DE2065013A1 - On demand pacemaker. Excretion from; 2025499 - Google Patents

Description

The invention relates to an on-demand heart pacemaker with a measuring arrangement for detecting natural heartbeats and a pulse generator for generating stimulation current pulses.

Emergency pacemakers are known to be electrical pacemakers Only deliver pulses to stimulate the heart when normal heartbeats are not present. Known cardiac pacemakers on demand generate stimulation current impulses with a fixed one Frequency. The stimulation current impulses are suppressed if a natural " Heartbeat occurs. Under no circumstances should the pacemaker monitoring the heart rate the heart rate allow it to drop below a predetermined lower frequency value. However, this can be done with known cardiac pacemakers occur when the pacemaker is exposed to periodic external electrical noise or interfering signals. Such signals can., namely, if its repetition rate is greater than the upper limit value for normal heartbeat speeds, a permanent one

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REMOTE PLAYER 0811/40 JO 18 · CABLE. * ELECTRICPATENT MÖNCHEN

Cause the pacemaker to be blocked even within periods of time, in which the measuring arrangement does not detect natural heartbeats.

The invention is based on the object of providing a cardiac pacemaker on demand to create, against a permanent blocking of the from Pacemaker delivered stimulation current impulses as a result of repetitive Interfering signals is secured.

Based on a pacemaker of the type mentioned above, this object is achieved according to the invention in that a stage which responds to repetitive noise signals is connected between the measuring arrangement and the pulse generator, which stage is provided with a coupling capacitor and two discharge paths for the coupling capacitor which have different time constants and of which the discharge path with a smaller time constant is only permeable for signals of one polarity. The discharge paths, which have different time constants, have the effect that the coupling capacitor is charged by repetitive noise or interference signals and thus the connection between the measuring arrangement and the pulse generator is blocked. The pacemaker goes consequently into an asynchronous mode, wherein the heart stimulation current pulses are applied at a fixed frequency until after the decay of the interference signals, the coupling capacitor clears the signal path from the measuring arrangement for, pulse generator again and d r pacemaker returns to the required operation.

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A structure that is particularly simple in terms of circuitry is obtained, if the discharge path with a larger time constant has a resistance and the discharge path with a smaller time constant has a series connection of a diode and a resistor. The time constants of the discharge paths are preferably used here dimensioned in such a way that the coupling capacitor is blocked by repetitive noise pulses with the one not let through by the diode Polarity and one over the range of normal heartbeat rates The frequency is charged and the passage of further noise impulses is blocked.

In the case of an on-demand pacemaker, in which the pulse generator has a timing element which controls the delivery of stimulation current pulses with a predetermined pulse interval and to the measuring arrangement a reset device is connected which resets the timer when a natural heartbeat occurs, the coupling capacitor is expediently connected between the measuring arrangement and the reset device controlled by it.

The invention is shown below on the basis of an exemplary embodiment explained in more detail. The single figure shows a schematic circuit diagram a cardiac pacemaker constructed according to the invention.

In the figure, an energy source in the form of a current source consisting of batteries 11 is illustrated. The positive clamp the power source 11 is connected to a positive bus line 12, while the negative terminal of the power source 11 is connected to a

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negative manifold 13 is connected. A capacitor 14; is connected between the bus lines 12 * 13 in order to attenuate supply voltage fluctuations in a known * manner. The emitter a transistor 15 is connected to the negative bus 13, while its collector via a resistor 16 to the positive manifold 12 is connected.

The emitters of two further transistors 19 »20 are connected to the negative bus line 13 via a resistor S3 Wk. The collector of the transistor 19 is connected to the positive bus line 12, while the base of the transistor 19 via a resistor 21 to the bus line 12 and üiä & r a resistor 22 is connected to the bus line 13 · The collector of the transistor 20 is connected to the bus line 12 via a resistor 24 and is connected to the bus line 12 via a capacitor IS *

The emitter of transistor 26 is directly connected with the Sam- ^ melleitung 12 is connected, while the base is connected to the collector of the transistor 20 and the collector is in communication with a AhSchlußpunkt 10th The connection point 10 is connected to the base of the transistor 20 via a resistor 27 and a capacitor 20 in series therewith.

