WO2008064682A2

WO2008064682A2 - A system and a method for dimensionality reduction of ecg signals for ecg analysis and presentation

Info

Publication number: WO2008064682A2
Application number: PCT/DK2007/000526
Authority: WO
Inventors: Claus Graff; Mads Peter Andersen; Thomas Bork Hardahl; Johannes Jan Struijik; Joel Q. Xue
Original assignee: Aalborg Universitet
Priority date: 2006-11-30
Filing date: 2007-11-29
Publication date: 2008-06-05
Also published as: WO2008064682A3

Abstract

The present invention relates to a system and a method for deriving a high level of information from an Electrocardiogram (ECG) and the use of this method and system. The purpose of the invention is to obtain at least one synthesized lead to give a better representation of any ECG segment than provided by any single physically obtained or derived lead. A further purpose of the invention is to find the one vector-projection for each obtaining of all possible vector-projections containing the largest possible amount of information about the ST-T segment. This can be achieved if the plurality of signals obtained from the body are mathematically expressed into calculation means as multi-dimensional ECG representations where the system performs a transformation of the multi-dimensional signals in relation to an optimal orientation of at least one projection vector regarding relevant information of a predefined segment of the signal into at least one synthesized ECG representation. The derived ECG representation can be used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome.

Description

A system and a method for dimensionality reduction of ECG signals for ECG analysis and presentation.

Field of the Invention The present invention relates to a system and a method for deriving a high level of information from an electrocardiogram (ECG) obtained from a human or animal body using an apparatus for measuring a plurality of electrical signals from the body and processing the signal for forming a multi lead ECG signal, where the system is further processing the multi lead ECG signals.

Background of the Invention

US 5,127,401 describe a technique for improving detection of the pacing artefact in patients having artificially paced myocardial contractions. The improved detection is accomplished by sensing all three commonly monitored ECG leads. Each lead is dif- ferentially amplified and rectified to produce a signal of absolute value. The resulting three signals are algebraically summed and differentiated. Because the pacing artefact consists of higher frequency components than the naturally occurring QRS complex, it can easily be detected by its much larger first derivative. Reliable detection of the artificial pacing artefact is extremely important in monitoring and programming implant- able pacers. It is necessary to accurately determine whether a pacing pulse has been delivered and precisely measure the time of its occurrence.

US 6,810,282 concern a method for automatically selecting a physiological data manipulation process. After raw data including an asynchronous component having diag- nostic information and including a synchronous component are received, the asynchronous component is separated from the synchronous component. A data manipulation process based on the diagnostic information is automatically selected based on the signal conditions generated during an analysis process.

US 2005/0004481 concern a system and a method for non- invasive ECG detection and diagnosis. The system comprises a multiplicity of electrodes applied to a patient, a data acquisition system for acquiring high-resolution ECG data from the patient; and a processor programmed to process the acquired data in accordance with two or more different ECG analysis algorithms, and then derive a prediction score for a particular clinical end point as a function of the respective results of those ECG analysis algorithms.

Both US 2005/0038352 and US 6,920,350 describe a method of displaying a representation of a physiological signal produced by a patient. The method includes the acts of obtaining a portion of at least one physiological signal acquired from the patient, determining an area to display, and constructing a virtual image representing at least a portion of the patient. The virtual image includes (M) polygonal areas. The method further includes transforming the obtained signal to a plurality of values, assigning each value to one of the (M) polygonal areas, assigning a visual characteristic to each polygonal area based in part on the assigned values and displaying at least a portion of the virtual image including the assigned visual characteristics. The invention further provides a method of optimal feature selection for the classification of the physiologi- cal signals produced by a patient.

US 2005/0154279 concern a system and a method for registering a representation of a probe with an image. One embodiment of a method comprises locating a feature of or relating to a heart with a probe, which is inside the body and registering a representa- tion of the probe with an image of the heart using the feature.

US 2005/0154281 concerns a system and a method for a registering a representation of a probe with an image. One embodiment of a method comprises acquiring an image of or pertaining to a heart and registering a representation of a probe, which is in or adja- cent to the heart with the image using a heart vector of the heart.

