JP3909710B2 - Ventricular volume measuring device and ventricular volume measuring method - Google Patents

Description

  The present invention relates to a ventricular volume measuring device and a ventricular volume measuring method, and more particularly to a ventricular volume measuring device and a ventricular volume measuring method using a conductance catheter. Its purpose is to measure the effective value of voltage change without using a complicated circuit, to overcome the effective value change due to aging of the circuit frequency, and to reduce the calculation load of effective value calculation An object of the present invention is to provide a ventricular volume measuring device and a ventricular volume measuring method that can be performed.

  As a method for examining cardiac function, a method of taking an electrocardiogram is known. This method is relatively easy and widely used, but since the electrocardiogram signal is an indirect signal that appears outside the human body, it is difficult to accurately grasp the state of the heart, and it is difficult to analyze the signal. It was necessary. There are also symptoms that do not appear in the electrocardiogram signal, which may lead to oversight of heart abnormalities.

On the other hand, methods using echocardiography or MRI are known as methods for measuring ventricular volume, which is an important factor in quantitatively evaluating cardiac function. In these methods, the ventricular volume is measured using a spheroid model from one-dimensional or two-dimensional measurement values obtained by echocardiography or MRI.
However, these methods require a very long time for measurement, and are not a method for directly measuring a ventricular volume, but have a problem of poor reliability. There is also a problem that the measuring device is expensive.

On the other hand, a conductance catheter method is known as a method for directly examining the ventricular volume. In this method, as shown in FIG. 7, a conductance catheter (2) in which several (5 in the illustrated example) segments (21s ₁ ) to (21s ₅ ) are formed along the longitudinal direction is prepared. This is introduced from the apex of the heart H toward the aortic valve or from the aortic valve toward the apex (not shown), between the electrodes (22d ₁ ) and (22d ₆ ) at both ends of the conductance catheter (3). A weak current of a predetermined high frequency, for example, a weak current of 20 KHz and 30 μA, is steadily passed between the electrodes (22d ₂ ) and (22d ₃ ) at both ends of each segment (21s ₂ ) (21s ₃ or 21s ₄ ) in the middle part , (22d ₃ ), (22d ₄ ) or (22d ₄ ), (22d ₅ ) is measured.
By passing the above-mentioned high-frequency weak current through the conductance catheter (2), a three-dimensional electric field is formed in the ventricle using the intraluminal blood as a medium, and the change of this electric field, that is, the conductance (reciprocal of impedance) The voltage changes between the electrodes (22d ₂ ) and (22d ₃ ) on both ends of each segment 21s ₂ (21s ₃ or 21s ₄ ), between (22d ₃ ) and (22d ₄ ), or between (22d ₄ ) and (22d ₅ ). Measured as change.

Since a certain relational expression is established between the conductance of each segment and the ventricular volume, the ventricular volume can be obtained by measuring the conductance of each segment.
As a conductance catheter used in such a conductance catheter method, for example, those disclosed in Patent Documents 1 and 2 are known.

When measuring ventricular volume using a conductance catheter, the parallel conductance of the myocardium and surrounding tissues has an effect on the measured conductance, and in order to measure the ventricular volume more accurately, remove the effect of the parallel conductance. A correction value is required.
Conventionally, the parallel conductance has been measured by a hypertonic saline administration method or the like, but as a method that can measure the parallel conductance more easily, for example, Patent Documents 3 and 4 include, For example, a method has been proposed in which two different frequencies are supplied, such as 20 KHz and 2 KHz, and the parallel conductance derived from the myocardium or the like is measured using the difference in electrical conductivity frequency characteristics between blood and myocardium.

JP-A-5-269136 Japanese Patent Laid-Open No. 10-137209 JP 62-84740 A U.S. Pat. No. 4,840,182

However, the method for measuring ventricular volume using a conductance catheter has the following problems.
In a conventional ventricular volume measurement method using a conductance catheter, a narrowband bandpass analog filter and an analog circuit for calculating an effective value are used for AC separation. However, due to the secular change, the frequency of the AC generator and the filter that are matched with each other changes, and the effective value fluctuates, and the ventricular volume cannot be measured stably for a long period of time. There is also a problem that the circuit configuration becomes complicated.

  The problem of the analog circuit described in paragraph [0008] can be solved by sampling a signal and performing AC separation and effective value processing by digital processing. However, in order to perform the above-described digital processing using a digital filter and an effective value calculation operation, it is necessary to perform high-speed sampling (about 10 times the excitation frequency) and a large number of double-precision real product-sum operations. For this purpose, it is necessary to operate the DSP and CPU at high speed, and it is not possible to reduce power consumption or reduce the size, which is a feature of digital processing.

