Abstract: An electrolytic capacitor with several conductive layer portions, including some anode layers and some cathode layers in alternating arrangement. A set of insulator layers is interleaved with the conductive layers, and the conductive and insulator layers are laminarly stacked with an anode layer being outermost on one surface. The stack is positioned adjacent a metal heat sink, with an outer insulator layer positioned between and closely contacting the stack and the heat sink. The cathode layers may be connected to the heat sink.

Abstract: A medical device includes a sensing unit for creating digital data representing the electrical activity of a heart and a controller for, among other things, predicting the onset of an arrhythmia in the heart. From the digital data created by the sensing unit, the controller extracts data that represents the QRS complex of the heart cycle over several cardiac cycles and calculates the power spectrum for each QRS complex. Then, for each QRS complex, the controller calculates the fraction of energy in the power spectrum that falls within one or more frequency bands. The controller than calculates variance of these energy fractions over a number of cardiac cycles. A change, such as a decrease, in the variance presages the onset of an arrhythmia.

Abstract: Methods and apparatus for achieving atrial defibrillation in a heart. Atrial pacing is first conducted from a single pacing site so as to have the desired effect of maximizing the extent of phase-locked area of atrial tissue. Next, an ADF shock is introduced, if still needed, to achieve atrial defibrillation. ADFT energy requirements have been shown to be dramatically reduced on account of using a pacing rate set proportionally to the atrial fibrillation cycle length such that large areas of atrial tissues are phase-locked, and consequently atrial defibrillation can be effected in the patient with greatly reduced energy requirements for ADFTs.

Abstract: Methods and apparatus for achieving atrial defibrillation in a heart. Atrial pacing is first conducted from multiple pacing sites in a synchronous manner so as to have the desired effect of maximizing the extent of phase-locked area of atrial tissue. Next, an ADF shock is introduced, if still needed, to achieve atrial defibrillation. ADFT energy requirements have been shown to be dramatically reduced on account of using pacing rates set proportionally to the sensed atrial fibrillation cycle length(s) such that large areas of atrial tissues are phase-locked, and consequently atrial defibrillation can be effected in the patient with greatly reduced energy requirements for ADFTs.

Abstract: An abrasion resistant implantable lead is described including a protector for preventing abrasion to lead insulation. A helix-shaped protector can be placed around portions of the implantable lead to prevent frictional contact between the lead and the metallic casing of an implantable medical device, known as a pulse generator. The protector can have a cross-section and end-view of various shapes. The protector can be made of a flexible, elastomeric biocompatible material and can be coated by a hydrophilic surface to minimize the coefficient of friction between the protector and the casing of the pulse generator. The protector can have an inner cross-sectional diameter equal to or less than an outer cross-sectional diameter of the lead insulation, ensuring a snug fit. A toolkit for selecting, sizing and positioning the proper protector is described.

Abstract: A method for treating arrhythmias which includes the steps of detecting an arrhythmia, and, in response to detection of the arrhythmia, delivering electrical energy to a targeted part of myocardial tissue in such a manner as to create a transient conduction block in the targeted part of the myocardial tissue without causing permanent damage to the targeted part of the myocardial tissue. The electrical energy can be continuous or pulsed RF, or continuous or pulsed DC. The detected arrhythmia can be atrial fibrillation, atrial flutter, ventricular fibrillation, or other type of arrhythmia. The targeted part of the myocardial tissue constitutes a critical part of the reentrant pathway or reentrant circuit required to sustain the detected arrhythmia. The electrical energy is preferably delivered via a catheter-based electrode which is in direct contact with the targeted part of the myocardial tissue, for either a prescribed period of time or until the arrhythmia is no longer detected (i.e., is terminated).

Abstract: An implantable atrial defibrillator for converting atrial arrhythmias into normal sinus rhythm includes a patient activated mode, a programmable safety timer, and means for deactivating the patient activated mode. The programmable safety timer starts counting down when AF is detected. If the safety timer times out before the patient activates delivery of an atrial defibrillation shock, the device will deactivate the atrial defibrillation function, and will not allow an atrial defibrillation shock to be delivered until the physician reactivates it with a programmer. This allows the physician to administer anticoagulants to the patient prior to atrial cardioversion. The preferred length of time between AF detection and lock out of the atrial defibrillation function is 24 hours.

Abstract: A method of manufacturing a capacitor for use in an implantable cardiac defibrillator by forming a set of conductive sheets with the same profile having a sacrificial portion. An alignment figure is formed in each sheet, and the sheets are stacked and aligned by registering the alignment figures with each other. The sacrificial portions are removed from each of the sheets, which are secured together and positioned in a capacitor housing. Each sheet may include two major portions joined by the sacrificial portion, so that each major portion may become part of a separate capacitor stack after the sacrificial portion is removed, doubling manufacturing throughput.

Abstract: A method of manufacturing a capacitor by highly etching a foil sheet, and at selected relief portions of the sheet, reducing the surface area coefficient. An anode sheet is cut from the foil sheet and assembled with other capacitor components. The surface area coefficient may be reduced by coining or mechanically compressing at the selected relief portions, and an oxide layer may be formed on the sheet after coining.

