Abstract: The apparatus is used for sensing opening and closing of a tricuspid valve in a heart, for using those sensings to determine stroke volume, and for controlling pacing of a heart relative to changes in stroke volume. The apparatus comprises a pacer, a pacing lead coupled to the pacer and having a lead body, a pressure sensor mounted in the lead body and a pacing electrode, circuit means in the pacer coupled to the sensor for sensing the opening of the tricuspid valve during each heart cycle and for sensing the closing of the tricuspid valve during each heart cycle; means for calculating ejection time from the openings and closings of the tricuspid valve; means for calculating the change in ejection time, .DELTA.ET, from calculations of ejection time; means for calculating changes in stroke volume, .DELTA.SV, means for determining the required change in heart rate, .DELTA.R, relative to the change in stroke volume, .DELTA.

Abstract: The apparatus paces a heart in accordance with the heart/pacer rate needed to produce a required cardiac output while a person is exercising or undergoes emotional stress in response to changes in venous blood vessel diameter. The apparatus includes a pacer adapted to be implanted in a human body and having a pulse generator and control circuitry, which may be realized by a microprocessor, therein; a pacing lead adapted to be implanted in a heart having a tip electrode adapted to engage and supply pacing pulses to a right ventricle of a heart; a piezoelectric sensor for determining changes in diameter of a vein in the human body; and computing circuitry including the control circuitry, for relating the changes in venous blood vessel diameter with the required pacing rate needed to supply a desired cardiac output and for causing the pacer to pace the heart at the required rate when the heart is not naturally paced.

Abstract: A cardiac pacer is provided which includes a pulse generator for providing pacing pulses and an electrical lead for connection to a chamber of the heart. A pair of separate sensing amplifiers sense selected activity of the heart chamber. One of the sensing amplifiers has a slightly lower threshold and thus a slightly higher sensitivity level than the other sensing amplifier. The thresholds of the respective sensing amplifiers are automatically adjusted so that the first sensing amplifier will sense the selected activity of the heart chamber and the other sensing amplifier will not sense the selected activity.

Abstract: The apparatus for pacing a heart in accordance with the heart rate needed to produce a required cardiac output while the person is exercising, comprises a pacer adapted to be implanted in a human body and having a pulse generator and control circuitry (e.g. including a microprocessor) therein, a pacing lead adapted to be implanted in a right ventricle in a heart and having a distal electrode adapted to engage and supply pacing pulses to the apex of the right ventricle and a pressure sensor or impedance sensing electrode mounted in or on the lead.

Abstract: The apparatus for pacing a heart in accordance with the heart rate needed to produce a required cardiac output relative to the partial pressure of carbon dioxide in the blood, pCO.sub.2, while the person is exercising comprises a pacer adapted to be implanted in a human body and having a pulse generator and control circuitry (e.g. including a microprocessor) therein, a pacing lead adapted to be implanted in a heart and having a distal electrode adapted to engage and supply pacing pulses to a right ventricle of a heart and a pCO.sub.2 sensor for sensing pCO.sub.2 of the blood in the heart. An algorithm and routine utilizing same are stored in the control circuitry (microprocessor) and are adapted to relate pCO.sub.2 with the required heart rate or change in rate, .DELTA.R, needed to supply a desired cardiac output and to cause the pacer to pace the heart at the required heart rate when the heart is not naturally paced.

Abstract: A method for sensing opening and closing of a tricuspid valve in a heart, for using those sensings to determine stroke volume, and for controlling pacing of a heart relative to changes in stroke volume, utilizing a pacing lead having a lead body and a pressure sensor mounted in the lead body, said method comprising the steps of: sensing the opening of the tricuspid valve during each heart cycle; sensing the closing of the tricuspid valve during each heart cycle; determining ejection time from the openings and closings of the tricuspid valve; calculating the change in ejection time, .DELTA.ET, from determinations of ejection time; calculating changes, in stroke volume, .DELTA.SV,; determining the required change in heart rate, .DELTA.R, relative to the change in stroke volume, .DELTA.SV,; and adjustng the pacing rate of a pacer relative to the required change in heart rate, .DELTA.R.

Abstract: The pacing lead includes a catheter distal end portion which has a piezoelectric device therein and which is adapted to be inserted into a human heart. The device can be a ceramic bimorph or can be made of polyvinylidene fluoride film for generation of electrical energy upon contraction of the heart. The piezoelectric device is designed to generate electrical energy in response to movement of the implanted pacing lead and in the preferred embodiment is incorporated into the wall of the catheter of the lead as a longitudinal or spiral configured strip of film having piezoelectric properties.

Abstract: The apparatus and method are utilized in controlling an implanted device, such as a cardiac pacer, by use of acoustic vibrations generated by a tuning fork. These vibrations are applied externally to the skin overlying the implanted device and are sensed by a transducer within the implanted device. The transducer generates an electrical signal of a frequency correlated to the tuning fork frequency. An amplifier and tuned filter are utilized to detect predetermined frequencies within the electrical signals produced by the transducer and to direct the processed signals to a programmable electronic device for control of the implanted device.

