DE2338540A1 - PULSE GENERATOR USED IN A PACEMAKER THAT GENERATES PULSES WITH CONSTANT ENERGY - Google Patents

Description

Dr.-lng. E. BERKENFELD · DIpl.-I.i «j. H. BERK ENFOLD, Pateni Attachment act indications

on the submission of July 26, 1973 VA // Name d. Note WILSON GREATBATCH LTD.

A pulse generator that can be used in a cardiac pacemaker to generate pulses of constant energy

The invention relates to electrical pulse generators and in particular, a new and improved pulse generator that generates pulses of constant energy despite a change of the electrical input to the pulse generator.

One area of application of the invention is medical electronic Pulse generator for use in an artificial cardiac pacemaker, although the principles of the invention are disclosed in US Pat can be used in various ways. Most battery operated pulse generators used to have mercury batteries used, which have a relatively constant voltage during their service life. Lately Batteries such as the lithium iodine cells and thermoelectric core batteries have been developed which are powered by a charged voltage, which gradually decreases over the life of the battery. The end of life is any arbitrary point in time at which the battery voltage drops below an acceptable value, such as the acceptable level of battery voltage in an artificial pacemaker. At this point, however, these batteries fail still has a considerable remaining energy capacity which could be exploited if a remedy were found. de to adapt to the reduced tension.

It is therefore an object of the invention to provide a new and improved electrical pulse generator, which generates an output pulse with almost constant energy, despite decreasing battery voltage when the battery is exhausted.

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Another object of the invention is to provide a pulse generator in which the last remaining chemical Battery capacity, which is only available at reduced voltage, is converted into a usable state instead of into the Battery left unused and wasted.

Yet another object of the invention is to provide a pulse generator which produces a precisely increasing pulse duration, when the battery voltage decreases, so that the condition of the battery can be accurately determined by measuring the pulse duration.

Another object of the invention is to provide a pulse generator for use in an artificial cardiac pacemaker which can be interrogated so that the safety factor of the system can easily be determined at any point in time _e

Yet another object of the invention is to provide a new and improved artificial cardiac pacemaker which ensures a relatively constant safety factor of the system over the entire expected service life of the battery.

The invention provides an electrical pulse generator used, for example, in an artificial cardiac pacemaker will. The output pulses generated by the pulse generator are kept at a constant energy, despite changes in the electrical current amount of the source, especially when the battery nears depletion, so that the duration of the output pulses is gradually increased as its amplitude decreases as the battery ages. When the battery voltage decreases, this is detected by voltage-dependent means in the electrical circuit that forms the pulses and causes a change in one Component of the RC element of the pulse generator, such as of the resistor or the capacitor in the circuit to increase the time constant of the circuit by a required value change, especially increase. In addition, the enlarged

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Pulse duration can be used as an indication of the aging of the battery.

The invention therefore relates to a pulse generator for generating pulses which are constant despite decreasing battery voltage Exhibit energy. An oscillator coupled to the battery generates pulses, each of which has an amplitude proportional to the battery voltage and a duration proportional to is proportional to the resistance of an RC element consisting of a resistor and a capacitor connected to the oscillator is. When the battery voltage decreases, it becomes voltage dependent Switching device effective to increase the resistance of the RC element, so that the duration of the pulses is increased by the Keep pulse energy constant. The pulse generator can be advantageous used in an implanted artificial pacemaker to generate stimulating output pulses with a constant Generate energy when the battery nears depletion.

The foregoing and additional advantages and features of the invention result from the following detailed description with reference to the drawings, in which shows:

Figure 1 is a schematic diagram of a battery operated Pulse generator in which the duration of the output pulses becomes an easily determinable circuit parameter is proportional, and

Figure 2 is a schematic diagram of a pulse generator for generating of output pulses, which according to the invention a & travel constant energy.

