JPH04197364A - Pacemaker - Google Patents

Abstract

PURPOSE:To prevent a comparing circuit from detecting a pacing pulse and the after potential succeeding it without providing a switching circuit not to detect the pacing pulse. CONSTITUTION:A pacing pulse generating circuit 9 generates pacing pulses at a preset adjustable time period, when the R-wave is detected by a comparing circuit 6, the pacing pulse is reset by a pacing pulse resetting circuit 8, and no pacing pulse is outputted to an input/output terminal 2. If no R-wave is detected by the comparing circuit 6 within a preset period when the next R-wave should be detected after the previous R-wave is detected, a pacing pulse is outputted from the pacing pulse generating circuit 9 to the input/output terminal 2. If no R-wave is detected by the comparing circuit 6 within a preset period thereafter, a pacing pulse is again outputted, and these actions are continued until the R-wave is detected by the comparing circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pacemaker of the type that detects intracardiac electrocardiograms using electrodes placed in the heart and outputs pacing pulses from these electrodes. This invention relates to a pacemaker that does not mistakenly detect pacing pulses as intracardiac electrocardiograms.

For patients with acute bradycardia or bradycardia arrhythmia,
In an emergency and temporary setting, a catheter with two electrodes is placed in the right ventricle, a lead wire from the electrode is guided outside the body through the catheter, a pacemaker is connected to the end of this lead wire, and basing is performed. There is a way to do it.

The pacemaker used in this basing method is called an external pacemaker.

Among these external pacemakers, a so-called demand-type pacemaker is mainly used, which performs pacing when the heartbeat of the living body falls below a set beat rate, but does not perform pacing when the heartbeat exceeds the set beat rate. Therefore, an intracardiac electrocardiogram (peak value 2 to 20 mV) generated between the two electrodes of a catheter inserted into the right ventricle was detected by a pacemaker, and the cycle interval between the R wave of the electrocardiogram and the next R wave was set. If the time is longer than the number of beats, a pacing pulse (peak value 2 to 4 V, pulse width 1 to 3
m S ) is applied between the same two electrodes, which is designed to cause contraction of the myocardium through the myocardium.

This pacemaker has the same input and output electrodes, so it must sometimes input a weak voltage and sometimes output a high voltage.

In addition, the potential generated between the two electrodes in the right ventricle is not only an intracardiac electrocardiogram, but also a slow-changing variable, that is, a baseline fluctuation, and a large and long-lasting afterpotential that occurs after a pacing pulse is given. In other words, a residual potential as if a large capacitor (electrostatic capacitance) were connected in parallel between the electrodes is input.

This residual potential is shown by reference numeral A in FIG. 8, and an example of a pseudo load circuit that can reproduce the residual potential in a pseudo manner is shown in FIG. Note that the symbol B in FIG. 8 is a pacing pulse.

Therefore, in a circuit that detects intracardiac electrocardiograms, unless the pacing pulse B and afterpotential A are prevented from entering the detection circuit, these potentials will be detected.
It cannot be distinguished from an intracardiac electrocardiogram.

In addition, normally, after detecting the intracardiac electrocardiogram, the detection circuit
A function is provided to stop detection for 300 milliseconds. This is to avoid detecting S waves, T waves, or premature contractions that follow the R wave of the intracardiac electrocardiogram as shown in FIG. 10. Therefore, if a pacing pulse etc. is detected incorrectly, the next two
This method has the disadvantage that intracardiac electrocardiography cannot be detected for 50 to 300 milliseconds.

Therefore, it is customary to include a circuit that synchronizes with the start time of the pacing pulse and closes the detection circuit using a switch or the like until the end of the afterpotential.

The detection circuit usually includes an amplifier and a comparator, and a filter is often attached in front of the comparator to allow only the R wave of the intracardiac electrocardiogram to pass through. In such a detection circuit, the switch may be attached to a location where the detection circuit is closed by the following method.

1 Place a switch in series in front of the amplifier and open it.

2 Place a large resistance in series in front of the amplifier, then place a switch in parallel and close it.

3 Place a switch in series after the amplifier and open it.

4. Place a resistor in series after the amplifier, then place a switch in parallel and close it.

The switches used for these are transistors, especially FET switches.