US 2005/0154282 concern a system and a method for registering a representation of a probe with an image. One embodiment of a method comprises acquiring an image pertaining to an organ or a structure inside a body and registering a representation of a probe, which is inside the body with the image, the representation of the probe and the image being registered to substantially the same point in a bodily cycle. 2005/0288600 concerns a cardiac monitoring and/or stimulation methods and systems provide monitoring, defibrillation and/or pacing therapies. A signal processor receives a plurality of composite signals associated with a plurality of sources, separates a signal using a source separation algorithm, and identifies a cardiac signal using a selected vector. The signal processor may iteratively separate signals from the plurality of composite signals until the cardiac signal is identified. The selected vector may be updated if desired or necessary. A method of signal separation involves detecting a plurality of composite signals at a plurality of locations, separating a signal using source separation, and selecting a vector that provides a cardiac signal. The separation may include a principal component analysis and/or an independent component analysis. Vectors may be selected and updated based on changes of position and/or orientation of implanted components and changes in patient parameters such as patient condition, cardiac signal-to-noise ratio, and disease progression.

This patent application selects one vector from the plurality of vectors as a selected vector based on a selection criterion and uses the signal associated with the selected vector. Herby, information from that single vector is used for the further processing.

US 2002/0082510 concerns amethod of analyzing the electrocardiogram ("ECG") using a set of vectors mathematically derived from the heart vector. The entire ECG waveform of one representative heartbeat is analyzed as a time series of vectors taken at selected time intervals. The vector set consists of the heart vector, the vector of deviation, vector of abnormality, delta vector, the delta vector deviation, and the delta vector abnormality. The analysis system can be applied to two or any greater number of ECG leads represented on planar axes, orthogonal spatial axes, or four or more axes in multidimensional space. The normal range of the ECG in this method is delineated by an adaptive multi-dimensional polyhedron in space to which the unknown ECG is compared. This is accomplished by utilizing a computer platform and the software program to support the required mathematical calculations.

The cited documents concern vector representation of ECG signals, and some documents describe selecting one vector representation containing the most relevant data content. This selection will reduce relevant data not represented in the selected vector representation and thereby lead to a wrong diagnosis of the ECG signal.

Object of the Invention The main purpose of the invention is to obtain at least one synthesized lead to give a better representation of any ECG segment than provided by any single physically obtained or derived lead, whether it is the ST-T segment, another segment or a combination of any of these.

A further purpose of the invention is to find the one vector-projection for each by obtaining every possible vector-projection containing the largest possible amount of information about the ST-T segment, which covers the repolarization of the cardiac tissue.

Description of the Invention

This can be achieved with a system as described in the preamble to claim 1, if the system is modified so that the system can further express the plurality of signals derived at the body mathematically and transform the plurality of signals obtained from the body into multidimensional ECG representations, and further perform a transforma- tion of the multidimensional signals in relation to an optimal orientation of at least one projection vector signal into at least one synthesized ECG representation.

The derived ECG representation can be used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome. The derived ECG repre- sentation can also be used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration or other segments.

This can also be achieved by extraction of components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pursuit (PP), Singular Value Decomposition (SVD), and similar techniques. The synthesized lead can also be calculated and extracted from a transformed (e.g. inverse Dower transformation) ECG representation by PCA, ICA, NLCA, FA, PP, SVD and similar techniques.

The system can analyse and process the ECG signals into a three dimensional Vector cardiogram (VCG) representation, from which at least one synthesized ECG lead is generated, which comprises a combination of the information contained in the ECG from any single lead configuration that can be obtained or linear combination of obtained leads. In such a transformation, it is possible to achieve an X-, a Y- and a Z-lead that are orthogonal and easy to visualize.

The transformation can be performed by using the inverse Dower-method, i.e. by multiplying a matrix composed of the 8 physically obtained leads (I-II + Vl- V6) with the inverse Dower matrix.

The synthesized ECG representation can be calculated and extracted from at least three existing or transformed ECG lead representations belonging to the same ECG obtaining.

As an alternative, the synthesized ECG representative can be calculated or extracted from a higher number of the multi leads for a heartbeat.

The synthesized ECG lead representation can be based upon predefined segments of any combination of at least three of the obtained leads to visualize and analyse the ECG segment of interest.

