Method of, and apparatus for, determining the starting point and the end point of closed signal patterns

Claims

What we claim is:

1. A method of determining the starting point and the end point of a spatial closed signal pattern in a time sequence of individual ones of such spatial closed signal patterns, each of which is constituted by a series of measured signals, said method comprising the steps of:

arrangiang a predetermined number of electrodes in a predetermined configuration at a living being to be investigated and receiving said time sequence of spatial closed signal patterns by means of said electrodes;

subdividing a predetermined period of time which is associated with a selected one of said individual spatial closed signal patterns, into a first time interval and a second time interval;

sampling said selected individual spatial closed signal pattern and determining, at each one of a predetermined number of sampling moments associated with said first time period, the distance between a predetermined number of sampling points associated with said predetermined number of sampling moments in said first time interval, on the one hand, and a predetermined number of sampling points associated with a predetermined number of sampling moments in said second time interval, on the other hand;

ascertaining the minimum value of said distances determined between said predetermined sampling points associated with said first time interval and said predetermined sampling points associated with said second time interval; and

defining a selected sampling point associated with said first time interval and a selected sampling point associated with said second time interval, between which said minimum distance exists, as said starting point and as said end point, respectively, of said selected individual spatial closed siqnal pattern.

2. The method as defined in claim 1, further including the step of:

selecting a reference point by means of which said first time interval and said second time interval are separated from each other.

3. The method as defined in claim 1, wherein:

the step of subdividing said predetermined period of time which is associated with said selected individual spatial closed signal pattern into said first time interval and said second time interval, entails the step of fixing said first time interval and said second time interval by means of a common moment of time at which a spatial slope of said selected individual spatial closed signal pattern has a predetermined value.

4. The method as defined in claim 3, further including the step of:

presetting a predetermined spatial slope value for said spatial slope of said selected individual spatial closed signal pattern at said common moment of time;

determining said common moment of time which fixes said first time interval and said second time interval, in a first approximation, by the moment of time at which the spatial slope of a first one of said time sequence of individual spatial closed signal patterns has a spatial slope value essentially equal to said preset predetermined spatial slope value;

determining individual spatial slope values of further individual spatial closed signal patterns following said first individual spatial closed signal pattern in said time sequence; and

determining an average spatial slope value from said individual spatial slope values determined for said further individual spatial closed signal patterns and using such average value for presetting said predetermined spatial slope value for each one of said individual spatial closed signal patterns at said common moment of time.

5. The method as defined in claim 1, further including the steps of:

projecting each one of said individual spatial closed signal patterns into an orthogonal coordinate system; and

determining spatial distances in said orthogonal coordinate system into which each said individual spatial closed signal pattern has been projected.

6. A method of recording a measured signal constituted by measured data which vary in time and space and form a time sequence of recurring individual spatial closed signal patterns, said method comprising the steps of:

receiving and recording as a function of time the measured data which constitute said measuring signal;

selecting a reference point for each one of said recurring individual spatial closed signal patterns;

determining, on the basis of said selected reference point, for each one of said recurring individual spatial closed signal patterns, a first time interval and a second time interval located at opposite sides of said reference point;

sampling a preselectable number of first measured data and related first moments of time which are associated with said first time interval and sampling a preselectable number of second measured data and related second moments of time which are associated with said second time interval;

determining the spatial distance between the measured data associated with said sampled first measured data and the measured data associated with said sampled second measured data; and

determining a pair of sampled first and second measured data with which a minimum value of said spatial distance is associated and thereby ascertaining a starting point and an end point for each one of said recurring individual spatial closed signal patterns.

7. The method as defined in claim 6, further including the steps of:

placing a predetermined number of sensors in a predetermined spatial configuration at an object to be investigated; and

the step of receiving and recording said measured data as a function of time entailing the step of receiving and recording the variation in time and space of a predetermined characteristic of said object by means of receiving and storing measured data which are measured by said sensors and which vary in time and space in correspondence with said predetermined characteristic of said object to be investigated.

8. The method as defined in claim 7, wherein:

said step of selecting said reference point includes the step of selecting, in a selected one of said recurring individual spatial closed signal patterns, a point at which said selected individual spatial closed signal pattern has a predetermined spatial slope.