The present invention has been made in order to solve the above-described problems of the prior art, and the invention according to claim 1 is characterized in that electrodes are provided at regular intervals to form a plurality of segments, and at both ends of the electrodes. A conductance catheter that measures a voltage change between other segments except for the segments at both ends when an arbitrary high-frequency weak current flows between the electrodes, and a sampling means that samples the measured voltage change to obtain a sample value An effective value calculating means for calculating an effective value from the sample value, and a power supply unit for supplying required power to the conductance catheter, the power supply unit being different between two electrodes at both ends of the conductance catheter. The two different frequencies are configured such that one frequency is n times the other frequency (where n is an integer of 2 or more). The weak current supplied at the two different frequencies is synchronized, and the sampling means is synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency. The voltage change between the electrodes is sampled using a frequency twice as high as the one frequency, and the effective value calculation means is a time point when the weak current supplied at the other frequency shifts from a negative value to a positive value. Using the 2n sample values, the difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is taken as the effective value of one frequency, and the sum of the first to n-th sample values and n + 1 The difference from the sum of the 2nd to 2nth sample values is the effective value of the other frequency, and the ventricular volume is measured using the effective value of the one frequency and the effective value of the other frequency. The present invention relates to a ventricular volume measuring device.
The invention according to claim 2 is characterized in that one of the plurality of segments of the conductance catheter is provided with one blood conductivity measuring electrode. It relates to a measuring device.
According to a third aspect of the present invention, there is provided the blood conductivity measuring electrode, sampling means for obtaining a sample value by sampling a voltage change between electrodes located in the vicinity of the blood conductivity measuring electrode, and the sample value An effective value calculating means for calculating an effective value, wherein the power supply unit is a weak current at two different frequencies between the blood conductivity measuring electrode and an electrode located in the vicinity of the blood conductivity measuring electrode. The two different frequencies are set such that one frequency is n times the other frequency (where n is an integer of 2 or more), and the two different frequencies The weak current supplied at the first frequency is synchronized, and the sampling means uses a frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency. Sample the voltage change between the electrodes and The effective value calculation means uses the 2n sample values from the time when the weak current supplied at the other frequency shifts from the negative value to the positive value, and uses the sum of the even-numbered sample values and the odd-numbered sample values. And the difference between the sum of the first to nth sample values and the sum of the (n + 1) th to 2nth sample values as the effective value of the other frequency. The ventricular volume measuring device according to claim 2, wherein blood conductivity is calculated from an effective value of one frequency or an effective value of the other frequency.

In the invention according to claim 4, four blood conductivity measurement electrodes are arranged in one of the plurality of segments of the conductance catheter, and both ends of the four blood conductivity measurement electrodes are arranged. 2. The ventricular volume measuring device according to claim 1, wherein the electrodes are current application electrodes, and the pair of electrodes inside are voltage measurement electrodes.
The invention according to claim 5 comprises sampling means for sampling a voltage change between the voltage measuring electrodes to obtain a sample value, and an effective value calculation means for calculating an effective value from the sample value, wherein the power supply The unit is configured to supply a weak current between the voltage application electrodes at two different frequencies. One of the two different frequencies is n times the other frequency (where n is 2 or more). The weak currents supplied at the two different frequencies are synchronized, and the sampling means has a maximum value of the weak current supplied at the one frequency and The voltage change between the electrodes is sampled using a frequency twice as high as one frequency synchronized with the minimum value, and the effective value calculation means is configured so that the weak current supplied at the other frequency is changed from a negative value to a positive value. 2n sample values from the time of transition to The difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is the effective value of one frequency, and the sum of the first to n-th sample values and the n + 1-th to 2n-th sample values 5. The ventricular volume measurement according to claim 4, wherein the blood conductivity is calculated from the effective value of the one frequency or the effective value of the other frequency, with the difference from the sum of the two being the effective value of the other frequency. Relates to the device.
The invention according to claim 6 relates to the ventricular volume measuring device according to any one of claims 1 to 5, wherein the conductance catheter is provided with a pressure sensor.

In the invention according to claim 7, electrodes are provided at regular intervals to form a plurality of segments, and an arbitrary high-frequency weak current is passed between the electrodes at both ends of the electrodes to remove the segments at both ends. In the ventricular volume measurement method using a conductance catheter for measuring a voltage change between segments, one frequency of the weak current is n times the other frequency (where n is an integer of 2 or more). Weak currents supplied at two different frequencies set in such a way that the weak currents are synchronized and one of them is synchronized with the maximum and minimum values of the weak currents supplied at said one frequency. 2n samples from the time when the weak current supplied at the other frequency shifts from a negative value to a positive value using the voltage change between the electrodes sampled using a frequency twice the frequency as a sample value. Use value The difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is the effective value of one frequency, and the sum of the first to n-th sample values and the n + 1-th to 2n-th sample values The present invention relates to a ventricular volume measuring method characterized in that a difference from the sum is an effective value of the other frequency and the ventricular volume is measured using the effective value of the one frequency and the effective value of the other frequency.