The synthesized lead can be calculated from the original ECG leads by Principal Component Analysis (PCA), where the synthesized ECG representation is selected from the principal components' ECG representation. The synthesized ECG representation can be derived from the ST-T segment and is used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome.

The synthesized ECG representation can be derived from the ST-T segment and is used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration.

The synthesized ECG representation can be derived from the entire length of an ECG or any segment on the ECG, such as the P-wave or the QRS-complex or other segments of interest, using the segment of interest to diagnose heart diseases showing changes in these specific segments.

The invention further concerns a method for deriving a high level of information from an Electrocardiogram (ECG) obtaining of a human or animal body, which is performed by further processing the plurality of ECG signals into calculation means for a mathematical expression of the plurality of signals obtained from the body into a multidimensional ECG representation, and further performing a mathematical transformation of the multidimensional signals in relation to an optimal orientation of at least one projection vector regarding relevant information of a predefined segment of the signal into at least one synthesized ECG representation.

The method can also concern the use of Principal Component Analysis (PCA) for extraction and calculation of the information obtained from the ECG leads for generating synthesized ECG representations, where the synthesized ECG representation is selected from the principal component ECG representation.

The synthesized EGG lead representation can be based on components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pursuit (PP), Singular Value Decomposition (SVD), and similar techniques. The method can analyse and process the obtained ECG signals into a tree-dimensional representation e.g. by inverse Dower transformation, from which representation at least one synthesized ECG lead is generated, which synthesized ECG lead comprises a combination of the information contained in the obtained ECG leads from any single ECG lead configuration that can be obtained or from any linear combination of obtained ECG leads.

The synthesized ECG lead can be calculated from the original ECG leads by Principal Component Analysis (PCA) where the synthesized ECG representation is selected from the principal component ECG representation.

The dimensionality reduction of the obtained ECG data can be achieved by Inverse Dower Matrix (IDM) or extraction of components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pursuit (PP), Singular Value Decomposition (SVD) and similar techniques.

The synthesized ECG representation is preferably derived from the ST-T segment and can be used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome.

The synthesized ECG representation can be derived from the ST-T segment and can be used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration.

The invention further concerns use of a system as described in the claims 1-12, or a method as described in claims 13-21, based on obtained ECG lead signals or linear combinations of obtained leads, a single synthesized ECG lead is generated, which synthesized ECG lead can contain more information than provided by any single physically obtained or derived ECG lead, which synthesized ECG lead is used for a manually or computer based ECG analysis for diagnostic purpose.

The synthesized ECG representation is derived from the ST-T segment and can be used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome or other heart diseases resulting in changes in the ST-T segment morphology or duration.

By combining parameters the system and/or method may form the different groups. When combining parameters from different groups, a much better result is achieved than when using parameters from the same group only. The parameters can be an elevation of the curve; they can be the morphology of the curve; or they could be time- deviations as an example of possible parameters. When combining parameters, a precise analysis can take place because a specific combination of parameters can indicate a specific disease, and it is possible to effectively select between ECG-signals looking very much alike, but which indicate different diseases.

The system and/or method can analyse the QT interval of the ECG curvature for indicating Long QT syndrome. This way the Long QT syndrome can be indicated in an objective and effective manner right after children are born, thus it is possible to start a treatment of Long QT syndrome as early as possible. The method can differentiate between different genotypes of the Long QT Syndrome, which is important for the treatment. Hereby the correct medical treatment can begin.

The system and/or method can analyse ST-elevation myocardial infarction by analysing at least the following parameters: ST-elevation, ST-morphology, T-wave morphology and Q-wave morphology. This way a very effective indication for ST- elevation myocardial infarction is achieved and the correct activity may begin as early as possible.

The system and/or method can test for Non ST-elevation myocardial infarction by analysing at least the following parameters: ST depression, T-wave morphology and Q-wave morphology. Non ST-elevation myocardial infarction can also be detected in a highly effective way and correct treatment can begin.

The system and/or method can test for Cardiomyopathia by analysing at least the fol- lowing parameters: P-wave morphology, QRS-duration, S-Wave morphology, T-wave morphology. Cardiomyopathia can in this way be effectively detected.