9. The method as defined in claim 8, wherein:

said step of selecting said reference point includes the step of selecting as said reference point a point at which said selected individual closed signal pattern has a maximum spatial slope.

10. The method as defined in claim 9, wherein:

said step of selecting said point at which said selected individual spatial closed signal pattern has a maximum spatial slope, includes the step of selecting a predetermined time interval substantially encompassing said selected individual spatial closed signal pattern and subdividing said time interval into a sequence of successive sections, determining the spatial slope in each one of said successive sections and selecting the section having a maximum spatial slope; and

defining the first occurring moment of time associated with said section having the maximum slope as said point constituting said reference point.

11. The method as defined in claim 10, further including the steps of:

repeating the determination of the maximum spatial slope of said individual spatial closed signal pattern for different ones of said sequence of said individual spatial closed signal patterns; and

determining an average value of the maximum spatial slope of the individual spatial closed signal patterns from the maximum spatial slopes determined for said different individual spatial closed signal patterns and for the selected individual spatial closed signal patterns.

12. The method as defined in claim 11, further including the step of:

defining a predetermined upper value and a predetermined lower value of said maximum spatial slope and thus a predetermined spread of acceptable values for said maximum spatial slope of said individual spatial closed signal patterns at said reference point.

13. The method as defined in claim 7, wherein:

said step of determining said first time interval includes the step of selecting as said first time interval a time interval which extends from the moment of time associated with said reference point to a preceding moment of time in the region of the starting point of said selected individual spatial closed signal pattern; and

said step of determining said second time interval including the step of selecting as said second time interval a time interval extending from said moment of time associated with said reference point to a following moment of time in the region of the end point of said selected individual spatial closed signal pattern.

14. The method as defined in claim 7, wherein:

said step of placing a predetermined number of sensors in a predetermined spatial configuration at an object to be investigated includes the step of placing a predetermined number of electrodes in said predetermined spatial configuration at the body of a living being; and

the step of receiving and recording said measured data including the step of measuring and recording the variation in time and space of an electric potential which occurs in said living being, in the form of a vector diagram constituted by a time sequence of recurring individual spatial closed electrode potential patterns which are constituted by a predetermined number of loops and which are received and recorded in a rectangular coordinate system defined by said predetermined spatial configuration of said predetermined number of electrodes.

15. The method as defined in claim 14, further including the steps of:

scanning said predetermined number of electrodes at a predetermined scanning frequency; and

feeding said measured electrode potentials measured at related scanning moments of time via an analog-to-digital converter to a measured data storage and storing therein said measured individual spatial closed electrode potential patterns in digital form at associated addresses which correspond to the related scanning moments of time.

16. The method as defined in claim 15, further including the steps of:

operatively connecting said measured data storage to an arithemetic logic unit;

transmitting successively measured electrode potentials mesured at related scanning moments of time within a predetermined time interval substantially including a preselected loop of a selected individual spatial closed electrode potential pattern from said measured data storage to said arithemetic logic unit and determined by means of two of said successively measured electrode potentials and two of said related scanning moments of time a predetermined slope of said preselected loop in said rectangular coordinate system;

determining a predetermined spatial slope of said preselected loop of said selected individual spatial closed electrode potential pattern from the predetermined slopes in said rectangular coordinate system;

defining as said reference point the first occurring scanning moment of time associated with said predetermined spatial slope; and

transmitting said predetermined spatial slope of said preselected loop of said selected individual spatial closed electrode potential pattern to said measured data storage.

17. The method as defined in claim 16, wherein:

said step of determining said predetermined slope of said preselected loop in said rectangular coordinate system entails the step of determining by means of two successively measured electrode potentials and two of said related scanning moments of time a maximum variation in the electrode potential with time and thus a maximum slope;

said step of determining the predetermined spatial slope of said preselected loop entails the step of determining the maximum spatial slope; and

said step of transmitting said predetermined spatial slope entails the step of transmitting said maximum spatial slope of said preselected loop to said measured data storage.

18. The method as defined in claim 17, wherein:

said steps of determining and transmitting said maximum spatial slope of said preselected loop of said selected individual spatial closed electrode potential pattern includes the step of determining and transmitting the maximum positive spatial slope.