Abstract: An active overload detection and protection circuit for protecting a host device (e.g., an implantable cardiac therapy device) from potential damage due to high voltage transients applied to an I/O node thereof. The protection circuit includes an I/O circuit coupled to the I/O node, the I/O circuit having low-impedance and high-impedance modes, a current overload detection circuit coupled to the I/O circuit which detects a current overload condition induced by a high voltage transient, and which generates an overload detect signal in response, and, a mode changing circuit which changes the mode of the I/O circuit from the low-impedance mode to the high-impedance mode in response to the overload detect signal. The protection circuit further includes a reset circuit which generates a reset signal a prescribed time after the overload detect signal is generated, wherein the mode changing circuit is responsive to the reset signal to change the mode of the I/O circuit.

Abstract: A method for detecting or classifying cardiac arrhythmias using interval irregularity. The method includes the steps of detecting a patient's cardiac activity and looking at a first selected criterion such as the patient's heart rate exceeding a preset rate threshold to determine if a tachycardia is present. When the first criterion is met, a window of N successive cardiac intervals is selected for analysis. A selected number of the shortest and longest intervals are ignored and the difference between the remaining longest and shortest intervals is calculated to provide a measure of interval irregularity indicative of the origin of the cardiac rhythm. In one embodiment, a parameter n is set such that 0.ltoreq.n<N/2, and the intervals in the window are ordered from shortest to longest with the shortest being interval 1 and the longest being interval N.

Abstract: A system and method for optimal sensing of cardiac events includes registering electrical activity from a cardiac event in a patient's heart and entering a refractory period after the cardiac event has been registered. The system and method further includes detecting when the electrical activity from the cardiac event has settled into a baseline region for a predetermined period of time, whereby the refractory period is ended at such time. The method may also implement a minimum backup timer and a maximum backup timer, which are set to predetermined minimum and maximum time periods, respectively, when the refractory period begins. In this case, the system ends the refractory period, either: (1) when the electrical activity settles into a baseline region for a predetermined period of time and the minimum time period elapses, or (2) when the maximum time period elapses, whichever occurs first.

Abstract: A continuous sheath of open-celled porous plastic, preferably ePTFE, is used on the outside of a medical lead, extending along the lead body and the electrodes. Because the plastic is open-celled, when the pores are filled with saline, the lead can deliver electrical energy through the pores in the plastic. Pore size is chosen to discourage tissue ingrowth while allowing for defibrillation energy delivery and electrical signals through it. The porous plastic has a biocompatible wetting agent applied to it to speed the process of filling the pores with saline.

Abstract: An electrolytic capacitor having several cathode layers and several anode layers stacked in a single housing. At least some of the anode layers are electrically interconnected in a group electrically isolated from another group of electrically interconnected anodes. Separate electrical connections permit the separate groups to be independently connected to external circuitry.

Abstract: An aluminum electrolytic capacitor with an aluminum housing defining a chamber, and having a feed-through aperture providing communication with the chamber from outside of the housing. A number of aluminum anode layers are positioned within the chamber, and a feed-through member formed of a first conductive material occupies the feed-through aperture. The feed-through member has an inner end extending into the chamber, an outer end extending externally from the housing, and an insulative sleeve encompassing an intermediate portion of the feed-through member and directly contacting the housing at the feed-through aperture to prevent electrical contact between the feed-through member and the housing. A connection element formed of a second different conductive material is attached to the inner end of feed-through member and spaced apart from the housing. A compressible insulative gasket may be positioned between the housing and the connection element to provide insulation and a fluid seal.

Abstract: A method for making anode foil plates for use with layered electrolytic capacitors and capacitors made with such plates. A high purity aluminum foil is provided for generation of anode foil plates. Sheets of the foil are highly etched to provide a very high surface area. Following the etch process, the foil is partially cut or punched into plates from the etched sheets in the general shape of the finished capacitor housing with a portion remaining connected to the supporting foil. The supporting foil with the partially punched-out etched plates are subjected to a forming process by applying a voltage to the plates in the presence of an electrolyte to provide formed anode foil plates with edges which do not have to be reformed during capacitor aging and which do not have any particulates at cut edges. The formed anode plates are layered with cathode plates and separators in a capacitor housing with an electrolyte to provide a finished capacitor.

Abstract: A method for ensuring two-sided telemetry in implantable cardiac therapy devices by making at least one of the following operating parameters selectable (reversible): (1) the direction of current detection of the telemetry circuitry of the implantable cardiac therapy device; (2) the direction of the magnetic field produced by the transmit coil of an external telemetry device (programming wand); (3) the direction of the magnetic field produced by the T/R coil of the implantable cardiac therapy device; and/or (4) the direction of current detection of the telemetry circuitry of the programming wand. In a presently contemplated implementation, when it is desired to read-out data from the implantable cardiac therapy device and/or to re-program the device parameters, a telemetry operation is attempted in the normal manner, i.e., it is initiated by the programming wand.

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 extractable lead and method for chronic blood contacting use. The new lead contains a hydrogel coating having a thickness increase greater than 10% when hydrated. A thick coating is used to provide a shear layer so that the coating tears during extraction, either at the coating/lead interface, between layers of the coating itself, or at the coating/tissue interface. Furthermore, because of the flexibility of such a thick coating, contracture of any fibrous capsule that may have formed is not a problem during extraction, since instead of contracting onto the lead, it contracts onto the flexible coating which can be extracted out of the tight capsule.

Abstract: An electrolytic capacitor with several conductive layer portions, including some anode layers and some cathode layers in alternating arrangement. A set of insulator layers is interleaved with the conductive layers, and the conductive and insulator layers are laminarly stacked with an anode layer being outermost on one surface. The stack is positioned adjacent a metal heat sink, with an outer insulator layer positioned between and closely contacting the stack and the heat sink. The cathode layers may be connected to the heat sink.