JP5695480B2 - Nerve stimulator and method of operating neurostimulator - Google Patents

Description

  The present invention relates to a nerve stimulation apparatus and a method for operating the nerve stimulation apparatus.

  Conventionally, it is known that the vagus nerve decreases heart rate and delays atrioventricular conduction when excited by stimulation. A neurostimulator that treats arrhythmia and heart failure is known by stimulating the vagus nerve a certain time after the R wave or P wave is detected in synchronism with an electrocardiographic signal by utilizing the action of the vagus nerve. (For example, see Patent Documents 1 and 2).

Special table 2008-534218 JP-T 2009-531156

  However, when the heart rate changes, the way in which the heart periodically changes is also changed. For example, even after the same time has elapsed since the appearance of the R wave, the state of the action potential and blood flow of the cardiomyocytes differs between when the heart rate is fast and when it is slow. That is, in the case of the nerve stimulation devices of Patent Documents 1 and 2, nerve stimulation is performed on different heart states when the heart rate changes, and nerve stimulation can always be performed on the heart at an appropriate timing. There is a problem that you can not.

  The present invention has been made in view of the above-described circumstances, and provides a nerve stimulation apparatus that can always perform nerve stimulation at an appropriate timing according to the state of the heart, and a method for operating the nerve stimulation apparatus. Objective.

ただし、Φｔは、前記生理信号検出部によって検出された最新の心室インピーダンス、Φｔ−Δｔは、Φｔが検出される所定の時間Δｔ前に検出された心室インピーダンス、Φｍｅａｎは、直前の１心拍内において算出された心室インピーダンスの平均値であり、前記位相θは、Φｔ−ΔｔがΦｍｅａｎと等しく、かつ、ΦｔがΦｍｅａｎよりも大きいときに０である。 In order to achieve the above object, the present invention provides the following means.
The present invention relates to a nerve stimulation unit that supplies electrical stimulation to nerves that control the heart, a physiological signal that periodically changes in synchronization with the activity of the heart, and a right ventricular electrode connected to the right ventricle and a left A physiological signal detector that detects a ventricular impedance between the left ventricular electrode connected to the ventricle , and a phase calculator that calculates the phase θ in one cycle of the ventricular impedance detected by the physiological signal detector from Equation 1. And a control unit that controls the nerve stimulation unit to supply the electrical stimulation when the phase θ calculated by the phase calculation unit is a predetermined phase.

However, Φt is the latest ventricular impedance detected by the physiological signal detector, Φt−Δt is the ventricular impedance detected before a predetermined time Δt when Φt is detected, and Φmean is within the immediately preceding heartbeat. The average value of the calculated ventricular impedance, and the phase θ is 0 when Φt−Δt is equal to Φmean and Φt is larger than Φmean.

According to the present invention, by supplying electrical stimulation to the nerve from the nerve stimulation unit, the heart rate can be changed to the normal range or the atrioventricular conduction can be delayed to treat arrhythmia or heart failure. .
In this case, electrical stimulation is supplied to the nerve when the physiological signal detected by the physiological signal detection unit has a predetermined phase within one cycle. That is, the timing at which electrical stimulation is supplied also changes according to the change in heart rate, and electrical stimulation is supplied when the heart is in substantially the same state in each cardiac cycle. Thereby, it is possible to always perform nerve stimulation at an appropriate timing according to the state of the heart.
Moreover, the physiological signal detection unit can detect a ventricular impedance as the physiological signal, thereby acquiring a signal that more accurately matches the cardiac cycle as the physiological signal.

In the reference example of the invention, the physiological signal detection unit, and with the physiological signal, the action potential of myocardial cells, it is also possible to detect the electrocardiographic signal or blood pressure.
By doing in this way, a signal more accurately matched with the cardiac cycle can be acquired as a physiological signal.

Moreover, in the said invention, it is preferable that the said predetermined phase is (pi) / 2 or / and 3 (pi) / 2.
By doing in this way, a nerve is stimulated at a timing at which the heart easily responds more sensitively to a stimulus in one heartbeat, and the therapeutic effect by the nerve stimulation can be improved.

Moreover, in the said invention, the arrhythmia determination part which determines the state of the said heart based on the time interval of a heartbeat, the defibrillation part which supplies a high voltage | pressure pulse to the said heart, and the pacing part which supplies a pacing pulse to the said heart And the control unit may control the nerve stimulation unit, the defibrillation unit, or the pacing unit based on the determination by the arrhythmia determination unit.
By doing so, various arrhythmias can be treated.