However, there is a small amount of leakage current in these switches, which may enter the circuit through the switch and become switching noise, which is detected by the comparator in the subsequent stage, so it is necessary to sort out the switch components. be.

In addition, if a switch is placed in front of the amplifier, it will be placed just before or after AC coupling, so when the switch is opened or closed when there is the baseline fluctuation potential, the potential accumulated in the AC coupling capacitor will be The input is in the form of pulses, which may be detected by the comparator, and countermeasures against these are required, making design difficult.

Such inconveniences may also occur in implantable pacemakers.

The present invention is intended to solve the problems associated with the conventional techniques as described above, and is to prevent pacing pulses from being mistakenly detected as intracardiac electrocardiograms without generating switching noise or the like. The purpose is to provide a pacemaker without

iKairitaka 1 In order to achieve such an objective, the pacemaker according to the present invention includes an electrode placed in the heart to detect intracardiac electrocardiograms, and an R wave of the intracardiac electrocardiograms input from the electrodes. In order to detect the , determines the period of the R wave, and when the R wave is detected at a period less than a predetermined interval, the pacing pulse is not output from the electrode, and when the R wave is not detected at the predetermined interval or more, the pacing pulse is output. =7- is placed on the input side of the comparator circuit, and converts the input signal into the comparator circuit into a positive or negative unipolar signal. an absolute value circuit connected between the absolute value circuit and an input of the comparator circuit; and a unipolar input signal that enters the comparator circuit from the absolute value circuit when a pacing pulse is output from the electrode. a pulse pull-down circuit that applies a pull-down pulse with a polarity opposite to that of the input signal for a predetermined period of time and whose potential is higher than that of the input signal to prevent an input signal of a predetermined value or more having the same polarity as the output of the absolute value circuit from being input to the comparator circuit; It is characterized by further having the following.

According to the pacemaker according to the present invention, the pacing pulse and subsequent afterpotential can be detected in the comparison circuit without providing a switching circuit to prevent pacing pulses from being mistakenly detected as intracardiac electrocardiograms. Never. Further, even if a switching circuit is used, pulses caused by its leakage current will not affect R wave detection by the comparison circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Below, a pacemaker according to the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a block diagram of a pacemaker according to an embodiment of the present invention, and FIG. 3. 4 is a schematic diagram showing signal waveforms in each circuit shown in FIG. 1, FIG. 5 is a circuit diagram that further embodies the block diagram shown in FIG. FIG. 2 is a circuit diagram of main parts of a pacemaker according to an embodiment.

The circuit configuration of a pacemaker according to an embodiment of the present invention shown in FIG. 1 is applied to, for example, an extracorporeal pacemaker.

The input/output terminal 2 is connected, for example, to a basing catheter having an electrode placed in the ventricle through a lead wire or the like.

Intracardiac electrocardiograms collected by a basing catheter placed in the ventricle are R waves with a peak value of 2 to 20 mV, and the polarity is sometimes positive and sometimes negative. This depends on the location of the electrode at the tip of the catheter and the location of the endocardium it contacts.

Therefore, the centripetal electrocardiogram detection circuit needs to detect both polarities. Normally, in an external pacemaker, the input/output terminal 2 is AC-coupled to attenuate frequencies below about 20 Hz in order to avoid baseline fluctuations of intracardiac electrocardiograms, so even unipolar electrocardiograms are differentiated due to this AC coupling. becomes bipolar.

An amplifier circuit 3 is connected to the input/output terminal 2.

The amplifier circuit 3 amplifies the weak electrocardiogram input manually from the input/output terminal 2 by several hundred times. The waveform of the electrocardiogram input to the input/output terminal 2 is shown in FIG. 2.3 (A). Also, the waveform before this waveform is differentiated and input to the amplifier circuit 3 is shown as a second waveform.
This is shown in Figure 3 (B). The waveform shown in Figure 3 has the polarity reversed from the waveform shown in Figure 2, and as mentioned above, depending on the position of the catheter, it is difficult to know which waveform will enter the input/output terminal 2. do not have.