19. The method as defined in claim 18, wherein:

said step of placing a predetermined number of electrodes and measuring and recording the variation in time and space of the electrode potential includes the step of picking up a time sequence of recurring vector cardiograms containing a predetermined number of loops and constituting said sequence of recurring individual spatial closed electrode potential patterns;

said step of transmitting successive measured electrode potentials measured at related scanning moments of time within a predetermined time interval includes the step of selecting a time interval of a duration approximately equal to the duration of a QRS-loop of an individual one of said recurring vector cardiograms; and

said step of defining said reference point includes the step of determining the first occurring scanning moment of time which is associated with said maximum positive slope in the QRS-loop of said individual vector cardiogram.

20. The method as defined in claim 19, further including the steps of:

determining the maximum positive spatial slopes of the preselected loops of a predetermined number of individual ones of said time sequence of recurring vector cardiograms;

determining an average maximum positive spatial slope from the maximum positive spatial slopes determined for each one of the preselected loops of said predetermined number of individual vector cardiograms;

comparing the average maximum positive spatial slope with the individual maximum positive spatial slopes of the preselected loops of said predetermined number of individual vector cardiograms, and, as a result of such comparison, determining upper and lower limiting values and a predetermined acceptable spread of maximum positive spatial slope values; and

transferring said upper and lower limiting values of said spread of acceptable maximum positive spatial slope values to said measured data storage.

21. The method as defined in claim 20, further including the steps of:

selecting from said predetermined number of individual vector cardiograms a selected number of individual vector cardiograms, the preselected loops of which have a maximum positive spatial slope value within said predetermined acceptable spread of maximum positive spatial slope values;

determining the first one in the time sequence of said selected number of individual vector cardiograms;

transferring a first sample of electrode potentials measured during a first time interval, which extends from a preselected moment of time preceding said reference point of said preselected loop of the first one of said selected number of individual vector cardiograms to a first moment of time preceding said preselected moment of time, from said measured data storage to a first data storage operatively connected thereto by means of said data and address bus;

supplying addresses associated with said first sample of measured electrode potentials from said measured data storage to a first address counter by means of said data and address bus;

transferring a second sample of electrode potentials measured during a second time interval, which extends from a further preselected moment of time following said reference point of said preselected loop of said first one of said selected number of individual vector cardiograms to a second moment of time following said further preselected moment of time, from said measured data storage to a second data storage by means of said data and address bus; and

supplying addresses associated with said second sample of measured electrode potentials from said measured data storage to a second address counter by means of said data and address bus.

22. The method as defined in claim 21, further including the step of:

selecting as said first time interval a time interval extending from a preselected moment of time preceding said reference point by about 20 milliseconds to a first moment of time preceding said reference point by a time period in the range of 60 to 140 milliseconds and including the starting point of said preselected loop of said first one of said selected number of individual vector cardiograms; and

selecting as said second time interval a time interval extending from a further preselected moment of time following said reference point by about 20 milliseconds to a second moment of time following said reference point by a time period in the range of 160 to 200 milliseconds and including the end point of said preselected loop of said first one of the selected number of individual vector cardiograms.

23. The method as defined in claim 18, further including the steps of:

controlling the determination of said spatial slope of said preselected loop of said selected individual spatial closed electrode potential pattern by means of a program sequencer operatively connected to said arithmetic logic unit and to said measured data storage by means of a data and address bus.

24. The method as defined in claim 16, further including the steps of:

determining the spatial slopes of the preselected loops of a predetermined number of individual spatial closed electrode potential patterns of said time sequence of individual spatial closed electrode potential patterns;

determining an average spatial slope from the spatial slopes determined for each one of the preselected loops of the predetermined number of said individual spatial closed electrode potential patterns;

comparing the average spatial slope with the individual spatial slopes of the preselected loops of said predetermined number of individual spatial closed electrode potential patterns, and, as a result of such comparison, determining upper and lower limiting values and a predetermined acceptable spread of spatial slope values; and

transferring said upper and lower limiting values of said spread of acceptable spatial slope values to said measured data storage.

