JP2011024759A - Device and method for detecting fibrillation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly detect fibrillation while cutting down a necessary power consumption. <P>SOLUTION: The fibrillation detector 1 is provided. It includes an electrocardiograph signal detector 3 to detect the electrocardiograph signal of the heart A, an impedance measuring part 4 to measure the impedance of the heart A, a control part 6 to control the impedance measuring part 4, so that the impedance measuring part 4 can start impedance measurement on a prescribed delay time after the potential of the electrocardiograph signal detected by the detector 3 exceeds a prescribed threshold value, and a fibrillation determination means 7 to determine the fibrillation of the heart A based on the impedance value measured by the impedance measuring part 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fibrillation detection device and a fibrillation detection method.

  2. Description of the Related Art Conventionally, devices that detect fibrillation, pulmonary congestion, or pulmonary edema based on the impedance of the heart that changes depending on the volume of the heart and blood flow are known (for example, Patent Document 1 and Patent Document 2). reference.).

JP-A-56-109673 Special table 2007-508861

  However, Patent Document 1 has a problem that power consumption increases because impedance measurement is continuously performed. In particular, in the case of a device implanted in the body such as a pacemaker, there is a problem that the burden on the patient increases when the battery life is shortened and the frequency of replacement is increased. Also, a function of measuring impedance only when the heart rate is high is disclosed, but in this case, it is necessary to detect a plurality of heart rates in order to determine an increase in the heart rate. That is, there is a problem that the time from occurrence to detection is delayed in fibrillation that requires rapid treatment of the heart after occurrence.

  In Patent Document 2, since it is not intended to detect fibrillation, it is unclear whether it can be used appropriately for detection of fibrillation. Even if it is used for detection of fibrillation, there is a problem that fibrillation cannot be detected quickly because impedance is determined from an average value in a plurality of beats.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a fibrillation detection device and a fibrillation detection method capable of quickly detecting fibrillation while reducing power consumption. .

In order to achieve the above object, the present invention provides the following means.
The present invention relates to an electrocardiogram signal detection unit that detects an electrocardiogram signal of the heart, an impedance measurement unit that measures the impedance of the heart, and the potential of the electrocardiogram signal detected by the electrocardiogram signal detection unit is a predetermined threshold value. The control unit that controls the impedance measurement unit so that the impedance is measured after a predetermined delay time from the time exceeding the time, and the fibrillation of the heart is determined based on the impedance value measured by the impedance measurement unit There is provided a fibrillation detection device comprising fibrillation determination means.

According to the present invention, when an R wave appears in the electrocardiogram signal detected by the electrocardiogram signal detection unit, the control unit detects the appearance of the R wave because the potential of the raised electrocardiogram signal exceeds a predetermined threshold. The control unit causes the impedance measurement unit to measure the impedance after the predetermined delay time, that is, at a time when the heart is sufficiently expanded and the impedance becomes substantially maximum. At this time, if the heart does not sufficiently expand due to fibrillation, a lower impedance is measured than in the normal state, and the fibrillation determination unit determines fibrillation based on a decrease in the measured impedance value.
That is, since the impedance is intermittently measured for each heartbeat to determine the presence or absence of fibrillation, the occurrence of fibrillation can be detected quickly while reducing the power consumption of the fibrillation detection device.

In the above invention, when the potential of the electrocardiogram signal exceeds the predetermined threshold, the predetermined threshold is raised to a predetermined magnitude with respect to the potential of the electrocardiogram signal, and then for a predetermined time. A threshold adjustment unit that lowers the predetermined threshold by a predetermined width may be provided.
By doing so, when the baseline of the electrocardiogram signal fluctuates in the vertical direction of the potential, the threshold also fluctuates, and waves and noise other than the R wave appearing in the electrocardiogram signal exceed the threshold and the R wave Is prevented from being erroneously detected. Thereby, the detection accuracy of the R wave can be improved.

