WO2005058156A1 - A system and a method for analysing ecg curvature for long qt syndrome and drug influence - Google Patents
A system and a method for analysing ecg curvature for long qt syndrome and drug influence Download PDFInfo
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- WO2005058156A1 WO2005058156A1 PCT/DK2004/000722 DK2004000722W WO2005058156A1 WO 2005058156 A1 WO2005058156 A1 WO 2005058156A1 DK 2004000722 W DK2004000722 W DK 2004000722W WO 2005058156 A1 WO2005058156 A1 WO 2005058156A1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
- A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
- A61B5/346—Analysis of electrocardiograms
- A61B5/349—Detecting specific parameters of the electrocardiograph cycle
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
Definitions
- the present invention relates to a system for analysing drug influence on ECG curvature and Long QT Syndrome where at least one among a number of different parameters is isolated, which system has an input means connected to an ECG source, where the different parameters of a received ECG curvature are indicated and/or isolated and for indicating possible symptoms.
- the present invention further relates to a method for analysing drug influence on ECG curvature, which curvature contains a number of parameters.
- the heart generates an electrical signal which can be measured as an ECG, which can be recorded as an ECG diagram.
- ECG-signal P,Q,R,S,T and U are due to depolarisation and repolarisation of the heart.
- Ponset 2 marks the beginning of the P wave.
- Qonset 4 marks the beginning of the Q wave.
- Rpeak 6 marks the top of the R wave.
- the Jpoint 8 marks the end of the S wave.
- Tstart 10 marks the beginning of the T wave.
- Tpeak marks 12 the top of the T wave.
- Tend 14 marks the end of the T wave.
- the QT interval starts at Qonset 4 and ends at Tend 14.
- the QT curvature is the part of the ECG curvature between Qonset 4 and Tend 14.
- US 5, 749,367 describes a heart monitoring apparatus and method wherein an electrocardiograph signal is obtained from a patient and processed to enhance the salient features and to suppress noise.
- a plurality n of values representative of the features of the electrocardiograph signal are generated and used in a Kohonen neural network to gen- erate an n dimensional vector.
- This vector is compared with a stored plurality m of n dimensional reference vectors defining an n dimensional Kohonen feature map to determine the proximity of the vector to the reference vectors. If it is determined by the Kohonen neural network that the vector is within or beyond a threshold range of the reference vectors, a signal is the output, which can be used to initiate an event such as the generation of an alarm or the storage of ECG data.
- US 2002/143263 describes a system comprised of a medical device and a method for analyzing physiological and health data and representing the most significant parameters at different levels of detail, which are understandable to a lay person and a medi- cal professional.
- Low, intermediate and high-resolution scales can exchange information between each other for improving the analyses; the scales can be defined according to the corresponding software and hardware resources.
- a low-resolution Scale I represents a small number of primary elements such as the intervals between the heart beats, duration of electrocardiographic PQ, QRS, and QT-intervals, amplitudes of P-, Q-, R-, S-, and T-waves. This real-time analysis is implemented in a portable device that requires minimum computational resources.
- the set of primary elements and their search criteria can be adjusted using intermediate or high-resolution levels.
- serial changes in each of the said elements can be determined using a mathematical decomposition into series of basis functions and their coefficients.
- This scale can be implemented using a specialized processor or a computer organizer.
- high-resolution Scale III combined serial changes in all primary elements can be determined to provide complete information about the dynamics of the signal.
- This scale can be implemented using a powerful processor, a network of computers or the Internet.
- the system can be used for personal or group self- evaluation, emergency or routine ECG analysis or continuous event, stress-test or bedside monitoring.
- the aim of the invention is to achieve a system and a method for diagnosing Long QT Syndrome in an objective, fast and effective way by indication of a number of symptoms derivable from an ECG curve.
- a further aim of the invention is to achieve an effective test of drug influence on ECG curvature.
- any symptom of Long QT Syndrome having an indication (influence) in the ECG curvature can be detected in an objective, automated and very fast way.
- the system might be used under field conditions such as in ambulances or in other situations where a fast indication of heart diseases is needed in order to help the patient in a correct way as early as possible.
- the analysis that takes place in an ambulance on its way to the hospital can by transmitting the results to the hospital allow the doctor at the hospital to give feedback to the personnel in the ambulance so that the correct treatment of the patient may start.
- the hospital can prepare the correct activity for the incoming patient.