25. The method as defined in claim 24, further including the steps of:

selecting from said predetermined number of individual spatial closed electrode potential patterns a selected number of individual spatial closed electrode potential patterns, the preselected loops of which have a spatial slope value within said predetermined acceptable spread of spatial slope values;

determining the first one in the time sequence of said selected number of individual spatial closed electrode potential patterns;

transferring a first sample of electrode potentials measured during a first time interval, which extends from the moment of time associated with said reference point of said preselected loop of said first one of said selected number of individual spatial closed electrode potential patterns to a preceding moment of time in the region of the starting point of said preselected loop of said first one of said selected number of individual spatial closed electrode potential patterns, from said measured data storage to a first data storage operatively connected thereto by means of said data and address bus;

supplying addresses associated with said first sample of measured electrode potentials from said measured data storage to a first address counter by means of said data and address bus;

transferring a second sample of electrode potentials measured during a second time interval, which extends from said moment of time associated with said reference point of said preselected loop of said first one of said selected number of individual spatial closed electrode potential patterns to a following moment of time in the region of the end point of said preselected loop of said first one of the selected number of individual spatial closed electrode potential patterns, from said measured data storage to a second data storage by means of said data and address bus; and

supplying addresses associated with said second sample of measured electrode potentials from said measured data storage to a second address counter by means of said data and address bus.

26. The method as defined in claim 25, further including the steps of:

storing the measured electrode potential associated with said reference point and the address of said reference point at a null address in said measured data storage;

determining the spatial distances between the first measured electrode potentials stored in said first data storage and the second measured electrode potentials stored in said second data storage;

transmitting each determined spatial distance to an intermediate storage operatively connected to said arithmetic logic unit and supplying the associated addresses to an intermediate address storage;

sequentially comparing by means of a comparator the spatial distances determined between the first measured electrode potentials of said first sample stored in said first data storage and the second measured electrode potentials of said second sample stored in said second data storage;

determining the minimum spatial distance between the first measured electrode potentials of said first sample and the second measured electrode potentials of said second sample;

defining the first measured electrode potential of said first sample and the related address associated with said minimum spatial distance as the starting point of said preselected loop of said first one of the selected number of individual spatial closed electrode potential patterns;

defining the second measured electrode potential of said second sample and the related address associated with said minimum spatial distance as the end point of said preselected loop of said first one of the selected number of individual spatial closed electrode potential patterns; and

transmitting said first measured electrode potential and said second measured electrode potential and the related addresses to a null address of said measured data storage.

27. The method as defined in claim 26, further including the steps of:

repeating the steps of determining and transmitting the first and second measured electrode potentials and the related addresses associated with the minimum spatial distance as the starting point and as the end point for the preselected loops of the remaining ones of the selected number of individual spatial closed electrode potential patterns and which preselected loops have a predetermined spatial slope value within said predetermined acceptable spread of predetermined spatial slope values.

28. The method as defined in claim 25, further including the steps of:

storing a maximum measured electrode potential associated with the preselected loop of the first one of said selected individual spatial closed electrode potential pattern at a null address in said measured data storage;

determining the spatial distances between the first measured electrode potentials stored in said first data storage and the second measured electrode potentials stored in said second data storage;

comparing by means of a comparator the spatial distances determined between the first measured electrode potentials of said first sample stored in said first data storage and the second measured electrode potentials of said second sample stored in said second data storage with the maximum measured electrode potential stored in said measured data storage at the null address thereof and storing the smaller one of the two data in said measured data storage at said null address thereof;

sequentially comparing by means of said comparator the spatial distances determined between all of the first measured electrode potentials of said first sample stored in said first data storage and all of the second measured electrode potentials of said second sample stored in said second data storage, with the datum stored in said measured data storage at the null address thereof such that the minimum spatial distance is stored at said null address of said measured data storage as a result of the comparing operation;

defining the first measured electrode potential and the related address associated with said minimum spatial distance as the starting point of the preselected loop of said first one of the selected individual spatial closed electrode potential patterns; and

defining the second measured electrode potential and the related address associated with said minimum spatial distance as the end point of the preselected loop of said first one of the selected number of individual spatial closed electrode potential patterns.

29. The method as defined in claim 28 further including the steps of:

repeating the steps of determining the first and second measured electrode potentials and the related addresses associated with the starting point and with the end point of the preselected loops of the remaining ones of the selected number of individual spatial closed electrode potential patterns and which preselected loops have a predetermined spatial slope value within said predetermined acceptable spread of predetermined spatial slope values.