The emitter of a transistor 30 is connected to the negative bus 13, while the collector of this transistor. via a resistor 31 to the base of the transistor ¹ --.- 2O anger: - /

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is closed and the base is coupled to the connection point 10 via a resistor 33 and a diode 32 connected in series therewith. The connection point 10 is also connected to the base of the transistor 15 via a resistor 29. The collector of transistor 30 is also connected to a variable resistor 36. The wiper of the variable resistor 36 is connected to the positive collecting line 12 via a resistor 37. The collector of transistor 30 is also, via two capacitors 34 angekop- 35 to the negative bus line 13 λ pelt.

The emitter of a transistor 40 is connected to the negative bus 13 connected while the collector of the transistor across a diode 38 to the collector of transistor 30 and the base via a diode 41 and a resistor in series therewith 42 is connected to the negative manifold 13. Of the The collector of the transistor 40 is also via a capacitor 39 coupled to the bus 13, while the base of the transistor 40 also via a resistor 43 to the collector ™ line 13 is in communication.

The emitter of a transistor 48 is connected to the positive bus 12, while the collector of the transistor is connected through a resistor 46 to the negative bus 13 in Connection. The collector of the transistor 48 is also coupled to the negative bus 13 via a capacitor 45 and to the base of the transistor 40 via a connector

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capacitor 44 connected. A resistor 51, a capacitor 52 and a resistor 53 are in series between the positive one Bus 12 and the negative bus 13. The gate or the g-pole of a field effect transistor 55 is connected to a connection point connected between the capacitor 52 and the resistor 53, while the source or the s-pole to the positive Bus 12 and the sink or d-pole to the base of the Transistor 48 is connected. A diode 57 is between ρ source and sink of the field effect transistor 55.

The emitter of a transistor 60 is through a resistor 61 and a capacitor 62 in parallel therewith with the positive one Manifold 12 connected. The collector of transistor 6O. is connected to the negative manifold 13 via a resistor 63 and connected through a capacitor 58 to the base of the transistor 48 coupled. The base of transistor 6O is over a resistor 66 connected to the positive bus line 12. -

The sink of a field effect transistor 65 is connected to the base of the Transistor 60 connected while the source of the field effect transistor is connected to the negative bus line 13 via a resistor 67 and a capacitor 68 lying parallel thereto. The gate of the field effect transistor 65 is over two Diodes 71, 72 connected in parallel and with opposite polarity are connected to the negative bus line 13.

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The collector of transistor 15 is coupled to an electrode 75 via a capacitor 74. The electrode 7S is connected to the gate of the field effect transistor 6S via a capacitor 76 and a resistor 7§ connected to it Another electrode BÖ is connected to the negative collecting line 13. The connection point 10 is coupled via a diode 79 to the connection between ^1, the capacitor §2 and the resistor 53,

To the working method of the VeranisöhäUliehten arrangement hehj s§i assumed that there were no natural heartbeats and that the pulse generator of the pacemaker with the normal paint follow-up exemption has worked. Furthermore, let ddvon that an output pulse has just ended;

The pulse generator comprises the transistors 19, 20 »26 and Üö as well as the associated circuit components in particular the Capacitors 28 and 35. The transistor 15 forms the output transistor.

During the last output pulse, the capacitor 74 was discharged for a period determined by the pulse generator. The pulse generator is switched off during the pulse intervals. The transistor 15 is blocked. The capacitor 74 recharges through a circuit that is controlled by the current

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source 11 via the manifold 12, the resistor 16, the capacitor 74, the electrodes 75 and 80 and the heart and over the collecting line 13 leads back to the power source 11. This causes the coating connected to the collector of transistor 15 to become of the capacitor 74 is positive with respect to the other coating.