The system and/or method can test for Brugada Syndrome by analysing at least the following parameters: PR-duration, ST-elevation, ST-morphology and T-wave mor- phology. Hereby it is achieved that Brugada Syndrome is detected in a very effective and fast way.

The system and/or method can test for Right bundle branch block RBBB by analysing at least the following parameters: QRS-duration, QRS -morphology, T-wave morphol- ogy and ST-elevation. This way an indication of Right bundle branch block RBBB is effectively achieved.

The system and/or method can test for Left bundle branch block LBBB by analysing at least the following parameters: QRS-duration, R-wave morphology and T-wave mor- phology. An effective indication of Left bundle branch block LBBB is also possible with this method or by using the system.

The system and/or method can test for Short QT Syndrome by analysing at least the following parameters: Q-T duration and T-wave morphology. Short QT Syndrome can also be analysed effectively.

The system and/or method can test for Hyperkalemia by analysing at least the following parameters: P-wave morphology, T-wave morphology, QRS duration, QT duration and PR duration. Hereby indication of Hyperkalemia is achieved in a highly effective manner. The system and/or method can test for Hypokalemia by analysing at least the following parameters: QT-duration, T- wave morphology and ST-depression. Hereby, effective indication of Hypokalemia is achieved.

The system and/or method can test for peri/myocarditis by analysing at least the following parameters: ST-elevation, ST-morphology, Q- wave morphology and PR- depression. Hereby, effective detection of peri/myocarditis is achieved.

The system and/or method can test for Right Ventricular Hypertrophy by analysing at least the following parameters: Q-wave morphology, QRS-duration, S-wave morphology and T- wave morphology. Hereby, effective indication of Right Ventricular Hypertrophy is indicated.

The system and/or method can test for Left Ventricular Hypertrophy by analysing at least the following parameters: Q-wave morphology, QRS-duration, S-wave morphology and T-wave morphology. Also Left Venticular Hypertrophy can be detected effectively.

The system and/or method can test for Arrhythmogenic Right Ventricular Dysplasia by analysing at least the following parameters: QRS-duration, S-wave morphology and T- wave morphology. Hereby, it is achieved that Arrhythmogenic Right Ventricular Dysplasia is detected effectively.

Application of the technology This representation can be used to do visualization and analysis of the ECG whether it is manually done by a doctor or automatically by a computer in order to establish a diagnosis. Just like it is done on the standard ECG leads.

The application of the technology is to calculate a synthesized ECG lead representa- tion based on existing ECG lead obtaining that can be used for visualization and analysis of the ECG. The synthesized lead can be calculated from the original ECG leads derived at the human body by Principal Component Analysis (PCA), where the synthesized ECG representation is selected from the principal components' ECG rep- resentations. This can also be achieved by extraction of components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pursuit (PP), Singular Value Decomposition (SVD), and similar techniques.

The synthesized lead can also be calculated and extracted from a transformed (e.g. inverse Dower transformation) ECG representation by PCA, ICA, NLCA, FA, PP, SVD, and similar techniques.

The synthesized ECG representation can be calculated from at least three existing ECG lead representations belonging to the same ECG obtaining. At least one representative calculated or extracted beat from each lead might be required. The synthesized ECG lead representation can be based upon predefined segments or the entire length of any combination of at least three of the existing leads, and can be used to visualize and analyse the ECG segment of interest.

The ST-T segment

The synthesized ECG representation can be derived from the ST-T segment (fig.l) and can be used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome. The derived ECG representation can also be used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration.

Fig. 1 shows a representative beat from a lead (left) that can be segmented to extract the ST-T segment (right). Extracted ST-T segments from at least 3 leads can subsequently be used to derive the synthesized ECG representation of that segment.

Other segments

The synthesized ECG representation can be derived from any segment on the ECG, such as the P-wave or the QRS-complex or other segments of interest. This can be used to diagnose heart diseases showing changes in these specific segments. Connection of multiple derived ECG representation segments

A representative calculated or extracted beat, segment of a beat or longer representation can be split up into multiple sub-segments from which a synthesized ECG representation can be derived from each sub-segment. The multiple synthesized ECG repre- sentations can then be combined to form the original length representation (fig. 2).

