JPH02218341A - Simulator of electric phenomenon of heart - Google Patents

Abstract

PURPOSE:To carry out simulation on a model which is similar to an actual heart by providing a heart model setting means, cell excitation memory means, excitation cell temporary memory means, and an excitation propagation processing means. CONSTITUTION:A heart geometrical model setting means 3 sets a block consisting in I, J, K pieces respectively in the longitudinal, lateral, and height directions, and an arbitrary block is allotted to a cell, and the pacing time is determined by designating an arbitrary cell to a cell for carrying out autoexcitation, and an arbitrary cell in the rest cells is used as a cell for carrying out excitation propagation, and stored, determining the no-correspondence time and propagation speed. A cell excitation time memory means 9 memorizes the excitation time of all the cells which are obtained at all the time from the start of simulation, and an excitation cell temporary memory means 8 memorizes the cell excited in the previous step time, at an arbitrary step time. the excitation propagation processing means 8 memorizes the cell excited at the pertinent step time as new data in the excitation cell temporary memory means 8 again. With such constitution, the excitation propagation processing time can be reduced drastically.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for calculating and displaying electrical phenomena of the heart within a human body, and particularly relates to excitation propagation processing thereof.

(Prior art) A heart model is constructed from a collection of cells, and the excited state of each cell is determined by applying a predetermined rule based on the electrophysiological characteristics of the heart cells to each cell, and the electrophysiology of the heart is determined from the excited state. Simulators designed to obtain phenomena are known.

(Problems to be Solved by the Invention) However, in such conventional simulators, the heart model used is a simple two-dimensional model, for example, due to restrictions on the number of memory and calculation speed of the computer.
Also, refractory period, propagation speed, etc. were not taken into account. For this reason, it was not possible to perform a simulation based on a model close to an actual heart model.

Therefore, an object of the present invention is to enable simulation using a three-dimensional model by considering the refractory period, propagation velocity, etc. of each cell in the heart model and simplifying the propagation process. To provide a simulator of cardiac electrical phenomena that can be simulated using a model close to the human heart.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention constructs a heart model using a collection of cells, and applies predetermined rules based on the electrophysiological characteristics of the heart cells to each cell. ■ In the vertical, horizontal, and height directions, respectively, in a simulator that determines the excited state of cells and obtains the electrophysiological phenomena of the heart from that excited state.

Set blocks for each J, assign any block among them to a cell, designate any cell among them as a cell that performs automatic excitation, set a pacing time, and then a heart model setting means for determining and storing a refractory period and a propagation velocity for any cell that performs excitation propagation; and a cell excitation time storage means for storing the excitation times of all cells obtained at all times from the start of the simulation. and, at an arbitrary step time, an excited cell temporary storage means for storing excited cells at the previous step time; and at the arbitrary step time,
a cell that automatically excites based on the pacing time;
Excitation is transmitted based on the cell excited at the previous step time stored in the excited cell storage means, the previous cell excitation time stored in the cell excitation time storage means, the refractory period, and the propagation speed. and excitation propagation processing means for determining which cells start to become excited by the step time, and re-storing the cells excited at the relevant step time in the excited cell temporary storage means as new data. It is characterized by

(Operation) According to this configuration, in the process of excitation propagation processing,
It is sufficient to judge whether or not only cells in the vicinity of cells that were excited at the previous step time are excited.
Therefore, the processing time can be significantly reduced. Moreover, as a result, refractory period, propagation velocity, etc. can be taken into consideration, and simulation can be performed using a model that is closer to reality.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 is an overall configuration diagram of a simulator according to the present invention. In the figure, reference numeral 1 is for setting various conditions for simulation, and heart model setting means 2 includes means 3 for setting a geometric model of the heart, and electricity for various cells defined by this heart geometric model setting means 3. and means 4 for setting physiological characteristics. Furthermore, 5 is a means for setting the position and angle of the heart, and 6 is a means for setting the torso.

