Abstract: An implantable cardioverter defibrillator for generating biphasic waveforms to treat cardiac dysrhythmias creates the second phase of the biphasic waveform from an active low energy source, rather than from a capacitive charge storage system. A high voltage first phase of the biphasic waveform is generated from the charge stored in a typical capacitive charge storage system. A low voltage second phase is generated from the continuous discharge of an active low voltage power source. By using an active low voltage power source system to directly produce the second phase of the biphasic waveform, the overall size and power requirements of the implantable device can be reduced.

Abstract: The present invention provides a biophysical-electronic system and method embodied in a defibrillation system with a range of pulse durations under 6 milliseconds, which is precisely the optimal range. The present invention provides an implantable defibrillator that delivers such waveforms. The present invention specifies optimal pulse duration for a given capacitor size, a determination that takes into account both the time constant of the system and the characteristic time (chronaxie) of the cardiac tissue. In addition to enhancing defibrillation effectiveness, the present invention provides size reduction in the implantable system, or the increased battery (and hence system) life, or some of both. The lower-energy shocks also reduce tissue damage from defibrillation procedures.

Abstract: The model that is developed in the 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. The apparatus makes use of the mathematical definition of optimum pulse duration by storing in the control circuitry of the defibrillation system the actual measured value of the particular capacitor incorporated in the system.

Abstract: The present invention uses the chronaxie, a characteristic time that enters into heart defibrillation. The present invention defines a figure of merit for physiologically effective current for characterizing and evaluating a defibrillation pulse. Using this figure of merit then, the present invention compares defibrillation-pulse options and to determine optima for capacitance, tilt, and pulse duration. The combined abilities of optima determination and quantitative comparison of options provides for shorter pulses and lower capacitance values than have been in common use in the prior art. The overall result of the present invention is the specifying of smaller, more efficient implantable defibrillator designs.

Abstract: An implantable defibrillator system for generating biphasic waveforms comprises a self-contained human implantable housing containing a capacitor system for storing an electrical charge, a power supply for charging the capacitor system, and a controller for selectively discharging the electrical charge as a biphasic countershock to be delivered through at least two electrodes in response to a sensing of a cardiac dysrhythmia in the human patient. The controller includes a system for controlling a first duration of a first phase of the biphasic countershock such that the discharge of the electrical charge is of a first polarity and the first duration is variable and a system for controlling a second duration of a second phase of the biphasic countershock such that the discharge of the electrical charge is of a second polarity that is opposite from the first polarity and the second duration is fixed.

Abstract: An electrode system for an implantable cardioverter defibrillator. The electrode system includes a conductive structure which is physically and electrically connected to the housing or can of the implantable cardioverter defibrillator and is used as an electrode in combination with an existing implantable cardioverter defibrillator electrode or electrodes. The electrode system provides a therapeutically significant increase in the effective surface area of the implantable cardioverter defibrillator's electrodes without requiring an additional header connection, feedthru, or cable.

Abstract: A defibrillation electrode apparatus which provides defibrillating, pacing, and sensing functions with the use of fewer conductors. Conductor requirements are minimized by solid-state multiplexing that is accomplished at the distal end of the apparatus. The apparatus comprises:a. a body structure;b. a number "X", wherein X is at least 3, of electrode members disposed on the body structure for electrical communication with the exterior environment;c. a number "X-Y", wherein Y is a number between 1 and X-2, of conductive lead members, each lead member being communicatively connected to at least one electrode member and extending therefrom to a predetermined point on the body structure, and wherein each electrode member is connected to one lead member and at least one lead member is connected to more than one electrode member; andd. a rectifier connected between at least one lead member and at least one electrode member.

Abstract: A method for rapidly and accurately determining defibrillation thresholds. The method comprises the steps of delivering an initial shock series to a patient, the shock series comprising at least two shocks of differing energy levels, determining an estimated shock level adjustment based on the initial shock series, and delivering at least one adjusted shock of a predetermined energy level based on the estimated shock level adjustment. The technique uses optimized search criteria as opposed to the conventional step-wise decrease and increase techniques. An apparatus for implementing the method is also disclosed.

Abstract: An implantable defibrillator having programmable shock waveforms and paths where each successive waveform may be of a different shape and form, and delivered to and through an area of the human heart in a desired sequence. The shock waveforms can be delivered independently through certain areas of the heart or through different areas of the heart to the can electrode or to a patch electrode at a computed common time. Alternatively, a first shock waveform or set of shock waveforms can be delivered through one or more areas of the heart followed by a delivery of time sequenced delayed shock waveform or forms through specific areas of the heart to the can electrode or patch electrode.

Abstract: An implantable cardioverter defibrillator (ICD) system employs polymer film capacitor technology for the capacitor system. Unlike existing ICD systems which utilize electrolytic capacitors, the ICD system of the present invention utilizes polymer thin film capacitors to deliver an electrical countershock having an effective pulse duration of greater than the chronaxie duration of the human heart from a maximum stored energy of less than about 35 joules when charged to a maximum charging voltage of at least about 800 volts. Preferably, the polymer thin film capacitors having a dielectric thickness of between about 1,000 nm and 10,000 nm and an effective capacitance of the less than about 80 .mu.F with a maximum charging voltage of less than about 1500 volts or a maximum peak current of less than about 30 amperes.

