JP2999252B2 - pacemaker - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a type of pacemaker which detects an intracardiac electrocardiogram by an electrode placed on the heart and outputs a pacing pulse from the electrode. The present invention relates to a pacemaker that does not erroneously detect as intracardiac electrocardiogram.

TECHNICAL BACKGROUND OF THE INVENTION A patient with acute bradycardia or bradyarrhythmia is urgently and temporarily indwelled with a catheter having two electrodes in the right ventricle, and the lead from the electrodes is disconnected. There is a method in which the lead is led out of the body through a catheter, a pacemaker is connected to the end of the lead wire, and pacing is performed.

The pacemaker used for this pacing method is called an extracorporeal pacemaker.

In this extracorporeal pacemaker, a pacemaker of a type called a demand type, which performs pacing when the heartbeat of a living body falls below a set number of beats and does not perform pacing when the heartbeat exceeds the set number of beats, is used. Therefore, the intracardiac electrocardiogram (peak value 2 to 20 mV) generated between the two electrodes of the catheter placed in the right ventricle was detected by a pacemaker, and the period interval between the R wave of the electrocardiogram and the next R wave was set. If it is longer than the time corresponding to the number of beats, a pacing pulse (peak value 2 to 4 V, pulse width 1 to 3 mS) is applied between the same two electrodes, and this is made to cause contraction of the heart muscle through the heart muscle. .

In this pacemaker, the input electrode and the output electrode are the same, and it must input a weak voltage at one time and output a high voltage at another time.

The potential generated between the two electrodes in the right ventricle is not only an intracardiac electrocardiogram, but also has a slowly changing fluctuation, that is, a baseline fluctuation, and a large and long time called an after-potential generated after applying a pacing pulse. , That is, as if a large capacitor (capacitance) was connected in parallel between the electrodes.

This residual potential is indicated by reference numeral A in FIG. 10, and an example of a pseudo load circuit capable of reproducing the residual potential in a pseudo manner is indicated by reference numeral "20" in FIG. It should be noted that reference symbol B in FIG.
Is a pacing pulse.

Therefore, in a circuit for detecting an intracardiac electrocardiogram, unless the pacing pulse B and the after-potential A are prevented from entering the detection circuit, these potentials are detected and cannot be discriminated as an intracardiac electrocardiogram.

In the circuit for detecting intracardiac electrocardiography, first, the input side is removed by AC coupling with a cutoff frequency of 10 to 30 Hz to remove baseline fluctuations, and then amplified by an amplifier by several hundred times, or high-frequency noise is removed. To this end, only the R wave of the intracardiac electrocardiogram is passed through a low-pass filter, and the signal is emphasized. This is detected by a comparator when an R wave having a certain amplitude or more is input.

Also, usually, after the detection circuit detects the intracardiac electrocardiogram,
A function to stop detection for 00 milliseconds is provided. this is,
S wave, T following R wave of intracardiac electrocardiogram as shown in FIG.
This is to prevent the detection of waves, extraordinary contractions, and the like. Therefore, if a pacing pulse or the like is erroneously detected, there is a disadvantage that the intracardiac electrocardiogram cannot be detected for 250 to 300 milliseconds thereafter.

Therefore, it is customary to attach a circuit that closes the detection circuit by a switch or the like until the end of the after-potential in synchronization with the start timing of the pacing pulse.

In such a detection circuit, as a place where the switch is attached, the detection circuit may be closed by the following method.

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

2. Put a resistor in series before the amplifier, then put a switch in parallel and close it.

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

4. Put a resistor in series after the amplifier, then put 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 enters the circuit through the switch and causes switching noise, which may be detected by a comparator at the subsequent stage. is there.

Further, when the switch is placed in front of the amplifier, immediately before or immediately after the AC coupling, when the switch is opened and closed in the presence of the baseline fluctuating potential, the potential stored in the capacitor of the AC coupling becomes It may be input in a pulsed form and detected by a comparator, and it is necessary to take a countermeasure against them and design is difficult.

Such inconvenience may also occur in an implantable pacemaker.

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems associated with the prior art as described above, and without erroneously detecting a pacing pulse as an intracardiac electrocardiogram without generating switching noise or the like. Aims to resist pacemakers.