As the capacitor 74 charges, the capacitor also becomes 35 charged via the variable resistor 36 and the resistor 37. Because the capacitor 39 is charged at an earlier point in time and during the last impulse in the absence of it of a natural heartbeat has not discharged for the reasons explained in more detail below, the capacitor has 39 has no significant influence on the charging time of the capacitor 35. The capacitor 34 is a high frequency bypass capacitor, which prevents the pulse generator from being switched on due to interference and as a result is much smaller than the capacitor 35, so that it what the clock control of the pulse generator as far as is concerned, can essentially be neglected.

The transistors 19, 20 are known as differential amplifiers switched to provide a temperature compensation for the switch-on point of the transistor 20 and a maintain substantially constant timing for the pulse generator. The resistors 21, 22, 23 and 24 act as Bias resistors for the transistors 19, 20. The capacitor 25 is a resistor. 24 leakage capacitor connected in parallel. ._ * ,. ",.

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When the capacitor 35 is sufficiently charged, the Transistor 20 turned on by the positive potential that is transmitted from the capacitor 35 to the base of the transistor 20. The current flowing through transistor 2O causes a drop the collector voltage of the transistor, so that the transistor 26 is steered up at its base. Because the transistor 26 becomes live, a positive potential appears from the Collective line 12 at connection point 10.

The positive potential at the connection point 10 is fed back via the capacitor 28 as positive feedback to the base of the transistor 20 in order to turn it on even more and to keep it in a current-carrying state. Furthermore, the positive potential at the connection point 10 is transmitted via the diode 32 and the resistor 33 to the base of the transistor 30, whereby the transistor 30 is turned on and the capacitor 35 is discharged. Further, the positive potential arrives at the connection point 10 via the resistor 29 to the base of a output transistor 15, which is also controlled open. As a result, the capacitor 74 discharges via a circuit which leads back to the capacitor 74 via the collector-emitter path of the transistor 15, the electrode 80, the heart and the electrode 75. Finally, the positive potential present at connection point 10 is transmitted via diode 79 as a blocking signal, which prevents the preamplifier from detecting the pacemaker pulse as if it were a natural heartbeat or an R-wave, as will be explained in more detail below,

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Due to the blocking of the transistor 30, a capacitor 35 discharges quickly. The transistor 3O remains live until the positive potential at the connection point 10 disappears. The positive potential at the connection point 10 is present as long as the transistor 26 is turned on, which in turn is determined by the turn-on time of the transistor 20. The transistor 20 remains turned on for a period of time which is determined by the charging time of the capacitor 28 over which the . is transferred positive potential at node 1O As a result, the charging time of the capacitor 28 is the duty cycle ^of: pulse generator before, so that it determines the oN period of the output transistor 15 and the width of the output pulse.

When the capacitor 28 is charged to such an extent that the potential at the base of the transistor 20 is no longer sufficient to keep the transistor 20 current-carrying, the transistor 20 blocks. This also blocks the transistor 26; the positive potential at connection purikt 1Ö disappears. As a result of this, the transistor 30 and the output transistor 15 are blocked. The capacitors 74 and 35 then begin to charge again in the manner described above. The pulse generator cycle is repeated provided that a natural heartbeat does not occur.

The measuring amplifier of the pacemaker comprises the field effect transistor 65, the transistors 6O and 48 and the associated ones Circuit components. The resistors 46, 61, 63, 66 and 67

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are _1s biasing resistors for the associated transistors. The capacitors 62 and 68 represent bypass capacitors. The field effect transistor 65 and the transistor 60 are biased in such a way that they operate in Α mode and amplify input signals of any polarity. Resistor 77 provides a DC reference voltage for the gate of the field effect transistor 65. The resistor 78 represents a limiting resistor that limits together with the diodes 71, 72, the input voltage ύ supplied to the gate of the field effect transistor 65th