According to the first aspect of the present invention, the effective value of the AC voltage can be measured without using a complicated circuit, and the effective value change due to aging of the circuit frequency does not occur. A ventricular volume measuring device capable of measuring a ventricular volume stably for a period can be provided.
According to the second and third aspects of the present invention, there is no need to separately collect blood and measure the blood conductivity when calculating the ventricular volume, and the test animal and the measurer can be separated from each other at a distance. Ventricular volume can be measured even when present.
According to the inventions of claims 4 and 5, since there is less measurement error and more accurate blood conductivity can be measured compared to the case where blood conductivity is measured by the two-electrode measurement method, more accurate blood conductivity can be measured. It becomes possible to measure the ventricular volume.
According to the sixth aspect of the present invention, the intraventricular pressure of the subject or test animal can be measured simultaneously, and the heart function can be more accurately evaluated.

Hereinafter, a ventricular volume measuring device and a ventricular volume measuring method according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a ventricular volume measuring apparatus according to the present invention.
A ventricular volume measuring device (1) according to the present invention comprises a conductance catheter (2), a power source (3), and a device body (4).

A conductance catheter (2) is introduced into the ventricle. The conductance catheter (2) has a plurality of segments (five in the illustrated example) (21s) in which electrodes (22d _{1 to} 22d ₆ ) are provided at regular intervals, similarly to the conventional conductance catheter described with reference to FIG. _{1 to} 21s ₅ ) are formed, and a plurality of segments (5 in the illustrated example) (21s _{1 to} 21s ₅ ) having electrodes (22d _{1 to} 22d ₆ ) at both ends are abutted in the longitudinal direction. . Then, between the two electrodes (22d ₁ , 22d ₆ ) on the outer sides of the segments (21s ₁ , 21s ₅ ) at both ends, any power is supplied from the power supply unit (3) as will be described later. A high-frequency weak current (for example, 3 to 5 μA) is allowed to flow, and other segments (21 s _{2 to} 21 s ₄ ) excluding the segments (21 s ₁ , 21 s ₅ ) at both ends (hereinafter referred to as conductance measurement segments). ) Is measured.

The number of conductance measurement segments and the distance between the electrodes (22d _{1 to} 22d ₆ ) are not particularly limited, and may be set as appropriate according to the size of the heart to be measured. Usually, measuring the change in voltage in at least one conductance measurement segment when measuring the ventricular volume of the mouse heart, but measuring at least three conductances when measuring the ventricular volume of the rabbit heart Measuring voltage changes in segments requires measuring voltage changes in a minimum of five conductance measurement segments when measuring the ventricular volume of a human heart. The electrodes may be arranged at a distance that can secure the number of conductance measurement segments. For example, when measuring the ventricular volume of the rat heart, the conductance measurement is performed when the distance between the electrodes is set to about 2 mm. A sufficient number of segments can be secured.

The power supply unit (3) includes a battery (31), a high-frequency oscillator (32) such as a crystal, and a frequency divider (33). In addition to supplying necessary power from the battery (31) to each part of the signal detection unit (5) and each part of the ventricular volume measuring device (1), the conductance catheter (2 Between the electrodes (22d ₁ , 22d ₆ ) at both ends of (), an arbitrary high-frequency weak current flows. The signal from the high-frequency oscillator (32) is also supplied to the sample and hold circuits (51a, 51b, 51c), and is used to synchronize sampling.
In the present invention, the frequency dividing circuit (33) is provided, the frequency of the weak current supplied to the conductance catheter (2) can be changed, and the conductance in the ventricle can be measured at two different frequencies. Configured to be able to. The two frequencies supplied to the conductance catheter (2) are, for example, 20KHz and 2KHz, one frequency (hereinafter may be referred to as f1) and the other frequency (hereinafter may be referred to as f2). N times (where n is an integer of 2 or more). Then, one frequency (f1) and the other frequency (f2) are synchronized with each other, and a weak current flows between the electrodes (22d ₁ , 22d ₆ ) at both ends of the conductance catheter (2).
That is, in the present invention, the conductance in the ventricle can be measured at two different frequencies. Thereby, the parallel conductance derived from the myocardium or the like can be measured by using the difference in the electrical conductivity frequency characteristics between the blood and the myocardium.