SUMMARY OF THE INVENTION In order to achieve the object, a pacemaker according to the present invention detects an electrode placed in the heart to detect an intracardiac electrocardiogram, and detects an R wave of the intracardiac electrocardiogram input from the electrode. In order to perform the above, when a signal of a predetermined value or more is input, the input signal is detected as an R wave, and a comparison circuit that generates an output signal in that case, based on an output signal of the comparison circuit, When the period of the R wave is determined and the R wave is detected at a period equal to or shorter than a predetermined interval,
A pacing pulse generating circuit that outputs a pacing pulse from the electrode when the pacing pulse is not output from the electrode and an R wave is not detected for a predetermined interval or more, wherein the pacing pulse is output from the electrode. If
To the input signal input to the comparison circuit, a pull-down pulse having a polarity opposite to the positive or negative unipolar potential determined by the comparison circuit and higher than the input signal for a predetermined time is added, and the determination polarity of the comparison circuit is added to the comparison circuit And a pulse pull-down circuit for preventing an input signal having the same polarity and having a predetermined value or more from being input.

According to such a pacemaker according to the present invention, the pacing pulse and the after potential subsequent thereto are detected in the comparison circuit without providing a switching circuit for preventing the pacing pulse from being mistakenly detected as an intracardiac electrocardiogram. Nothing. Even if a switching circuit is used, a pulse due to a leakage current or the like does not affect the detection of the R wave by the comparison circuit.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a pacemaker according to the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 is a block diagram of a pacemaker according to one embodiment of the present invention, FIGS. 2, 3, and 4 are schematic diagrams showing signal waveforms in the course of each circuit shown in FIG. 1, and FIG. 5 is shown in FIG. FIGS. 6, 7, 8, and 9 are circuit diagrams each of which further embodies the block diagram, and FIGS. 6, 7, 8, and 9 are main part circuit diagrams of a pacemaker according to another embodiment of the present invention.

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

The input / output terminal 2 is connected to a pacing catheter having electrodes implanted in the heart, for example, through a lead wire.

An intracardiac electrocardiogram collected by a pacing catheter implanted in the heart is an R wave having a peak value of 2 to 20 mV, and its polarity may be + or-. This depends on the location of the electrode at the tip of the catheter and the location of the endocardium with which it has contacted.

Therefore, the intracardiac electrocardiographic detection circuit needs to detect both polarities. Normally, in an extracorporeal pacemaker, the input / output terminal 2 is AC-coupled in order to escape from the baseline fluctuation of the intracardiac electrocardiogram, and is attenuated at about 20 Hz or less. To be bipolar.

An amplification circuit 3 is connected to the input / output terminal 2. The amplification circuit 3 amplifies the weak electrocardiogram input from the input / output terminal 2 several hundred times. The waveform of the electrocardiogram input to the input / output terminal 2 is shown in FIGS. Further, the waveform before this waveform is differentiated and input to the amplifier circuit 3 is shown in FIG.
Shown in The waveforms shown in FIG. 3 are obtained by reversing the polarities of the waveforms shown in FIG. 2. As described above, it is not known which waveform enters the input / output terminal 2 depending on the mounting position of the catheter.

A filter circuit 4 is connected to the amplifier circuit 3.
The filter circuit 4 includes a low-pass filter, a high-pass filter, and the like, and extracts an R-wave component. This R wave is directly input to the comparison circuit 6. R from filter circuit 4
The output signal of the wave has a waveform as shown in FIGS.

In the comparison circuit 6, for example, a slight threshold is provided on the positive electrode side. Therefore, when the R wave having the positive wave is not input, the comparison circuit 6 is not triggered because the comparison circuit 6 is below the comparison level. When the R wave is input and exceeds the comparison level, the comparison circuit 6 The trigger pulse is inverted and output to the detection stop circuit 7 and the pacing pulse reset circuit 8. The waveform of the R wave input to the comparison circuit 6 is
As shown in FIGS. 2 and 3 (C), the waveform of the R-wave input to the input / output terminal 2 changes inversion in accordance with the forward / reverse of the waveform. Since the above positive wave is input to the comparison circuit, the R wave can be detected. However, since a waveform that changes inversion in accordance with the normal or reverse of the waveform of the R wave input to the input / output terminal 2 is input to the comparison circuit 6, an inverted waveform as shown in FIG. In this case, a detection time delay t occurs as compared with the case where a waveform as shown in FIG. 2 is input. Since the detection time delay t is about 30 to 50 milliseconds, there is no problem.

