposed near the lead in the ventricle. The signal from the sensor is supplied via the lead to circuitry in the enclosure, wherein the signal is amplified and is supplied to an edge detector, which detects an increasing or positive edge of the signal.

Abstract: A device for determining the respiration rate and/or respiration depth of a patient includes a sensor for sensing heart sounds and an analyzer for analyzing the variation of the amplitude of the sensed heart sounds to determine the respiration rate and/or respiration depth from this amplitude variation. An apparatus for monitoring the respiration of a patient includes such a device and the analyzer is arranged to determine an anomaly in the amplitude variation of the sensed heart sounds as an indication of a respiration anomaly.

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 medical device has a housing containing an accelerometer which detects vibrations of the housing. The accelerometer generates a vibration signal in response to the detected vibrations, which is supplied to a signal processing unit. The signal processing unit generates, for each of a number of predetermined frequency ranges, a parameter value indicative of a defined attribute of the vibration signal. The signal processing unit forms a ratio between any two of these parameter values, and emits at least one status value dependent on this ratio. The status value is uniquely indicative of a predetermined type or level of cardiac activity, and the status values can be used as a control signal for controlling therapy, such as cardiac stimulation, administered by the implantable medical device.

Abstract: An evoked response detector for a heart stimulator determines evoked response in the presence of polarization. The heart stimulator has a pulse generator which produces stimulation pulses of varying amplitudes, and a lead adapted for introduction into the heart of a patient is connected to the pulse generator for delivering stimulation pulses to the heart. The evoked response detector includes measuring and memory circuitry for measuring and storing the electrode signals picked up by the lead in response to the delivered stimulation pulses, at least one of these stimulation pulses having a sufficiently high amplitude for obtaining capture. Each measured electrode signal contains two signal components, one of these signal components being proportional to the amplitude of the associated stimulation pulse and the other signal component being substantially constant, independent of the associated stimulation pulse amplitude.

Abstract: An implantable heart stimulator includes a unit for setting a maximum allowable stimulation rate and an ischemia detector. An analysis unit and control unit and connected to the ischemia detector and to the setting unit for controlling the setting unit so as to lower the maximum allowable stimulation rate in response to the detection of an ischemic state.

Abstract: An ischemia detector includes repolarization sensor which senses repolarization of the heart of a patient and delivers corresponding repolarization signals to a detecting unit and a workload sensor which senses the workload of the patient and delivers corresponding workload signals to the detecting unit. The detecting unit identifies a state of ischemia as existing upon the occurrence of a predetermined relation between sensed repolarization and sensed workload.