Fig. 2 shows a representative segment from one lead corresponding to the duration of a beat (left) that can be split up into multiple sub-segments (centre). The multiple sub- segments can be used to derive multiple synthesized ECG representations that can be combined to form the original length signal.

The main purpose of this technology is to give a better representation of any ECG segment than provided by any single physically obtained or derived lead whether it is the ST-T segment another segment or a connection of some of these. This representa- tion can be used to do an analysis of the ECG whether it is done manually by a doctor or automatically by a computer in order to establish a diagnosis just like it is done on the standard ECG leads.

APPLICATION EXAMPLE INTRODUCTION

In this application example, we present one possible embodiment of the invention. This example facilitates detection of Long QT Syndrome by ST-T segment morphology analysis as described in the unpublished Struijk et al.and international patent application number WO 2005/058156 Al.

Additional work based on Struijk et al. has shown that it is preferable to perform the calculations necessary to detect Long QT Syndrome on a single representative ST-T segment. This can be achieved for instance by making a representative median beat from each of the 12 standard ECG leads and then by choosing a preferred lead for the morphology analysis. In Struijk et al. chooses the precordial V5 lead for their computations and achieves good results. But an important question is left unanswered. Is the V5 lead the best single lead to use for the ST-T segment morphology analysis, or is it possible to obtain more information about the repolarization of the heart (the ST-T segment) by looking at another single lead configuration that can be recorded or any linear combination of recorded leads.

By using the present invention for analysis of the ECG signal from a single lead configuration that can be recorded or any linear combination of recorded leads, it is possible to synthesize a single lead containing more information than provided by any single physically recorded or derived lead about the ST-T segment. It is our thesis that this synthesized ST-T segment will constitute a better basis for the ST-T segment morphology analysis than any of the single lead configurations that can be recorded or any linear combination of recorded leads.

Twelve standard ECG leads are obtained from the body as shown in Fig. 3 and Fig. 4 and a representative beat is calculated from these leads. All twelve leads represent the time course of propagation of activation of the cardiac tissue. This propagation front forms a three-dimensional loop inside the heart, and each of the twelve leads is thus a projection of this loop in one single direction - onto one single lead- vector. Of course the loop can be projected onto an infinite number of lead-vectors, and the twelve obtained vectors are as such only examples of possible projections.

Our aim is to find the one vector-projection (of all possible) that contains the largest possible amount of information about the ST-T segment, which is the part of the three- dimensional loop that covers the repolarization of the cardiac tissue.

According to theory, 3 leads are sufficient to span the three-dimensional space in which the loop takes place. Hence we can either settle for a lower number n of obtained leads, than n=12 (n>3) or transform the multiple, obtained leads into three single leads and represent the three-dimensional loop in this way.

hi this application example we choose to perform such a transformation to achieve an X-, a Y- and a Z-lead that are orthogonal and easy to visualize. We can perform the transformation by using the inverse Dower-method, i.e. by multiplying a matrix com posed of the 8 physically obtained leads (MI + V1-V6) with the inverse Dower matrix shown in Table I.

It is also possible to use other transformation methods - some of which utilize fewer original leads, e.g. the Marquette-method.

Fig. 5 shows the result of the Dower-transformation.

From the three orthogonal X-, Y- and Z-leads, we can visualize the propagation loop in the XY-, YZ- and XZ-planes as shown on Fig. 6. This is called a vector-cardiogram. It is now clear that the QRS-loop and the T-loop do not "point" in the same primary direction in the three-dimensional space. Therefore, the optimal lead-vectors for projection of each of the loops do not point in the same direction either.

Since we would like to focus on the ST-T segment of the ECG (the T-loop of the vector-cardiogram), it is best to choose the lead-vector that will optimize the projection of the T-loop. By analyzing the T-loop alone, we can calculate the optimal one- dimensional projection (lead) of this loop as shown in Fig. 7.

In this application example, we choose to calculate the optimal projection by performing Principal Component Analysis (PCA) in Matlab 7.0.0.19920 (R14). We can perform the PCA either based on a number of the original twelve leads or merely on the three XYZ leads obtained by transformation of the physically obtained leads. In this example, we choose the latter.

