Abstract: The present invention is directed to a conductive electrolyte for use in high voltage electrolytic capacitors and to an electrolytic capacitor impregnated with the electrolyte of the present invention for use in an implantable cardioverter defibrillator (ICD). The electrolyte according to the present invention is composed of a two solvent mixture of ethylene glycol and an alkoxy-substituted alcohol, such as 2-methoxyethanol, 2-ethoxyethanol, or 2-butoxyethanol. Dissolved in this mixture is a combination of acids including at least one straight chain aliphatic dicarboxylic acid of carbon chain length from eight to thirteen (C8 to C13) and a longer chain dicarboxylic acid, where the acid functional groups are separated by 34 carbons (referred to as “dimer acid”). As further additives, boric acid and hypophosphorous acid can be added, with the former providing corrosion inhibition in the finished capacitor, and the latter resulting in lower leakage currents and better voltage droop characteristics.

Abstract: The heart failure (HF) status of a patient is determined based on the morphology of a signal representative of arterial pulse pressure. The signal can be a plethysmography signal that is produced by a implantable sensor or a non-implanted sensor. The signal can be produced by a chronically implantable sensor. In one embodiment, a time derivative signal is produced based on a signal representative of arterial pulse pressure. The time derivation signal can be used to determine maximum and minium peaks of,the signal representative of arterial pulse pressure. Alternatively, HF status can be assessed directly from the time derivative signal.

Abstract: A method for detecting an arrhythmia hidden by rapid pacing in a rate adaptive pacemaker/defibrillator. Unmasking a potential arrhythmia is accomplished by lengthening the pace cycle length by a small amount for a number of cycles followed by a shortening of the pace cycle length for the same number of cycles giving an average pacing rate equivalent to the desired rate. This can occur at all times or only when conditions make arrhythmia masking possible. Changing the pace cycle by a small amount over a number of cycles will move the arrhythmia and paced rhythm out of synchronization. Forcing the pacer to continue sensing the arrhythmia is accomplished by insuring that the pacer's sense refractory is less than one half of the pacing cycle length. This is done by constraining the programming of that value to one half the minimum pacing cycle length or using an adaptive sense refractory period.

Abstract: The heart failure (HF) status of a patient is determined based on the frequency characteristics of a signal representative of arterial pulse pressure. The signal can be a plethysmography signal that is produced by a implantable sensor or a non-implanted sensor. The signal can be produced by a chronically implantable sensor.

Abstract: The present invention is directed to a conductive electrolyte for use in high voltage electrolytic capacitors and to an electrolytic capacitor impregnated with the electrolyte of the present invention for use in an implantable cardioverter defibrillator (ICD). The electrolyte according to the present invention is composed of a two solvent mixture of ethylene glycol and di(ethylene glycol); a combination of boric acid with an aliphatic dicarboxylic acid of carbon chain length from eight to thirteen, such as suberic, azelaic, sebacic, undecanedioic, dodecanedioic, or brassylic acid; a very long chain dicarboxylic acid, where the acid moieties are separated by 34 carbons; and a nitro-substituted aromatic compound as a degassing agent, such as 3-nitroacetophenone or 2-nitroanisole. This electrolyte is then titrated with a light amine such as ammonia, diethylamine, dimethylamine, trimethylamine, or triethylamine.

Abstract: An implantable cardiac stimulation device with a hybrid battery network having first and second batteries with different battery chemistries connected in parallel with each other. The first dense cell battery has a higher resistance and greater energy density than the second fast cell battery, and the fast cell battery has greater current carrying capability than the dense cell battery. The dense cell battery has a higher voltage than the fast cell battery. In one embodiment the dense cell is a Lithium Carbon Monofluoride cell and the fast cell is a Lithium Silver Vanadium Oxide cell. During high current demand of high voltage capacitor charging, the fast cell provides the vast majority of the current due to its lower resistance. Following capacitor charging, the fast cell is recharged from the dense cell at a rate limited by the voltage difference between the cells.