If a pulse of any polarity occurs at electrode 75, it becomes via the capacitor 76 and the resistor 78 effective on the parallel connection of the two diodes 71, 72. There the field effect transistor 65 is biased for Α operation, reinforced he a pulse of any polarity, which is limited by the diodes 71, 72 and the resistor 78. this leads to to a potential change at the drain of the field effect transistor 65, which is noticeable at the base of the transistor 60 and is further strengthened by this. As a result, there is a potential change at the collector of transistor 60, which differentiates and passed through capacitor 58 to the base of transistor 48. In the illustrated embodiment the transistor 48 is connected as a C amplifier. He's turned on when the negative portion of the differentiated signal passing through capacitor 58 reaches the base of transistor 48. The diode 57 prevents the capacitor 58 from moving due to a sequence of negative potential jumps at the collector

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of transistor 60 charges.

As a result of the transistor 48 being energized, the Collector of the transistor more positive. This positive signal runs through a stage, which is described in more detail below in the presence of repetitive interfering signals causes the reset to a fixed cycle. First of all, just be mentions that the positive signal reaches the base of transistor 40 via capacitor 44 and turns it on. The fact that transistor 40 is energized becomes normal Charging cycle of the capacitor 35 interrupted. The pacemaker is switched to its waiting rate: which is lower than the normal rate of the pulse generator.

The measuring amplifier has a refractory period or recovery time _i which is primarily caused by the bypass capacitors 62 and 68. The values of these capacitors are selected in such a way that the capacitors are charged in the presence of an input signal passing through the measuring amplifier. The discharge time of the capacitors 62,. 68 forms a refractory period for the measuring amplifier. The capacitors should be selected carefully as they also affect the gain of the amplifier. ,,

As described above, the measuring amplifier detects a pulse of any polarity occurring at the electrode 75 in order to influence dq through the frequency of the pulse generator. In order to

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this cannot happen if the one appearing on electrode 75 Pulse - is the pulse generated by the pacemaker and not a natural heartbeat or R-wave a blocking circuit is provided, which consists of the field effect transistor 55, resistor 51, capacitor 52 and resistor consists. As explained above, this is done at the connection point 10 occurring positive potential, which controls the output transistor 15, also via the diode 79 to the blocking circuit. The positive potential appears at the gate of the field effect transistor 55, which essentially increases the gate potential the value of the source potential of the field effect transistor 55 is raised will. In this way, the blocking bias voltage is eliminated and the field effect transistor 55 is turned on. As a result, a positive potential appears at the base of transistor 48, so that it is kept blocked. It can therefore no pulses pass from the measuring amplifier to the pulse generator. The measuring amplifier gives a small recovery pulse ab, which, following the refractory period, causes j by the charge and discharge of capacitors 62, 68, appears at the base of transistor 48. This recovery impulse however, is not of sufficient size to turn on transistors 48 and 40 unless there is a repetitive Interference signal before, as explained in more detail below. The capacitor 52 has the purpose of the field effect transistor 55 unlocked for a period of time sufficient to prevent the pacing pulse from breaking transistor 48 tax, which is, however, measured in such a way that the recreational

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pulse can reach the base of transistor 48. The condenser 52 is discharged by the pulse coming from the connection point 10 runs off through the diode 79. During reloading the capacitor 52 holds a positive potential at the gate of the Field effect transistor 55 upright to the transistor for a Period of time to keep the live state through the resistance value lying in the charging path of the capacitor 52 is determined. In this way, the pacemaker according to FIG. 1 prevents the normal pulse generator from output frequency by determining the own output pulse being affected. ; ■