Further, 7 indicates a calculation means for simulation, 8 a cell excitation processing means, 9 a means for storing the calculation result, and 10 further calculates the potential on the body surface (torso) based on the calculation result. Vector electrocardiogram calculation means 11
, Body surface potential data storage means 13.12 Body surface potential calculation means for outputting the data to the electrocardiogram calculation means 12, 13~! 5 is a storage means for each data, and 16 is an output means for displaying output to the display means 17.

The cardiac geometric model setting means 2 is configured from I x J A geometric model of the heart is created by assigning arbitrary blocks among the blocks to cells.

FIG. 2 shows an example of the configuration of such a geometric model setting means. The operating means 20 is for specifying the cross section and cell type of the cardiac geometric model to be changed or newly set, and the cross section can be specified by any cross section number of length l, width j, and height k. It is. The basic block storage means 21 stores the coordinates of each block in the aforementioned 11 width and J1 height. The geometric model storage means 22 stores models that have already been created or models that are currently being set, and stores, for example, cell coordinates and cell types. Section number determination means 23
determines the section number specified by the operating means. Based on the output signal of the determining means 23, the section display data output means 24 outputs the section display data based on the data of the geometric model storage means 22. Similarly, the adjacent cross section display data output means 25 outputs display data of a cross section adjacent to the cross section, and the orthogonal cross section display data output means 26
outputs display data of a cross section perpendicular to the cross section.

In addition, the designation of the above cross section is I, J, Kl! Any coordinate plane among the marks can be specified, and the orthogonal cross section can also be determined by this.

When the cross-section is displayed in this way, the necessary cell correction or addition operation is also performed by the operation means 20, and according to the output, the cell type changing means 28 to 30 are changed to a predetermined cross-section via the cell type determining means 27. Change or add cell types in .

These cell types are the types of cells that make up the heart;
For example, the sinoatrial node, atrial myocyte, atrioventricular node, bundle of His, leg,
Purkinje fiber network cells, ventricular myocardial cells, and special cells that can be defined by the user are provided. Note that the characteristics of these cells are determined by electrophysiological characteristic setting means 4, which will be described later.

With the above configuration, a predetermined cross section is displayed by the display means 32 via the output means 31.

When the above series of setting operations is completed, the modified or set data is stored again in the geometric model storage means.

Note that this display means 32 can also be used as the display means 17 shown in FIG. FIG. 3 shows the above operating procedure in the form of a flowchart, and FIG. 4 shows the display by the display means during the setting operation. In Fig. 4, 33 indicates the corrected ki cross section on the I-J plane, and 34°35 indicates the adjacent ki-1, ki+, respectively.
1 shows a cross section. Further, 36 indicates a cross section perpendicular to them. Furthermore, during each display, 37a.

37b, 37c, 37d, etc. each indicate the type of cell; 37a indicates a Purkinje fiber network cell; 37b indicates an atrial muscle or ventricular muscle cell; 37c, 37d indicates a cell in an ischemic state according to its stage. It is.

As described above, according to the present embodiment, when setting and modifying the cardiac geometric model, the surrounding area of the modified portion can be visually recognized at the same time, so that the modification, setting, etc. can be easily performed.

The electrophysiological characteristic setting means 4 provides parameters such as action potential characteristics, propagation velocity, pacing time, etc. to the various cells specified by the cardiac geometric model setting means 3.

Table 1 shows such parameters, and in this example, 16
It is possible to freely change the settings of the type parameters. Further, FIG. 5 shows the correspondence between the action potential waveform and each of its parameters.

As is clear from Table 1 and FIG. 5, the action potential waveform in this example is 0 phase 40.1 phase 41.2 phase 42
．． Each phase is determined by defining each of the 43 parts of the four phases as a straight line, and giving each end point of these straight lines as parameters of time and potential. Also, the membrane potential V of the three-phase 44 in the curved part -
(X) is sample data S i (Xi, yi) (
St to S7) is determined by the following Lagrange interpolation polynomial.