- the system could be very important for
- the system can analyse drug influence on a number of persons, where analyses are made before and repeated after drug influence, where selected parameters are compared and/or combined. It is, hereby, achieved that a drug might be tested for having influence on the ECG curvature of a number of persons. This can be very important for accentance of new drugs. This svstem and also described as a method is able to relatively short period, and where the decision if a new drug should be rejected because of having negative influence of the ECG, or the drug can be accepted. This decision can be taken relatively fast.
- ECG curvature from a source, - indicating a number of different parameters contained in the received ECG curvature, - storing the parameters in storage means, selecting disease specific parameters in the storage means - selecting parameters from at least three groups, which groups comprise parameters of symmetry, flatness, duration and/or complexity - combining selected parameters in mathematical analysing means - representing the result of the mathematical analysis as a point in a coordinate system comprising at least one axis, - comparing the actual placement in the coordinate system with a number of reference parameters stored in a memory, - analysing the QT curvature of the ECG for indicating drug induced changes.
- the analysing process can be repeated in the system for further selected parameters in order to achieve more reliable results.
- the system or the method can be repeated several times with different combinations of parameters.
- a deviation of parameters from the stored data indicating symptoms of Long QT Syndrome or drug influence may also be interpreted for further reference.
- the system or method analyses the parameters chosen from at least three main groups, such as groups of parameters of symmetry, flatness, complexity and duration relating tn thfi actual ECG curvature. In this wav. it is achieved that the parameters are grouped cific number of possible parameters. Keeping the number of parameters relatively small, the analysis takes place in a faster way.
- the group of symmetry might comprise at least the following parameters:
- v[n] is the ECG signal.
- Tpeakjend Tend — Tpeak and v[n] is the ECG signal.
- v[n] is the ECG signal.
- F4 Flatness parameter, F3 normalized by the size of the R wave, calculated by t thhee f foorrmmuullaa-: F3 FA - I v[Rpe ⁇ :] - v[Jpo int]
- v[n] is the ECG signal.
- Tstart-Tend-interval surrounding Tpeak calculated by the formula:
- n Tstart A and v[n] is the ECG signal.
- F8 Flatness parameter, F7 normalized by the size of the R wave, calculated by the formula: p% - E7 I v[Rpea&] - v[jpo int]
- v[n] is the ECG signal.
- v[n] is the ECG signal.
- F9 Flatness parameter, F9, normalized by the size of the R wave, calculated by the formula: E9 10 : v[Rpe ⁇ Ar] - v[jpo int]
- E9 10 v[Rpe ⁇ Ar] - v[jpo int]
- E16 v[Tpeak], where v[n] is the ⁇ CG signal.
- N max The Hill parameter, evaluated by least square fitting of the repolarisa- tion integral, RI(t), from the Jpoint to the following Ponset as described by Kanters et al., "T wave morphology analysis distinguishes between KvLQTl and HERG mutations in long QT syndrome", Heart Rhythm (2004) 3, 285-292:
- QTc The Q-T interval normalized by the square root of the R-R interval according to Razett's formula: _ Tend - Qoi ⁇ set RR
- the group of complexity might contain at least the following parameters:
- C2 Number of phases between Tstart and Tend, where a phase is defined as a singly connected part of the wave that is entirely above or entirely below the iso-electric line; the minimum number is one.
- the groups of parameters could contain further parameters, and the groups may contain a number of subgroups.
- 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.
- a pre- cise analysis can take place because a specific combination of parameters can indicate
- the system and/or method can analyse the QT curvature of the ECG for indicating
- the Long QT syndrome can be indicated in an objective and effective manner which might occur in postsyncopal cardiac examination.
- the method can differentiate between different genotypes of the Long QT Syndrome, which is important for the treatment. It can, hereby, be achieved that the correct medical treatments can be started.
- the system and the method can be used for test of drug influence on ECG curvature.
- the system can be trained, where the parameters' values are calculated for individual subjects, where an analysis of the parameters is performed such as a pattern classification method based on supervised learning, such as Discriminant Analysis, Nearest Neighbor Techniques, Multilayer Neural Networks, Decision Trees and Rule Based Methods or combinations of these.
- supervised learning such as Discriminant Analysis, Nearest Neighbor Techniques, Multilayer Neural Networks, Decision Trees and Rule Based Methods or combinations of these.
- the final classification function is at least based on data from at least one LQT or drug influenced group and Normal subjects stored as a training set with the consequences that the classification method is improved by adding new subjects to the training set, which new subject can be tailored to demographic or gender differences.