Fig. 1 shows a pulse generator 10, which a pair of output terminals 11, 12 and comprises the generator 10 which is operated by an electrical power source in the form of a battery 15 _o produces output pulses which is parallel to a load

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which is connected to the terminals 11, 12, such as a load resistor 16. Each pulse has an amplitude which is substantially equal to the output voltage of the battery 15. Each pulse has an energy proportional to the product of its amplitude and its duration. When the pulse generator 10 is used in an artificial cardiac pacemaker, at least one of the electrodes 11, 12 is surgically placed in contact with a patient's heart. In particular, the electrode 12 is surgically placed in contact with the heart chamber of the patient's heart. The electrode 11, which can act as an indifferent or reference electrode, can be implanted under the skin elsewhere on the patient's body. The electrode 11 can also be placed in contact with the heart of the patient, the electrodes 11 and 12 are connected to the pulse generator 10 by lines or wires, which are made of a moisture-proof and non -reactive material for the human body, such as silicone or * ⁷ a suitable plastic, wrapped _{or similar}

In the current line of Figure 1 is the positive terminal of the battery connected to the output terminal 11 by a line 18. The negative terminal of battery 15 is through the collector-emitter path a transistor serving as a current amplifier is coupled to the output terminal 12. In particular, a transistor 20 a base terminal 21, a collector terminal 22 and an emitter terminal 23 on. The collector terminal 22 is connected by a line 24 to the output terminal 12 and the emitter terminal 23 is through a line 25 is connected to the negative terminal of the battery 15.

The pulse generator 10 also includes a pair of transistors, which are connected to form a complementary positive feedback oscillator. In particular, the oscillator contains a first transistor 28 having base, collector and emitter terminals 29, 30 and 31, and a second transistor

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32, which has a base terminal 33 which is directly connected to the collector terminal 30 of the transistor 28, as well as a collector terminal 34 and an emitter terminal 35. The base terminal 29 of the transistor 28 is connected to one terminal of a resistor 37, the other terminal of which is connected to the connection point a pair of resistors 39, 40 is connected, which form a voltage divider network, which is connected in parallel with the battery 15 between the line 18 and the line 25. The emitter terminal 31 of the transistor 28 is connected by a line 41 to the junction of a pair of series-connected resistors 43, 45 which form a voltage divider network connected between the collector terminal 34 of the transistor 32 and the line 25. The emitter terminal 35 of the transistor 32 is connected directly to the line 18 by a line 50. The collector terminal 34 is also connected to one terminal of a capacitor 53, the other terminal of which is connected to the base terminal 29 of the transistor 28, and the collector terminal 34 is also connected to the base terminal 21 of the transistor 20 via a resistor 35.

The pulse generator 10 finally contains a switching transistor 6β, which determines whether the capacitor 53 is in a charging or discharging state. In particular, transistor 60 has base, collector and emitter terminals 61, 62 and 63 on. The base terminal 61 is connected to the collector terminal 34 of the transistor 32 via a resistor 65. The emitter terminal 63 is connected directly to the line 25 and the collector terminal 62 is connected to the cathode of a diode 65, the anode of which Via a resistor 67 with the capacitor 53 and with the base terminal 29 of the transistor 28 is connected.

The circuit of Figure 1 operates in the following way:

The battery 15 has a voltage of 3 volts and the voltage between the output terminals 11, 12 is either approximately +3 V or 0 V, depending on whether the transistor 20 is conductive or non-conductive.

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tend is. The transistors 28 and 32 are of a complementary nature, i.e. the transistor 28 is an NPN transistor and the transistor 32 is a PHP transistor. Therefore, when the transistor 28 closes begins to conduct, transistor-32 also begins to conduct, as will be readily apparent to those skilled in the art. If it is assumed that the transistor 28 is initially not conductive, the transistor 20 is switched off and there is no current flow through a Load instead, which is connected to the output terminals 11, 12. Accordingly, the voltage across the terminals 11, 12 is the same 0 V. The capacitor 53 begins to be charged positively via the resistor 32 to a value that corresponds to the base-emitter voltage drop of the transistor of about 0.5 V, and for a time which is approximately the product of the value of the resistor 37 and corresponds to the capacitance of the capacitor 53, expressed in seconds. If a value of 2 megohms for the resistor 37 and assuming a capacitance of 0.47 microfarads for capacitor 53, this time is approximately one second. In addition Time at which the voltage on the capacitor 53 is +0.5 V, the transistor 28 begins to conduct, which the transistor 32 to Brings saturation, which in turn brings the switching transistor 60 to saturation. As a result, all elements of the transistor 32 brought almost to the positive voltage of the battery 15, which is 3 V, and both sides of the capacitor 53 increase by the battery voltage of 3 V. This turns on the transistor 20, which causes a current flow between the Output terminals 11, 12 made possible for example by the load resistor 16, and the voltage in parallel with the terminals 11, 12 rises to the voltage of the battery 15, which is 3V. 'Since both sides of the capacitor 53 increase by 3V, the Voltage at the base terminal 29 of the transistor 28 +3.5 V. The capacitor 53 now begins to move across the resistor 67, the Dio * - de 65 and the collector-emitter path of the saturated transistor 60 to the negative terminal of the battery 15 to discharge, causing the waste the voltage at the base terminal 29 of the transistor 28 causes. During the discharge, the voltage is applied to the emitter terminal 31 of transistor 28 by the voltage dividing effect of