The signal detector (5) is a part for detecting a ventricular volume signal obtained from the conductance catheter (2). As shown in FIG. 1, on the signal input side, a plurality of (three in the illustrated example) differential amplifiers (51a, 51b, 51c) with sample-and-hold circuits are used for conductance signals which are ventricular volume signals. A voltage change stored in the sample and hold circuit is sequentially sampled corresponding to each of the _three conductance measurement segments (21s ₂ , 22s ₃ , 22s ₄ ) in the middle part of the catheter (2). Sampled by means (52).

The sampling means (52) samples the measured voltage change to obtain a sample value.
Specifically, the sampling means (52) uses a frequency twice the one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency (f1) between the electrodes. The voltage change is sampled sequentially for each of the conductance measurement segments (21s ₂ , 22s ₃ , 22s ₄ ).

Each signal (sample value) output from the signal detection unit (5) is transmitted to the arithmetic processing unit (6) and subjected to predetermined processing.
At this time, these signals may be transmitted to the arithmetic processing unit (6) by wire, or may be transmitted to the arithmetic processing unit (6) by radio. For example, when transmitting by radio, in the above configuration, the sample values of a plurality of segments sampled by the signal detection unit (5) are converted into position modulation pulses (PPM waves), and the signals of the plurality of segments are time-division multiplexed. It becomes. The pulse train of modulated pulses including signals of a plurality of segments can be exemplified by a method in which the transmitter is transmitted on a fixed carrier wave.
When each signal output from the signal detection unit (5) by radio is transmitted to the arithmetic processing unit (6), the restraint of the subject or the test animal can be released, and the ventricular volume in a normal living state is measured. be able to.

The arithmetic processing unit (6) is calculated by the effective value calculating means (61) for calculating the effective value from the sample value obtained by sampling by the sampling means (52) and the effective value calculating means (61). And a volume calculation means (62) for calculating a ventricular volume from the effective value.
The effective value calculating means (61) calculates effective values of two different frequencies (f1, f2) from the sample values obtained by sampling by the sampling means (52) according to a certain rule.
Specifically, the effective value calculation means (61) has 2n (however, n is 2 or more) from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value. The difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is used as the effective value of one frequency (f1). Also, from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value, the sum of the first to nth sample values and n + 1 are used using 2n sample values. The difference from the sum of the 2nd to 2nth sample values is the effective value of the other frequency (f2).

With reference to FIG. 2, a method of calculating effective values of two different frequencies (f1, f2) will be described. FIG. 2 shows sample values of 1 to 20, from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value, from the first sample value. Up to the 20th sample value is shown. The vertical axis represents voltage change and the horizontal axis represents time. One frequency (f1) is 10 times the other frequency (f2), that is, n = 10.
As shown in FIG. 2 (a), using 2 × 10 sample values, the effective value of one frequency (f1) is an even-numbered (2, 4,..., 18, 20) sample value. It can be calculated by the difference between the sum of (group B in FIG. 2A) and the sum of odd-numbered (1, 3,..., 19) sample values (group A in FIG. 2A). it can.
The effective value of the other frequency (f2) is the sum of the first to tenth sample values (group C in FIG. 2B) and the 11th to 20th samples using 2 × 10 sample values. It can be calculated by the difference with the sum of the sample values up to (the D group in FIG. 2A).

  The effective values of two different frequencies (f1, f2) calculated by the effective value calculating means (61) are output to the volume calculating means (62). In the volume calculation means (62), the parallel conductance is calculated from the effective values of two different frequencies (f1, f2), and necessary calculation processing is performed together with other various parameters, for example, blood conductivity. Volume etc. are calculated.

The ventricular volume measuring device according to the present invention can directly process the filtering process and the effective value calculation process by directly sampling the alternating current, and the effective value fluctuation at the time of alternating current separation can be obtained by a simple circuit configuration. Can be prevented. In addition, each effective value calculation can be calculated by (2n-1) times of addition / subtraction processing, and a ventricular volume measuring device with an extremely small calculation processing load can be provided.
In addition, since the ventricular volume measuring device according to the present invention can supply two different frequencies, the parallel conductance, which is a correction value for calculating the ventricular volume, does not require any special operation and is more accurate. Parallel conductance can be measured.

Next, the operation of the ventricular volume measuring device according to the present invention will be described.
In the measurement, first, the conductance catheter (2) is introduced into the heart chamber. In that case, the chest is opened under anesthesia, and the conductance catheter (2) is set in the heart.
When the apparatus is set and activated as described above, a conductance signal that is a ventricular volume signal is generated in the conductance catheter (2), and this signal is sampled by the signal detector (5) to obtain a sample value. The sample value is sent to the arithmetic processing unit (6), and effective values corresponding to two different frequencies are calculated.
Further, in the arithmetic processing unit (6), the parallel conductance is calculated from the effective values corresponding to the two different frequencies, and the ventricular volume is calculated from the change in conductance between the conductance measurement segments.