- reference values based on the training set can be selected from the most critical group of persons with reference to the parameters that are going to be tested.
- the mathematical analysis chooses the optimal (small) parameter set out of the complete set (large) from all categories, which values are stored as ref. values. It should be made clear that the final classification functions are based on data from at least one LQT or drug influenced group and Normal subjects (the training set) with the consequences that the dis-
- This invention also comprises the use of a system for analysing ECG curvature for test of drugs, which system has input means connected to an ECG source, wherein at least one among a number of different parameters is isolated and stored in the system, where the different parameters of a received ECG curvature are indicated and/or isolated for indicating possible symptoms, where a number of selected parameters, are combined in at least a first mathematical analysis, where the result of the analysis is represented as a point in at least one coordinate system, comprising at least one axis, where the system compares the actual placement in the coordinate system with a number of reference parameters stored in the system, for indicating symptoms having influence on the ECG curvature, and analysing the QT curvature of the ECG for indicating drug induced changes to the ECG curvature, where the parameters of the ECG curvature are calculated before and after a drug test for a number of subjects, where the difference for selected parameters between before and after testing is calculated for each subject, where a mathematical analysis of selected parameters for a number of subjects gives statistical significance for
- the Long QT Syndrome is a genetic disorder characterized by abnormal cardiac repolarisation resulting in prolonged QT duration, syncopal episodes and increased risk of than 90% of all LQTS patients.
- the QT interval duration is the only ECG-based quantifier of LQTS used in clinical practice today. However duration is only a gross estimate of repolarisation and does not allow perfect discrimination between KvLQTl, HERG and normal subjects. Studies have shown that T-wave morphology parameters are useful discriminators in LQTS, but no single parameter has proven to be sufficient.
- Stepwise discriminant analysis was performed to obtain two discriminant functions based on the five strongest discriminatory parameters.
- the resulting discriminant functions include 2 duration-, 2 symmetry- and 1 flatness parameter.
- the two functions classify all subjects correctly (p> 0.0001, p ⁇ 0.005).
- Further discriminant analysis with a reduced number of parameter categories implied that superior classification is obtained when using all three parameter categories presented.
- a combination of parameters from the three categories symmetry, flatness and duration of repolarisation was sufficient to correctly classify ECG recordings from the KvLQTl, HERG and normal subjects in this study. This multivariate approach may prove to be a powerful clinical tool.
- LQTS Long QT Syndrome
- the duration of the QT interval is only a gross estimate of repolarisation since T-wave morphology is also important when characterizing the QT interval. This is evidenced by the fact that approximately 10% of all mutation carriers have a normal Bazett corrected QTc ( ⁇ 440ms) and 40% of KvLQTl and HERG carriers show QTc values between 410-470 ms that overlap with non-carriers. Conversely only 2% of all carriers present with a normal ST-T pattern and a normal QT interval. Morphological aberrations thus carry major implications for the identification of ab- normal repolarisation and have been included as diagnostic criteria equivalent to that of a positive family history for LQTS.
- Cardiologists already include a qualitative assessment of T-wave morphology from the ECG in order to obtain information that augments the clinically established QT interval measurement and facilitates discrimination between LQTS genotypes.
- qualitative description of repolarisation morphology may be biased due to intra- and interpersonal variability thus indicating the need for a standardized quantitative measure of this parameter.
- Data acquisition was carried out with the subjects resting in supine position.
- the equipment used for data acquisition was a portable digital ECG recording system, "Cardio Perfect Resting ECG system” manufactured by Cardiocontrol. Recording was divided into three sessions. Data was collected from 8 leads (I-III, N2-N6) with a sampling rate of 1200Hz. Signal recording length was 75 s. in the first session and 150 s. in the last two sessions.
- the method is based on prior work published by Website et al. and uses adaptive thresholdin ⁇ techni ⁇ ues aonlied to a dieitallv filtered and differentiated sienal. A mi- nor extension to the algorithm was incorporated to enable the detection of Tstart. Tstart was detected with a technique equivalent to the technique for detecting Tend.
- Figure 2 shows an example of the result of the event detection algorithm.
- the QT interval and the repolarisation process was done on the basis of an ECG signal with stabilized baseline. This was achieved through preliminary signal processing.
- the "raw" ECG was filtered by a Kaiser window high pass filter with a cut-off frequency of 0,5 Hz, 40 dB damping in 0,25 Hz and 0,1 dB ripple in the pass- band.