The detection stop circuit 7 is a circuit for stopping the detection by the comparison circuit 6 for a predetermined time after the detection based on the output signal when the comparison circuit 6 detects the R wave of the intracardiac electrocardiogram. This predetermined time is determined by the intracardiac electrocardiogram R as shown in FIG.
Sufficient time to avoid detecting an S wave, T wave, or extra systole following the wave, and generally
250-300 milliseconds.

The detection stop circuit 7 is connected to the pacing pulse generation circuit 9 together with the pacing pulse reset circuit 8 or is connected to the pacing pulse reset circuit. The pacing pulse generation circuit 9 is connected to the input / output terminal 2.

The pacing pulse generation circuit 9 is a circuit that generates a pacing pulse at a predetermined time period that can be adjusted in the present embodiment. When the comparison circuit 6 detects an R wave, the pacing pulse reset circuit 8 causes the pacing pulse reset circuit 8 to perform pacing. The pulse is reset so that no pacing pulse is output to the input / output terminal 2. If the comparison circuit 6 does not detect the R wave within a predetermined time after the detection of the R wave, the pacing pulse is sent from the pacing pulse generation circuit 9 to the input / output terminal 2. Is output. After that, if no R wave is detected by the comparison circuit 6 within a predetermined time, a pacing pulse is further output.
And continues until an R wave is detected. As described above, since the input / output terminal 2 is connected to the catheter having the electrode implanted in the heart, pacing of the heart can be performed by the pacing pulse output from the input / output terminal.

Such a pacing generation circuit 9 is also connected to a pulse reduction circuit 10. The output signal from the pulse reduction circuit 10 is connected to the input side of the comparison circuit 6. When the pacing pulse is output from the pacing pulse generator 9 to the input / output terminal 2, the pulse lowering circuit 10 applies a positive or negative unipolar signal determined by the comparator 6 to the input signal input to the comparator 6. It has a function of preventing the input of an input signal having a predetermined value or more to the comparison circuit 6 by applying a pull-down pulse having a polarity opposite to the potential and higher than the input signal for a predetermined time.

When the potential determined by the comparison circuit 6 has a positive polarity, that is, when a slight threshold is provided on the positive electrode side, a negative polarity having a polarity opposite to the positive polarity as shown in FIG. The pulse is input to the input side of the comparison circuit 6. The pulse width (time) T of the negative polarity must be equal to or greater than the influence time of the pacing pulse input from the input / output terminal 2 and the after-potential thereof.
150 milliseconds. Further, the pulse potential V of the negative polarity is input from the input / output terminal 2 and passed through the amplifier circuit 3 and the filter circuit 4 as shown in FIG. 4 (A) and the maximum waveform potential V _{2 of the} pacing pulse and its after potential. Must be larger than Then, the comparison circuit 6
On the input side of FIG. 3, the pulse shown in FIG. 4B is added to the waveform shown in FIG. 4A corresponding to the pacing pulse and its after potential, resulting in the waveform shown in FIG.

Even if the waveform shown in FIG. 4C is input to the comparison circuit 6, the pacing pulse and the waveform corresponding to its after potential have been sufficiently lowered by the reduction pulse, so that the comparison for detecting a signal of a predetermined value or more is performed. In the circuit 6, the signal is not erroneously detected as an R wave. In the above description of the operation, the comparison level by the comparison circuit 6 is positive. However, even if the circuit is configured with all the characteristics reversed, the operation is exactly the same, and the lowering may be read as the raising.

With such a configuration, the pacing pulse and its after-potential will not be erroneously detected as an R wave by the comparison circuit 6 without using a switch element. Also,
Even if a switch element is used, the pulse due to the leakage current or the like does not affect the detection of the R wave. This is because this switch operation is performed on the negative side opposite to the polarity of the signal to be detected (no positive noise is generated).