The ventricular volume measuring device (1) according to the present invention can also be configured to measure an intracardiac electrogram.
FIG. 3 is a diagram showing a schematic configuration of a ventricular volume measuring device (1) configured to be able to measure an intracardiac electrocardiogram. Parts that are not necessary for the description are omitted.
In the ventricular volume measuring device (1) shown in FIG. 3, a differential amplifier (51d) with a sample and hold circuit for an intracardiac electrocardiogram signal is provided as a part of the signal detector (5) described in paragraph [0018]. ing. A differential amplifier (51d) with a sample-and-hold circuit for an intracardiac electrocardiogram signal is connected to the two electrodes (22d ₁ and 22d ₅ ) of the conductance catheter (2). The signal stored in the sample and hold circuit is sampled by the sampling means (52), and then transmitted to the arithmetic processing unit (6) to be subjected to predetermined processing. Specifically, the electrocardiogram calculation means (63) is 2n (where n is an integer greater than or equal to 2) from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value. The sum of all sample values is used as an ECG signal.

  By being configured to be able to measure the intracardiac electrogram, it is possible to measure the intracardiac electrogram at the same time as measuring the ventricular volume, and to grasp the state of the heart more accurately.

Furthermore, in the ventricular volume measuring device (1) according to the present invention, the conductance catheter (2) can be provided with blood conductivity measuring electrodes for measuring blood conductivity.
Examples of the method for measuring blood conductivity include a two-electrode measurement method and a four-electrode measurement method.
FIG. 4 is a partial schematic explanatory view of a ventricular volume measuring device (1) capable of measuring blood conductivity by a two-electrode measurement method. Parts that are not necessary for the description are omitted.
The power supply unit (3) includes a high-frequency oscillator (32) and a frequency divider (33). By supplying power from the high-frequency oscillator (32), there is an arbitrary gap between the blood conductivity measurement electrode (70) provided in the conductance catheter (2) and the electrode (22d ₃ ) located in the vicinity of this electrode. A weak high-frequency current is applied. In addition, since the frequency dividing circuit (33) is provided, the frequency of the weak current supplied to the current applying electrode (70, 22d ₃ ) can be changed. As this circuit, the circuit described in paragraph [0017] can be used. That is, between the electrode (22d ₁ , 22d ₆ ) at both ends of the conductance catheter (2), the blood conductivity measurement electrode (70) and the electrode (22d ₃ ) located in the vicinity of this electrode are passed between. Currents of two frequencies (f1 and f2) similar to weak currents of two frequencies (f1, f2) are caused to flow in synchronization. Ventricular volume measurement and blood conductivity measurement are performed by stopping the other current during one measurement by time division.
In the ventricular volume measuring device (1) shown in FIG. 4, the blood conductivity measuring electrode (70) is provided in one of the plurality of segments (21s _{1 to} 21s ₅ ). In addition, a differential amplifier (51e) with a sample-and-hold circuit is provided for a blood conductivity signal as a part of the signal detector (5) described in paragraph [0018].
A differential amplifier (51e) with a sample-and-hold circuit for blood conductivity signals is connected to a blood conductivity measurement electrode (70) and an electrode (22d _{3 in the} figure) located in the vicinity of this electrode. The signal stored in the sample and hold circuit is sampled by the sampling means (52) in the same manner as the sampling described in paragraph [0019]. That is, the sampling means (52) uses the frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency (f1) to change the voltage between the electrodes. , Segment (21s ₆ ).
Next, the sample value obtained by sampling is transmitted to the arithmetic processing unit (6) and subjected to predetermined processing. Specifically, the effective value calculation means (61) described in paragraph [0021] can be used. That is, the effective value calculation means (61) has 2n pieces (where n is an integer of 2 or more) from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value. The difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is used as the effective value of one frequency (f1). Also, from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value, the sum of the first to nth sample values and n + 1 are used using 2n sample values. The difference from the sum of the 2nd to 2nth sample values is the effective value of the other frequency (f2).
The calculated effective value is output to the volume calculating means (62), and blood conductivity is calculated from the effective value of one frequency (f1) or the effective value of the other frequency (f2). Blood conductivity is used to calculate ventricular volume.