30. An apparatus for recording and processing a signal constituted by measured data which vary in time and space and define a time sequence of recurring individual spatial closed signal patterns, comprising:

a measuring unit containing a predetermined number of sensors for sensing said signal;

a measured data storage;

said measured data storage storing the measured data and their associate addresses and containing a null address storage at which the measured data associated with a starting point and an end point of each said individual spatial closed signal pattern is stored;

an analog-to-digital converter having an input side and an output side;

said analog-to-digital converter being connected on its input side to said measuring unit and being connected on its output side to said measured data storage;

means for determining a slope of each one of said individual spatial closed signal patterns at a preselectable reference point and for transmitting the measured datum and address of said preselected reference point to said measured data storage;

a data and address bus operatively interconnecting said means for determining said preselected reference point and said measured data storage;

a sampling unit;

said sampling unit containing first sampling means for sampling a first sample of measured data and their associated addresses which precede said reference point in each one of said individual spatial closed signal patterns;

said sampling unit further containing second sampling means for sampling a second sample of measured data and their associated addresses which follow said reference point in each one of said individual spatial closed signal patterns;

said first sampling means and said second sampling means being operatively connected to said measured data storage by means of said data and address bus;

means for sequentially determining the spatial distance between the measured data of said first sample and the measured data of said second sample;

comparating means operatively connected to said means for sequentially determining said spatial distances and comparing said spatial distances, in order to determine a minimum spatial distance;

said comparating means being operatively connected to said measured data storage and transferring the measured datum of said first sample which is associated with said minimum spatial distance to said null address of said measured data storage; and

a program sequencer operatively connected to said measured data storage, said slope determining means, said sampling unit, and said comparating means and controlling the slope determination, the sampling operation and the comparating operation.

31. The apparatus as defined in claim 30, wherein:

said slope determining means and said comparating means form parts of a common arithmetic logic unit.

32. The apparatus as defined in claim 30, wherein:

said first sampling means comprise a first data storage and a first address storage; and

said second sampling means comprising a second data storage and a second address storage.

33. The apparatus as defined in claim 30, wherein:

said predetermined number of sensors comprises a predetermined number of electrodes arranged in a predetermined spatial configuration at the body of a living being to be investigated; and

said time sequence of recurring individual spatial closed signal patterns constituting a time sequence of recurring individual spatial closed electrode potential patterns of a vector cardiogram.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to the commonly assigned, copending U.S. Application Ser. No. 06/464,765, filed Feb. 7, 1983, and entitled "Method and Apparatus for Cardiogoneometry", the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a new and improved method of, and apparatus for, determining the starting point and the end point of a spatial closed signal pattern in a time sequence of individual ones of such spatial closed signal patterns, each of which is constituted by a series of measuring signals.

Spatial closed signal patterns of the aforementioned type may constitute, for example, physiological measuring signals which are picked up from a living being by means of electrodes and such spatial closed signal patterns occur, for example, in the as-such known methods of vector cardiography. Such a method is described in detail in European Patent Publication No. 0,086,429 and the aforementioned cognate U.S. Application Ser. No. 06/464,765. In this method as well as in other known methods of vector cardiography the starting points and the end points, for example, of the P-, QRS- and T-loops or waves are visually determined by the physician who must interpret the curves presented to him or her. This is evident, for example, from "Computers in Cardiology", 1982, IEEE, page 429 et seq. entitled "Automated Vector Cardiographic Analysis by an Inexpensive Microprocessor" (ISBN No. 0-8186-0024-1). It also follows therefrom that the determination of the starting points and of the end points by computation using an electronic computer tends to yield still less reliable results than the simple visual determination.

A further possibility for determining the starting point and the end point of a signal pattern as produced in the known vector cardiogram comprises the steps of selecting sections from a present signal pattern in which the signal does not or nearly does not change with time. An electrical starting, end, or base potential can be attributed to such sections which indicates that the starting point and the end point of the signal pattern are located in the region of such sections. However, when such a procedure is used, the definition of the starting point and of the end point is still indefinite with respect to time.

The determination of the starting point and the end point of a signal pattern is particularly difficult when the signal pattern has superimposed thereon oscillations of a very low frequency. In a vector cardiogram, for example, such an oscillation is effected by the breathing of the investigated person or patient. When the vector cardiogram is recorded under circulatory stress, such oscillations distort the signal pattern to such a degree that the determination of the starting point and the end point with sufficient reliability by means of the hitherto known methods is impossible.

