Abstract: A data communication system for control of transcutaneous energy transmission to an implantable medical device is disclosed having an implantable medical device with rechargeable batteries and a single coil that is employed both for energy transmission and data telemetry. Control circuitry in the implantable device senses battery voltage and current through the battery, encodes those values by use of a multiplexer, and transmits the sensed and encoded values through the coil to an external energy transmission device. The external device includes a coil that is electromagnetically coupled to the coil in the implantable device for receiving the encoded signals and for transmitting energy to the implantable device. The external device decodes the transmitted values and transmits those to a controller for controlling energy transmission.

Abstract: A method and apparatus for monitoring balanced biphasic current pulses used for measuring impedance in cardiac stimulators involves detecting imbalances between the pulses of opposite polarity. Such imbalances are potentially harmful to cardiac stimulator users. By converting the two different pulse phases into potentials, a determination can be made as to whether adequately balanced pulses are being generated. If an imbalance is detected, corrective action can be taken quickly enough to avoid harmful effects to the stimulator user.

Abstract: A method and apparatus for analyzing cardiac information involves recording both atrial and ventricular information related to a recognized event. This information can then be transmitted by telemetry to the physician and graphed on a common graph which plots both atrial and ventricular information over the time period of the event. This technique allows greater ability to discern the true nature of these events, including whether a given event is a sinus tachycardia due to exercise or a ventricular tachycardia which might necessitate treatment. Therefore, the present invention enables more accurate analysis of cardiac information and thereby makes possible the more appropriate application of treatment.

Abstract: A cardiac simulation system including a patient warning apparatus. The cardiac stimulator is an implantable pacemaker or defibrillator or combination which can be programmed to automatically alter the voltage of its output stimulus, in particular, to increase the voltage of the output stimulus whenever a condition exists requiring patient notification or warning. A specialized auxiliary lead with a shunt circuit can be connected to a standard socket of a cardiac stimulator header and a standard lead, such as a cardiac pacemaker lead, can then be connected to the auxiliary lead. The auxiliary lead allows a stimulation electrode to be implanted near excitable tissue in a secure fashion to assure stimulation of tissue. The auxiliary lead includes an apparatus for shunting electrical current from the standard stimulation electrode implanted in or near the patient's heart to the auxiliary electrode in the presence of a stimulation pulse with a voltage at or above a preselected level.

Abstract: An implantable subcutaneous data port for transferring data received from a sensor implanted within a subject. The data port electrically connects to the sensor and includes a control circuit electrically connected to an access port. The control circuit includes a current loop transmitter which modulates a current loop signal with voltage outputs from the sensor. This current loop signal transmits through the access port to an externally located current loop receiver which converts the current loop signal into an output voltage. Needle electrodes are insertable through the skin of the subject to the access port and provide an electrical interface between the control circuit and current loop receiver.

Abstract: An improved transcutaneous energy transmission device is disclosed for charging rechargeable batteries in an implanted medical device and to minimize peak temperature rises in the implanted device. A current with a sinusoidal waveform is applied to a resonant circuit comprising a primary coil and a capacitor. Current is induced in a secondary coil attached to the implanted medical device. Two solid state switches are used to generate the sinusoidal waveform by alternately switching on and off input voltage to the resonant circuit. The present invention charges the batteries using a charging protocol that either reduces instantaneous charging current or duty cycle of a fixed charging current as the charge level in the battery increases. Peak temperature rises are less while delivering comparable electrical charge of the battery than for prior charging systems.

Abstract: An optically-controlled high-voltage switch for an implantable defibrillator. A three-terminal high-voltage-tolerant semiconductor switch exhibits high conductivity between its high-voltage terminal and its common terminal in response to a low control voltage applied between its control terminal and its common terminal, where the low control voltage exceeds a characteristic threshold value, and exhibits low conductivity between same where the control voltage is less than the characteristic threshold value. A photovoltaic coupler/isolator having a light emitting device and a photovoltaic device, optically coupled to and electrically isolated from each other, is in circuit communication across the control and common terminals. A low voltage current source drives the light emitting device of the photovoltaic coupler/isolator.