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Resistors 43 and 45 held at about +1 V. When the decreasing voltage at the base terminal 29 of the transistor 28 falls below a value reaches about +1.5 V, in other words the voltage at the emitter terminal 31 plus the base-emitter voltage drop of 0.5 V, transistor 28 is almost turned off. As a result, the transistor 32. is also almost turned off and the Transistor 20 stops conducting, so that the current flow through the load between the output terminals 11, 12 comes to a standstill comes. This point in time corresponds to the end of the output pulse when the voltage decreases to zero.

The pulse duration is therefore the same as the discharge time required in the present case. If for the resistor 67 a value of 850 ohms is assumed, the discharge time and accordingly the pulse duration is about 0.42 milliseconds. When the value of the resistance 67 were two k-ohms, the discharge time would be about 1.0 MHi-seconds. When transistors 28 and 32 are off the voltages at the emitter terminal 31 of the transistor change. 28 and at the collector terminal 34 of the Transistor 32 suddenly drops to 0 V. When the voltage at collector terminal 34 is 0 V, transistor 60 is switched off. However, the voltage on capacitor 53 cannot suddenly change, and if transistor 60 is now non-conductive, the capacitor 53 can no longer discharge via the resistor 67 and the diode 65. The capacitor 53 therefore seeks to discharge through the resistors 43 and 45, which causes the voltage at the base terminal 29 of the transistor 28 in negative Direction decreases by 3 volts to a value of -1.5 V. At this point the previous process repeats itself. While of an operation that generates an output pulse, the fluctuations in the voltage at base terminal 29 are as follows: Beginning of charging -1.5 V, end of charging +0.5 V, beginning of discharge +3.5 V, end of discharge +1.5 V. According to the In the example above, the duration of each pulse is about 0.42 milsecond and the time between pulses is about 1.0 millisecond.

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In view of the foregoing, it is determined that the duration of the output pulses is the product of the value of the resistance 67 and the capacitance of the capacitor 53 is almost directly proportional, which together form an RC element with the oscillator of the circuit of Figure 1 is connected to regulate the pulse duration. When the value of the resistance component of the RC element is reduced during periods of high battery voltage and then increased, that is to say can be brought back to the original value, it is determined according to the invention that the pulse duration increases as the battery voltage decreases, wcby the pulse energy is kept constant.

In Fig. 2 there is a pulse generator 70 for generating output pulses shown, which have constant energy according to the invention. The pulse generator 70 has a pair of output terminals 71, 72 provided. If the pulse generator 70 is used in an artificial cardiac pacemaker, at least one of the electrodes are surgically placed in contact with a patient's heart. The electrode 72 is, for example surgically placed in contact with the ventricle of the patient's heart. The electrode 71, which as a an indifferent or reference electrode is implanted under the skin in another part of the patient's body or also placed on a surgical bed in contact with the patient's heart. The electrodes 71, 72 are connected to the pulse generator 70 connected by lines or wires, which with a moisture-proof and for the human body non-reactive material, such as silicone or a corresponding plastic, are wrapped. A source of electrical power in the form of a battery 73 is provided and the positive terminal thereof is through a lead 74 to the output terminal 71 connected. The negative terminal of battery 73 is coupled to output terminal 72 through the collector-emitter path a transistor 76 serving as a current amplifier and having base, collector and emitter terminals 77, 78 and 79. The collector terminal 78 is connected by a line 80 to the output terminal 72 and the emitter terminal 79 is connected by a line 82

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connected to the negative terminal of the battery 73.