(n=3) Table 1 Parameter Table 2 As described above, in this example, the action potential waveform can be defined with a small number of data, and the number of memories can be reduced and the model can be made more complex. .

Further, according to the electrophysiological characteristic setting means, it is possible to freely set the electrophysiological characteristics such as the action potential waveform of any cell constituting the heart in cooperation with the cardiac geometric model setting means 3, and the actual A heart model that closely resembles the heart can be constructed.

Tables 2 and 3 show examples of setting each parameter, with Table 2 showing the Purkinje fiber network cells and Table 3 showing the ventricular myocardial cells.

The heart position setting means 5 and the torso setting means 6 include a sixth
As shown in the figure, a torso 50 and a heart 5 placed therein
The torso setting means 6 sets the size, shape, etc. of the torso, and the heart position setting means 5 sets the position, angle, etc. of the heart with respect to the torso.

Table 3 Next, the calculation means 7 for simulation will be explained.

The excitation processing means 8 comprises an excitation propagation processing means 8a and an excitation cell temporary storage means 8b. At the start of the simulation, the excitation propagation processing means 8a determines the cell that starts automatic excitation based on the data from the cardiac geometric model setting means 3 and the electrophysiological characteristic setting means 4, and stores it in the cell excitation storage means. 9 and also stored in the excited cell temporary storage means 8b.

From the next step onwards, cells that start excitation due to the transmission of excitation by the cells stored in the excited cell temporary storage means 8b at each step time are selected based on the cell coordinates and electricity by the cardiac geometric model setting means 3. It is determined from the propagation velocity refractory period set in the physiological characteristic setting means 4, the previous excitation time stored in the cell excitation propagation processing means 9, etc., and searching for automatically excited cells set in the electrophysiological characteristic setting means 4. Find cells that newly start excitation, store them in the cell excitation storage means 9, re-store them in the excited cell temporary storage means 8b, and repeat the same operation thereafter to see the process by which the excitement is propagated. Process.

FIG. 7 shows the above operation in the form of a flowchart. Step 1 is to set the propagation time calculated by the simulator, which is set to 3 seconds in this embodiment. Steps 2 and 3 are initial settings, and in this example, the step time T is 3 m5ec, P W F
is the data stored in the excited cell temporary storage means 8b, XC
T indicates data stored in the cell excitation storage means 9, respectively.

Then, in each step, the step time is advanced one by one, and in step 5, the end is determined. Step 6 is to search for cells that are automatically excited at time T from the electrophysiological characteristic setting means 4 and the cardiac geometric model setting means 3, and to create a PWF.
In the process of storing the data and XCT data, step 7 is to find the cell where the excitation starts by the above-mentioned propagation.
data, the process of storing it in XCT data, step 8 is P
Each figure shows the process of replacing WF data.

Incidentally, FIG. 8 shows the operation of determining whether or not cells within the propagation possible range are in the refractory period in step 7 of the excitation propagation process described above, and T pr in step 1.
e indicates the previous excitation time stored in the cell excitation storage means 9, and RF in step 2 indicates the refractory period stored in the electrophysiological characteristic setting means 4. Step 3 shows the process of storing excited cells.

As described above, according to the cell excitation propagation processing means according to the present embodiment, processing is performed by focusing only on the peripheral area of a cell that is excited at any given time, that is, a cell to which excitation may be transmitted. Since this is done, calculation time can be shortened.

Next, the body surface potential processing means 10 will be explained. FIG. 9 shows the operation of the body surface potential processing means 10. First, step! , the cell excitation time and electrophysiological characteristic setting means 4 of the cell excitation time memory means 9 described above
Based on the action potential waveform of , the centripetal electromotive force distribution at every other cell interval is determined, and the current dipole moment is determined.

Here, δ represents electrical conductivity, and φ represents the membrane potential of the cell.