SUMMARY OF THE INVENTION

Therefore, with the foregoing in mind it is a primary object of the present invention to provide a new and improved method of, and apparatus for, determining the starting point and the end point of a spatial closed signal pattern in a time sequence of individual ones of such spatial closed signal patterns, each of which is constituted by a series of measuring signals, in a manner which is not afflicted with the aforementioned drawbacks and limitations of the hitherto known methods.

Another important object of the present invention is directed to the provision of a new and improved method of, and apparatus for, determining the starting point and the end point of a spatial closed signal pattern in a time sequence of individual ones of such spatial closed signal patterns, each of which is constituted by a series of measuring signals, in such a manner that the moment of time associated with the starting point and the end point is unambiguously determined.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the method of the present development is manifested by the features that, a predetermined number of electrodes is arranged in a predetermined configuration at a living being to be investigated and by means of these electrodes there is received the time sequence of individual ones of the spatial closed signal patterns. A predetermined period of time associated with a selected spatial closed signal pattern is subdivided into a first time interval and a second time interval and the spatial closed signal pattern is sampled. During this sampling operation there is determined, at each one of a predetermined number of sampling moments associated with said first time interval, the distance between selected ones of a predetermined number of sampling points associated with said predetermined number of sampling moments in said first time interval, on the one hand, and selected ones of a predetermined number of sampling points associated with a predetermined number of sampling moments associated with said second time interval, on the other hand. A minimum value of the distances between the predetermined sampling points associated with the first time interval and the predetermined sampling points associated with the second time interval is determined. The sampling point associated with the first time interval and the sampling point associated with the second time interval, between which the minimum distance exists, are respectively defined as the starting point and the end point of the selected individual spatial closed signal pattern.

As alluded to above, the present invention is not only concerned with the aforementioned method aspects, but also relates to a novel construction of an apparatus for recording a measured signal constituted by measured data which vary in time and space and define a time sequence of recurring individual closed signal patterns.

To achieve the aforementioned measures the inventive apparatus for recording a signal constituted by measured data which vary in time and space and define a time sequence of recurring individual closed signal patterns, in its more specific aspects comprises:

a measuring unit comprising a predetermined number of sensors for sensing said signal;

a measured data storage;

said measured data storage storing the measured data and their associate addresses and containing a null address storage at which the measured data associated with a starting point and an end point of each individual closed signal pattern are stored;

an analog-to-digital converter which is connected on its input side to the measuring unit and on its output side to the measured data storage;

means for determining a slope of each one of the individual closed signal patterns at a preselectable reference point and for transmitting the measured datum and address of the preselected reference point to the measured data storage;

a data and address bus operatively interconnecting the means for determining the preselected reference point and the measured data storage;

first sampling means for sampling a first sample of measured data and their associated addresses which precede the reference point in each one of the individual closed signal patterns;

second sampling means for sampling a second sample of measured data and their associated addresses which follow the reference point in each one of the individual closed signal patterns;

the first sampling means and the second sampling means being operatively connected to the measured data storage by means of the data and address bus;

means for sequentially determining the spatial distances between the measured data of the first sample and the measured data of the second sample;

comparating means operatively connected to the means for sequentially determining the spatial distances and comparing the determined spatial distances in order to determine a minimum spatial distance;

the comparating means being operatively connected to the measured data storage and transferring the measured datum of the first sample which is associated with the minimum spatial distance to the null address of the measured data storage; and

a program sequencer operatively connecting the measured data storage, the slope determining means, the first sampling means, the second sampling means, and the comparating means and controlling the slope determination and the sampling and comparating operations.

The advantages achieved by the invention are essentially that the magnitude of the measured signal excursions can be exactly determined after the moments of time associated with the starting point and the end point have become known and therefrom also the signal magnitudes at these points have become known. The signal magnitude at the starting point and at the end point yields a reference magnitude. Also, different signals within a signal pattern can be precisely delimited from each other.

In a vector cardiogram the cardiac action of a person or patient investigated is observed by means of the temporal variations of the electromagnetic field which is generated by the heart and which can be represented by a vector. By means of the vector cardiogram attempts are made to follow the direction and magnitude of the vector. For this purpose the vector or rather its projection on a number of planes is considered. In practice this results in a number of temporally interrelated signal patterns. A reliable diagnosis and interpretation of the individual signals can be obtained only when the starting point and the end point of each individual signal of the different signal patterns are known. For the diagnosis there are also important, in addition to the magnitude and direction of the vector, the point of onset of the QRS-, P- and of the T-loop or wave, the starting moment of time and the length of the intervals therebetween.