As in the circuit of FIG. 1, the pulse generator 70 includes one complementary positive feedback oscillator consisting of an NPN transistor 84, which has base, collector and 33 Having emitter terminals 85, 86 and 87, and a PNP transistor 90, which has a base terminal 91 which is directly connected to the collector terminal 86 of the transistor 84, as well as a Collector terminal 92 and an emitter terminal 93. The base terminal 85 of the transistor 84 is connected to one terminal of a resistor 95 connected, the other terminal of which is connected to the junction of a pair of resistors 97, 98 which form a voltage divider network form, which is connected between the lines 74 and 82 to the battery 73 in parallel. The emitter terminal 87 of the Transistor 84 is connected by line 100 to the junction point of a pair of series resistors 102, 103, which form a voltage divider network which is connected between the collector terminal 92 of the transistor 90 and the line 82. The emitter terminal 93 of the transistor 90 is connected directly to the line 74 by a line 105, the collector terminal 92 is also connected to one terminal of a capacitor 108, the other terminal of which is connected to the base terminal 85 of transistor 84 is, and the collector terminal 92 is also connected to the base terminal 77 of the transistor 76 via a resistor 110.

The pulse generator 70 also contains switching transistors which determine whether the capacitor 108 is in the Aö # charging or discharging state. In particular, a first switching transistor e 115 has base-j collector and emitter terminals 116, 117 and 118, the base terminal 116 being connected via a resistor 120 to the collector terminal 92 of the transistor 90 _o The emitter terminal 118 is connected directly to the line 82 and The collector terminal 117 is connected to the cathode of a diode 122, the anode of which is connected via a resistor 124 to the capacitor 108 and to the base terminal 85 of the transistor 84. A second switching transistor 126 is also provided, which has base, collector and emitter terminals 127, 128 and 129

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having. The emitter terminal 129 is directly connected to the line 82 and the collector terminal 128 is connected to the cathode of a diode 130, the anode of which via a resistor 132 with the capacitor 108 and the base terminal 85 of the transistor 84 is connected. The pulse generator 70 finally contains voltage-dependent Devices which are connected to the base terminal 127 of the transistor 126 and via the transistor 90 to the battery 73 are connected. In particular, a plurality of Zekner diodes 134 connected in series is provided, in the present case four diodes »The cathode of the diode at one end of the series combination is connected through a line 136 to the base terminal 127 of the Transistor 126 connected. The base terminal 127 is also connected to the line 82 via a resistor 137. The anode of the Diode at the opposite end of the series combination is connected to the collector terminal via resistor 138 and line 139 92 of transistor 90 connected.

The oscillator of the pulse generator of FIG. 2 generates output pulses, each of which has an energy which is proportional to the product of the first and second pulse parameters in the form of the pulse amplitude and the pulse duration, respectively. The first pulse parameter, that is to say the pulse amplitude, is proportional to a parameter of the electrical power source, which in the present example is the voltage of the battery 73. In fact, the pulse amplitude is equal to the square of the pulse voltage divided by the value of the load resistance, the pulse voltage being substantially equal to the voltage of the battery 73. The capacitor 108 and the resistors 124, 132 form an RC element which is connected to the oscillator and controls the size of the second output pulse parameter, which is the pulse duration. The resistors 124 and 132 together form a component of the RC element, which has an optionally variable size, and the second output pulse parameter, i.e. the pulse duration, is closed . proportional to the size of this component. The switching transistor 126 and the Zener diodes 134 form a control device which is connected to the electrical power source, that is to say

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connected to battery 73 when transistor 90 is on is, as well as with the RC element to change the size of the component according to the change in the size of the parameter the electrical power source, i.e. the voltage of the battery 73. As a result, the second output pulse parameter, that is, the pulse duration is changed so that the energy of the output pulses is kept constant.

