Dual battery power system for an implantable cardioverter defibrillator with voltage booster

Abstract

An improved dual battery power system uses two separate battery power sources for an implantable cardioverter defibrillator, each having optimized characteristics for monitoring functions and for output energy delivery functions, respectively. The monitoring functions are supplied electrical power by a first battery source, such as a conventional pacemaker power source in the form of a lithium iodide battery which is optimized for long life at very low current levels. The output energy delivery functions are supplied by a separate second battery source, such as a pair of lithium vanadium pentoxide batteries, which is optimized for high current drain capability and low self-discharge for long shelf life. The first battery source provides electrical power only to the monitoring functions of the implantable cardioverter defibrillator, and the second battery source provides all of the electrical power for the output energy delivery functions.

Description

RELATED APPLICATIONS[0001]This application is a continuation-in-part application of an application filed in the United States Patent and Trademark Office on Jul. 16, 1992, entitled DUAL BATTERY SYSTEM FOR IMPLANTABLE DEFIBRILLATOR, Ser. No. 07 / 913,626, now U.S. Pat. No. 5,235,979 which is a file-wrapper continuation of an application by the same title filed on Mar. 3, 1991, both of which are assigned to the assignee of the present invention, and the disclosure of which is incorporated by reference in the present application. This application is related to a co-pending application filed in the United States Patent and Trademark Office on Mar. 15, 1993, entitled IMPLANTABLE CARDIOVERTER DEFIBRILLATOR HAVING A SMALLER DISPLACEMENT VOLUME, Ser. No. 08 / 033,632,<?delete-end id="DEL-S-00002" ?> <?insert-start id="INS-S-00001" date="20050816" ?>U.S. Pat. No. 5,405,363, which issued on Apr. 11, 1995, and which is assigned to the assignee of the present invention and the disclosu...

AI Technical Summary

Benefits of technology

[0014]The major advantage of the present invention is that each battery source voltage can be optimized for the particular circuit wherein it is used. The first battery source is preferably a relatively low current, low voltage source, from 1.5 to 3.0 V typically; whereas the second battery source is preferably comprised of as high of a current and voltage as battery chemistry and battery packaging efficiencies allow, typically ranging from 6 to 18 V.

[0015]Unlike existing implantable cardioverter defibrillators, a preferred embodiment of the present invention utilizes a separate hardware-based, low-power monitoring circuitry to monitor for certain wake-up conditions which will then activate the output delivery circuitry which includes a microprocessor that performs further detection and, if necessary, selects an appropriate cardioversion / defibrillation therapy to be delivered. The output delivery circuitry includes additional hardware circuitry that, when enabled, can deliverydeliver pacing therapy pulses with energy supplied from the output power source battery without the need to wake the microprocessor.

[0016]Because the two batteries of the present invention can be optimized for their particular functions, different assumptions about the total energy requirements of the implantable cardioverter defibrillator can be made. For example, all existing manufactured implantable cardioverter defibrillators provide power systems which are designed to supply an initial number of defibrillation countershocks of at least 250 shocks. In a single battery system, even when no shocks are delivered, the number of remaining shocks in the device decreases with age due to the fact that the energy for the monitoring functions are drawn from this battery. In the present invention, assuming good charge retention of the output battery, essentially no energy is drawn from the output battery until an electrical pulse therapy is delivered. Consequentially, one advantage of the dual battery system of the present invention is that a smaller initial number of defibrillation countershocks can be specified for an implanted device, while maintaining the same minimum expected life span for the device, thereby allowing a reduction in the overall size of the implanted device.

[0017]Another advantage of a preferred embodiment of the present invention includes a backup protection feature whereby energy from the output power source battery can be used to power the monitoring circuitry in the event that the monitoring power source battery ceases to function. A further advantage of a preferred embodiment of the present invention includes a booster feature which regulates the system supply voltage to prevent ripple in the supply voltage during capacitor charging. Still anotherother advantages include a greater longevity provided for by lowering energy drain by the monitoring circuitry, the simplified circuit design that results in a decrease in the risk of high internal currents causing interference to other parts of the low current monitoring and control circuitry, and the ability to use rechargeable batteries.

Problems solved by technology

Some of these parameters have some measure of mutual exclusively, making it difficult to optimize the battery of electronics without making compromises to the design of the implantable device.

As the device ages, its ability to deliver an adequate number of defibrillating shocks declines as the battery is depleted by the monitoring electronics.

Similarly, if a patient receives a large number of shocks soon after implant, the remaining monitoring life is reduced.

Thus, it is difficult to assess the condition of the battery and its remaining useful life after it has been in use for a period of time.

A further disadvantage of the single battery configuration is that the ideal voltage requirements for the monitoring and output functions are opposite.

All existing manufactured implantable cardioverter defibrillators have compromised between these two demands by using a single battery system or configuration which is typically comprised of two lithium silver vanadium pentoxide cells electrically connected in series to produce an output battery voltage of about 6 V. The battery voltage must be elevated via an inverter circuit to the firing voltage of about 750 V. The net result is that power is wasted in both the monitoring and output circuits because the monitoring circuit which requires only 2-3 V must operate from a relatively high 6 V source, and the output circuit whose efficiency is a function of the supply voltage must operate from the relatively low 6 V source.

Unfortunately, neither of these devices resulted in practical, manufactured implantable cardioverter defibrillators and the dual battery approach was abandoned in both cases.

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