- Other filters are subsequently used: a lowpassfilter for noise reduction and a notch filter for reduction of 50 Hz or 60 Hz interference.
- the isoelectric line is defined as the straight line that connects the PQ interval before the QT interval at hand and the PQ interval after the QT interval at hand. The iso-electric line relative to zero is subtracted from the QT interval analysed.
- T-wave morphology In order to characterize the T-wave morphology, a number of parameters were selected. The parameters were chosen to cover each of the three categories: Twave symmetry, T-wave flatness and duration. The parameters are listed and described in table 1.
- Parameters S1-S4 and F1-F8 is based on the calculation of modified skewness and kurtosis measures defined as symmetry and flatness in the following.
- the T- waves were modelled as probability mass distributions (figure 3) and assigned a centre
- m2 is the standard deviation of the signal:
- FIG. 2 Isoelectric lines (dashed lines) in the signal are calculated from one P-Q interval to the following P-Q interval (Qstart - 20 ms). The line values are subtracted from the corresponding ECG signal values giving the distances v(n). The result of this procedure is shown as an area plot with basis on the zero-line.
- Figure 3 a) Example probability mass distribution used when calculating standard skewness and kurtosis measures, b) Modified frequency distribution used in this study for calculating the modified skewness and kurtosis measures. Signal values v(n) are shown in figure 2. PARAMETER DESCRIPTION
- F5 Kurtosis evaluated in a symmetric interval 10 % of the Tstart-Tend interval surrounding Ttop with Ttop as mean.
- F6 F5 normalized by absolute Rtop-Qnadir value.
- F 10 F9 normalized by absolute Rtop-Qnadir value.
- QTc The Q-T interval normalized by the square root of the R-R interval according to Bazett's formula.
- D2 Time interval from Tstart to Tend D3 Time interval from Tstart to Ttop. D4 Time interval from Ttop to Tend.
- the table above shows a Complete list of the parameters used to characterize T-wave morphology. Parameters belong to one of three categories: symmetry, flatness and duration.
- m3 is the modified skewness of the signal:
- m4 is the modified kurtosis of the signal:
- T-wave morphology parameters for the acquired, pre-processed ECG recordings were evaluated using Matlab 6.0. Only valid data were analyzed - i.e. data from leads where the signal was not corrupted by high frequency noise and where the event detection algorithm was successful in detecting the relevant events with satisfactory precision. Parameter means and standard deviations were calculated for every T-wave in the signal on all leads. A great interlead variation in T-wave morphology may be an indicator of LQTS. Interlead variance was therefore examined by calculating the standard deviation of the lead means for each parameter.
- Figure 4 Scatterplot showing classification of individuals by genotype. Separation of groups was carried out by 2 discriminant functions with 5 variables that characterize repolarisation by computation of symmetry, flatness and duration. 3. Results
- the discriminant functions were based on data from all KvLQTl, HERG and normal subjects.
- the 5 parameters included in both discriminant functions are listed in table 2.
- the discriminative efficiency of both generated functions was statistically significant after inclusion of all 5 parameters (function 1: pO.OOOl, function 2: p ⁇ 0.005).
- a scatterplot was generated from the discrimination functions and groupings of indi- vidual genotypes can be seen in figure 4.
- the dotted lines were read from the SPSS generated territorial map and manually added. The lines reflect borderlines where the differences between each pair of discrimination functions are zero. All 16 processed ECG's were correctly classified and showed at least one discriminatory characteristic as defined by the 5 parameters included in the discrimination functions. Cross valida- tion of both discriminant functions was done with the leave-one-out method and all 16 subjects were again correctly grouped. Reducing the number of variables resulted in misclassified cases due to lack of one or more discriminatory characteristics.
- HERG and KvLQTl was higher than that of normal individuals (figure 5e). However overlap existed between all three groups preventing separation of the groups by QTc. Since no single parameter included in the discrimination functions was able to separate KvLQTl, HERG and normal, we proceeded to investigate the classification effi- ciency provided by the three primary categories represented by the parameters in the functions. This was carried out by generating new discrimination functions using parameters from one category only while excluding the other two. Then, from the new discrimination functions three additional functions were generated, this time allowing the inclusion of parameters from combinations of two categories. Scatterplots illustrat- ing the results of this analysis are shown in figures 6a-f.
