Abstract: A contact spring is provided within a connector for use in a pacemaker having a radially deflectable projections enhancing contact with an inserted lead and is square shaped so as to fit within an annular extending gap in the housing so that the corners of the square shape of the spring are captured within the annular gap and prevents pull out of the spring when an electrical lead is inserted or removed.

Abstract: An improved apparatus and method are described for providing a measurement of the charge depleted from a battery used in an implantable device such as a cardiac pacemaker. The measurement is provided not by measuring the voltage level or impedance of the battery, but rather by continuously measuring the electrical current drawn from the battery and integrating that measured current over an integration time period. A precision current-sensing resistor provides a sense signal having a voltage that varies according to the magnitude of current being drawn, and this sense signal is integrated using a voltage-controlled oscillator circuit and counter, which are implemented using CMOS circuitry arranged in a switched-capacitor topology.

Abstract: An electrode device which has a proximal end and distal end, contains of a number of thin, insulated electrical conductors each with a proximal end and a distal end, the conductors being equipped with implantable electrode contacts means which are electrically connected to the conductors. These contacts are designed to be brought into electrical contact with tissue in one or more cavities in a human body. Each conductor in the cable device is supported by a pre-shaped stiffening element which runs along and is connected to the conductor, made of an elastic polymer material, resorbable in vivo, which is biodegradable and biocompatible. The stiffening element imparts an arched shaped to the conductor, at least in the area in which its contact is located, to cause the contact to press against the adjacent cavity wall. The cable device also includes a longitudinal channel in which a stylet can be inserted for temporary, linear stretching of the cable device and the arched sections of its conductors.

Abstract: An improved system is disclosed for telemetering data bidirectionally between two devices such as an implantable device and an external programmer. The two devices both include clock generators that operate at the same nominal frequency, but only one of the devices (i.e., the programmer) includes a phase-locked loop receiver that adjusts the frequency and phase of its clock signal to match that of the received data. The clock generator of the other device (i.e., the implantable device) generates a fixed-phase clock signal, which is selectively inverted or not inverted, to adjust its phase by 180.degree.. This selective 180.degree. adjustment enables the programmer's phase-locked loop receiver to have a reduced, .+-.90.degree. pull-in range, which simplifies its construction and reduces the time required to achieve synchronization.

Abstract: An active medical implant has a hermetically sealable capsule formed by a first part and a second capsule-closing part, whereby the capsule is arranged to hold a battery unit and an electronics unit, conductors for electrically connecting the battery to the electronics unit and contacts with associated conductors arranged on the exterior of the capsule for connection to electrodes. The first part and the second part are made of an essentially biocompatible material, and a partition wall is arranged to form a first essentially closed space in the first part for the battery unit, and an electrically insulating layer, impermeable to battery chemicals, is arranged on the surfaces of the biocompatible material facing the first closed space. An additional space is formed for the electronics between the capsule-closing part and the partition wall.

Abstract: An implantable pacemaker effectuates a capture verification method that minimizes the expenditure of battery current. A capture verification test is performed only occasionally, on a sampled basis, following delivery of a stimulation pulse. If capture is not verified, a loss of capture response mode is invoked that searches for an appropriate capture threshold, and when found, sets the stimulation energy at a level that is a prescribed safety factor above the capture threshold. All testing for capture is performed only after the heart rhythm has been measured, a short test pacing interval is selected that will be likely to overdrive the native rhythm, and the test pacing pulse delivered is delivered at the shortened interval so that the likelihood of fusion will be minimal.

Abstract: A magnetic field sensor comprises a substantially planar core member having flux concentrating fins, and relatively narrow segments that interconnect the fins so that an external magnetic field becomes concentrated within the segments. A quality factor (Q) of a single coil which is wrapped around the segments is monitored to measure or detect the presence of an external magnetic field. To measure an external field, a current is passed through the coil to charge the coil with a known quantity of energy. A circuit of the sensor then measures the quantity of energy returned by the coil to measure the Q of the coil, and to thereby measure the external magnetic field. The magnetic sensor is suitable for pacemaker applications as a substitute for reed switches.

Abstract: A capacitor optimized for use in an implantable medical device such as an implantable defibrillator is disclosed. In its simplest form, the capacitor comprises a thin planar dielectric sheet that has an array of cells open to one or both sides. Metallization is applied to the surface of the cells such that the walls of adjacent cells form a capacitor with the wall that separates the cells serving as the dielectric. The metallization pattern that forms the electrical connection to the cells may be patterned to limit the allowable current flow to each individual cell, thereby providing a fuse in the case of local dielectric failure.

Abstract: A system and method for ambulatory monitoring and programming of an implantable medical device are provided. The system enables ambulatory communication between a modified programmer/analyzer and an implantable medical device having telemetric communication capability. This is accomplished through the use of an ambulatory interface unit which may be conveniently attached to the patient's body using a belt or harness. The ambulatory interface unit wirelessly communicates with both the programmer/analyzer and the implantable medical device thereby providing for improved patient mobility. The ambulatory interface unit may include an integral telemetry head or may be connected to the telemetry head by a communication cable.

