Abstract: An electrophysiology diagnostic device generating a high voltage (HV) pulse of a predetermined shape, which device is electrically connected to a patient's heart, i.e., a load resistance and which device includes a microprocessor and a load resistance measuring device, includes of a rapid response voltage threshold determination (RRVTD) circuit. The RRVTD circuit receives an actual signal corresponding to the HV pulse waveform, compares the actual signal with a desired signal and produces an error signal when the actual signal deviates from the desired signal by a predetermined threshold value. A method for operating a RRVTD circuit is also described.

Abstract: A tennis racket with handle and head coupled with an interconnection insert provides torsional elasticity and vibration damping. The racket handle has a mating extension extending toward the head and the head includes a mating extension extending toward the handle such that the handle and head mate together at the mating extensions. The handle extension has a tongue with two bores and a pair of elastic bushings extending through bores. The head mating extension comprises a recess or U-shaped channel which receives the tongue and includes a pair of securing pins extending through the bushings and being rigidly secured to the sides of the recess or channel. The bushings and pins are positioned transverse to the longitudinal extent of the handle and parallel to the racket face. The bushings perform a shock absorbing function, provide torsional elasticity and control the racket stiffness.

Abstract: A method for defibrillating a patient's atria with an implantable defibrillator having defibrillation synchronized to the atrial fibrillation waveform. The defibrillator is used to detect fibrillation in a patient's aria, monitor at least one atrial fibrillation signal across two electrodes, then deliver a high energy shock during a period of atrial fibrillation when the cycle lengths are stable within a desired measure of the cycle lengths monitored during the monitoring time period. The shock is then delivered synchronous with the R wave to avoid inducing ventricular fibrillation. The defibrillator also includes a timer so that if the desired cycle length stability is not reached within a specified time limit, the shock will be delivered with less stringent cycle length stability criteria.

Abstract: A method of manufacturing an implantable electrode using a mold having a chamber with a compressible interior surface portion. Encapsulant and a conductive lead are placed into the chamber, and the mold is closed. With the mold closed, the compressible interior surface portion of the mold is biased against the lead at a region of contact with the lead, such that the biasing squeezes or excludes any encapsulant from between the lead and the mold at the region of contact. The electrode may have a body having an active portion with a smoothly contoured surface. The active portion may include a conductive wire partially embedded in an electrically insulative encapsulant, with the surface of the active portion comprising a major insulative surface portion defined by the surface of the encapsulant, and a plurality of curved conductive surface portions defined by exposed portions of the surface of the wire.

Abstract: A method for making a co-radial, multi-polar coiled cable lead. The method includes the steps of attaching a first end of a coated cable to a mandrel using a first end fixture. The coated cable comprises one or more cable strands, where each strand is made from one or more filaments. After the first end of the cable is attached to the mandrel, the cable is wound around the mandrel to form a coiled cable. A second end of the coiled cable is then attached to the mandrel using a second end fixture to retain the coiled cable under tension. Second stage processing is then performed on the coiled cable so that the end fixtures may be subsequently removed from the coiled cable without the coiled cable unwinding. After the second stage processing is complete, the coiled cable can be used in the manufacture of an implantable lead.

Abstract: Intracardiac lead for compliant fixation of a distal end of the lead to cardiac tissue. A fixation helix is disposed at the distal end of the lead. The fixation helix has a first end rigidly attached to the compliant fixation device and a second end that is sharpened to facilitate insertion of the fixation helix into cardiac tissue. The fixation helix can be designed to provide for either electrically active or inactive fixation. Once the lead is implanted in the cardiac tissue, the compliant fixation device, connecting the lead with the fixation helix, reduces the amount of lead movement that is transferred to the patient's tissue at the site of implantation of the fixation helix and reduces those forces from lead movement that could cause dislodgment of the fixation helix.

Abstract: A digitally controlled trim circuit which includes a plurality of resistors connected in series between a circuit node and a reference voltage, a plurality of first solid-state switches (e.g., PMOS transistors) connected in series across respective ones of the resistors, a plurality of multiplexers each having an output coupled to the gate electrode of a respective one of the first switches, a plurality of first control lines coupled to a first input of respective ones of the multiplexers, a plurality of second control lines coupled to a second input of respective ones of the multiplexers, and a plurality of fuses coupled to respective ones of the first control lines. The trim circuit is operable in a trim test mode in response to a first logic level of a select control signal coupled to the select input of each of the multiplexers, and is operable in a fuse-program mode in response to a second logic level of the select control signal.