A filter circuit 4 is connected to the amplifier circuit 3. The filter circuit 4 consists of a low-pass filter, a high-pass filter, etc., and extracts the R-wave component. Normally, this R-wave is directly applied to the comparator circuit 6. In the present invention, the absolute value circuit 5 (double-wave rectifier) circuit) to the comparator circuit 6. The R wave output signal from the filter circuit 4 is
The waveform is as shown in Figure (C).

The absolute value circuit 5 converts the input signal waveform into a wave of either positive or negative polarity. Thereafter, it is applied to either a positive or negative comparator circuit 6 to detect an R wave. analogy lfl
The output of the absolute value circuit 5 is set to be positive, and a positive wave is detected by a comparison circuit 6 having a slight threshold on the positive side. That way, when the R wave is not input, the comparison circuit 6 will not trigger because it is below the comparison level, and when the R wave is input and exceeds the comparison level, the comparison circuit 6 will not trigger.
is inverted and outputs the trigger pulse to the detection stop circuit 7 and the pacing pulse reset circuit 8.

The output waveform of the absolute value circuit 5 that converts into a positive polarity wave is shown, for example, in FIG. 2.3 (D). As shown in these figures, if the waveforms are passed through the absolute value circuit, even if a waveform of opposite polarity is input to the input/output terminal 2, the output waveform of the absolute value circuit 5 becomes the same waveform.

When the R wave of the intracardiac electrocardiogram is detected by the comparison circuit 6, the detection stop circuit 7 operates for a predetermined period of time after detection based on the output signal.
This is a circuit for stopping detection by the comparison circuit 6.

This predetermined time is sufficient to avoid detecting S waves, T waves, or premature contractions that follow the R wave of the intracardiac electrocardiogram as shown in FIG. ,2
It is 50-300 milliseconds.

This detection stop circuit 7 is connected to the pacing pulse generation circuit 9 together with the pacing pulse reset circuit 8, or
Or connect to the pacing pulse reset circuit.

The pacing pulse generation circuit 9 is connected to the input/output terminal 2.

In this embodiment, the pacing pulse generation circuit 9 is a circuit that generates a pacing pulse at an adjustable predetermined time period, and when the comparison circuit 6 detects an R wave, the pacing pulse reset circuit 8 resets the pacing pulse. The pulse is reset so that no pacing pulse is output to the input/output terminal 2. If the comparator circuit 6 does not detect an R wave within a predetermined period of time after the R wave is detected and the next R wave is to be detected, a pacing pulse is sent from the pacing pulse generation circuit 9 to the input/output terminal 2. is now output. After that, during a predetermined period of time, the comparator circuit 6
If no R wave is detected in the comparison circuit 6, a pacing pulse is further output, and this operation continues until the comparison circuit 6 detects an R wave. As described above, the input/output terminal 2 is connected to a catheter having an electrode implanted in the heart, so that pacing of the heart can be performed by the pacing pulse output from the input/output terminal.

Such a basing generation circuit 9 is also connected to a pulse pull-down circuit 10. The output signal from the pulse reduction circuit 10 is connected to the input side of the comparator circuit 6. When a pacing pulse is output from the pacing generation circuit 9 toward the input/output terminal 2, the pulse pull-down circuit 10 applies a signal having a polarity opposite to that of the unipolar input signal input from the absolute value circuit 5 to the comparator circuit 6. It also has a function of applying a lowering pulse of a potential greater than the input signal for a predetermined period of time to prevent an input signal of a predetermined value or more from being input to the comparator circuit 6.

When the output signal from the absolute value circuit 5 is of positive polarity, the fourth
A negative pulse with a polarity opposite to the positive one as shown in FIG. 6(B) is inputted to the input side of the comparator circuit 6.