In the above invention, the control unit controls the impedance measurement unit to measure impedance after a plurality of different delay times from the time when the potential of the electrocardiogram signal exceeds the predetermined threshold, The fibrillation determination means may determine fibrillation based on the difference in impedance measured at the plurality of different delay times.
At the time of fibrillation in which the volume change of the heart is small, the difference in impedance measured at different times is smaller than that in the normal state. Thus, by determining fibrillation from the amount of change in impedance, it is possible to detect fibrillation with higher accuracy while suppressing the influence of fluctuations in the baseline of impedance.

Further, in the above invention, a heart rate measurement unit that measures the heart rate of the heart is provided, and the control unit controls the predetermined delay time based on the heart rate measured by the heart rate measurement unit. It is good as well.
As the heart rate changes, the rate of heart volume change, that is, the time from when the R wave appears until the heart volume is maximized also changes. Therefore, by shortening or lengthening the delay time according to the increase or decrease of the heart rate, it is possible to improve the detection accuracy of fibrillation by measuring the impedance at the timing when the impedance becomes substantially maximum.

  The present invention also includes an electrocardiogram signal detection step for detecting an electrocardiogram signal, an R wave detection step for detecting the appearance of an R wave based on the potential of the electrocardiogram signal detected in the electrocardiogram signal detection step, Based on the impedance measurement step of measuring the impedance of the heart after a predetermined delay time from the time when the appearance of the R wave was detected in the R wave detection step, and the impedance value measured in the impedance measurement step, There is provided a fibrillation detection method comprising a fibrillation determination step for determining fibrillation of the heart.

According to the present invention, when an R wave appears in the electrocardiogram signal detected in the electrocardiogram signal detection step, it is detected in the R wave detection step. Then, the impedance that has become approximately maximum after a predetermined delay time from the appearance of the R wave is measured by the impedance measurement step, and the fibrillation determination step determines fibrillation from the decrease in the measured impedance value.
Thereby, the impedance is intermittently measured for each heartbeat, and fibrillation can be detected quickly while reducing power consumption.

  In the above invention, when the R wave detection step detects the appearance of an R wave when the potential of the electrocardiogram signal exceeds a predetermined threshold value, and the electrocardiogram signal exceeds the predetermined threshold value, A threshold adjustment step of increasing the predetermined threshold to a predetermined magnitude with respect to the potential of the electrocardiogram signal and then decreasing the threshold by a predetermined width during a predetermined time may be provided.

In the above invention, the impedance measuring step measures the impedance of the heart after a plurality of different delay times from the time when the R wave is detected, and the fibrillation determining step is performed in the impedance measuring step. Fibrillation may be determined based on the difference in impedance at a plurality of measured delay times.
Further, the above invention includes a heart rate measuring step for measuring the heart rate of the heart, and a delay time adjusting step for adjusting the delay time based on the heart rate measured in the heart rate measuring step. It is good.

  According to the present invention, it is possible to quickly detect fibrillation while reducing power consumption.

1 is an overall configuration diagram of a fibrillation detection device according to an embodiment of the present invention. (A) It is a figure explaining the relationship between the electrocardiogram signal and the threshold value with respect to the electrocardiogram signal, and (b) the relationship between the electrocardiogram signal of (a) and the impedance of the heart. It is a flowchart explaining operation | movement of the fibrillation detection apparatus of FIG. It is a figure explaining the relationship between (a) electrocardiogram signal and (b) impedance at the time of heart fibrillation. It is a figure which shows the timing of the measurement of the impedance by the modification of the fibrillation detection apparatus of FIG. It is a figure which shows another modification of the fibrillation detection apparatus of FIG.

A fibrillation detection device 1 according to an embodiment of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the fibrillation detection device 1 according to the present embodiment includes two leads 2A and 2B inserted into the heart A, an electrocardiogram signal detection unit 3 that detects an electrocardiogram signal, An impedance measurement unit 4 that measures the impedance of the heart A by applying a minute current to the lead 2A, a threshold adjustment unit 5 that adjusts a threshold value Vth with respect to the potential of the electrocardiogram signal, and a minute current based on the potential change of the electrocardiogram signal And a fibrillation determination unit (fibrillation determination means) 7 that determines the presence or absence of fibrillation of the heart A.