Abstract: An implantable cardiac stimulation system having a patient warning system and an elongated electrode mounted near the can of the system for providing reliable stimulation for warning. The electrode has an extended length and a short width. The length is preferably at least double the width and more preferably at least four times the width. This extended length increases the probability that contact with the surrounding tissue will be achieved. The short width and rounded profile of the width, forming an "edge", on the other hand, increases the probability that a high enough current density will be achieved, causing stimulation to occur. The electrode may also be curved along its length, which tends to promote a "point" or small area contact between the electrode and the patient's tissue. The electrode may be mounted directly on the can or header of the cardiac stimulator or may be part of a separate pin electrode.

Abstract: A cardiac simulation system with a patient warning apparatus, including a pin electrode insertable into a standard female socket in the header of a dual chamber pacer or multi-function cardiac stimulator. The cardiac stimulator has at least two sockets in a header, such as is commonly found in a dual chamber pacemaker. Rather than stimulating both chambers of the heart, the dual chamber pacemaker is programmed to function as a single chamber pacemaker, with a standard lead connecting one socket and its associated circuitry to a selected chamber of the heart, usually the ventricle. The pin electrode is inserted in the other socket, usually used for the sensing and stimulation of the atrium, and additional programming is provided to the pacemaker or stimulator to automatically produce an output stimulus through the atrial socket to the pin electrode whenever a condition exists requiring patient notification or warning. The pin electrode includes a hood which fits around a selected part of a header.

Abstract: A bicompartmental tensiometer for use in prosthetic knee surgery, and in particular for use in revision knee surgery. The tensiometer comprises two parallel, independently operable jaws which are inserted between resected surfaces on the distal femur and the proximal tibia. The jaws are opened manually by the surgeon until the proper tension is placed on the collateral ligaments. Each of the jaws comprises two paddles which remain parallel to each other as they are opened. Moreover, the two jaws remain parallel to each other, or in the same angular orientation, when adjusted to be placed adjacent the condyles. Each jaw is held open by a pawl which engages a rack.

Abstract: A cardiac simulation system including a patient warning apparatus. The cardiac stimulator is an implantable pacemaker or defibrillator or combination which can be programmed to automatically alter the voltage of its output stimulus, in particular, to increase the voltage of the output stimulus whenever a condition exists requiring patient notification or warning. A specialized auxiliary lead with a shunt circuit can be connected to a standard socket of a cardiac stimulator header and a standard lead, such as a cardiac pacemaker lead, can then be connected to the auxiliary lead. The auxiliary lead allows a stimulation electrode to be implanted near excitable tissue in a secure fashion to assure stimulation of tissue. The auxiliary lead includes an apparatus for shunting electrical current from the standard stimulation electrode implanted in or near the patient's heart to the auxiliary electrode in the presence of a stimulation pulse with a voltage at or above a preselected level.

Abstract: A system for lead removal of both heart pacemaker leads and cardioverter-defibrillator endocardial leads comprising a flexible coil of flattened ribbon. Preferably, the ribbon is comprised of polyethylene or another suitable biologically compatible material. At a distal end of the coil, a cutting surface may be provided, such as a chisel-like edge at the distal end of the coil. A handle may be provided for twisting the coil onto the lead. The coil should be at least partially radiopaque or provided with a surface which is radiopaque so that its use may be observed in the body by fluoroscopy or other suitable means.

Abstract: A cardiac simulator including a patient warning apparatus, having an electrically conductive suture point in electrical communication with the patient warning apparatus. An electrically conductive suture passed through the suture point connects said stimulator mechanically and electrically to excitable tissue such as skeletal tissue. Inside the suture point is a connection for assuring a reliable electrical contact between the suture point and the suture. The cardiac stimulator automatically alters the peak voltage of its output stimulus whenever a condition exists requiring patient notification or warning. A specialized shunt circuit mounted within the stimulator or in the header of the stimulator re-directs electrical current from the standard stimulation electrode to the electrically conductive suture point. A controlled switch may be mounted within a hermetically sealed can of the stimulator to re-direct a stimulation pulse to the suture point. The controlled switch could also be mounted in the header.