The negative pulse width (time) T needs to be longer than the influence time of the pacing pulse input from the input/output terminal 2 and its afterpotential, and is generally 20 to 150 milliseconds. be. Further, the negative pulse potential V is input from the input/output terminal 2 to the amplifier circuit 3,
FIG. 4 after passing through the filter circuit 4 and absolute value circuit 5 (
It needs to be larger than the maximum waveform potential v2 of the pacing pulse and its afterpotential as shown in A). Then, on the input side of the comparison circuit 6, the pulse shown in FIG. 4(B) is added to the waveform shown in FIG. 4(A) corresponding to the pacing pulse and its after potential, and the pulse shown in FIG. 4(C) is added. It becomes a waveform.

Even if the waveform shown in FIG. 6(C) is input to the comparator circuit 6, the waveform corresponding to the pacing pulse and its afterpotential has been sufficiently lowered by the lowering pulse, so that a signal of positive polarity exceeding a predetermined value will not be detected. The detecting comparison circuit 6 will not erroneously detect the signal as an R wave. In the above explanation of the operation, the output of the absolute value circuit 6 is positive, but even if the output of the absolute value circuit 6 is made negative and all subsequent polarities are reversed, the circuit will operate in exactly the same way. You can read it as ``to raise''.

With this configuration, the pacing pulse and its afterpotential will not be mistakenly detected as an R wave by the comparator circuit 6, even without using a switch element. Furthermore, even if a switch element is used, pulses caused by its leakage current will not affect R wave detection. This is because this switching operation is performed on the negative side, which is opposite to the polarity of the signal to be detected (no positive noise is generated).

A more specific example of a pacemaker as shown in Figure 1 A circuit diagram is shown in Figure 5.

In FIG. 5, reference numeral 2a is an input/output terminal, and 3a is an amplifier circuit, which is composed of an operational amplifier and has an amplification factor of several hundred times. Reference numeral 4a denotes a filter, and this filter is, for example, a low-pass type, and has an operational amplifier buffer. Reference numeral 5a denotes an absolute value circuit, and this absolute value circuit is of a typical type using two operational amplifiers, and is designed to output a positive output signal. Reference numeral 6a denotes a comparison circuit, which operates an operational amplifier as a comparator, and is used by finely adjusting the comparison potential to the positive side. This comparison circuit 6a outputs a positive output signal when a potential higher than the comparison potential is input, and otherwise outputs a negative output signal. The output from the absolute value circuit 5a is passed through the resistor 15 to the comparing means 6a.
It is designed to be connected to the input end of the

Reference numeral 11 denotes a switch signal generator operating on a negative power supply, and the switch signal generator level-shifts the basing output to a negative level, and synchronizes with the rise of the basing output and outputs the It is composed of a 1-shot multivibrator that can output a negative output from O from ``0'' and from negative to 0 from output ``Q'', and the output starts in synchronization with the rising edge of the pacing pulse, The output is designed to stop after 10 to 100 milliseconds. The output side of the switch signal generator 11 is connected via a resistor 13 to the input end of the comparator circuit 6a. These switch signal generator 11 and resistor 13
and 15 pulses, forming a pulse pull-down circuit 10 as shown in FIG. FET16 instead of resistor 13
may be used to operate the FET with the output rQJ. In addition, as shown in FIG. 6-7, the signal generator 1
Connect an open collector or open drain transistor from the output of 1 to the input terminal of the comparator circuit 6a, connect their emitters or sources to a negative power supply, and switch all of them or their gates at a negative potential. It is also possible by

The code 12 in FIG. 5 indicates approximately 25 minutes after detecting the cardiac electrocardiogram.
This is a one-shot multivibrator that stops detection for 0 to 300 milliseconds. This multivibrator 12 receives the output signal of the comparison circuit 6a, sends a reset signal to the pacing pulse generation circuit 9a, and has the function of resetting the output of the pacing pulse from the pacing pulse generation circuit 9a to the input/output terminal 2a. have

That is, this multivibrator 12 has a detection stop circuit 7 and a pacing pulse reset circuit 8 shown in FIG.
corresponds to

The pacing pulse generation circuit 9a is composed of two l-shot multivibrators, and the pulse interval and pulse width are determined by tl and t2. Reference numeral 14 is a pacing pulse output stage.