- the first two functions included parameters that characterize the symmetrical properties of the Twave. 83.1% of the 16 subjects were correctly classified. Arrows in figure 6a indicate the 3 misclassified subjects. A second discriminant analysis was performed using flatness parameters. This resulted in 93.8% correctly classified subjects. Only one subject was not correctly classified as indicated by the arrow on figure 6b. The misclassified case was the same HERG subject incorrectly classified using symmetry parameters. The discriminatory efficiency of duration parameters was also evaluated. Discrimination nna1v ⁇ ji ⁇ 3 p. ⁇ nltp.d in 93.8% correctlv classified sub ects. One HERG subject was mis- waves similar to those found in KvLQTl. However the duration parameters failed to identify this morphological feature, thus reducing classification performance.
- S4meanN5 - Lead N5 mean modified skewness evaluated in a symmetrical interval surrounding Ttop and corresponding to 20% of the interval between Tstart-Tend. c) D4std - Interlead standard deviation of the time interval from Ttop to Tend, d) S5meanN5 - Lead N5 mean of the ratio between the time interval from Tstart to Ttop and the corresponding time interval from Ttop to Tend, e) Lead N5 mean QTc.
- Figures 6d-f show the results of three separate discriminant analysis using combinations of parameters from two categories. It can be noted that classification of subjects was perfect in all cases, even when repolarisation duration was not considered (figure 6d).
- Figure 6. a) The result of discriminant analysis using symmetry parameters resulted in three misclassified cases (arrows). Visual inspection of the ECG's revealed no apparent abnormalities to indicate the reason for incorrect misclassification. b) The result of discriminant analysis using flatness parameters. One incorrectly classified HERG subject was identified (arrow) even though no obvious visual abnormality indicated a different genotype, c) Result of discriminant analysis using duration parameters.
- QTc parameter alone emphasizes the hypothesis that additional parameters are needed to classify LQTS individuals. By combining parameters from two categories it was found that the discriminatory strength was increased.
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Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
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CA002550224A CA2550224A1 (en) | 2003-12-19 | 2004-10-20 | A system and a method for analysing ecg curvature for long qt syndrome and drug influence |
EP04762941A EP1696792A1 (en) | 2003-12-19 | 2004-10-20 | A system and a method for analysing ecg curvature for long qt syndrome and drug influence |
JP2006544212A JP2007514488A (en) | 2003-12-19 | 2004-10-20 | System and method for analyzing electrocardiogram curvature and drug effects in long QT syndrome |
US10/596,617 US7991458B2 (en) | 2003-12-19 | 2004-10-20 | System and a method for analysing ECG curvature for long QT syndrome and drug influence |
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US53066503P | 2003-12-19 | 2003-12-19 | |
EP03029363A EP1543770A1 (en) | 2003-12-19 | 2003-12-19 | A system and a method for analysing an ECG signal |
US60/530,665 | 2003-12-19 | ||
EP03029363.3 | 2003-12-19 |
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US (1) | US7991458B2 (en) |
EP (2) | EP1543770A1 (en) |
JP (1) | JP2007514488A (en) |
CN (1) | CN1953705A (en) |
CA (1) | CA2550224A1 (en) |
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WO2007106781A2 (en) * | 2006-03-10 | 2007-09-20 | University Of Rochester | Ecg-based differentiation of lqt1 and lqt2 mutation |
WO2008064679A1 (en) * | 2006-11-30 | 2008-06-05 | Aalborg Universitet | System and method for analyzing complex curvature of ecg curves |
US20100004549A1 (en) * | 2006-10-03 | 2010-01-07 | General Electric Company | System and method of serial comparison for detection of long qt syndrome (lqts) |
US7840259B2 (en) | 2006-11-30 | 2010-11-23 | General Electric Company | Method and system for electrocardiogram evaluation |
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- 2004-10-20 CN CNA2004800418801A patent/CN1953705A/en active Pending
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- 2004-10-20 JP JP2006544212A patent/JP2007514488A/en active Pending
- 2004-10-20 WO PCT/DK2004/000722 patent/WO2005058156A1/en active Application Filing
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Also Published As
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US20070208264A1 (en) | 2007-09-06 |
CN1953705A (en) | 2007-04-25 |
EP1543770A1 (en) | 2005-06-22 |
US7991458B2 (en) | 2011-08-02 |
EP1696792A1 (en) | 2006-09-06 |
JP2007514488A (en) | 2007-06-07 |
CA2550224A1 (en) | 2005-06-30 |
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