Abstract: An implantable defibrillator generates defibrillation shocks for providing antitachycardia therapy. The shocks have an intensity, i.e. amplitude and/or duration, which is dynamically changed in accordance with whether defibrillation shocks having a particular intensity are successful or not. In this manner, changes either in the cardiac condition or the interface between the defibrillation electrodes and the cardiac tissues, or other causes which may have an effect on the effectiveness of the defibrillation shocks.

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: A back-up pulse generator for a pacemaker having a first energy storing component for storing energy to be delivered in a stimulation pulse and connectable to means for conducting the stimulation pulse to the heart, the back-up pulse generator including a back-up pulse energy storing component for emitting a back-up pulse after a failure to sense an evoked response from a preceding stimulation pulse. The back-up pulse energy storing component substantially permanently stores energy at a higher voltage than the energy stored in the first energy storing component.

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: For an implantable medical devices, a system is provided for welding electrically conductive ribbon, typically stainless steel, to electrically conductive wire, typically platinum, the melting point of steel being substantially lower than that of platinum. An aperture is formed in the ribbon having an opening smaller than that of the wire. The ribbon is engaged with the wire such that the aperture is generally coextensive with the wire. Thereupon, a pulse laser beam is directed transversely of the ribbon through the aperture and onto the wire to simultaneously melt the wire and the ribbon and to create a homogeneous mix of the molten steel and platinum in the region surrounding the aperture. Thereafter, operation of the laser beam is discontinued to allow solidification and thereby achieve a welded connection between the ribbon and the wire.

Abstract: A rate responsive implantable pacemaker generates a metabolic demand parameter which is converted into a corresponding metabolic indicated parameter. The parameter is used to determine certain characteristics related to an exercise period and the patient, including exercise duration and intensity. These characteristics are used to dynamically calculate an exercise recovery period during which the pacing rate is elevated above a rate indicated by the metabolic parameter. Preferably, fuzzy logic circuitry is used for this purpose.

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: An implantable cardioverter/defibrillator/pacemaker (ICD) device having tiered level therapies, detects an arrhythmia through an electrode adapted to be coupled to a patient's heart. An output capacitor is coupled to the electrode through an output switch. A charging circuit, coupled to the output capacitor, charges the output capacitor to a programmed energy level. A control circuit, coupled to the charging circuit and the output switch, generates control signals to control the charging of the output capacitor and the closure of the output switch in accordance with a prescribed tiered therapy.

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 heart stimulating device for avoiding problems related to fusion beats contains a pulse generator for delivering stimulation pulses to a patient's heart and having a basic escape interval, a detector with a filter which senses QRS characteristics in IEGM signals, a logic stage which controls the pulse generator, and a detector without a filter which senses QRS characteristics in IEGM signals. The logic stage activates the detector without a filter preceding an end of the basic escape interval and prolongs the basic escape interval by a predetermined extension interval if the detector without a filter senses a QRS indication.

Abstract: An implantable device programmer includes a variety of features for allowing a clinician to perform an automated and customized follow-up examination of a patient having an implanted cardiac implantable device, the implantable device being of the type which captures and stores various types of diagnostic data for subsequent retrieval and evaluation. A custom protocol feature of the programmer allows the clinician pre-specify and then semi-automatically follow an ordered sequence of protocol steps, each protocol step involving the interrogation of the implantable device and the display by the programmer of associated implantable device data (such as a heart rate histogram, or the results of a ventricular capture test). When the clinician initiates a custom protocol, the programmer automatically retrieves all of the diagnostic data records of the protocol in the protocol order.

Abstract: An accelerometer-based, multi-axis physical activity sensor for use with a rate-responsive pacemaker, and a method for fabricating the sensor, are provided. The multi-axis physical activity sensor includes a cantilever beam having a film of a piezoelectric polymer adhered to each surface of an electrically conductive substrate. The piezoelectric films are highly resistant to fracturing during manufacture and in use, and they provide a strong output signal when stressed in response to bodily accelerations. A mass is mounted to a free end of the cantilever beam, and is substantially offset with respect to a planar surface of the beam so as to impart multi-axis sensitivity to the physical activity sensor. The accelerometer-based, multi-axis physical activity sensor provides an output signal that is communicated to pacemaker circuitry using a pair of electrical conductors.

Abstract: A pacing lead having a stylet introduced anti-inflammatory drug delivery element advanceable from the distal tip electrode. The element is preferably formed as a moldable biocompatible composite material. The element has a biocompatible matrix material which may be combined with drugs and therapeutic agents to deliver the drugs and agents by co-dissolution or diffusion to the point of either passive or active fixation. The drug delivery element may be rigid and serve to center an active fixation mechanism, preferably a helix, which penetrates the myocardium.

Abstract: A flow sensor adapted for placement along a pacing lead or other catheter comprises a thermopile formed on the outer surface of a tubular substrate. The thermopile comprises a plurality of interconnected conductors of an alternating metal type. Junctions between conductors of the thermopile are alternately located near the longitudinal ends of the flow sensor, so that a voltage generated by the thermopile indicates the difference in temperature between the ends of the flow sensor. To measure blood flow with the flow sensor, an alternating current is induced through the thermopile to heat the flow sensor in a generally symmetrical manner. A voltage generated by the thermopile is then measured to obtain a sample of the magnitude and direction of the velocity of blood flow.

Abstract: A system for delivering low pain cardioversion shocks to the heart wherein the system provides a waveform to the heart for cardioversion purposes to result in less stimulation of sensory nerves surrounding the heart. In one embodiment, the system includes a controller and a plurality of controlled switches that can be configured so that the heart receives a waveform through one or more resistors from a capacitor. The controller is configured to manipulate the switches so that the waveform that is applied to the heart is applied for more than 10 milliseconds so that the ratio of stimulation of the cardiac cells to the stimulation of sensory cells is approximately one. In another embodiment, the controller configures the switches so that a first capacitor discharges to charge a second capacitor through a resistor wherein the second capacitor is in parallel with the heart.

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: An implantable medical device has a pulse generator for generating electrical pulses, an electrical energy storage element connectable to an output stage, and an electrode arrangement for conducting the electrical pulses to tissue, the electrode arrangement having an input end and an output end. The output means of the pulse generator is connectable to the input end of the electrode arrangement, and the capacitance of the output stage is less than 1 .mu.F and the electrode arrangement has a capacitor with a capacitance greater than 1 .mu.F.

Abstract: A rate responsive pacemaker with improved response to exercise onset includes a detector for detecting a metabolic parameter indicative of the patient's metabolic demand. The metabolic demand parameter derived therefrom is analyzed either using a heart rate sensitive zero crossing detector or a derivative calculator and used to generate an optimized pacing rate.

Abstract: A rate responsive pacemaker includes a noise sensor for sensing noise on the leads. If noise is detected, the pacemaker switches to a mode wherein a metabolic demand parameter is ignored. The noise is preferably detected by using test signals which are also used to measure the metabolic demand parameter.

Abstract: A rate responsive implantable pacemaker generates a metabolic demand parameter such as a thoracic impedance which is converted into a corresponding metabolic indicated parameter. During the conversion, intermediate parameters, such as either tidal volume and respiration rate, or a derivative of the metabolic demand parameter are used by a cross-check circuit to insure that artefacts due for example to stroke volume noise are eliminated. The peak limiter is used to limit the metabolic indicated rate to an acceptable range. Both protection circuits use fuzzy logic components.