Abstract: A method for monitoring the progression of the disease of a heart failure patient is provided. An implantable or other ambulatory monitor senses acoustic signals including heart and lung sounds within the patient. Significant changes in the energy content of either the heart or lung sounds is indicative of a heart failure exacerbation. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.

Abstract: The present invention is directed to a gelled electrolyte and to an electrolytic capacitor impregnated with the gelled electrolyte of the present invention for use in an implantable cardioverter defibrillator (ICD). The electrolyte gel according to the present invention is generated by the addition of a gelling agent, preferably D-mannitol, to a conventional electrolyte. The gelling agent of the present invention can be used in ethylene glycol based electrolyte systems with or without a polar organic cosolvent. Dissolved in this mixture is an aliphatic dicarboxylic acid of carbon chain length from eight to thirteen (C8 to C13) as the ionogen. In order to achieve the necessary electrolyte conductivity, an amine is added to adjust the electrolyte pH to within a range of 6-10. An amount of D-mannitol is added to the electrolyte to reach the final weight percent of 8-15% by weight of the total electrolyte mixture.

Abstract: Cardiac performance associated pacing parameters is improved by applying evolutionary algorithms that maintain a plurality of sets of pacing parameters for pacing a heart. An initial plurality of sets of pacing parameters are determined. A cardiac performance value is determined for each of the plurality of sets of pacing parameters. At least one set of pacing parameters is selected from the plurality of sets of pacing parameters based on the cardiac performance values. An updated plurality of sets of pacing parameters is then created based on the selected at least one set of pacing parameters. These steps (except for determining the initial plurality of sets of pacing parameters) are repeating a plurality of times, wherein each time the steps are repeated, the updated plurality of sets of pacing parameters most recently created are used.

Abstract: A method and apparatus for forecasting arrhythmia based on real-time intact intracardiac electrograms. Real-time changes in the electrograms that may be used to predict an impending arrhythmia are identified from non-arrhythmic complexes of the intracardiac electrogram prior to the onset of a spontaneous arrhythmia. One embodiment relies on a running comparison between the morphology of a normal sinus template and a sequence of complexes within a running window. In an alternative embodiment the comparison is made between a pre-arrhythmic template and the acquired electrogram wherein a high correlation is an indicator of an impending arrhythmia. The analysis may be performed continuously or periodically.

Abstract: An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses optical plethysmography responsive to variations in arterial pulse amplitude to detect the hemodynamic status of a patient. A light source and light detector are positioned for a reflected-light configuration on a device housing and coupled to electronic circuitry in the housing via a hermetic feedthrough. In one embodiment, the light source and detector are positioned in a recess in a wall of the device housing and surrounded by an encapsulant. The source and detector are positioned for a reflected-light configuration and are preferably an infrared (IR) LED and photodiode, respectively. The source and detector may be placed in a single recess that is created when the device housing is manufactured. An opaque optical barrier is place between the source and detector, which ensures that no light passes between them without first interacting with the overlying tissue.

Abstract: A method for detecting an arrhythmia hidden by rapid pacing in a rate adaptive pacemaker/defibrillator. Unmasking a potential arrhythmia is accomplished by lengthening the pace cycle length by a small amount for a number of cycles followed by a shortening of the pace cycle length for the same number of cycles giving an average pacing rate equivalent to the desired rate. This can occur at all times or only when conditions make arrhythmia masking possible. Changing the pace cycle by a small amount over a number of cycles will move the arrhythmia and paced rhythm out of synchronization. Forcing the pacer to continue sensing the arrhythmia is accomplished by insuring that the pacer's sense refractory is less than one half of the pacing cycle length. This is done by constraining the programming of that value to one half the minimum pacing cycle length or using an adaptive sense refractory period.

Abstract: A method for monitoring the progression of the hemodynamic status of a heart failure patient. An implantable or other ambulatory monitor senses the patient's electrocardiogram (ECG) and calculates R-R intervals. The R-R intervals are used to calculate a measure of heart rate variability (HRV). Significant excursions from the average of the HRV measure are indicative of a heart failure exacerbation. Alternatively, vascular plethysmography provides a measure of pulse amplitude. Significant reduction in pulse amplitude and pulse amplitude variability are indicative of a heart failure exacerbation. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.