ただし、Φｔは、前記生理信号検出部によって検出された最新の心室インピーダンス、Φｔ−Δｔは、Φｔが検出される所定の時間Δｔ前に検出された心室インピーダンス、Φｍｅａｎは、直前の１心拍内において算出された心室インピーダンスの平均値であり、前記位相θは、Φｔ−ΔｔがΦｍｅａｎと等しく、かつ、ΦｔがΦｍｅａｎよりも大きいときに０である。 The present invention also relates to a method for operating a nerve stimulation apparatus, which is synchronized with a heart activity acquired between a right ventricular electrode connected to the right ventricle and a left ventricular electrode connected to the left ventricle. periodically phase calculating means for calculating a phase θ from equation (2) from varying ventricular impedance in one cycle of the ventricular impedance is activated, the nerve was calculated phase θ generates the electrical stimulation when the predetermined phase stimulation Provided is a method of operating a neurostimulator in which the means operates.

However, Φt is the latest ventricular impedance detected by the physiological signal detector, Φt−Δt is the ventricular impedance detected before a predetermined time Δt when Φt is detected, and Φmean is within the immediately preceding heartbeat. The average value of the calculated ventricular impedance, and the phase θ is 0 when Φt−Δt is equal to Φmean and Φt is larger than Φmean.

  In the above invention, the arrhythmia determination means for determining the presence or absence of occurrence of fibrillation, tachycardia and defibrillation is activated for each heartbeat, and when it is determined to be fibrillation, defibrillation that generates a high-pressure pulse If the means is activated and the tachycardia is determined, the nerve stimulation means is activated, and if it is determined to be a bradycardia, the pacing means for generating a pacing pulse may be activated. Good.

  According to the present invention, there is an effect that nerve stimulation can always be performed at an appropriate timing according to the state of the heart.

1 is an overall configuration diagram of a nerve stimulation apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure provided in the main body of the nerve stimulation apparatus of FIG. It is a figure explaining the phase in 1 period of ventricular impedance. It is a flowchart explaining operation | movement of the nerve stimulation apparatus of FIG. It is a flowchart which shows the nerve stimulation routine of the flowchart of FIG.

Below, the nerve stimulation apparatus 1 which concerns on one Embodiment of this invention is demonstrated with reference to drawings.
The nerve stimulation apparatus 1 according to the present embodiment includes a configuration for treating fibrillation by supplying a high-pressure pulse to the heart A, and a configuration for treating bradycardia by supplying a pacing pulse to the heart A. It is composed.

  As shown in FIG. 1, the nerve stimulation apparatus 1 according to the present embodiment includes a main body 2 embedded in the body and four leads 31 to 34 extending from the main body 2. At the tips of the four leads 31 to 34, a nerve electrode 31a, an RA (right atrial) electrode 32a, an RV (right ventricular) electrode 33a, or an LV (left ventricular) electrode 34a are provided. The nerve electrode 31a is connected to the vagus nerve (nerve) B existing in the vicinity of the heart A. The RA electrode 31a is connected to the right atrium, the RV electrode 32a is connected to the right ventricle, and the LV electrode 33a is connected to the left ventricle. In addition, a metal casing that encloses the main body 2 also functions as the CAN electrode 2a.

  As shown in FIG. 2, the main body 2 includes a heartbeat detection unit 4 that detects a heartbeat, an impedance detection unit (physiological signal detection unit) 5 that detects the impedance of the heart A, and stimulation pulses (electrical stimulation) to the vagus nerve B. ), A pacing unit 7 for supplying pacing pulses to the heart A, a defibrillation unit 8 for supplying high-pressure pulses to the heart A, and signals from the heart rate detecting unit 4 and the impedance detecting unit 5 And a CPU (Central Processing Unit) 9 that outputs a signal for instructing the nerve stimulation unit 6, the pacing unit 7 and the defibrillation unit 8 to operate, a storage unit 10, and a communication unit 11. .

  The heartbeat detection unit 4 detects an electrocardiogram signal by any one of the three electrodes 32a, 33a, 34a connected to the heart A (RA electrode 32a in the illustrated example), and the waveform of the detected electrocardiogram signal Based on the change, for example, the heartbeat is detected as an R wave appears in the electrocardiogram signal when the potential of the electrocardiogram signal exceeds a predetermined threshold. The heartbeat detection unit 4 outputs a heartbeat detection signal to the arrhythmia determination unit 91 (described later) and the storage unit 10 in the CPU 9 when a heartbeat is detected.