If a natural heartbeat or a. R-wave appears, a corresponding pulse occurs in the above described way dm capacitor 76 and resistor 78 on.-This Impulse runs through the measuring amplifier. If the natural Heartbeat or the R-wave arrives at electrode 75 at a time when there is no pacing pulse and at which the refractory period of the amplifier is completed, the transistor 48 is turned on. The latter controls in turn-the transistor 40 on. When the transistor 40 is conductive is, it forms a discharge path for the capacitor 39. The capacitor 39 has during normal operation of the The pulse generator is charged via the resistors 36, 37 and the diode 38. When transistor 30 is turned on, the To discharge capacitor 35, the diode 38 prevents the capacitor 39 from discharging. In normal operation, therefore, practically '

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only the capacitor 35 influences the timing of the pulse generator. However, when transistor 40 is turned on and the capacitor 39 discharges, a discharge takes place of the capacitor 35 via the diode 38 and the transistor 40. This completes the pulse generator's clock cycle deferred. -In addition, the via the resistors 36, 37 current flowing now between the capacitors 35 and

39 split up until the diode 38 due to the charge on the capacitor 39 is biased in the reverse direction. Since the capacity ^ is increased by connecting the capacitor 39 and the The current available via the resistors 36, 37 is practical remains the same, it takes a long time for the Capacitor 35 is charged to the potential at which transistor 20 of the pulse generator is turned on. Every time when a pulse passes through the measuring amplifier and the transistor

40 turns on, the entire pulse generator cycle will be as a result deferred. The next clocking cycle occurs at the waiting clock speed, which has a longer period than the normal pulse generator frequency. If during the waiting Q Another natural heartbeat occurs, the period becomes Pulse generator reset again and prevented from delivering a stimulus pulse; it starts working again at the waiting clock speed. So as long as a natural heartbeat has occurred during the waiting period, the pacemaker delivers no stimulus; after each natural heartbeat, the pacemaker pulse generator works with the waiting rate. When a waiting frequency period is completed without

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. that a natural heartbeat has occurred ", the pacemaker delivers a stimulus and immediately reverts to normal Pacing rate back, assuming no more natural heartbeats, to be determined »

The stage comprising the diode 41, the resistor 42, the resistor 43 and the coupling capacitor 44 causes the pulse generator to automatically switch to asynchronous operation at a third frequency which differs from both the first and the second frequency when the pacemaker is used exposed to repetitive external signals or interfering signals. In order to make address this stage, repetitive noise signals are required, the repetition frequency is greater by a predetermined minimum amount than the upper limit for normal heart beat speeds. The refractory period of the amplifier plays a role in specifying the pulse generator frequency in the presence of such interference signals.

For example, assume that the device is an external electrical noise with periodic behavior, such as a sine wave, is exposed and that the sine wave after the refractory period enters the measuring amplifier and as a result, noticeable at the collector of transistor 48 power, in such a case would if no noise reduction circuit were present, the sine wave would be transmitted via the coupling capacitor 44 and the transistor 40 would be turned on] the pulse generator constantly reset, which of course not

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is desired. In order to prevent this constant resetting of the pulse generator and the associated permanent blocking of the pacemaker regardless of the heart activity as a result of external noise, the diode 41 lets the positive part of the sine wave through the resistor 42 to ground. The negative part of this sine wave appears at resistor 43, which has a much greater resistance than resistor 42. As a result, when a succession of sine waves passes across capacitor 44, capacitor 44 charges with one plate connected to the collector of transistor ™ 48 becoming positive and the other plate becoming negative. This positive charge with respect to the sine wave source eventually blocks further positive parts of the sine wave and then prevents transistor 40 from turning on. However, if the time interval between positive pulses is long enough, such as within the range of normal heartbeat rates or during the refractory period of the amplifier the capacitor 44 has sufficient time to discharge itself through the resistor 43, whereby the blocking of the next incoming pulse and subsequent M der.Herzschlagimpulse with normal spacing is avoided.