Next, in step 2, the heart model is divided into m vertical planes, n horizontal planes, and horizontal planes to obtain m x n x blocks, and in order to represent each block with one dipole moment, we first divide the heart model into multi-dipole planes. Find the magnitude of moment Jm. The magnitude of this multi-dipole moment Jm is determined by the sum of the current dipole moments J1 determined in step 1 above. Next, in step 3, the weighted average Pm of the positions of the current dipole moment Jl is determined in order to determine the position of the multi-dipole moment Jm. Here P
i indicates the position of cell i. Then, in step 4, the body surface potential V is determined from the multi-dipole moments determined above. Here, Ao and Vo are the potential generated on the body surface under infinite-like medium conditions and its normal differential as n-dimensional vectors, A and B are the nXn coefficient matrix and n-dimensional vector obtained by the boundary element method, and α is the body of Vo. The surface integrals are shown respectively.

According to this method of calculating the body surface potential, compared to the conventional method of calculating the body surface potential directly from the current dipole moment of each cell, the multi-dipole moment J
Since the number of m is much smaller than the number of current dipole moments, the calculation time can be significantly reduced. Moreover, in this case, the calculation accuracy is 1/1 even when the block is divided into sections of about one-third of the ventricle for each axis.
It was said that the error was within 10%.

Furthermore, in this example, the current dipole moment was determined for every other cell by focusing on the fact that the centripetal electromotive force distribution can be expressed as a continuous function, so the calculation time using the three-dimensional model was further reduced to 8 minutes. The time can be reduced to 1, resulting in a significant time reduction. In this case as well, the calculation accuracy was excellent, being within 1%, as in the case above.

The body surface potential determined as described above is stored in the body surface potential data storage means 13, and the 12-lead electrocardiogram data calculation means 12 calculates 12-lead electrocardiogram data based on the body surface potential and stores the same. 15. Further, the vector electrocardiogram data calculation means 11 calculates vector electrocardiogram data from the value of the multi-dipole moment and stores the data in the storage means 14.

The display output means 16 displays a vector electrocardiogram on the display means 17 based on the data stored in the respective storage means 13-15.
It outputs and displays body surface electrograms, 12-lead electrocardiograms, etc.

In this embodiment, the display output means 16 can output a vector electrocardiogram and a 12-lead electrocardiogram while displaying their time correspondence on the same screen 61.

FIG. 10 shows a 12-lead electrocardiogram (■ to U6) and a vector electrocardiogram (front,
Left side, plane) shown. In each diagram, there is an arrow 6 pointing to the electrocardiogram.
0 is displayed. The position where this arrow is displayed (
Data points) indicate data obtained at the same time, and the direction of the arrow indicates the direction of time progression in each figure.

Therefore, according to such a display, vector electrocardiogram and 12
Not only can the time correspondence of the lead electrocardiogram be very easily performed, but also the time course direction (loop direction of the vector electrocardiogram) can be easily known, making it easier to understand each diagram.

FIG. 11 shows the configuration of the display output means for displaying the above-mentioned display, and shows the operation means 6 for determining the position of the arrow, that is, the corresponding time.
2. This corresponding time data is stored in the 12-lead electrocardiogram data storage means 63 to 74 and the vector electrocardiogram data storage means 14.
It is provided with data search means 63 for searching from a to 14c, and arrow display position determining means 64 for determining the display position and direction of the arrow from these data.

Incidentally, FIG. 12 is a flowchart showing an example of the above operation.

An example of the results of simulation performed by the simulator according to the present invention as described above is shown below.

FIGS. 13 and 14 show a 12-lead electrocardiogram (I-06) and a vector electrocardiogram, which are the results of simulations for a normal heart model and a heart model with apical hypertrophic myocardial disease, respectively. Comparing the two, in the case of the heart model of apical hypertrophic myocardial disease, V, , V4 of the 12-lead electrocardiogram
Giant negative T waves 65a and 65b appear in the leads, respectively. This is V in Figure 15 based on measurement data from clinical experiments.
,.

In the v4 visit, there is also a huge negative T wave 66a.