The circuit of Figure 2 operates in the following way:

The voltage between the output terminals 71, 72 is either approximately +3 V, which corresponds to the voltage of the battery 73, or 0 V, depending on whether the transistor 76 is conductive or non-conductive. Transistors 84 and 90 are of complementary nature, i.e. transistor 84 is an NPN transistor and transistor 90 is a PNP transistor. Thus, when transistor 84 conducts, transistor 90 begins to conduct as well. If it is assumed that the transistor 84 does not conduct initially, the transistor 76 is switched off and the voltage between the output terminals 71, 72 is 0 V. The capacitor 108 begins to be charged from the battery 73 via the resistor 95 to a positive value which is equal to the base-emitter voltage drop of the transistor 84 of about 0.5 V | j., and in a time which is determined by the product of the value of the resistor 95 and the capacitance of the capacitor 108, expressed in seconds. If the resistor 95 has a Fourth of about 2 megohms, and capacitor 108 has a capacitance of about 0.47 microfarads, this time is approximately one second _o If the value is reached of 0.5 V, the transistor 84, whereby the transistor 90 is brought to saturation with the result that all elements of the transistor 90 are brought almost to the positive voltage of the battery 73, i.e. 3 volts, and both sides of the capacitor 108 rise by 3 volts. This turns on transistor 76 and the voltage across terminals 71, 72 rises to 3 volts. • Since both sides of the capacitor 108 increase by 3 V, the voltage at the base terminal 85 of the transistor 84 is + 3.5 V.

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The capacitor 108 then begins to discharge via a path which is regulated according to the invention in the following manner.

The base terminal 116 of the switching transistor 115 is across the resistor 120 connected directly to the collector terminal 92 of the transistor 90. When transistor 90 is saturated, all elements are the same brought almost to the positive voltage of the battery 73 and therefore switching transistor 115 is saturated at all normal battery voltage values. When the tension of the Battery 73 is high, that is to say at or near the maximum value of 3 V, both switching transistors 115, 126 are saturated together and capacitor 108 has two discharge paths, one through resistor 124 and the other through resistor 132. Therefore, when the voltage of the battery 73 is high, the time constant for the capacitor 108 to discharge is too large of the resistance of the parallel combination of resistors 124 and 132 is proportional. As a result, the duration of the output pulses is proportional to the magnitude of the resistance of the parallel combination of resistors 124 and 132. In particular the base terminal 127 of the switching transistor 126 is initially driven by the series combination of Zener diodes 134, which via the Resistor 138 is connected to collector terminal 92 of transistor 90. In the embodiment shown, the Zener Diodes 134 have a combined voltage drop of approximately 2 volts. When the base-emitter voltage drop of transistor 126 is added, this means that only a battery voltage amplitude and accordingly output pulse voltages of more than 2.5 V den Switching transistor 126 will saturate. Therefore, when the voltage of the battery 73 drops below 2.5 V, the switching transistor becomes 126 less and less effective. At a battery voltage of 2.2 V, the switching transistor 126 is no longer saturated and the Capacitor 108 will not discharge through resistor 132. In other words, the discharge path through resistor 132 is blocked by the operation of the control device, which consists of the switching transistor 126 and the Zener diodes 134. Of the Capacitor 108 then has only one discharge path via the resistor

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stand 124. The pulse duration, which is proportional to the size of the resistance, increases as the size of the resistance is parallel Combination of resistors 124, 132 is smaller than the size of each resistor alone. While according to a preferred Embodiment of the invention, the resistance component of the RC element is changed to change the pulse duration, the capacitance component could be changed to increase the pulse duration change without departing from the scope of the invention.

According to an exemplary embodiment of the invention, resistor 124 has a value of 2,000 ohms and resistor 132 a value of 1,500 ohms. The parallel combination of resistors 124, 132 therefore has a value of approximately 850 ohms. Since the Capacitor 108 has a capacitance of 0.47 microfarads this is a time constant and accordingly a pulse duration of about 0.42 milliseconds when the capacitor 108 is across both Resistors 124, 132 discharges. When the voltage of the battery 73 decreases to 2.2V, so that the transistor 126 turns off is, the capacitor 108 discharges only through the resistor 124 with a time constant of 1.0 milliseconds. Therefore, if the The voltage of the battery 73 decreases from its initial value to 2.2 V, the duration of the output pulses increases from 0.4 milliseconds to 1.0 Milliseconds and the energy of the impulses remains relatively constant.