So if a noise signal, for example a 60 Hz AC voltage signal, is recorded, the pulse generator is activated immediately the waiting period is postponed. The charging process begins. As soon as the capacitor 44 is practically fully charged, a pulse is emitted. The pulse supplied by the pulse generator is recorded by the measuring amplifier, but is not allowed to pass through the blocking circuit. The detection of the pacemaker pulse causes the

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Measuring amplifier further signals for the duration of the refractory period blocked j while the capacitors 35, 39 with the waiting speed begin to charge and the capacitor 44 is discharged. If still repetitive at the end of the refractory period Interference signals are present, these are superimposed on the recovery pulse of the amplifier, so that parts of the pulse a Sufficiently large to make transistors 48 and 40 quick repeatedly on until the capacitor 44 is fully charged. Each time the transistors 48, 40 are turned on, the pulse generator is activated returned to its waiting period; however, since the capacitor 44 charges quickly and other glitches blocked, the timing cycle begins almost instantly. the Reset in the presence of repetitive noise signals (once when an output pulse is generated and possibly several times in quick succession at the end of the refractory period) can simply be a "double provision" are designated.

The pulse output and the double reset are repeated as long as interfering signals are present. In the presence of repetitive As a result of interference or noise signals, the pacemaker runs at a speed below normal and is below the waiting speed; it is not synchronized with natural heartbeats. The pacemaker pulse train period in the presence of repetitive noise signals represents approximately the sum of the waiting period and the refractory period of the measuring amplifier. If '

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For example, the waiting period is 1000 ms and the refractory period is 150 ms, the pacemaker period in the presence of repetitive interference signals is approximately 115O ms, which corresponds to a clock speed of approximately 52 beats per minute. This slowing down of the pacemaker in connection with the transition to asynchronous operation in the presence of repetitive noise signals is ideal for checking the functionality of the unit after implantation. G

It goes without saying that the described slowdown in connection with the transition to asynchronous operation in the case of a demand pacemaker without the characteristic of the waiting clock rate described above can be done in a similar manner by the simpler timing circuit provided in such arrangements is reset twice.

The arrangement should be able to be implanted as a whole in the body. For this purpose it has its own energy source equipped in the form of the battery 11. All circuit components can be accommodated in one substance or in substances, in particular encapsulated, which is or are practically inert to body fluids and tissues, The in the drawing schematically illustrated electrodes 75 and can on. one of several known ways directly with related to the heart muscle; they consist of an electrically conductive material, which is also opposite

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Body fluids and tissues are essentially inert.

The variable resistor 36 allows the normal frequency of the pulse generator to change. In addition, the capacitor 39 can be an adjustable capacitor or a plurality of capacitors exist, which are optionally einschaltbdr by means of a manual switch or the like to in this way the To be able to optionally set the waiting rate of the pacemaker.

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Claims (4)

Expectations 1. Demand pacemaker with a measuring arrangement for detecting natural heartbeats and a pulse generator for generating stimulation current pulses, characterized in that between the measuring arrangement (65, 60, 48) and the pulse generator (19, 20, 26, 30) a repetitive noise signals responsive stage is switched (41 to 44) (44) and two discharge paths is provided with a g coupling capacitor provided for the coupling capacitor having different time constants, and one of which provided with a smaller time constant discharge path is only permeable for signals of one polarity. 2. Demand pacemaker according to claim 1, characterized in that that the discharge path with a larger time constant has a resistor (43) and the discharge path with a smaller time constant a series circuit of a diode (41) and a resistor (42). 3. Demand pacemaker according to claim 2, characterized in that that the time constants of the discharge paths (41, 42; 43) are dimensioned such that the coupling capacitor (44) through repetitive noise pulses with the polarity blocked by the diode (41) and one over the range normal heartbeat rates 209 816/0794 and blocks the passage of more of these noise pulses 4. Demand pacemaker according to one of the preceding claims, in which the pulse generator emits stimulation current pulses having a predetermined pulse interval controlling timing element and connected to the measuring arrangement a reset device which resets the timer when a natural heartbeat occurs, characterized in that »That the coupling capacitor (44) between the measuring arrangement (65, 60, 48) and the reset device (40) controlled by it is switched. 209816/0794