Abstract: A single-pass transvenous lead for atrial sensing and pacing, ventricular sensing and pacing, as well as for ventricular and atrial defibrillation. The lead optimizes the positioning of the electrodes in various patients regardless of variations in these patients' hearts, by enabling independent adjustment of the spacing between various pacing, sensing and defibrillation electrodes, before and after implantation or insertion in the heart. The lead includes an elongated lead body, an outer sheath that extends coaxially with the lead body, and two atrial windows positioned along the outer sheath, adjustable relative to a reference point such as a distal pacing tip. The outer sheath includes an atrial section that is slidably adjustable along the lead body by means of an expandable member.

Abstract: A capacitor for an implantable cardiac defibrillator with a housing defining a chamber. A plurality of flat, stacked, charge storing layers reside within the chamber. Each of the layers includes at least a first and a second electrically conductive sheets separated by a sheet in between. The first sheet is electrically connected to the housing, and the second sheet is electrically isolated from the housing. The layers each have a periphery having at least one alignment element, with the second sheet extending to the periphery along at least a portion of the alignment element, such that the layers may be engaged at the alignment element to register the layers during assembly.

Abstract: An improved electrolytic capacitor is provided by producing an anode foil which has areas which are not subject to stress during manufacturing being highly etched and those areas which are subject to stress during manufacturing being lightly etched or not etched at all. The process of the invention provides an etch mask to cover during the etch process those portions of the anode foil which will be subjected to stress during construction of the capacitor. The highly etched areas, which are very brittle, provide increased capacitance and thus improved energy density. For layered or stacked capacitors, a weld tab is covered with the etch mask to allow connection of the anode layers. Additionally, strong edges may be maintained thereby reducing the possibility of cracking that would normally occur during the stamping and assembly operations.

Abstract: A capacitor and a method for making the capacitor using ultrasonic welding to join the cathode layers together are provided. The capacitor includes a housing defining a chamber with a step provided at an inner portion of the housing. A plurality of capacitor layers each including a cathode foil, a separator and an anode foil, each having alignment holes therein to precisely fit with alignment elements housing, is positioned within the chamber, with the alignment holes mating with the alignment elements. The housing is electrically conductive for connection to the cathode foils. Each cathode foil includes a cathode tab which extends away from the foil. The cathode tabs are pressed together and ultrasonically welded to the housing step abutting the periphery of the interior of the housing.

Abstract: An implantable cardiac pacemaker having a housing containing pacing circuitry, a signal generator, and an electromagnetic transducer. The transducer has an electrical input line connected to the signal generator, and an electrical output line connected to the pacing circuitry. Consequently, a forcing motion on the transducer sends an electrical signal to the pacing circuitry, and operation of the signal generator causes the transducer to vibrate. The pacemaker may also include a disablement switch connected to the signal generator, with the signal generator operating in response to activation of the switch to cause the transducer to generate an audible warning tone while the pacemaker is disabled.

Abstract: A ventricular tachycardia (VT) complex is distinguished from a sinus tachycardia or a supraventricular tachycardia. A template based on morphology of a normal sinus rhythm is collected. A test signal is compared against the template to determine how closely the test and template signals correspond based on morphology. The comparison is done based on peak information in the template and the test signal. A score is generated to indicate the degree of similarity between the template and the test signal. The peak information is extracted as follows. First, a group of three consecutive peaks having a largest cumulative peak amplitude is located in the template and in the test signal. The polarity, position and area of each peak within the group is then determined. The area of each peak is normalized. The polarities, positions and normalized areas represent the peak information that is used for comparison.

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 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 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.

Abstract: In a power supply circuit supplying a high voltage charger of an implantable cardioverter-defibrillator (ICD), a changer circuit switches the power source of the power supply circuit between a battery and an output signal of a step-up converter. The signal derived from the boost winding rises to a high voltage when the high voltage charger charges the storage capacitors of the ICD. A system current measurement circuit can be provided in the power supply circuit.

Abstract: A method for storing digitized electrogram and diagnostic data in a read/write memory of an implantable cardiac therapy device which includes the steps of configuring the memory into first and second memory blocks, configuring the first memory block into a plurality of successive EGM data records for storage of the electrogram data, and the second memory block into a plurality of successive diagnostic data records for storage of the diagnostic data, storing successive electrogram data corresponding to successive EGM trigger events in respective, successive ones of the EGM data records, and, storing successive diagnostic data corresponding to successive diagnostic trigger events in respective, successive ones of the diagnostic data records. The electrogram data is preferably written into the EGM data records in a wraparound, FIFO manner.

Abstract: A method for detecting cardiac arrhythmias which includes the steps of detecting a patient's cardiac activity, counting the number of intervals which satisfy a first selected criterion, and producing a sinus interval history count indicative of the number of such intervals which are counted, making a preliminary diagnosis of tachyarrhythmia upon detecting that the cardiac activity satisfies a second selected criterion, and, making a final diagnosis of tachyarrhythmia if the sinus interval history count is less than a selected maximum sinus interval history count, and otherwise, inhibiting a final diagnosis of tachyarrhythmia.