Abstract: A femoral knee prosthesis having a box internal geometry adjacent the femur which has four intersecting planes which extend from the medial side of the prosthesis to the lateral side. Shims of varying thickness can be added which retain the same internal box geometry. The internal geometry of the shims comprises three intersecting planes. Medial and lateral shims are provided. The internal geometry of the shims is translated slightly anteriorly as they increase in thickness. The shims may be added to either condyle independently, with different thickness on each side.

Abstract: A cardiac stimulator including a patient warning apparatus, having a real time-clock for delaying delivery of a warning stimulus until a preselected time of day. The time of day may be selected dynamically with respect to detected patterns of patient activity. The stimulator can adjust the time for delivery of patient warning based on the detected circadian rhythm of the patient. In one embodiment, the cardiac stimulator is an implantable pacemaker or defibrillator or combination which can also be programmed to automatically alter the peak voltage of its output stimulus, in particular, to increase the peak voltage of the output stimulus whenever a condition exists requiring patient notification or warning. A stimulus generator in the stimulator can delivers electrical current to the electrically conductive suture point or warning electrode at a preselected voltage level.

Abstract: An implantable endocardial lead with a retractable helix. A specialized stylet can be inserted into the lead at the proximal end and passed through the lead to the distal end. Located at the distal end of the lead is a piston supporting the helix. The piston is attached to a coiled trifilar conductor and has an electrode adjacent the helix. Immediately adjacent the piston proximally an additional first short coil of wire is interlocked between the wires of the trifilar conductor, providing a female thread within the conductor. The stylet has a second single strand short coil segment spot welded to the stylet adjacent a distal end thereof. The stylet is rotated to screw the second short coil segment on the stylet into the first short coil adjacent the piston.

Abstract: A heart valve prothesis rotator which also has an annealed stainless steel shaft which can be bent by the surgeon interoperatively. The shaft will retain its shape after bending. Surrounding the shaft is a drive coil which connects a rotator head at a proximal end of the shaft to a drive knob at a distal end of the shaft and adjacent a handle. By turning the drive knob, a surgeon can turn the rotator head, thus orienting the prosthetic heart valve. Torsional motion is carried along the path defined by the bendable shaft so that the rotator head can be turned without displacing the handle of the heart valve rotator.

Abstract: An implantable, rate responsive pacemaker, sensitive to impedance changes in the heart as an indicator of cardiac stroke volume, wherein the baseline impedance is eliminated from the measurement of impedance. In one embodiment, an adaptively controlled, balanced bridge is utilized to eliminate the baseline. A Wein bridge is provided having a variable reactance whose impedance is controlled continuously. In another embodiment, an impedance measurement is modified by a signal conditioner providing an appropriate varying offset through the use of a sample and hold circuit and other signal modifying circuits prior to converting the impedance measurement to digital information. In a third embodiment, a sample and hold circuit may be used to provide digital information through an A to D converter to a microprocessor which directly controls a variable reactance. The end voltage of a pacing capacitor is used as an indication of a baseline impedance.

Abstract: An implantable medical device, such as a pacemaker, cardioverter or defibrillator, having a detachable power source, so that either the power source or the electronic circuitry can be replaced. The electronic circuitry is enclosed within a first container and the battery or power source is enclosed within a second container. The two containers are coupled by tracks slidingly connecting the containers along substantially planar sections thereof. In a first embodiment, the tracks comprise dovetail tongue and groove configurations. In a second embodiment, the tracks comprise a bayonet-type connection having male and female parts. The male part comprises two parallel arms. The female part comprises two parallel rails having a relatively inflexible section adjacent a distal end of the rail. Proximally on the rail, there is a relatively flexible section.

Abstract: A fluidized bed apparatus which produces a pyrolitic carbon coating with improved wear and porosity characteristics of the coating by producing a more uniform flat temperature profile throughout a reaction chamber in the area where coating is taking place. The apparatus has heating coils surrounding a lower end of the reaction chamber placed immediately adjacent one another at tight spacing. This contrasts to previous apparatus wherein heating coils were spaced between 2 cm and 5 cm apart. The apparatus also has a multi-jet nozzle to control a flow of gases through the reaction chamber. The jets in the nozzle comprise passages which are oriented such that the length of the passages lie on a series of cones having common axes.