FIG. 5 shows a more specific circuit diagram of a pacemaker as shown in FIG.

In FIG. 5, reference numeral 2a denotes an input / output terminal, and 3a denotes an amplifier circuit, which is constituted by an operational amplifier and has an amplification factor of several hundred times. Reference numeral 4a is a filter.
For example, it is a low-pass type and has an operational amplifier buffer. Reference numeral 6a is a comparison circuit, which operates the operational amplifier as a comparator, and uses the comparison potential by finely adjusting the comparison potential to the positive side. In the comparison circuit 6a, when a potential higher than the comparison potential is input,
A positive output signal is output, and a negative output signal is output otherwise. The output from the filter circuit 4a is connected to the input terminal of the comparison circuit 6a via the resistor 15.

Reference numeral 11 denotes a switch signal generator operating on a negative power supply. The switch signal generator shifts the level of the pacing output to a negative level, synchronizes with the rise of the pacing output, and outputs 0 from the output "". It is composed of a one-shot multivibrator that can output more negative and can output from negative to 0 from the output "Q". The output starts to be output in synchronization with the rising of the pacing pulse, and several tens of millimeters to one hundred The output stops after 10 milliseconds. The output side of the switch signal generator 11 is connected via a resistor 13 to the input terminal of the comparison circuit 6a. The switch signal generator 11 and the resistors 13 and 15 constitute a pulse pull-down circuit 10 as shown in FIG.

FIG. 6 is a circuit diagram illustrating a simplified circuit diagram around the comparison circuit 6a shown in FIG. In the circuit shown in FIG.
An output signal from the amplifier circuit 3a is directly input to the comparison circuit 6a via the resistor 15. In this figure,
The switch signal generator is indicated by reference numeral 11a.

As another circuit example, as shown in FIG. 7, an open collector or open drain transistor 16 is connected to the input terminal of the comparison circuit 6a from the output of the signal generator 11, and these emitters or sources are negative. There is a circuit in which these bases or gates are switched at a negative potential. This circuit also allows the potential to be reduced to a negative potential.

Alternatively, as shown in FIG. 8, in a circuit before the input terminal of the comparison circuit 6a and continuing the DC coupling, for example, the input of the comparison circuit 6a is reduced to a negative value so that the input of the comparison circuit 6a is reduced.
If the inverting amplifier circuit 17 is connected by DC coupling before the input of, the input side of the inverting amplifier circuit 17 is pulled up positively by the switch potential generating circuit 11b having the same polarity as above but having the opposite polarity to the above. Is possible. Similarly, as shown in FIG. 9, if the inverting amplifier circuit 6a is directly connected before the input of the comparing circuit 6a, the potential of the non-inverting terminal of the inverting amplifier circuit 6a is changed as shown in FIG. Transistor 16
May be used to reduce the value to a negative value.

The same operation as described above can be performed by raising the comparison potential side of the comparison circuits 6 and 6a to a positive value, and this is more correct and easier for an electronic circuit designer. In order to prevent fluctuation, noise, a capacitor is inserted. Therefore, when this potential is largely moved, the speed is slowed down, and at the same time, when a semiconductor element is inserted here, the comparison potential fluctuates due to a temperature change,
The R-wave detection sensitivity varies, which is generally not preferable.

In the above, the comparison potential of the comparison circuit has been described as having a positive polarity. However, the same applies to the case where the comparison potential is set to be negative and the potential is raised to be positive by a switch signal.

On the other hand, the switch signal generators 11 and 11a start operating at the rise of the pacing pulse, and thereafter the time when the after-potential is expected to end (usually 30 seconds).
Although it is about 0 milliseconds, a one-shot multivibrator or the like that continues to operate until an attenuation circuit is provided and shortened to 30 to 150 milliseconds) or a microcomputer may be used. This output is driven as it is, or inverted or level-shifted, with a potential convenient for the switch potential generator.