The electrode for blood conductivity measurement (70) is provided in the vicinity of one electrode (22d _{3 in the} figure) of the plurality of electrodes (22d _{1 to} 22d ₆ ), so that the electrodes at both ends of the segment (21s ₆ ) Blood conductivity can be measured by the two-electrode measurement method according to (70, 22d ₃ ).
The reason why the electrode for blood conductivity measurement (70) is provided in the vicinity of one of the plurality of electrodes (22d _{1 to} 22d ₆ ) is that the volume of the heart changes momentarily due to pulsation. When the distance between the conductivity measuring electrode (70) and one of the plurality of electrodes (22d _{1 to} 22d ₆ ) is separated, blood conductivity can be measured by volume change accompanying pulsation. It is not possible. That is, the blood conductivity measuring electrode (70) and one of the plurality of electrodes (22d _{1 to} 22d ₆ ) are at a distance that is not affected by the change in ventricular volume accompanying the heart beat, that is, The measurement current from one electrode is provided at a distance such that it converges only on the intraventricular blood.
Specifically, for example, in the case of a Japanese white rabbit that repeatedly expands and contracts between about 6 to 12 mm in ventricular diameter, the electrode for blood conductivity measurement and one of the plurality of electrodes is about 0.5 It is preferable to provide a distance of mm.

  By providing the blood conductivity measurement electrode (70), blood conductivity can be measured by a two-electrode measurement method. For this reason, when calculating the ventricular volume, it is not necessary to collect blood separately to measure the blood conductivity. For example, the ventricular volume can be measured even when the test animal and the measurer are at a distance from each other. can do.

FIG. 5 is a partial schematic explanatory view of a ventricular volume measuring device (1) capable of measuring blood conductivity by a four-electrode measurement method. Parts that are not necessary for the description are omitted.
In the ventricular volume measuring device (1) shown in FIG. 5, the blood conductivity measuring electrode (71) is arranged in any one of the segments (21s _{1 to} 21s ₅ ) (in FIG. 5, the segment (21s ₂ ).).
As shown in FIG. 5, the blood conductivity measurement electrode (71) is composed of four electrodes (71a to 71d) arranged at regular intervals, and a pair of electrodes (71a, 71d) at both ends are A pair of electrodes (71b, 71c) positioned between the current application electrodes (71a, 71d) are voltage measurement electrodes.
The power supply unit (3) includes a high-frequency oscillator (32) and a frequency divider (33). Between the current application electrodes (71a, 71d) at both ends of the blood conductivity measurement electrode (71) provided in the conductance catheter (2) by supplying power from the high frequency oscillator (32), any high frequency is provided. A weak current of. Further, since the frequency dividing circuit (33) is provided, the frequency of the weak current supplied to the current application electrodes (71a, 71d) can be changed. As this circuit, the circuit described in paragraph [0017] can be used. That is, between the current application electrodes (71a, 71d), two currents similar to the weak currents of two frequencies (f1, f2) flowing between the electrodes (22d1, 22d6) at both ends of the conductance catheter (2) are provided. Currents of frequencies (f1 and f2) are flowed synchronously. Ventricular volume measurement and blood conductivity measurement are performed by stopping the other current during one measurement by time division.
In addition, a differential amplifier (51e) with a sample-and-hold circuit is provided for a blood conductivity signal as a part of the signal detector (5) described in paragraph [0018].
The differential amplifier (51e) with a sample-and-hold circuit for blood conductivity signals is connected to the blood conductivity measurement electrodes (71b, 71c). The signal stored in the sample and hold circuit is sampled by the sampling means (52) in the same manner as the sampling described in paragraph [0019]. That is, the sampling means (52) uses the frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency (f1) to change the voltage between the electrodes. Sampling.
The sample value obtained by sampling is transmitted to the arithmetic processing unit (6) and subjected to predetermined processing. Specifically, the effective value calculation means (61) described in paragraph [0021] can be used. That is, the effective value calculation means (61) has 2n pieces (where n is an integer of 2 or more) from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value. The difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is used as the effective value of one frequency (f1). Also, from the time when the weak current supplied at the other frequency (f2) shifts from a negative value to a positive value, the sum of the first to nth sample values and n + 1 are used using 2n sample values. The difference from the sum of the 2nd to 2nth sample values is the effective value of the other frequency (f2).
The calculated effective value is output to the volume calculating means (62), and blood conductivity is calculated from the effective value of one frequency (f1) or the effective value of the other frequency (f2). Blood conductivity is used to calculate ventricular volume.

When a current is passed between the current application electrodes (71a, 71d), a potential difference is generated in the blood between the current application electrodes (71a, 71d) corresponding to the conductivity and the distance. By measuring the voltage between the pair of voltage measurement electrodes (71b, 71c) arranged with a gap between the current application electrodes (71a, 71d), the blood conductivity corresponding to the current can be measured. .
The distance between the four electrodes (71a to 71d), that is, the distance between the current application electrodes (71a, 71d) is not affected by the change in the ventricular volume accompanying the pulsation of the heart. Are provided at a distance such that they converge only at. For example, four electrodes (91a to 91d) can be provided at intervals of 0.1 mm.