The pulse energy is equal to the product of the pulse power and the pulse duration. The pulse power is equal to the square of the Pulse voltage divided by the size of the load resistance. If a constant load resistance is assumed, the pulse energy decreases proportionally to the square of the pulse voltage. Therefore, if the pulse duration according to the invention is automatic is increased by an amount equal to the square of the decrease in the pulse voltage, the pulse energy can be proportionate can be kept constant even in the presence of a decreasing battery voltage.

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The voltage of a typical lithium-iodine cell, for example, decreases from 2.8 V to 2.2 V by the nominal end of its service life. The decrease by 0.6 V is about 22 % and in order to maintain a constant energy, the pulse duration must be increased by about 64 % . According to another example, it is assumed that the values of the capacitor 108 and the resistors 124, 132 of the RC element in the circuit of FIG. 3 milliseconds at the end of the battery life. If a load resistance of 500 OHm is assumed, which is connected in parallel to the terminals 71, 72, and values of 2.8 V and 2.2 V for the beginning and the end of the service life of the battery, together with the above-mentioned values of Pulse duration, it can be calculated that the pulse energy at the beginning and at the end of the battery life remains relatively constant at a value of 12.5 microjoules »The pulse generator according to the invention therefore generates an output pulse with almost constant energy despite decreasing battery voltage when the battery is exhausted . The last remaining chemical capacity of the battery, which is only available when the voltage is reduced, is converted into a usable state instead of being left unused and wasted in the battery. The pulse energy is not only kept relatively constant over the range of the operating time of the battery, but the pulse generator according to the invention extends the operating time of the battery to voltage levels which are about 25% lower than those which could be achieved without the invention.

In the circuit according to the invention there is an accurate and repeatable one Relationship between pulse duration and battery voltage. A normal oscilloscope can be used with a patient's body can be connected in the same way as an electrocardiographic apparatus to the pulse duration of an implanted Read cardiac pacemaker directly, which is designed according to the invention. The aging of the pacemaker battery can therefore be monitored by from the outside of the body

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the pulse is observed directly with an oscilloscope. A measurement of the pulse duration of a pulse generator according to FIG of the invention in a battery operated space capsule or other remotely located device Provide information about the condition of the battery, possibly from pulses used in normal telemetry, and without additional instruments.

According to the invention is a device for checking the safety factor of the system is provided, which removes the circuit that extends the pulse duration incoming interrogation signal is temporarily switched off in order to temporarily reduce the energy of the generated pulse by removing the initial State of the duration of the pulse is restored. As shown in Fig. 2, a usually open switch 142 is to the Combination of Zener diodes 134 by lines 144 and 146 connected in parallel. When the pulse generator 70 is used as an implanted artificial cardiac pacemaker, the Switch 142 may be a reed switch operated from the outside of the body. Such switches and how they work are known to the person skilled in the art. When switch 142 is closed to short the combination of Zener diodes 134, serves this to query the system. If the patient follows the pacemaker closely, even if the pulse duration is through the closure of the switch 142 is temporarily shortened, the patient's safety margin can be considered sufficient ", to secure it until the next review period. However, if the patient does not closely track the pacemaker when the Pulse duration is reduced by operating the switch 142, then its safety margin may be considered insufficient to warrant a reevaluation of the pacemaker. The switch 142 can also consist of a bipolar or field effect transformer, which is activated briefly by a remote high-frequency transmitter, as in the American Patent Application No. 47198 filed June 18, 1970 is described.

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The circuit according to the invention may include an output coupling capacitor included or not, which is connected in series to the line 80 of FIG. 2 or to the line 24 of FIG. While such capacitors are commonly present in cardiac pacemaker circuits, they are essential for an understanding of the invention are not essential and are therefore omitted for simplicity of description.

An artificial pacemaker guaranteed according to the invention a relatively constant safety factor of the system during the entire expected service life of the battery. In certain patients, an accidental shift of their pacemaker can have an abnormally high physiological level Generate electrode threshold. Such a threshold may be within the original capacity of the pacemaker but can become a marginal value if the battery voltage drops only slightly. Such a patient needed so far, a new operation long before the normally expected operating life of the pacemaker had expired. With a pacemaker according to the invention, such a patient does not need a new operation before the normally planned, optional exchange date. In other words, according to the invention the safety factor of the system remains proportionate throughout the life of the artificial pacemaker constant if a high but invariable physiological threshold is assumed.