Reference numeral 12 in FIG. 5 indicates about 250 after detecting an intracardiac electrocardiogram.
This is a one-shot multivibrator for stopping detection for up 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 resets the output of the pacing pulse from the pacing pulse generation circuit 9a to the input / output terminal 2a. That is, the multivibrator 12 corresponds to the detection stop circuit 7 and the pacing pulse reset circuit 8 shown in FIG.

Incidentally, the pacing pulse generator circuit 9a consists of two one-shot multivibrator, so as determine the pulse interval and the pulse width between t ₁ and t _2. Reference numeral 14 denotes pacing pulse output means.

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

For example, the pacemaker according to the present invention can be applied to an implantable pacemaker.

According to such a pacemaker according to the present invention, the comparison circuit does not detect the pacing pulse and the after potential subsequent thereto without providing the switching circuit for preventing the pacing pulse from being detected. Can be. Even if a switching circuit is used, a pulse due to a leakage current or the like does not affect the detection of the R wave.

Further, according to the circuit of the pacemaker according to the present invention, there is no need to be concerned with the type and quality of the switch, and stable production of the circuit is possible.

EXAMPLES Hereinafter, the present invention will be described with more specific examples, but the present invention is not limited to these examples.

 A circuit as shown in FIG. 5 was created.

As the amplifier circuit 3a, IC1 = 2 composed of LM4250
An operational amplifier having an amplification factor of 01 times was used. As the filter circuit 4a, a low-pass type operational amplifier (IC2 = LM425
The one having the buffer of 0) was used. As a comparison circuit, an operational amplifier (IC5 = LM4250) was used to perform a comparator operation, and the comparison potential was finely adjusted to the positive side before use. As the switch signal generator 11 operating on the negative power supply, the pacing output is level-shifted to a negative level, and the output from the output "" to the output "Q" is more negative than "0" in synchronization with the rising of the pacing output. From "", a one-shot multivibrator (IC6 = CMOS4538) that can output from negative to zero is used, output starts in synchronization with the rising of the pacing pulse, and stops after about 80 milliseconds .

The one-shot multivibrator 12, after detecting cardiac inwardly electrodeposition, 250-300 milliseconds, used as the stop detecting, as the pacing pulse generator circuit 9a, t ₁ and
It was used to define a pulse interval and the pulse width t _2.

When a pseudo load circuit as shown in FIG. 11 was connected to the input / output terminals of this circuit and operated, the pacing pulse and after potential were effectively removed, and there was no noise during switching.

[Brief description of the drawings]

FIG. 1 is a block diagram of a pacemaker according to one embodiment of the present invention, FIGS. 2, 3, and 4 are schematic diagrams showing signal waveforms in the course of each circuit shown in FIG. 1, and FIG. 5 is shown in FIG. Circuit diagrams further embodying the block diagram, FIGS. 6, 7, 8, and 9 are main part circuit diagrams of a pacemaker according to another embodiment of the present invention, respectively, and FIG. 10 is a graph showing a waveform of a pacing pulse. FIG. 11 is a circuit diagram of a pseudo load circuit, and FIG. 12 is a schematic diagram of an electrocardiogram. 2 ... I / O terminal, 6 ... Comparison circuit, 9 ... Pacing pulse generation circuit, 10 ... Pulse reduction circuit.

Claims (1)

(57) [Claims] An electrode placed in the heart for detecting an intracardiac electrocardiogram, and a signal not less than a predetermined value is input for detecting an R wave of the intracardiac electrocardiogram input from the electrode. A comparison circuit that detects that the input signal is an R-wave, and generates an output signal in that case; and determines a cycle of the R-wave based on an output signal of the comparison circuit. If it is detected periodically,
A pacing pulse generating circuit that outputs a pacing pulse from the electrode when the pacing pulse is not output from the electrode and an R wave is not detected for a predetermined interval or more, wherein the pacing pulse is output from the electrode. In this case, a pull-down pulse having a polarity opposite to the unipolar potential of either positive or negative and larger than the input signal for a predetermined time is added to the input signal input to the comparison circuit, and the comparison signal is compared to the comparison circuit. A pacemaker having a pulse pull-down circuit for preventing an input signal having the same polarity as a determination polarity of a circuit and having a predetermined value or more from being input.