Abstract: The present invention is a R-wave sensing system for an implantable cardiac arrythmia therapy device. In particular the present invention is a system having local detection electrodes for sensing a local electrical signal representing cardiac activity in a local area of a patient's heart and having global detection electrodes for sensing a global electrical signal representing cardiac activity in a global area of the patient's heart. First and second amplifiers for amplifying the local and global electrical signals detected are provided as are first and second filters for filtering the detected signals. A converter is provided for converting the local electrical signal detected by the local detection electrodes into a digital signal so as to generate a masking pulse.

Abstract: An implantable defibrillator derives a rectangular current waveform from a capacitor discharge by using a current limiter. This pulse-shaping method is equally applicable to single-path and multiple-path situations. A rectangular pulse delivers a maximum of energy for a given peak-field value with a particular electrode combination and pulse duration. Peak field is a measure of the tissue-damage potentiality of a particular discharge.

Abstract: A method and apparatus for controlling an implantable cardioverter defibrillator utilizes a back-biasing precharge circuit to precondition the heart before delivery of a biphasic electrical countershock. The back-biasing precharge circuit delivers a low voltage pulse to the implantable defibrillation electrodes that is opposite to the polarity of the initial phase of the biphasic countershock. In the event of a continuing cardiac arrhythmia which is not successfully converted by a single countershock, subsequent countershocks are delivered having alternating polarities from the preceding countershock such that both the polarity of the back-biasing pulse and the biphasic countershock are reversed as compared to the immediately preceeding countershock.

Abstract: A cardioversion/defibrillation catheter lead has selectively exposable outer conductors that increase the effective electrode area and that can be used to direct electrical countershock vectors delivered by the catheter lead. The lead includes an elongated catheter body having a proximal end, a distal end and a catheter length. The catheter body includes at least one electrical conductor surrounded by a dielectric tubular sheath and an outermost dielectric tubular sheath. Each electrical conductor is electrically connected to an electrical connector located at the proximal end of the catheter body and to a cardioversion/defibrillation electrode located long the catheter body between the proximal end and the distal end. At least a portion of the outermost dielectric tubular sheath includes structure for selectively removing that portion of the outermost tubular sheath, thereby creating an effective length of at least one of the electrodes which is longer than an original length of that electrode.

Abstract: An ICD detection method for sensing the occurrence of an R-wave improves the ability to distinguish R-waves from noise through the use of variable declining sensitivity thresholds. The method includes the consideration of the amplitude of at least the previous most recent R-wave to determine a declining threshold of sensitivity used to recognize a subsequent electrical signal as an R-wave. In the method, the amplitude of the previous R-wave may be classified, based upon amplitude, and based upon the classification, a desirable time constant for the declining threshold of sensitivity is provided as an exponential or reverse exponential decay. Alternatively, a piece wise use of various decay formulas may be combined and used to avoid false recognition of noise as an R-wave.

Abstract: An implantable cardioverter defibrillator (ICD) system features rate-responsive pacing capabilities. An electrical pulse generating device having a housing containing pulse generating circuitry is provided. A conductive lead connectable to the housing that has a first electrode, a second electrode and a coil electrode is provided. Switching circuitry is provided contained in the housing that switches the coil electrode between the rate-responsive sensing electrode to a defibrillation electrode. Control circuity is provided within the housing for controlling the delivery of modulating signals to the coil electrode and for sensing changes in resistance between the coil electrode and the housing. The control circuitry also causes an alteration of the pacing signal applied to the pacing electrode depending upon the change in the resistance sensed.

Abstract: A capacitor-discharge implantable cardioverter defibrillator (ICD) has a relatively longer device life of greater that 5 years. The longer life of the ICD is achieved by selecting and arranging the internal components of the ICD to deliver a maximum defibrillation countershock optimized in terms of a minimum physiologically effective current (I.sub.pe), rather than a minimum defibrillation threshold energy (DFT). As a result of the optimization in terms of a minimum effective current I.sub.pe, there is a significant decrease in the maximum electrical charge energy (E.sub.c) that must be stored by the capacitor of the ICD to less than about 30 Joules, even though a higher safety margin is provided for by the device. Due to this decrease in the maximum E.sub.

Abstract: A device and method for performing automatic battery maintenance as particularly applied in an implantable cardioverter defibrillator (ICD). The battery is maintained at a predetermined state-of-charge to enable charging a capacitor in the ICD to discharge high voltage pulse into a human patient via electrodes implanted in the patient.

Abstract: A staged energy storage system provides electrical energy to an implantable biomedical device by using the combination of a first stage energy source and a second stage energy concentration system. The second stage energy concentration system allows a lower density and/or lower voltage energy source to be used as the first stage energy source, thereby decreasing the battery cost, size and weight. In one embodiment, the second stage energy concentration system comprises a rechargeable battery. In another embodiment, the second stage energy capacitor system comprises a high energy density capacitor system. The staged energy storage system is ideal for internally charging a pulse-generating capacitor system within an implantable cardioverter defibrillator. In this embodiment, a high voltage transformer has a secondary side that is electrically connected to the pulse-generating capacitor system.

Abstract: The present invention is an implantable cardioverter defibrillator (ICD) system that is electrically connected to two or more implantable discharge electrodes for implantation into a human patient for treating cardiac dysrhythmias. The ICD system has a battery system and a stepup transformer for charging a capacitive storage system in response to a cardiac dysrhythmia detected by a sensing system. A plurality of electrodes are provided which are adapted to be implanted into a human patient. A primary capacitive energy storage system is provided and is corrected to the stepup transformer for storing and delivering a high voltage output of at least 1500 volts. A stepdown transformer is also provided which is connected between the primary capacitive energy storage system and the electrodes for reducing the high voltage output of the primary capacitive energy system to a safe level for the heart.