Abstract: An electronic electrode switching/selection circuit minimizes the number of feedthroughs from a pacer case to a pacer neck needed to connect with pacing lead electrodes that will be actively used during operation of a pacer. These feedthroughs can be electronically connected with the desired electrode by the physician either at the time of initial implantation or at any time subsequent thereto as may be required. The electronic connection to a feedthrough may be dedicated to a single feedthrough/electrode or electrode pair or the electrodes may be electronically sampled by circuitry in the pacer. The electrode switching/selection circuit may be located in the pacer neck, in an adapter between the pacer neck and a multielectrode lead, or in a multielectrode lead.Preferably, zener protection diodes are also provided which are connected ahead of the pacing circuitry before or after the electrode switching/selection circuit.

Abstract: The pacing lead with sensor is adapted to be inserted into a human heart and includes a piezoelectric device, such as a bimorph, for sensing the occurrence of a phenomenon in the heart. The piezoelectric device can be positioned in the heart while the signal it generates is carried outside the heart, where it can be utilized. The piezoelectric device of the present invention is designed to indicate a phenomenon occurring, and can measure the absolute and/or relative value of the phenomenon such as pressure. As a result, the piezoelectric device utilized is easy to construct and manufacture, and may be used without complicated equipment.

Abstract: A fully implantable programmable cardiac pacer includes two main pacing channels driven by a crystal oscillator circuit. For each channel, amplitude and pulse width are programmed in paired combinations corresponding to monotonically increasing charge density. Selectively combinable constant current sources are shared by each channel. A low battery indicator system samples battery voltage relative to two threshold levels. In magnet rate, if the main battery voltage is above the first threshold, the fixed pacer output will be 70 beats per minute. If the battery voltage is between the first and second threshold levels, the fixed pacer output will be 62.5 beats per minute. An emergency RC oscillator continuously produces an output at 52.5 beats per minute and one millisecond pulse width.

Abstract: The apparatus for pacing a heart in accordance with the heart rate needed to produce a required cardiac output while the person is exercising, comprises a pacer adapted to be implanted in a human body and having a pulse generator and control circuitry (e.g. including a microprocessor) therein, a pacing lead adapted to be implanted in a heart and having a distal electrode adapted to engage and supply pacing pulses to a right ventricle of a heart and, a pacer sensor for sensing right ventricular systolic pressure mounted on the lead. An algorithm and routine utilizing same are stored in the control circuitry (microprocessor) and are adapted to relate right ventricular systolic pressure and/or the time derivative of the pressure sensed with the required heart rate needed to supply a desired cardiac output and to cause the pacer to pace the heart at the required heart rate when the heart is not naturally paced.

Abstract: A piezoelectric device and method are provided for setting or adjusting parameters or functions of an implanted device, such as the pacing rate of a pacer, at the will of its user/wearer or others, simply by making slight impacts on the user/wearer's body near the implanted piezoelectric device. The device has a piezoelectric sensor which picks up the physical impact and converts it to an electrical signal. Additional amplification and detection/decoding circuits can be provided to strengthen the signal and to separate intentional impacts from any unintentional impacts and noise.

Abstract: The system includes a sensor assembly comprising a body implantable physiological sensor for controlling a body implantable action device operable to act upon the body in response to changes in a physiological parameter sensed by the sensor. The body implantable action device can be a heart pacing device, a drug infusion pump, or other device which acts upon a human body. The sensor assembly includes a transmitter for transmitting coded signals to the action device which has programming circuitry for deciphering the signals received from the sensor assembly generated by the sensor which is in a location away from the location of the action device. Once these signals have been deciphered, the programming circuitry can adjust the output from the action device, such as the rate and A-V delay of pacing pulses from the pacing circuitry.

Abstract: A fully implantable programmable cardiac pacer includes two main pacing channels driven by a crystal oscillator circuit. For each channel, amplitude and pulse width are programmed in paired combinations corresponding to monotonically increasing charge density. Selectively combinable constant current sources are shared by each channel. A low battery indicator system samples battery voltage relative to two threshold levels. In magnet rate, if the main battery voltage is above the first threshold, the fixed pacer output will be 70 beats per minute. If the battery voltage is between the first and second threshold levels, the first pacer output will be 62.5 beats per minute. An emergency RC oscillator continuously produces an output at 52.5 beats per minute and one millisecond pulse width.

Abstract: A computer-controlled programmer having a user-interactive display is designed to control the parameters of a wide variety of implantable devices with different programming requirements. During programming, screen messages prompt the user to perform required actions by pressing lighted targets on the display screen. The programmer includes a console and a lightweight cable connected programming head. When the console is turned on, a self test routine automatically tests the programmer's batteries, memory banks and communications systems. For the communications test, the programmer employs a self-contained telemetry system which mimics the response of an implant. With certain implants, the programmer automatically changes programming options in response to information received from an implant as well as in response to selection of certain modes and lead configurations. The programmer software is designed to limit access to certain values and parameters which require the attendance of an authorized physician.