By virtue of the inventive method and apparatus the aforementioned data can be determined. With increasing heart beat the results which are obtained using the hitherto known methods become more and more unreliable. The reliability of the inventive method, however, is preserved also in these cases of increased heart beat.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is an illustration in a predetermined plane and along a time axis of a physiological measured signal which is picked up from a person or patient under investigation by means of electrodes;

FIG. 2 is an illustration of the measured signal as shown in FIG. 1 in space as well as in projection on three different planes;

FIG. 3 is a block diagram of an apparatus according to the invention for carrying out the method illustrated in FIGS. 4a, 4b, and 4c; and

FIGS. 4a, 4b, and 4c collectively represent a flow diagram or chart illustrating the steps of the inventive method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Describing now the drawings, it is to be understood that only enough of the inventive method and apparatus have been illustrated as needed for those skilled in the art to readily understand the underlying principles and concepts of the present development, while simplifying the showing of the drawings. Turning attention now specifically to FIG. 1, there has been shown as an example of a physiological measuring signal a section of a vector cardiogram curve 1. Therein electrode potential values which are picked up from an investigated person or patient by means of electrodes, are plotted on a time axis 2. Since the inventive method will be explained with reference to the examp1e of a vector which represents the heart action of a living being and which continuously changes its magnitude and direction as a function of time, the potential values illustrated in FIG. 1 can be considered as the magnitude of the vector projected into a predetermined plane.

Such a vector or the potential values associated with its tip or end point describes a time sequence of signal or electrode potential patterns each of which is described by the cardiologist as comprising a QRS-loop or wave, a T-loop or wave and a P-loop or wave. Sections 4 are interposed intermediate these loops or waves in curve 1 and these sections 4 are rather short and more or less indicate constant potential values.

FIG. 2 shows the vector in a triaxial coordinate system 5 defining an orthogonal or rectangular coordinate system and illustrates the vector at a specific moment of time by means of the arrow 6. This vector 6 starts from a null or zero point 7 and ends at points in space which together form the loops or waves 8, 9 and 10. The loop 8 of such vectorial illustration is also designated as QRS-loop, the loop 9 as T-loop and the loop 10 as P-loop. By means of the X, Y and Z axes of the coordinate system 5 an XZ plane, an XY plane and a ZY plane are defined. The loops 8, 9 and 10 can be projected onto these three planes such that further loops 8a, 8b, 8c; 9a, 9b, 9c; and 10a, 10b, 10c can be recognized. In order to facilitate the following explanations there are also entered individual points 11a to 19a and 11b to 19b, along the loops 8a and 8b, respectively.

In the following there are generally described the individual steps of the inventive method which permits the determination of the starting point and of the end point of recurring individual spatial closed signa1 or electrode potential patterns, specifically of, for example, a QRS-loop in a vector cardiogram. Since the vector in each such vector cardiogram successively describes a QRS-loop, a T-loop and a P-loop, it is important to know, for example, at which point and at which time the QRS-loop starts and ends because the QRS-loop gives the physician an indication with respect to certain aspects of the cardiac action while the T-loop or the P-loop give indications with respect to other aspects of the cardiac action. The inventive method can be analogously employed for determining the starting point and the end point of the P-loop or wave and of the T-loop or wave in a vector cardiogram or the starting point and the end point of any other recurring individual closed signal or electrode potential pattern.

In order to obtain reliable data about the position of the starting point 20 and the end point 21 of the QRS-wave or loop, see FIG. 1, it is essential to detect the movements of the vector and thus the QRS-loop 8, 8a, 8b, 8c in different planes. Therefore, during the preparation of a vector cardiogram, there are periodically or continuously detected in a manner which is known as such the values of the potential which is represented by the vector. The graphic illustration of such potential values, when plotted along the time axis 2, results in the curve 1 shown in FIG. 1. The graphic illustration of such potential values, when plotted in the XZ plane, in the XY plane, and in the ZY plane, results in the QRS-loops 8a, 8b, and 8c