If the conductance catheter (2) is inserted into the heart for a long time, blood components may adhere around the conductance catheter (2). When blood conductivity is measured by the two-electrode measurement method, the voltage may change due to blood components adhering to the periphery of the conductance catheter (2), and accurate blood conductivity may not be measured.
On the other hand, when the blood conductivity is measured by the four-electrode measurement method, even if blood components are attached around the conductance catheter (2), the influence of the attached blood components is smaller than the measured blood conductivity, Compared with the case of measuring by the two-electrode measurement method, it is possible to measure the blood conductivity more accurately.

  In the ventricular volume measuring device (1) according to the present invention, the conductance catheter (2) may be provided with a pressure sensor (not shown) for measuring ventricular pressure. By providing a pressure sensor, the state of the heart can be known more accurately. Although it does not specifically limit as a pressure sensor, It is preferable to use a piezoresistive element. This is because the ventricular pressure, which is superior in response to a gentle pressure change as compared with a pressure sensor using a piezoelectric element, can be accurately measured. A bias voltage is applied from a power supply unit (3) to a pressure sensor using a piezoresistive element. The signal measured by the pressure sensor is sent to a ventricular pressure signal detection unit (not shown) composed of a differential amplifier (not shown), and then output from the signal detection unit as a ventricular pressure signal. The

  The ventricular volume measuring apparatus according to the present invention can be suitably used for measuring the ventricular volume of large animals such as dogs, cats, cows, sheep, horses or humans in addition to small animals such as rats and mice. it can.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more clearly, this invention is not limited at all by the following Examples.
FIG. 6 shows measurement data obtained when the ventricular volume of a rat was measured using a ventricular volume measuring device having one conductance measurement segment.
When measuring the ventricular volume of the rat, weak currents of two different frequencies, f1 (20 KHz, 30 μA) and f2 (2 KHz, 30 μA), were applied to the electrodes at both ends of the conductance catheter.
FIG. 6A is a waveform diagram of the weak current applied to the electrodes at both ends of the conductance catheter.
(B) is a voltage change measured between the electrodes at both ends of the conductance measurement segment.
(C) is a graph showing the effective value of f2 calculated by the effective value calculating means from the sample value obtained by the sampling means from the measured voltage of (B).
(D) is a graph showing the effective value of f1 calculated by the effective value calculating means from the sample value obtained by the sampling means from the measured voltage of (B).
(E) is a graph showing an intracardiac electrocardiogram.

  The ventricular volume measuring device according to the present invention can measure the effective value of the voltage change without using a complicated circuit, can overcome the effective value change due to the secular change of the circuit frequency, and the effective value The calculation load of calculation can be reduced, and the ventricular volume of a human or a laboratory animal such as a mouse or a rat can be measured over a long period of time.

It is a block diagram which shows the outline of the ventricular volume measuring apparatus which concerns on this invention. It is a schematic explanatory drawing explaining the method of calculating the effective value of two frequencies (f1, f2) different from a sample value. It is a block diagram which shows the one part schematic structure of the ventricular volume measuring apparatus which concerns on another embodiment of this invention, and is a ventricular volume measuring apparatus comprised so that an intracardiac electrocardiogram signal could be measured. It is a block diagram which shows the one part schematic structure of the ventricular volume measuring apparatus which concerns on another embodiment of this invention, and is a ventricular volume measuring apparatus comprised so that a blood conductivity could be measured by the two-electrode method. . It is a block diagram which shows the one part schematic structure of the ventricular volume measuring apparatus which concerns on another embodiment of this invention, and is a ventricular volume measuring apparatus comprised so that a blood conductivity could be measured by the four-electrode method. . It is an example of the waveform figure of the signal obtained from the ventricular volume measuring apparatus which concerns on this invention. It is a figure which shows the use condition of a conductance catheter.

Explanation of symbols

1 ventricular volume measurement device 2 conductance catheter _22d 1 _{~22d 6} electrode _21s 1 _{~21s 6} segment 3 power unit 31 battery 32 RF oscillator 33 frequency divider 4 apparatus body 5 signal detector 51a~51e sample and hold circuit with a differential amplifier 52 Sampling means 6 Arithmetic processing section 61 Effective value calculating means 62 Volume calculating means 63 Electrocardiogram calculating means 70 Blood conductivity measuring electrodes 71a, 71d Current applying electrodes 71b, 71c Voltage measuring electrodes

Claims (7)