The leads 2A and 2B have a right ventricular lead 2A and a left ventricular lead 2B, each of which has a distal end disposed in the right ventricle or the left ventricle. The right ventricular lead 2A has V-tip 2a and V-ring 2b which are bipolar electrodes electrically insulated from each other at the tip, and the left ventricular lead 2B has CS-tip 2c which is a monopolar electrode at the tip. ing.
The electrocardiogram signal detection unit 3 detects an electrocardiogram signal by measuring a potential change between the V-tip 2a and the V-ring 2b.

  The impedance measuring unit 4 outputs a minute current between the V-ring 2b and the CS-tip 2c, and measures the voltage between the V-tip 2a and the CS-tip 2c. Then, the impedance of the heart A is measured from the relationship between the output current and the measurement voltage. At this time, the distance between the V-ring 2b and the CS-tip 2c changes with the pulsation of the heart A, thereby changing the impedance between the electrodes 2b and 2c. Increases and decreases during contraction.

  The threshold adjuster 5 first sets the threshold Vth to a value slightly smaller than the normal R-wave potential. Then, when the absolute value of the electric potential of the electrocardiogram signal detected by the electrocardiogram signal detection unit 3 exceeds a set value, a predetermined magnitude, for example, three times the potential at that time The threshold value Vth is increased to a value. In a normal heartbeat, after the T wave and before the time when the next R wave is expected to appear, the value is smaller than the peak value of the R wave and larger than the baseline noise or the normal P wave. Lower continuously. At this time, the slope of the decrease in the threshold value Vth may be a straight line or a curved line.

  The control unit 6 detects the difference between the V-ring 2b and the CS-tip 2c after a predetermined delay time Δt from the time t when the potential detected by the electrocardiogram signal detection unit 3 exceeds the threshold value Vth adjusted by the threshold value adjustment unit 5. The impedance measuring unit 4 is controlled so that a minute current is applied between them.

  When an R wave appears in the electrocardiogram signal, as indicated by a solid line in FIG. 2A, the absolute value of the potential of the electrocardiogram signal suddenly increased exceeds the threshold value Vth indicated by the broken line, and the R wave Is detected by the control unit 6. At this time, the threshold value Vth jumps up to a value sufficiently larger than the potential of the R wave, then falls again to a value smaller than the potential of the R wave, and the next appearing R wave again exceeds the threshold value Vth.

  Further, the heart A tries to start contraction due to the stimulation of the R wave, and as shown in FIG. 2B, the heart A is most relaxed after the time t when the appearance of the R wave is detected, and the heart A The most expanded state, that is, the impedance becomes maximum (see arrow). A predetermined delay time Δt is set so that the impedance of the heart A is measured at a timing when the impedance becomes substantially maximum.

The fibrillation determination unit 7 determines fibrillation when the impedance value measured by the impedance measurement unit 4 falls below a predetermined threshold value Zth. For example, the predetermined threshold value Zth is set to a value larger than the impedance value obtained in the past during fibrillation and smaller than the impedance measured in advance of the heart A of the patient.
When fibrillation is determined by the fibrillation determination unit 7, a defibrillation pulse generator (not shown) quickly supplies a defibrillation pulse between the defibrillation electrodes. As the defibrillation electrode, an electrode (not shown) may be used, or any one of the electrodes 2a to 2c may be used.

The operation and action of the fibrillation detection device 1 configured as described above will be described below with reference to the flowchart of FIG.
The fibrillation detection device 1 according to the present embodiment constantly detects a patient's electrocardiogram signal (electrocardiogram signal detection step S1), and detects the appearance of an R wave at time t when the potential of the electrocardiogram signal exceeds the threshold value Zth. Then (R wave detection step S2), a delay time Δt is delayed from time t (step S3), a minute current is output to the heart A, and the impedance is measured (impedance measurement step S4). Then, the measured impedance value is compared with a predetermined threshold value Zth to determine the presence or absence of fibrillation (fibrillation determination step S5).

