Cardiac Actuator

Abstract

A cardiac actuator, specifically an implantable heartbeat maker, has at least two voltage sources, such as batteries or accumulators, which can be interconnected in parallel, for supplying energy to the beat making circuit. The invention is particularly characterized by a switching device which provides alternating and separate switch connections of the individual voltage sources to the beat making circuit.

Description

This invention relates to a cardiac actuator, particularly an implantable heartbeat maker with at least two voltage sources, such as batteries or accumulators, which can be interconnected in parallel for supplying energy to the beat making circuit.

In heartbeat makers of this type it is known to connect the individual voltage sources through diodes with the beat making circuit. This provides that the voltage source having the highest voltage takes over the energy supply of the beat making circuit. The drawback is that the current supply takes place for a comparatively long time period from only one of the voltage sources. This is dangerous since when the first voltage source is discharged, the beat maker is not safe any more due to the fact that no precise data can be made about the life duration of the second voltage source. Furthermore there is an energy loss at the diodes due to the sieving voltages.

An object of the present invention is to provide a heartbeat maker of the described type wherein the individual voltage sources are substantially uniformly loaded, namely, they supply energy in the same way, and thus are equally slowly discharged. Furthermore, provision should be made that the entire voltage of the voltage sources should be provided to the greatest possible extent for the beat making circuit, thus avoiding drops in voltage which take place in the known circuit by the use of diodes.

Other objects of the present invention will become apparent in the course of the following specification.

In the accomplishment of the objectives of the present invention it was found desirable to provide a switching device for supplying energy to the beat making circuit of a heartbeat maker having at least two voltage sources adapted to be interconnected in parallel. The switching device provides for alternate and separate switch connections of the individual voltage sources to the beat making circuit.

The present invention provides that the individual voltage sources will be uniformly loaded and that the connection of the voltage sources to the beat making circuit, -- which preferably takes place by means of electronic switches (transistors), -- does not cause any losses in voltage.

According to a preferred embodiment of the present invention two separate voltage sources are used, normally consisting of two groups of batteries. When two voltage sources are used, the switching device, -- according to the present invention -- can be constructed in a particularly simple manner by providing a separate cut-out and closer switch between each voltage source and the beat making circuit and by using a bistable tipping stage as an actuating device for the operation of these switches. The bistable tipping stage is preferably operated by an astable multivibrator which at the same time can operate the proper time sequency of beat making impulses in the beat making circuit.

The present invention can be also effectively used when more than two voltage sources are provided. In that case according to a further embodiment of the present invention a counting switch is used which switches on the individual voltage sources one after the other in cycle to the beat making device by means of operable switching members (transistors).

The current supply for the switching device is also provided from available voltage sources, preferably however in such manner that the voltage is supplied through diodes to the switching device. This takes into consideration the fact that the switching device on the one hand requires less voltage and on the other hand has a lesser current consumption, so that voltage drop through the diodes can be disregarded.

A further embodiment of the present invention includes the use of a voltage measuring circuit with a signal giver which produces a signal at a set limit value of the switched on voltage source to prevent further connection of that voltage source to the beat making circuit. When two voltage sources are used the limiting value signal can be transmitted to the bistable tipping stage to provide a continuing switching of this stage to the other switch position. It can be also used to switch off the astable multivibrator. When more than two voltage sources are used the limiting value signal is used to influence the counting switch circuit in such manner, that the voltage source which leads to the release of the limiting value signal will not be considered any more during the cycling testing of the voltage sources. The voltage measuring circuit can be provided by a known comparator switching and can be so constructed that when it is less than the switched on voltage, the switching to the corresponding voltage source will not take place any more.

In accordance with the present invention the limiting value signal can be used to influence the frequency determining part of the heartbeat maker, so as to produce a specific preferably low impulse frequency which deviates from the previously set frequency and may amount, for example, to 60 imp./min. for heart stimulation. In this manner it is possible to control the voltage sources of an implanted heartbeat maker without examination.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing by way of example only, preferred embodiments of the inventive idea.

In the drawing:

FIG. 1 is a circuit diagram of a cardiac actuator of the present invention using two voltage sources.

FIG. 2 shows the same circuit diagram but amplified by a voltage measuring circuit for examining voltage conditions of the individual voltage sources .

FIG. 1 shows two battery groups 1 and 2 which feed through diodes 3 and 4 the astable multivibrator 5 and the bistable tipping stage 6. The two battery groups 1 and 2 feed individually through the electronic switches 7 and 8 the beat making circuit 9 having an outlet 10. The electronic switches 7 and 8 may consist of transistors and they form jointly with the stages 5 and 6 the switching device for an alternating and separate switching of the voltage sources 1 and 2 to the beat making circuit. The astable multivibrator 5 can be at the same time a functional part of the beat making circuit (as indicated in the drawing by a line connecting the parts 5 and 9) and can serve for producing the frequency with which stimulating impulses are produced by the beat maker.

In the illustrated embodiment the bistable tipping stage provides that the voltage sources 1 and 2 are used alternately in the rhythm of impulse delivery to feed the beat making circuit and thus also to supply the stimulating impulse energy by actuating alternately the switches 7 and 8.

Another embodiment of the present invention shown in FIG. 2 corresponds to a great extent to that shown in FIG. 1. The construction of FIG. 2 is provided only with an additional voltage measuring circuit 11 which is constructed as a comparator and which examines voltages transmitted by switches 7 and 8 to the beat making circuit 9 to determine whether or not they are above a predetermined value. If they are not, the voltage measuring circuit prevents through the conduit 12 the bistable tipping stage 6 from actuating the switch belonging to the used up voltage source and also causes the drop of the frequency of the beat making impulses to a previously set lower value. For that purpose the voltage measuring circuit 11 is connected by the conduit 13 with the astable multivibrator.

Obviously instead of two voltage sources several sources can be used and the described switching device can be replaced by a switching device operated by a calculator (binary counter). Connections used for that purpose are well known in the art.

Claims

1. A cardiac actuator, particularly an implantable heartbeat maker for producing heart stimulating impulses, comprising an outlet, at least two batteries, means interconnecting said batteries in parallel, a switching device comprising an astable multivibrator connected with said means, and a bistable multivibrator connected with said astable multivibrator, means for a separate connection of individual batteries, beat-making means connected to said outlet for applying the impulses to the heart to be stimulated, and means connecting said beat-making means individually with said batteries, said astable multivibrator and said bistable multivibrator for supplying impulses produced by said astable multivibrator to said bistable multivibrator for varying the switching from one battery to the other one for supplying said beat-making means, and for supplying said impulses to said beat-making means to determine the rate of the

2. A cardiac actuator according to claim 1, comprising voltage-measuring means having signal giver means and connected with said batteries, whereby, when an end value of the switched-on battery has been reached, the signal giver means produces a signal to prevent further connection of that battery to said voltage-measuring means and means transmitting the end value signal to said bistable multivibrator to permanently change this multivibrator into another switching position.