Abstract: An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses an acoustic transducer responsive to heart sounds to detect the hemodynamic status of a patient. A hermetic housing encloses the device electronics and the device housing includes at least one substantially planar face configured to act as a diaphragm in response to acoustic waves. A transducer positioned inside the device housing provides an output signal to the device electronics responsive to vibration of the diaphragm. Embodiments of the transducer include a piezoelectric element and laser interferometer. The hemodynamic information may be used in various ways including arrhythmia discrimination and pacing and sensing optimization.

Abstract: An apparatus for extracting activity information and position information from a composite signal generated by a motion sensor includes an analog to digital converter for converting the composite signal from analog to digital format. A wide-band low pass filter having a frequency response of about zero hertz to about ten hertz and a narrow low pass filter having a frequency response of about zero hertz to about 0.5 hertz filter the digitized composite signal. An adder subtracts the output of the narrow-band low pass filter from the output of the wide-band low pass filter. The resulting difference represents information regarding the activity level of the motion sensor, and the output of the narrow-band low pass filter represents information regarding the position of the sensor.

Abstract: The present invention relates to an improved method of impregnating electrolytic capacitor stacks or wound rolls with a polymer based electrolyte, such as a hydroxyethylmethacrylate (HEMA) or hydroxyethylacrylate (HEA) based electrolyte, to render them suitable for use in electrolytic capacitors, and to such electrolytic capacitors. The initiator to promote the polymerization of the polymer based electrolyte and a surface active wetting agent are deposited on the foil or in the stack or wound roll prior to impregnation of the stack or wound roll with a polymer based electrolyte, allowing the polymer based electrolyte solution to be warmed prior to impregnation to a temperature suitable for easy impregnation into the anode and cathode foil and paper. Polymerization does not begin until impregnation of the capacitor with the polymer based electrolyte and the surfactant allows the polymer based electrolyte to more fully incorporate itself into the microscopic features of the anode foil.

Abstract: A circuit for sequentially discharging two capacitors configured for independent discharge into heart electrodes to create a biphasic electrical shock. Upon determination that a therapeutic shock needs to be applied to a heart, the capacitors are charged. Once the capacitors are sufficiently charged, one of the capacitors is switched such that it begins to discharge into the heart. At an appropriate time, this capacitor is switched again such that it no longer discharges into the heart. At this time, the other capacitor is switched such that it begins to discharge into the heart, and at an appropriate time, it is switched such that is stops discharging into the heart. The two capacitors are preferably configured with opposite polarities so that the waveform applied to the heart by the sequential discharging of the two capacitors is biphasic.

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: A system and method for providing improved defibrillation thresholds. In one embodiment of the invention, following the detection of fibrillation, a pacing pulse train is applied to a pacing electrode placed in the low gradient region of the left ventricular freewall to capture the tissue. In one embodiment, a pacing rate of about 80-95% of the VF cycle length is applied to achieve capture. Once capture of the tissue of the critical region is achieved, a high energy shock is delivered when the captured tissue is in the process of activation. The defibrillation shock is delivered at the end of the pacing train, with a coupling interval of either about 80-95% of the pacing rate (i.e., about 64-90% of the VF cycle length), or, alternatively, about 5-20% of the pacing rate (i.e., about 4-19% of the VF cycle length).

Abstract: A method and apparatus for monitoring the hemodynamic status of a patient is provided. It comprises an implantable monitor with one or a plurality of sensors configured for extravascular placement, electronic circuitry that is coupled to the sensors and processes their output, a transmitter/receiver for conveying information between the monitor and an external unit, and a patient alert which notifies the patient if medical attention should be sought. The extravascular sensors include vascular plethysmography, heart and lung sounds, thoracic impedance, and ECG. In the preferred embodiment, the radio frequency transmitter/receiver provides for the automatic telemetry of data, without requiring the active participation of the patient or clinician. Thus data can be conveyed routinely and automatically, allowing more computationally demanding analysis to be done by an external device, or allowing human review at a central location. The monitor is particularly applicable to patients with heart failure.