  The impedance detection unit 5 applies a voltage between the RV electrode 33a and the LV electrode 34a, and measures the amount of decrease in the applied voltage, whereby the ventricle in the ventricular region sandwiched between the two electrodes 33a and 34a. The impedance Φ is detected. The ventricular impedance Φ is a numerical value representing the volume and blood flow of the ventricle. That is, the ventricular impedance Φ changes in synchronization with the contraction and expansion of the heart A and has the same cycle as the cardiac cycle.

  The impedance detection unit 5 outputs information on the detected ventricular impedance Φ to the storage unit 10. The storage unit 10 stores the input ventricular impedance Φ in time series. At this time, for example, the ventricular impedance Φ detected when the heartbeat detection signal is output so that the ventricular impedance Φ continuously detected at a sufficiently short time interval is associated with the timing of heartbeat detection. Is stored in the storage unit 10 by being flagged.

  The nerve stimulation unit 6 generates a stimulation pulse (electrical stimulation) and outputs the generated stimulation pulse to the nerve electrode 31a. By supplying a stimulation pulse to the vagus nerve B through the nerve electrode 31a, the vagus nerve B is stimulated to suppress the heartbeat and treat tachycardia.

  The pacing unit 7 generates a pacing pulse, and outputs the generated pacing pulse to an electrode selected in advance based on the patient's pathology, etc., among the electrodes 32a, 33a, and 34a arranged in the heart A. By supplying a parsing pulse locally to the heart A through the electrodes, the electrocardiogram signal is synchronized with the pacing pulse at the supplied site to treat the bradycardia.

  The defibrillator 8 generates a high voltage pulse having a voltage larger than the pacing pulse, and the generated high voltage pulse is selected from the CAN electrode 2a and the three electrodes 32a, 33a and 34a connected to the heart A It outputs between two electrodes (in the example shown, RV electrode 32a and CAN electrode 2a). By supplying a high-pressure pulse to the heart A via these two electrodes, the electrocardiographic signal is synchronized throughout the heart A to treat fibrillation.

  The CPU 9 calculates the phase θ of the arrhythmia determination unit 91 that determines the presence / absence of arrhythmia and the type of arrhythmia based on the heart rate detected by the heart rate detection unit 4, and the phase θ of the ventricular impedance Φ detected by the impedance detection unit 5. And a control unit 93 that controls operations of the nerve stimulation unit 6, the pacing unit 7, and the defibrillation unit 8.

  The arrhythmia determination unit 91 is based on the time interval when the heartbeat detection signal is input from the heartbeat detection unit 4, that is, based on the time interval of the heartbeat, and whether there is an arrhythmia and the type of arrhythmia if there is Determine. Specifically, the arrhythmia determination unit 91 has a predetermined first threshold value, second threshold value, and third threshold value in ascending order. The arrhythmia determination unit 91 determines that the heartbeat is fibrillation when the time interval of the heartbeat is equal to or less than a predetermined first threshold, and is tachycardia when the time is greater than the first threshold and equal to or less than the second threshold. If it is greater than or equal to the third threshold value, it is determined that the pulse is not in pulse. The arrhythmia determination unit 91 outputs an arrhythmia determination signal indicating the determination result to the control unit 93.

  The phase calculation unit 92 reads out all the ventricular impedances Φ detected by the impedance detection unit 5 from the storage unit 10 until the next heartbeat is detected after the heartbeat detection unit 4 detects the heartbeat. The average value Φmean of the impedance Φ, that is, the average value of the ventricular impedance Φ within one heartbeat is calculated by the equation (1). The phase calculation unit 92 outputs information on the calculated average value Φmean to the storage unit 10. Note that N in Equation (1) is the number of times the ventricular impedance Φ is detected within one heartbeat, that is, the number of data of the ventricular impedance Φ.

  The phase calculation unit 92 calculates the latest ventricular impedance Φt, the ventricular impedance Φt−Δt detected before Δt when the ventricular impedance Φt is detected, and the previous heartbeat from the storage unit 10. The average value Φmean is read from the storage unit 10. Then, the phase calculation unit 92 calculates the phase θ from the read ventricular impedances Φt, Φt−Δt and the average value Φmean by Equation (2). The phase calculation unit 92 outputs information on the calculated phase θ to the control unit 93.

  Here, when a map is created by plotting the value of the ventricular impedance Φt on the horizontal axis and the value of the ventricular impedance Φt−Δt on the vertical axis, as shown in FIG. 3, a trajectory that makes one round per heartbeat is drawn. . Here, the center of the amplitude in the horizontal axis direction and the vertical axis direction corresponds to the average value Φmean. In the map of FIG. 3, the angle corresponding to the coordinates (Φmean, Φmean) is the center O, and the angle between the point Pt indicating the ventricular impedance Φt and the center O is the phase θ calculated by the equation (2). That is, the phase θ represents the phase within one cardiac cycle of the ventricular impedance Φ.