Abstract: A retractable pen tether and a method for connecting a digitizer pen to a hand-held computer or other digitizer housing are provided. A tether attaches a digitizer pen to the digitizer to prevent the accidental loss of the digitizer pen. The tether length is variable so that an individual user can choose the desired amount of tether. The tether can be caused to retract into a cavity within the digitizer pen. The addition of the tether does not prevent storing the digitizer pen within a pen storage chamber of the digitizer housing. The tether mechanism and tether anchor are designed so that existing digitizer housings can be upgraded with tethered pens without extensive modifications to the digitizer housing.

Abstract: A transvenous endocardial lead comprises an elongated flexible body member encompassing an electrical conductor which has an electrode at its distal end. A stabilizer adjacent the distal electrode extends outwardly from the flexible body member by a distance no greater than approximately one-half of the shortest distance between a longitudinal axis and the outer peripheral surface for minimizing dislodgment of the distal end from an intended implanted position into the myocardial tissue of the heart and for preventing penetration of the distal end of the flexible body member into the myocardial tissue. The stabilizer may be employed in conjunction with conventional active or passive fixation members and may take a variety of forms.

Abstract: A sensor that is implantable within the body of a patient that provides an indication of movement and orientation of the patient. The sensor is comprised of a cylindrical enclosure having a central electrode positioned within the cavity formed by the enclosure that is co-axial with the axis of the cylinder. One or more peripheral electrodes are positioned within the cavity and extend in a direction parallel to the central electrode. An electrolytic fluid is positioned in the enclosure so that movement of the sensor results in variations in the amount of electrolytic solution between the central electrode and the one or more peripheral electrodes. An alternating current signal is applied to the central electrode and the one or more peripheral electrodes and the resulting voltage signal is measured between the central electrode and the one or more peripheral electrodes.

Abstract: A continuous sheath of open-celled porous plastic, preferably ePTFE, is used on the outside of an implantable lead, extending along the lead body and the electrodes, in such a way that the lead is isodiametric along its length, and is very strong in tension as is required for lead removal. Because the plastic is open-celled, when the pores are filled with saline, the lead can deliver defibrillation energy through the pores in the plastic. Pore size is chosen to discourage tissue ingrowth while allowing for defibrillation energy delivery through it.

Abstract: A device for manipulating a stylet unit for positioning an electrode cable in a body cavity has an elongate housing, an elongate, axial cavity in the housing and an operating slide, axially movable in relation to the housing, for attachment to a proximal end section of a tubular stylet sleeve in a stylet unit. An elongate coil spring is located in the cavity on the proximal side of the manipulation device. The coil spring forms an inner guide channel to prevent the buckling of the free, proximal end section of the stylet of the stylet unit in the cavity.

Abstract: Methods and apparatus are provided for annotating medical data in an implantable device programmer using digitally recorded sound. A display screen of the implantable device programmer preferably displays at least a portion of a patient data set. A user preferably designates a connection point of the patient data set. Voice signals from the user are received by a transducer and converted to electrical signals, which are then converted to digital data by an analog to digital converter. The digital voice data preferably are stored within a memory device of the implantable device programmer and preferably are linked to the connection point. A marker preferably is displayed on the display screen at a location corresponding to the connection point. The physician is able to listen to the voice annotation by selecting a playback button displayed on the display screen. Voice annotations preferably can be transcribed into text which preferably is displayed in a text window when the voice annotation marker is selected.

Abstract: A system and method for identifying and displaying medical data items which violate programmable alarm conditions are provided. The system of the present invention automatically alerts the medical practitioner if changes or deviations in parametric and physiologic medical data items violate programmable alarm conditions. The system also provides the medical practitioner with the ability to edit, disable, and enable programmable alarm conditions associated with one or more parametric and physiologic medical data items. The system also allows the medical practitioner to select a range of medical data to be used when the determination of whether any alarm conditions were violated is made.

Abstract: A method for defibrillating a patient's heart with an implantable defibrillator having defibrillation synchronized to the fibrillation waveform is disclosed. The defibrillator is used to detect fibrillation in a patient's heart, monitor at least two far-field fibrillation voltages across at least three spaced-apart electrodes while the high voltage capacitors are charging, then deliver a high energy shock during a period of ventricular fibrillation when the absolute values of the peak and trough voltages exceed a threshold based on a desired percentage greater than a running average of the absolute values of the peaks and troughs of the fibrillation voltages monitored during and after capacitor charging. The shock is then delivered synchronous with the next significant cardiac complex. The defibrillator also includes a safety timer so that if the threshold is not reached within a specified safe time limit, the high energy shock will be delivered without further delay.

Abstract: A method for electrically attaching electrode wire to a conductor in a defibrillation lead is disclosed. The method comprises melting the end of the wire with a hydrogen torch to form a ball of metal, then crimping or welding the ball to the conductor or to a joining piece attached to the conductor. Also, a hydrogen torch (water welder) may be used to join two or more electrode wires to each other.