The invention is not limited to the illustrated and described exemplary embodiments, the various Changes can be made without departing from the scope of the invention.

Claims

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Claims (1)

Dr.-lng. E. BERKENFELD · D: pl.-lng. H. BERKEKFCLD, patent attorneys, Cologne Attachment file number on the submission of July 26, 1973 VA // Name d. Note WILSON GREATBATCH LTD. PATENT CLAIMS 1. Pacemaker, labeled a) by a battery, b) by an oscillator coupled to the battery, to produce output pulses each of which has an energy equal to the product of amplitude and duration it is proportional, the amplitude of each pulse being proportional to the voltage of the battery, c) by an RC element which is connected to the oscillator and which regulates the size of the pulse duration, the RC element including a component which is an optionally variable Size, and where the pulse duration is proportional to the size of this component, d) by a control device, which is connected to the battery and to the RC element, to the size of the component to change according to a decrease in the voltage of the battery in order to increase the duration of the output pulses, to keep the energy of the impulses constant, and e) through a pair of output terminals connected to the oscillator at least one of which can be operatively coupled to a patient's heart. 2. Cardiac pacemaker according to claim 1, characterized in that the component consists of the resistance component of an RC element consists, which is connected in series with a capacitor Resistance is formed, and that the control device consists of a switch for controlling the size of the resistance component consists. Cardiac pacemaker according to Claim 2, characterized in that the resistance component consists of a pair of branch resistances that are connected in parallel, and that the switch is voltage-dependent and the switching off of a branch resistance W 75/5 409 8 Q 8/0413 Standes causes when the voltage of the battery drops to a predetermined one Value decreases. 4. pacemaker according to claim 1, characterized in that the RC element consists of a capacitor connected to the oscillator is connected, from a first resistor, which is connected to the capacitor, - and a discharge path for the Capacitor forms, and a second resistor, which is connected to the capacitor, and that the control device consists of a voltage-dependent switch that is connected to the second resistor is connected and usually allows the second resistor to provide a second discharge path for the Capacitor forms or blocks the second discharge path when the voltage of the battery has reached a predetermined value decreases. 5. Heart pacemaker according to claim 4, characterized in that the control device consists of: a) from a semiconductor switch which is in control relationship to the second resistor, and b) from Zener diodes, which are in control relationship to the battery and stand by the switch. 6. pacemaker according to claim 5, characterized by a usually an open switch which is connected in parallel to the Zener diodes and which, when closed, causes the To make control device temporarily ineffective, whereby the duration of the output pulses temporarily to the value before the actuation of the control device is returned. 7. Pulse generator, marked a) by an electrical power source, b) by an oscillator connected to the power source to produce output pulses, each of which is one Having energy which is proportional to the product of the first and second pulse parameters, where de :; "" first pulse parameter W 75/5 409808/0413 rameter is proportional to an electrical parameter of the power source, c) by an RC element that is connected to the oscillator and regulates the magnitude of the second output pulse parameter, the RC element including a component which is an optional having variable magnitude, and the second output pulse parameter proportional to the magnitude of this component is and d) by a control device which is connected to the power source and the RC element in order to adjust the size of the component change according to changes in the size of the electrical parameter of the power source, thereby changing the second output pulse parameter is changed in order to keep the energy of the impulses constant. 8. Pulse generator according to claim 7, characterized in that the first and second output pulse parameters the amplitude or the duration, and that the component of the RC element forms the resistance component of an RC element that consists of one a resistor connected in series to a capacitor. 9. Pulse generator according to claim 8, characterized in that the resistance component consists of a plurality of resistors and that the control device consists of a switch for controlling the number of components forming the resistance There is resistance, which is determined by the size of the electrical parameter of the power source. 10. Pulse generator according to claim 8, characterized in that the electrical power source consists of a battery and that the electrical parameter of the power source is voltage, that the resistance component consists of a pair of branch resistors connected to the capacitor of the RC element are, and that the switch is voltage-dependent and causes a branch resistor to be switched off when the The voltage of the battery decreases to a predetermined value. W 75/5 409808/0413