We use the Matlab-function "princomp" of the "Statistics Toolbox" to perform the analysis. The principal components achieved by performing the analysis are orthogonal vectors - the first component pointing in the direction covering the maximal amount of data variance in the loop, the second component pointing in the direction covering the second-largest amount of data variance in the loop etc. RESULTS

By projecting the three-dimensional T-loop onto the first three principal components of the obtaining, we obtain the three ST-T segment-signals shown in Fig. 8.

The "princomp"-function used in Matlab has the following declaration header:

[COEFF, SCORE, latent, tsquare] = princomp(X)

, where X is the input matrix (in our case consisting of the X-, Y- and Z-leads).

In the output "SCORE", we will find the projections of the signal onto the principal components. These ECG projections are plotted in Fig. 8.

The first component projection is the one single, calculated lead- vector that contains the largest possible amount of information about the time-course of the T-loop, when referring to the intrinsic properties of the PCA-method (maximum variance, orthogonality etc.).

The representative ST-T segment obtained from PCA-analysis constitutes a good basis for the following morphology analysis as shown in Fig. 9. Independent from anatomical differences, differences in electrode placement etc., the first PCA-lead will always reflect the maximum possible amount of information about the T-loop that can be gathered in only one dimension using PCA. We have achieved a concise dimensionality reduction in accordance with our original aim. Therefore, this synthesized curve is our natural choice of a representative ST-T segment from the obtaining in preference to one of the physically obtained leads, e.g. V3, V4 or V5.

TABLE I: The inverse Dower-matrix used for transformation from eight physically obtained leads to XYZ leads.

Fig. 3 shows normal electrode placement for the twelve standard leads ECG obtaining. The different leads obtain the electrical impulses of the heart from different angles.

Fig. 4 shows twelve standard leads ECG obtainings. A representative median beat from each of the original lead signals is calculated using 10 seconds of ECG.

Fig. 5 shows X-, Y- and Z-leads obtained by transformation of the original twelve leads by inverse Dower-transformation.

Fig. 6 shows the three-dimensional propagation loop projected onto the three orthogonal planes spanned by the X-, Y- and Z-leads.

Fig. 7 shows the projection of the propagation loop. When observing the projection of the propagation loop onto one of the three orthogonal planes, it is clear that the QRS- loop and the T-loop do not point in the same direction in space. Neither does the direction of the physical V4 or V5 leads reflect the optimal direction for projection of the T-loop as indicated below. It is possible to calculate a more optimal lead projection for each of the two loops, corresponding to different segments of the ECG signal.

Fig. 8 shows the result of performing Principal Component Analysis and projecting the original data onto the first three principal components. The PCAl -lead is our natural choice of a single, synthesized lead for the following ST-T segment morphology analysis.

Fig. 9 shows normal (group 1), LQTl-patients (group 2) and LQT2-patients (group 3) classified with the use of the method described in Struijk et al.('). On top, the calcula- tions were performed on a representative beat from lead V5. At the bottom, the calculations were performed on the derived PCAl-lead. The PCAl-plot shows better separation than the V5-plot, since all groups are separated perfectly on the PCAl-plot, but some patients from groups 2 and 3 overlap on the V5-plot. The PCAl-lead can be a better basis for the method of Struijk et al.C¹) than the V5-lead.

Claims

1. System for deriving a high level of information e.g. from an Electrocardiogram (ECG) derived at a human or animal body, which system performs at least the follow- ing steps:

measuring a plurality of electrical signals derived at the body

processing the signal for forming a multi lead ECG signal,

characterized in that the system at least further performs the following steps:

expresses the plurality of signals derived at the body mathematically

transforms the plurality of signals obtained from the body into multidimensional ECG representations,

performs a transformation of the multidimensional signals in relation to an optimal orientation of at least one projection vector signal into at least one synthesized ECG representation.

2. System according to claim 1, characterized in that the synthesized ECG lead is extracted and calculated from the obtained ECG leads by Principal Component Analysis (PCA) where the synthesized ECG representation is selected from the principal component ECG representation.

3. System according to claim 1, characterized in that the synthesized EGG lead representation is based on components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pur- suit (PP), Singular Value Decomposition (SVD), and similar techniques.

4. System according to claim 1 characterized in that the system analyses and processes the obtained ECG signals into a three-dimensional representation e.g. by inverse Dower transformation, from which representation at least one synthesized ECG lead is generated, which synthesized ECG lead comprises a combination of the information contained in the obtained ECG leads from any single ECG lead configuration that can be obtained or from any linear combination of obtained ECG leads.