  When the arrhythmia determination unit 91 determines fibrillation, the control unit 93 outputs a signal for outputting a high-pressure pulse to the defibrillation unit 8. In addition, when the arrhythmia determination unit 91 determines a bradycardia, the control unit 93 outputs a signal for outputting a pacing pulse to the pacing unit 7.

  In addition, when the tachycardia is determined by the arrhythmia determination unit 91, the control unit 93 outputs a signal for outputting a stimulation pulse to the nerve stimulation unit 6. At this time, the control unit 93 causes the phase calculation unit 92 to calculate the average value Φmean for one heartbeat, and then calculates the phase θ of the ventricular impedance Φ sequentially detected in the next heartbeat. Then, the control unit 93 causes the nerve stimulation unit 6 to output a stimulation pulse when the phase calculated by the phase calculation unit 92 reaches a predetermined phase θ1.

  Here, the predetermined phase θ1 is determined by a patient, a disease state, and the like. For example, when the nerve stimulation apparatus 1 is implanted in the body, a stimulation pulse is supplied to the vagus nerve B at a phase different from the cardiac cycle. Then, the phase in which the effect of reducing the heart rate appears most is determined as the predetermined phase θ1. The predetermined phase θ1 is preferably about π / 2 corresponding to the atrial diastole.

The storage unit 10 includes a RAM (Random Access Memory), a ROM (Read Only Memory), and the like.
The communication unit 11 transmits and receives data to and from a computer arranged outside the body by wireless communication. For example, the operator can change the operation setting of the nerve stimulation device 1 by transmitting a signal for changing the specification of each pulse to the CPU 9 via the communication unit 11 from the computer.

Next, the operation of the nerve stimulation apparatus 1 configured as described above will be described.
As shown in FIG. 4, the nerve stimulation apparatus 1 according to the present embodiment always detects a heartbeat (step S <b> 1) and starts determining whether or not an arrhythmia has occurred for each heartbeat (step S <b> 2). S4, S6). When the fibrillation occurs (step S2), the nerve stimulating device 1 supplies a high-pressure pulse to the heart A (step S3), and when tachycardia occurs (step S4), the vagus nerve B is stimulated. A pulse is supplied (step S5), and when a bradycardia occurs (step S6), a pacing pulse is supplied to the heart A (step S7). The nerve stimulation apparatus 1 repeats supply of pulses to the heart A until the time interval of the heartbeat returns to a normal range.

  Here, when a tachycardia occurs (step S5), the nerve stimulation apparatus 1 starts detecting the ventricular impedance Φ as shown in FIG. 5 (step S501). The neurostimulator 1 stores the ventricular impedance Φ for the first heartbeat after the tachycardia is determined (step S502), calculates the average value Φmean (step S503), and stores the calculated average value Φmean (step S503). Step S504). Then, the nerve stimulation apparatus 1 sequentially calculates the phase θ of the ventricular impedance Φ for the next heartbeat (steps S505 and S506). Then, when the phase of the ventricular impedance Φ is the predetermined phase θ1 (step S507), the nerve stimulation apparatus 1 supplies a stimulation pulse to the vagus nerve B (step S508), and ends the detection of the ventricular impedance Φ (step S507). S509).

  In this case, according to the present embodiment, the stimulation pulse is supplied at the same phase of each cardiac cycle. That is, when the heart rate changes, the time from the appearance of the R wave to the supply of the stimulation pulse also changes according to the change in the heart rate, and the stimulation pulse is supplied when the heart A is in the almost same activity state. Is done. Thereby, there is an advantage that the stimulation effect can be improved at the appropriate timing according to the state of the heart A to improve the therapeutic effect by stimulation of the vagus nerve B.

  In the present embodiment, the ventricular impedance has been described as an example of the biological signal, but the biological signal is not limited to this, and periodically changes in synchronization with the electrical activity of the heart A. I just need it. For example, an action potential of a cardiomyocyte, an electrocardiogram signal, or a blood pressure can be used as the biological signal.

When an action potential is used as a biological signal, for example, an action potential optical probe is provided instead of the impedance detection unit 5.
When blood pressure is used as a biological signal, for example, a blood pressure sensor connected to the main body is provided instead of the impedance detection unit 5.