Abstract: A low profile defibrillation catheter is disclosed which is much thinner than existing devices. The thin structure is provided by using the current conductor coil as a first electrode coil and the same materials as the conductor for the second electrode. The second electrode coil is bonded to the second conductor coil and wound in the same direction. The thin design is motivated by an electrical field analysis which reveals that the length of the catheter is the important determinant of defibrillation efficacy, and that the large radius and surface area of prior art devices were less beneficial.

Abstract: The model that is developed in the present invention is based upon the pioneering neurophysiological models of Lapicque and Weiss. The present model determines mathematically the optimum pulse duration, d.sub.p, for a truncated capacitor-discharge waveform employed for defibrillation. The model comprehends the system time constant, RC, where R is tissue resistance and C is the value of the capacitor being discharged, and also the chronaxie time, d.sub.c, defined by Lapicque, which is a characteristic time associated with the heart. The present model and analysis find the optimum pulse duration to be d.sub.p =(0.58)(RC+d.sub.c). Taking the best estimate of the chronaxie value from the literature to be 2.7 ms, permits one to rewrite the optimum pulse duration as d.sub.p =(0.58)RC+1.6 ms.

Abstract: The present invention is a pectorally implantable defibrillation system for delivering at least one electrical cardioversion/defibrillation countershock. The system has a housing designed to be implanted in a human patient, wherein the housing has an outer shell and an inner cavity. Pulse generating circuitry is positioned within the cavity for generating the at least one countershock. Circuitry is also positioned within the cavity to control delivery of the at least one countershock. At least one surface of the outer shell is electrically conductive to form an electrode for the system. Because of the close proximity between the housing electrode and the circuitry positioned within the housing, the circuitry is susceptible to undesired capacitive coupling effects. To reduce the capacitive coupling effects, a slew rate limiting circuit is connected between the pulse generating circuitry and the electrode formed on the housing.

Abstract: The invention relates to an ablation catheter which controls the temperature and reduces the coagulation of biological fluids on a tip of a catheter, prevents the impedance rise of tissue in contact with the catheter tip, and maximizes the energy transfer to the tissue, thereby allowing an increase in the lesion size produced by the ablation. The ablation catheter includes a tip for applying electrical energy to biological tissue. Passages are positioned within the tip in a variety of manners for directing a fluid flow through the tip to the exterior surface of the tip to control the temperature and form a protective fluid layer around the tip. Monitoring structure is also positioned within the tip for measurement of the electrical potentials in a biological tissue. Ablation electrode structure is also positioned within the tip for application of ablative energy to the biological tissue.

Abstract: A method and apparatus for inducing fibrillation generates a continuous fibrillation waveform from the internal battery source of an implantable cardioverter defibrillator. The continuous fibrillation waveform has a voltage of at least 5 volts and not more than 50 volts and a duration of not less than 500 milliseconds and is applied though the at least two implantable electrodes so as to induce fibrillation in the heart of the human patient.

Abstract: The invention discloses a catheter for use with an implantable cardioverter in which the catheter has at least two discharge electrodes positioned along the length of the catheter in such a fashion as to place each electrode in the optimal position to effect atrial and ventricular cardioversion and defibrillation.

Abstract: A method and apparatus for treating ventricular tachycardia arrhythmias using an ICD system delivers a series of stepped cardioversion pulses that include at least a first and second cardioversion countershock of low energy values that are less than about 5 joules. The energy values of each cardioversion countershocks increase in stepped progressions such that the low energy value of the first cardioversion countershock is less than the second and all subsequent cardioversion countershocks. The use of a series of stepped cardioversion pulses minimizes the possibility of "overstimulating" heart cells in any reentrant loop that are causing the ventricular tachycardia. As a result, the possibility of inducing fibrillation by the cardioversion therapy is significantly decreased. The leading edge of each of the series of stepped cardioversion pulses is sufficient to just stimulate any heart cells that are in phase 4, but is not strong enough to stimulate heart cells that are in phase 3.

Abstract: A main energy delivery electrical circuit for use in an implantable cardioverter defibrillator device comprises a low power output primary defibrillator battery, a high power output intermediate power intensifying capacitor system, a switch for permitting the intermediate power intensifying capacitor system to rapidly charge a main energy delivery capacitor, and a main energy delivery capacitor. The main energy delivery capacitor is configured for discharging, in a first pulse, an electrical charge derived from the primary battery, and for discharging certain subsequent pulses of electrical charge derived from the intermediate power intensifying capacitor system. The circuit permits the implantable cardioverter defibrillator device to deliver multiple closely spaced defibrillation pulses to a heart.

Abstract: The present invention is a physician's interface expert system that allows a physician not well versed in ICD parameters to program at least one parameter into an ICD using the physician's existing knowledge of the patient's medical history. The programmable ICD system is composed of an implantable portion and a programming device external from the patient's body. The implantable portion has pulse generating circuitry, control circuitry including parameter storage, a receiver and at least one electrical lead for placement in the patient's heart. The programming device contains an operator interface device that receives a first set of values from the operator. A translator is provided in the programming device for translating the first set of values into a second set of values formatted in accordance with the programmable parameter settings of the implanted device. Finally, a transmitter is provided in the programming device to transmit the second set of values to the receiver of the implanted device.

Abstract: A defibrillator for pectoral implant in a patient wherein the metal housing or case of the defibrillator is utilized as an electrode and is operative to supply electrical pulses. The housing is coated with an oxidation resistant material to optimize electrode function.