Electrodes are provided at regular intervals to form a plurality of segments, and an arbitrary high-frequency weak current is passed between the electrodes at both ends of the electrodes to measure a voltage change between other segments excluding the segments at both ends. A conductance catheter;
Sampling means for sampling the measured voltage change to obtain a sample value;
An effective value calculating means for calculating an effective value from the sample value;
A power supply unit for supplying required power to the conductance catheter,
The power supply unit is configured to supply a weak current at two different frequencies between electrodes at both ends of the conductance catheter, and the two different frequencies have one frequency n times the other frequency (provided that n Is an integer greater than or equal to 2), and the weak currents supplied at the two different frequencies are synchronized,
The sampling means samples a voltage change between the electrodes using a frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency,
The effective value calculation means uses 2n sample values from the time when the weak current supplied at the other frequency shifts from a negative value to a positive value, and uses the sum of the even-numbered sample values and the odd-numbered sample values. The difference from the sum of the values is the effective value of one frequency, and the difference between the sum of the first to nth sample values and the sum of the (n + 1) th to 2nth sample values is the effective value of the other frequency.
A ventricular volume measuring apparatus, wherein a ventricular volume is measured using an effective value of one frequency and an effective value of the other frequency.   The ventricular volume measuring device according to claim 1, wherein one of the plurality of segments of the conductance catheter is provided with one blood conductivity measuring electrode. Sampling means for sampling the voltage change between the blood conductivity measuring electrode and the electrode located in the vicinity of the blood conductivity measuring electrode to obtain a sample value;
An effective value calculating means for calculating an effective value from the sample value,
The power supply unit is configured to be able to supply a weak current at two different frequencies between the blood conductivity measurement electrode and an electrode located in the vicinity of the blood conductivity measurement electrode, and the two different frequencies are , One frequency is set to n times the other frequency (where n is an integer of 2 or more), and the weak currents supplied at the two different frequencies are synchronized,
The sampling means samples a voltage change between the electrodes using a frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency,
The effective value calculation means uses 2n sample values from the time when the weak current supplied at the other frequency shifts from a negative value to a positive value, and uses the sum of the even-numbered sample values and the odd-numbered sample values. The difference from the sum of the values is the effective value of one frequency, and the difference between the sum of the first to nth sample values and the sum of the (n + 1) th to 2nth sample values is the effective value of the other frequency.
The ventricular volume measuring device according to claim 2, wherein blood conductivity is calculated from the effective value of the one frequency or the effective value of the other frequency. In one of the plurality of segments of the conductance catheter, four blood conductivity measuring electrodes are arranged,
The ventricular volume according to claim 1, wherein electrodes at both ends of the four blood conductivity measurement electrodes are current application electrodes, and a pair of electrodes inside are voltage measurement electrodes. measuring device. Sampling means for sampling a voltage change between the voltage measuring electrodes to obtain a sample value;
An effective value calculating means for calculating an effective value from the sample value,
The power supply unit is configured to be able to supply a weak current between the voltage application electrodes at two different frequencies, and one of the two different frequencies is n times as high as the other frequency (where n is 2). And the weak current supplied at the two different frequencies is synchronized, and
The sampling means samples a voltage change between the electrodes using a frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency,
The effective value calculation means uses 2n sample values from the time when the weak current supplied at the other frequency shifts from a negative value to a positive value, and uses the sum of the even-numbered sample values and the odd-numbered sample values. The difference from the sum of the values is the effective value of one frequency, and the difference between the sum of the first to nth sample values and the sum of the (n + 1) th to 2nth sample values is the effective value of the other frequency.
The ventricular volume measuring apparatus according to claim 4, wherein blood conductivity is calculated from an effective value of the one frequency or an effective value of the other frequency.   The ventricular volume measuring device according to any one of claims 1 to 5, wherein the conductance catheter is provided with a pressure sensor. Electrodes are provided at regular intervals to form a plurality of segments, and an arbitrary high-frequency weak current is passed between the electrodes at both ends of the electrodes to measure a voltage change between other segments excluding the segments at both ends. A ventricular volume measurement method using a conductance catheter,
The weak current is a weak current supplied at two different frequencies set so that one frequency is n times the other frequency (where n is an integer of 2 or more) , The weak current is synchronized,
The voltage change between the electrodes sampled using a frequency twice as high as one frequency synchronized with the maximum value and the minimum value of the weak current supplied at the one frequency is used as a sample value,
The difference between the sum of the even-numbered sample values and the sum of the odd-numbered sample values is calculated using 2n sample values from the time when the weak current supplied at the other frequency shifts from a negative value to a positive value. The effective value of one frequency is used, and the difference between the sum of the first to nth sample values and the sum of the (n + 1) th to 2nth sample values is the effective value of the other frequency,
A ventricular volume measuring method, wherein the ventricular volume is measured using the effective value of the one frequency and the effective value of the other frequency.

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