  In the present embodiment, the timing of supplying the stimulation pulse is controlled by sequentially calculating the phase θ of the ventricular impedance Φ within one heartbeat based on the equations (1) and (2). Instead, for example, in the first heartbeat after the detection of tachycardia, the time from the time when the heartbeat was detected to the time corresponding to the predetermined phase θ1 is calculated, and the heartbeat is detected in the next heartbeat. The stimulation pulse may be supplied when the time calculated from the time has elapsed. In this way, even if the heart rate changes, the stimulation pulse can be supplied with the same phase in each cardiac cycle.

In the present embodiment, the stimulation pulse is supplied once per heartbeat, but the number of times the stimulation pulse is output can be changed as appropriate.
For example, stimulation of the vagus nerve B is also effective in treating atrial and ventricular dyssynchrony. Therefore, tachycardia and atrial and ventricular dyssynchrony can be treated by outputting a stimulation pulse even when the phase corresponding to the ventricular diastole is about 3π / 2.

  Moreover, in this embodiment, the case where the vagus nerve B was stimulated to treat tachycardia was exemplified, but other nerves that govern the activity of the heart A are stimulated to treat other pathologies of the heart A. You can also. For example, it is possible to treat bradycardia by stimulating a sympathetic nerve that raises the heart rate as a nerve.

DESCRIPTION OF SYMBOLS 1 Neural stimulation apparatus 2 Main body 2a CAN electrode 4 Heart rate detection part 5 Impedance detection part (physiological signal detection part)
6 nerve stimulation part (nerve stimulation means)
7 Pacing section (pacing means)
8 Defibrillator (Defibrillation means)
9 CPU
DESCRIPTION OF SYMBOLS 10 Memory | storage part 11 Communication part 31-34 Lead 31a Neural electrode 32a RA electrode 33a RV electrode 34a LV electrode 91 Arrhythmia determination part (arrhythmia determination means)
92 Phase calculation unit (phase calculation means)
93 Control part A Heart B Vagus nerve (nerve)

Claims (5)

A nerve stimulation unit that supplies electrical stimulation to the nerves that govern the heart;
Physiological signal detection periodically detecting a ventricular impedance between a right ventricular electrode connected to the right ventricle and a left ventricular electrode connected to the left ventricle. And
A phase calculation unit that calculates the phase θ in one cycle of the ventricular impedance detected by the physiological signal detection unit from Formula 1 ;
A nerve stimulation apparatus comprising: a control unit that controls the nerve stimulation unit to supply the electrical stimulation when the phase θ calculated by the phase calculation unit is a predetermined phase.

However,
Φt is the latest ventricular impedance detected by the physiological signal detector,
Φt−Δt is a ventricular impedance detected before a predetermined time Δt when Φt is detected,
Φmean is an average value of ventricular impedance calculated within the last one heartbeat,
The phase θ is 0 when Φt−Δt is equal to Φmean and Φt is greater than Φmean. The nerve stimulation apparatus according to claim 1, wherein the predetermined phase θ is π / 2 or / and 3π / 2. An arrhythmia determination unit that determines the state of the heart based on a time interval of a heartbeat;
A defibrillator for supplying high pressure pulses to the heart;
A pacing unit for supplying pacing pulses to the heart,
The nerve stimulation device according to claim 1 or 2 , wherein the control unit controls the nerve stimulation unit, the defibrillation unit, or the pacing unit based on the determination by the arrhythmia determination unit. A method of operating a nerve stimulator comprising:
Obtained between the connected left ventricular electrode in the right ventricular electrode and the left ventricle, which is connected to the right ventricle, in one cycle of the ventricular impedance from the ventricle impedance varies periodically in synchronism with the cardiac activity The phase calculation means for calculating the phase θ from Equation 2 is activated,
An operation method of a nerve stimulation apparatus in which nerve stimulation means for generating electrical stimulation operates when the calculated phase θ is a predetermined phase.

However,
Φt is the latest ventricular impedance detected by the physiological signal detector,
Φt−Δt is a ventricular impedance detected before a predetermined time Δt when Φt is detected,
Φmean is an average value of ventricular impedance calculated within the last one heartbeat,
The phase θ is 0 when Φt−Δt is equal to Φmean and Φt is greater than Φmean. Arrhythmia determination means that determines the presence or absence of occurrence of fibrillation, tachycardia and bradycardia for each heartbeat,
When it is determined that fibrillation is detected, defibrillation means that generates a high-pressure pulse is activated, and when it is determined that tachycardia is detected, the nerve stimulation means is activated and is determined to be a bradycardia. 5. The method of operating a nerve stimulation apparatus according to claim 4 , wherein when determined, a pacing means for generating a pacing pulse is activated.

Images