The present invention is not limited to the embodiments described above,
Various modifications can be made within the scope of the present invention.

For example, it is possible to apply the pacemaker according to the present invention to a pacemaker implanted in the body.According to the pacemaker according to the present invention, the switching circuit for preventing the detection of pacing pulses. It is possible to prevent the pacing pulse and subsequent afterpotential from being detected in the comparator circuit without providing a pacing pulse. Further, even if a switching circuit is used, pulses caused by its leakage current will not affect R wave detection.

Furthermore, due to the circuit of the pacemaker according to the present invention ('L
There is no need to be particular about the type or quality of the switch, and stable production of circuits is possible.

[Examples] The present invention will be explained below using more specific examples, but the present invention is not limited to these examples.

The amplifier circuit 3a, which has a circuit as shown in FIG.
It was. As the filter circuit 4a, a low-pass type one having a buffer of an operational amplifier (IC2=LM4250) was used. As the absolute value circuit 5a, an operational amplifier (
IC3, 4 = LM4250) This is a typical format with two ICs, and one with a positive output was used. As a comparison circuit, an operational amplifier (IC5=LM4250) is used,
It was operated as a comparator, and the comparison potential was finely adjusted to the positive side. The switch signal generator 11 operating with a negative power source shifts the level of the basing output to a negative level, and synchronizes with the rising edge of the basing output to output one output from 0 to a negative output power. rQJ
From here, a 1-shot multivibrator (IC6 = CMO34538) that can output from negative to 0 was used, and the output began to be output in synchronization with the rising edge of the pacing pulse.
The output will stop after about 60 milliseconds.

The one-shot multivibrator 12 is one that stops detection for 250 to 300 milliseconds after detecting the centripetal electrocardiogram, and the pacing pulse generation circuit 9a uses tl and t2 to control the pulse interval and pulse pulse. I used one with a fixed width.

When a pseudo load circuit as shown in FIG. 9 was connected to the input and output terminals of this circuit and operated, pacing pulses and afterpotentials were effectively removed, and there was no noise during switching.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pacemaker according to an embodiment of the present invention, and FIG. 3. 4 is a schematic diagram showing signal waveforms in each circuit shown in FIG. 1, FIG. 5 is a circuit diagram that further embodies the block diagram shown in FIG. FIG. 8 is a graph showing the waveform of a pacing pulse, FIG. 9 is a circuit diagram of a pseudo load circuit, and FIG. 10 is a schematic diagram of an electrocardiogram. 2. Input/output terminal, 5. Absolute value circuit, 6. Comparison circuit, 9. Pacing pulse generation circuit, 10. Pulse pull down circuit. 0 (5)〉 〉 + 1 〉 ! 0 (5)■ 〉〉- 1, CI+ °\ ヱ匡01'+

Claims (1)

[Claims] An electrode placed in the heart to detect an intracardiac electrocardiogram, and a case where a signal of a predetermined value or more is input to detect the R wave of the intracardiac electrocardiogram input from this electrode. a comparison circuit that detects that the input signal is an R wave and generates an output signal in that case; and a comparison circuit that determines the cycle of the R wave based on the output signal of the comparison circuit and determines whether the R wave is equal to or less than a predetermined interval. A pacemaker comprising: a pacing pulse generation circuit which does not output a pacing pulse from the electrode when an R wave is detected at a period of 100 m or more, and outputs a pacing pulse from the electrode when an R wave is not detected at a predetermined interval or longer; an absolute value circuit that is placed on the input side of the comparator circuit and converts the input signal that enters the comparator circuit into a positive or negative unipolar signal, and is connected between the output of the absolute value circuit and the input of the comparator circuit. and when a pacing pulse is output from the electrode, a pull-down pulse of opposite polarity and higher potential than the input signal is applied for a predetermined time to the unipolar input signal input from the absolute value circuit to the comparison circuit. . A pacemaker further comprising a pulse reduction circuit that prevents input signals of a predetermined value or more having the same polarity as the output of the absolute value circuit from being input to the comparison circuit.