At this time, when the heart A is beating normally, a sufficiently large impedance value is measured and exceeds a predetermined threshold value Zth, and it is determined that there is no fibrillation.
On the other hand, when fibrillation occurs in the heart A, as shown in FIGS. 4A and 4B, the impedance of the heart A whose function to expand is reduced is less fluctuated. The value (see the arrow in FIG. 4B) is lower than that in the normal state, falls below a predetermined threshold Zth, and is determined to be fibrillation. Then, a defibrillation pulse is quickly output to the heart A (step S6).

  Thus, according to the present embodiment, the presence or absence of fibrillation is determined by measuring the impedance at one point for each heartbeat. Thereby, unlike the case of detecting fibrillation by continuously measuring impedance, there is an advantage that power consumption can be greatly reduced. In addition, the time resolution of fibrillation detection is improved and the occurrence of fibrillation is detected more quickly than in the case where the heart rate is determined over a plurality of heartbeats or the average value of impedance is calculated. Thereby, after fibrillation occurs, there is an advantage that treatment for defibrillation is performed quickly to stop fibrillation, and damage to the patient due to fibrillation can be suppressed.

  In addition, by changing the threshold value Vth for the potential of the electrocardiogram signal in synchronization with the potential of the electrocardiogram signal, the baseline of the electrocardiogram signal fluctuates and waves or noise other than R waves are erroneously detected as R waves, It is prevented that the potential of the R wave becomes lower than the threshold value Vth and is not detected. Thereby, there exists an advantage that the detection accuracy of R wave is hold | maintained and the detection accuracy of fibrillation can be improved.

  In the above embodiment, a minute current is applied between V-ring 2b and CS-tip 2c, and the voltage is measured between V-tip 2a and CS-tip 2c. There is no particular limitation on the combination of electrodes used for the measurement.

In the above embodiment, the impedance is measured after the delay time Δt from the time t when the R wave is detected, but instead, after the first delay time Δt1, as shown in FIG. The impedance may be measured after the second delay time Δt2.
The first delay time Δt1 is set in the same manner as the predetermined delay time Δt in the above embodiment. The second delay time Δt2 is set to a time when the impedance is sufficiently smaller than the maximum value when the heartbeat is normal.

  When fibrillation occurs in the heart A and the volume change of the heart A becomes smaller, the difference between the impedance values measured at different times t + Δt1, t + Δt2 becomes smaller than that in the normal time, and the fibrillation determination unit 7 determines the measured impedance. When the value difference falls below a predetermined threshold value, it is determined that fibrillation is present. Thereby, even if the baseline of the impedance fluctuates, fibrillation is determined based on the amount of time variation of the impedance that has a small influence, and detection accuracy of fibrillation can be improved.

Moreover, in the said embodiment, as FIG. 6 shows, the heart rate measurement part 8 which measures the heart rate of the heart A is provided, and based on the heart rate measured by this heart rate measurement part 8, a control part 6 may adjust the delay time Δt.
The heart rate measurement unit 8 measures the heart rate based on the electrocardiogram signal measured by the electrocardiogram signal detection unit 3.

  The amount of change of the volume of the heart A per unit time is proportional to the heart rate, and the time from the stimulation by the R wave to the maximum volume of the heart A is also considered to change according to the heart rate. Accordingly, the control unit 6 controls the delay time Δt so that the delay time Δt is shortened when the heart rate is large, and Δt is lengthened when the heart rate is small. As a result, the impedance measurement timing is adjusted so that the impedance is measured at a time when the impedance becomes substantially maximum, and the detection accuracy of fibrillation can be improved.