5. System according to claim 4, characterized in that the synthesized ECG lead is extracted and calculated from the three dimensional ECG representation by Principal Component Analysis (PCA) where the synthesized ECG representation is selected from the principal component ECG representation.

6. System according to claim 4, characterized in that the synthesized EGG lead representation is calculated and extracted from the three dimensional ECG representation by PCA, ICA, NLCA, FA, PP, SVD and similar techniques.

7. System according to one of the claims 1-6, characterized in that the synthesized ECG representation is calculated from the ST-T segment and is used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome.

8. System according to one of the claims 1-6, characterized in that the synthesized ECG representation is calculated from the ST-T segment and is used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration.

9. System according to one of the claims 1-6, characterized in that the synthesized ECG representation is calculated from any segment on the ECG, such as the P-wave or the QRS-complex or other segments of interest, using the segment of interest to diagnose heart diseases showing changes in these specific segments.

10. Method for deriving a high level of information from an Electrocardiogram (ECG) obtained from a human or animal body, which is performed by the followings steps of operation: obtaining a plurality of electrical signals from the body, processing the signal for forming multi ECG lead signals,

characterized in further processing the plurality of ECG signals into calculation means for a mathematical expression of the plurality of signals obtained from the body into a multidimensional ECG representations, performing a mathematical transformation of the multi dimensional signals in relation to an optimal orientation of at least one projection- vector regarding relevant information of a predefined segment of the signal into at least one synthesized ECG representation.

11. Method according to claim 10, characterized in that the method analyses and processes the obtained ECG signals into a tree-dimensional representation e.g. by inverse Dower transformation, from which representation at least one synthesized ECG lead is generated, which synthesized ECG lead comprises a combination of the infor- mation contained in the obtained ECG leads from any single ECG lead configuration that can be obtained or from any linear combination of obtained ECG leads.

12. Method according to claim 10, characterized in that Principal Component Analysis (PCA) is used to extract and calculate the information obtained from the ECG leads for generating synthesized ECG representations, where the synthesized ECG representation is selected from the principal component ECG representation.

13. Method according to claim 11, characterized in that the synthesized EGG lead representation is based on components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pursuit (PP), Singular Value Decomposition (SVD), and similar techniques.

14. Method according to claim 10, characterized in that the synthesized ECG lead is calculated from the original ECG leads by Principal Component Analysis (PCA) where the synthesized ECG representation is selected from the principal component ECG representation.

15. Method according to one of the claim 10, characterized in that the dimensionality reduction of the obtained ECG data is achieved by extraction of components calculated by Independent Component Analysis (ICA), Nonlinear Component Analysis (NLCA), Factor Analysis (FA), Projection Pursuit (PP), Singular Value Decomposi- tion (SVD) and similar techniques.

16. Method according to one of the claims 10-15, characterized in that the synthesized ECG representation is derived from the ST-T segment and is used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome.

17. Method according to one of the claims 10-15, characterized in that the synthesized ECG representation is derived from the ST-T segment and is used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration.

18. Method according to one of the claims 10-15, characterized in that the synthesized ECG representation is derived from the entire length of an ECG or any segment on the ECG, such as the P-wave or the QRS-complex or other segments of interest, using the segment of interest to diagnose heart diseases showing changes in these spe- cific segments.

19. Use of a system as described in the claims 1-9, or a method as described in the claims 1-18, characterized in that based on obtained ECG lead signals or linear combinations of obtained leads, a single synthesized ECG lead is generated, which synthe- sized ECG lead contains more information than provided by any single physically obtained or derived ECG lead, which synthesized ECG lead is used for a manual or computer based ECG analysis for diagnostic purpose.

20. Use according to claim 19, characterized in that the synthesized ECG representation is derived from the ST-T segment and is used for diagnosis of congenital Long QT Syndrome or in drug testing for acquired Long QT Syndrome.

21. Use according to claims 20, characterized in that the synthesized ECG representation is derived from the ST-T segment and is used to diagnose other heart diseases that result in changes in the ST-T segment morphology or duration.