66b is observed, which supports the reliability of this simulator.

In addition, FIG. 16 shows an example of the body surface potential waveform as a result of the calculation. Display numbers 1 to 12 are numbers in the torso direction on the torso in FIG. 6, and display numbers 1 to 6 are numbers in the torso direction in FIG. They are shown on the torso in correspondence with the numbers in the height direction of the torso. In FIG. 6, R, L, F, V, and NV6 each indicate the measurement position of the 12-lead electrocardiogram.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, in the process of excitation propagation processing, the presence or absence of excitation is determined only for cells that are automatically excited and cells that are likely to transmit excitation. By doing so, the processing time can be greatly reduced, and the processing speed can be increased. Furthermore, it is possible to perform simulations using a model that is closer to reality and can also take into account refractory periods, propagation speeds, and the like.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a simulator according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of the configuration of a cardiac geometric model setting means, FIG. 3 is a flowchart showing a procedure for setting a geometric model, and FIG. Figure 5 is a diagram showing the display screen when setting the model, Figure 5 is a diagram showing the action potential waveform, Figure 6 is a diagram showing the torso and heart, Figure 7 is a flowchart showing the procedure of excitation propagation processing,
Figure 8 is a flowchart showing the determination of the refractory period, Figure 9 is a flowchart showing the procedure for determining body surface potential, and Figure 10 is a flowchart showing the procedure for determining the body surface potential.
The figure shows a display example of a 122-lead electrocardiogram and a vector electrocardiogram, Fig. 11 shows a display output means, Fig. 12 is a flowchart showing the procedure of arrow display, and Fig. 13 shows a 12-lead electrocardiogram in a normal model. Figure 14 is a diagram showing a vector electrocardiogram. Figure 14 is a diagram showing a 12-lead electrocardiogram and vector electrocardiogram based on a heart model of apical hypertrophic myocardial disease. Figure 15 is a diagram showing a 122-lead electrocardiogram as a result of clinical measurements by a patient with the same disease. , FIG. 16 is a diagram showing a body surface potential waveform. In the drawing, 2 is a heart model setting means, 3 is a heart geometric model setting means, 4 is an electrophysiological characteristic setting means, 5 is a heart position setting means,
6 is a torso setting means, 8 is an excitation propagation processing means, 8b is an excited cell temporary storage means, 9 is an excitement storage means, 10 is a body surface potential processing means, 13 is a body surface potential data storage means, 1
5 is a 122-lead electrocardiogram data storage means, 16 is a display output means, 17 is a display means, 20 is an operation means, 50 is a torso,
60 is an arrow, 62 is a display time designation operation means, and 64 is an arrow display position/direction determining means (direction display means).

Claims (1)

[Claims] A heart model is constructed by a collection of cells, and the excited state of each cell is determined by applying a predetermined rule based on the electrophysiological characteristics of the heart cells to each cell. In a simulator designed to obtain physiological phenomena, I, J, and K blocks are set in the vertical, horizontal, and height directions, and any block among them is assigned to a cell, and any cell within the block is assigned to a cell. a heart model setting means for specifying a cell that performs automatic excitation and determining a pacing time, and further determining and storing a refractory period and a propagation velocity for any cell among the remaining cells as a cell that performs excitation propagation, and starting the simulation. cell excitation time storage means for storing the excitation times of all cells obtained at all times from 1 to 3; excitation cell time storage means for storing, at any step time, cells excited at the previous step time; , At the arbitrary step time, a cell that is automatically excited based on the pacing time, a cell that was excited at the previous step time that is stored in the excited cell storage means, and a cell that is stored in the cell excitation time storage means. Based on the previous cell excitation time, the refractory period, and the propagation speed, the cell that starts excitation by transmitting the excitation is determined, and the excited cell is temporarily stored as new data for the cell that is excited at the step time. 1. A simulator of cardiac electrical phenomena, comprising: excitation propagation processing means for re-memorizing the excitation propagation in the means.