Abstract: A method and apparatus for progressive recruitment of cardiac fibrillation uses an implantable defibrillator to deliver a multiple, discontinuous pulse waveform that is comprised of a series of smaller recruitment pulses delivered prior to delivery of a larger defibrillating pulse. Instead of using multiple identical pulses to accomplish defibrillation, the present invention decreases the overall energy required for effective defibrillation with a single, larger defibrillation pulse by using multiple, smaller recruitment pulses to recruit or capture as many heart cells as possible into a primary one of the many activation wavefronts in a fibrillating heart. By synchronizing the heart cells recruited in this manner, the effectiveness of the single, larger defibrillation pulse is increased, thereby decreasing the maximum stored energy required for defibrillation.

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: The present invention uses switches to set the topology and polarity of a circuit that includes capacitors to deliver an electric pulse to a heart during a defibrillation procedure. The waveform of the electric pulse is biphasic, in that it is a positive portion of the pulse followed by a negative portion of the pulse. The topology and polarity of the circuit are utilized to produce a waveform that approximates the ideal waveform for the specific situation. The circuit provides for combinations of capacitors variously in series and in parallel and changing the topology and polarity of the circuit during discharge of the capacitors.

Abstract: The invention relates to a steering system for a catheter tip. The system includes wire members that extend through a catheter wall that are used to pull a distal portion of the catheter tip causing controlled, predetermined bending at the tip. Anchoring members located near the catheter tip connect the distal end of the catheter with wire members. The steering system also contains control members which are located at a proximal portion of the catheter and are used to control the pull on the wire members. Steering enhancement members are also included in the steering system which facilitate the bending of the catheter wall.

Abstract: An ablation catheter system, including a guiding/mapping catheter assembly and a laser catheter. The guiding/mapping catheter includes ring electrodes, tip electrodes, a moveable fixation wire, and a central catheter lumen for an ablation catheter. A laser catheter includes an optical fiber for passing laser energy, tip electrodes, an optical fiber port, and thermocouples on the end of hypodermic tubing.

Abstract: A defibrillator having a connector utilizing a plurality of ports aligned therein to accommodate sensing leads, and positive and negative defibrillator electrode leads. The positive defibrillator leads are internally connected in common and can facilitate the use of two positive defibrillator leads. Alternative embodiments illustrate methods of having different post polarities for use in situations where having different electrode polarities is beneficial. Other alternative embodiments illustrate methods for limiting current or EMF through one of the commonly wire defibrillator ports.

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 potential energy transfer to the tissue, thereby allowing an increase in the lesion size produced by the ablation. The ablation catheter includes a catheter body. The ablation catheter also includes a tip for monitoring electrical potentials, and applying electrical energy to a biological tissue. A fluid source is positioned at one end of the catheter for supplying a fluid flow through the catheter to the tip means. Passages are positioned within the tip in a variety of manners for directing the fluid flow through the tip means 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 structure for measurement of the electrical potentials in a biological tissue.

Abstract: A programmable implantable cardioverter defibrillator (ICD) provides signals from a plurality of cardiac sensing modalities to a control circuit within the ICD that analyzes the signals and determines whether to deliver an electrical countershock therapy. An interdependent detection parameter threshold is programmably established for each of a programmably selectable combination of two or more cardiac sensing modalities by selecting at least two corner points that will define a boundary condition for a given cardiac dysrhythmia. Whenever the threshold is exceeded, the control circuit automatically diagnoses a cardiac dysrhythmia and delivers a preprogrammed electrical countershock therapy regimen for the diagnosed dysrhythmia. Multiple interdependent detection parameter thresholds may be combined in a variety of ways. More than one combination of two or more cardiac sensing modalities may be used to define a multivariant boundary condition for the given cardiac dysrhythmia.

Abstract: A low profile defibrillation catheter which is much thinner than existing devices. The thin structure is provided by using the current conductor as the electrode. The thin design is motivated by an electrical field analysis which reveals that the length of the catheter is the important determinant of defibrillation ability, and that the large radius and surface area of prior art devices was not beneficial.

Abstract: An implantable cardioverter defibrillator (ICD) device in operated in an overcharged final countershock condition so as to provide greater efficacy and broader treatment modality for the device. Instead of delivering a repeated series of up to five countershocks at the maximum rated charging voltage in response to a persistent ventricular arrhythmia as is done in existing ICD systems, an overcharged final countershock is delivered for which the electrolytic capacitor charge storage system of the ICD system is charged at a voltage that exceeds a maximum voltage specification. By delivering an overcharged final countershock, the present invention increases the chances of reversing a persistent ventricular arrhythmia which has become increasingly resistant to electrical therapy the longer the arrhythmia persists.