In this case, fibrillation may be determined together with the heart rate measured by the heart rate measuring unit 8.
When the measured value of impedance falls below the threshold value Zth, the fibrillation determination unit 7 causes the heart rate measurement unit 8 to measure the heart rate from a predetermined number of heartbeats, and when the measured heart rate is greater than the predetermined threshold value, Determine fibrillation. In this way, fibrillation can be detected more accurately, and the number of heartbeats required for fibrillation determination can be reduced compared to the case where fibrillation is detected only from the heart rate. Fibrillation can be detected quickly.

  In the above embodiment, the impedance measuring unit 4 measures the impedance of the heart A from the minute current applied between the V-ring 2b and the CS-tip 2c, but instead includes a capacitor. A voltage pulse may be output between the V-ring 2b and CS-tip 2c from the discharge circuit, and the impedance of the heart A may be measured from the voltage of the voltage pulse. In this case, the impedance of the heart A is measured based on the discharge time of the capacitor and the voltage drop of the measured voltage pulse.

1 Fibrillation Detection Device 2A Right Ventricular Lead 2B Left Ventricular Lead 2a V-tip
2b V-ring
2c CS-tip
3 ECG signal detection unit 4 Impedance measurement unit 5 Threshold adjustment unit 6 Control unit 7 Fibrillation determination unit (fibrillation determination unit)
8 Heart rate measurement unit A Heart S1 ECG signal detection step S2 R wave detection step S4 Impedance measurement step S5 Fibrillation determination step

Claims (8)

An electrocardiogram signal detector for detecting an electrocardiogram signal of the heart;
An impedance measuring unit for measuring the impedance of the heart;
A control unit that controls the impedance measurement unit so that the impedance is measured after a predetermined delay time from the time when the potential of the electrocardiogram signal detected by the electrocardiogram signal detection unit exceeds a predetermined threshold;
A fibrillation detection device comprising: fibrillation determination means for determining fibrillation of the heart based on an impedance value measured by the impedance measurement unit.   When the electric potential of the electrocardiogram signal exceeds the predetermined threshold value, the predetermined threshold value is increased to a predetermined magnitude with respect to the electric potential of the electrocardiogram signal, and then is increased by a predetermined width during a predetermined time. The fibrillation detection device according to claim 1, further comprising a threshold adjustment unit that reduces the predetermined threshold. The control unit controls the impedance measurement unit to measure the impedance after a plurality of different delay times from the time when the potential of the electrocardiogram signal exceeds the predetermined threshold,
The fibrillation detection apparatus according to claim 1, wherein the fibrillation determination unit determines fibrillation based on a difference in impedance measured at the plurality of different delay times. A heart rate measuring unit for measuring the heart rate of the heart;
The fibrillation detection device according to claim 1, wherein the control unit controls the predetermined delay time based on a heart rate measured by the heart rate measuring unit. An ECG signal detection step for detecting an ECG signal;
An R-wave detection step for detecting the appearance of an R-wave based on the potential of the ECG signal detected in the ECG signal detection step;
An impedance measurement step for measuring the impedance of the heart after a predetermined delay time from the time when the appearance of the R wave is detected in the R wave detection step;
A fibrillation detection method comprising: a fibrillation determination step of determining fibrillation of the heart based on the impedance value measured in the impedance measurement step. The R wave detection step detects the appearance of an R wave when the potential of the electrocardiogram signal exceeds a predetermined threshold;
When the electrocardiogram signal exceeds the predetermined threshold value, the predetermined threshold value is raised to a predetermined magnitude with respect to the potential of the electrocardiogram signal, and then the threshold value is increased by a predetermined width during a predetermined time. The fibrillation detection method according to claim 5, further comprising a threshold adjustment step for reducing the threshold. The impedance measuring step measures the impedance of the heart after a plurality of different delay times from the time when the appearance of the R wave is detected;
The fibrillation detection method according to claim 5, wherein the fibrillation determination step determines fibrillation based on differences in impedance at a plurality of different delay times measured in the impedance measurement step. A heart rate measuring step for measuring the heart rate of the heart;
The fibrillation detection method according to claim 5, further comprising a delay time adjustment step of adjusting the delay time based on the heart rate measured in the heart rate measurement step.

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