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Serial ECG management and control of the comparison process should be dynamically driven by patient data. The functional architecture requirements are specified for a computerized ECG processing system integrating serial analysis. The concepts of reference investigations and temporal events are first explained. A conceptual reference model is proposed which stratifies the serial analysis process into a few generic strategies which will be instantiated into several types of serial comparison processing tasks as a function of the clinical evolution of the patient. This model is an extension of the OEDIPE core data model developed and implemented during the AIM #2026 project.

The prerequisite for future development and assessment of serial electrocardiographic analysis programs is the availability of easy to use database management systems for storage and retrieval of electrocardiographic data and results and efficient means for electronic interchange of digital electrocardiographic data. The basic aim of project 2026 of the European program for advanced informatics in medicine is to encourage "open European data interchange and processing for electrocardiography" (OEDIPE) and to provide objective decision support techniques in the field of quantitative electrocardiology. The final objective is to develop demonstration systems for the follow-up evaluation of (1) selected populations with heart disease, (2) integrating serial analysis, (3) decision support, (4) open databases, and (5) communication protocols, which will foreshadow large-scale monitoring of ambulatory or critically ill patients at home, during their transportation in an emergency vehicle, or during their stay in a hospital. The first-year objectives and achievements of the OEDIPE project are briefly described. Emphasis is put on the management of serial electrocardiographic records and data and on the control strategies for the management of the serial analysis process.

Performance requirements and national, as well as international, standards for computer-assisted electrocardiography are behind today's technology. Upgrading is urgently needed from a legal point of view, as well as from a technologic point of view. In Europe a new directive on medical devices requires that instruments with a measurement function have to provide the appropriate measurement accuracy and that manufacturers must specify its measurement accuracy. This study addresses the problem. A description for a new testing system for computer-assisted electrocardiography is given. Also, new tools, for example, the Conformance Testing Services database, and minimum performance requirements for testing computer-assisted electrocardiographs are described and discussed.

In the SCP-ECG project (AIM #1015) of the pilot AIM Programme a standard communications protocol was developed for computerized electrocardiography, consisting of standards for the interchange, encoding and storage of digital ECG data. Part of this work is continued under the main AIM Programme (January 1992- December 1994) as AIM Project #2026, entitled "Open European Data Interchange and Processing for Computerized Electrocardiography (OEDIPE)" and was taken up by the CEN/TC 251 Committee as a priority item, for implementation into an official European Standard in Health Care Informatics. The objectives and implementation of this Standard are described in the present paper.

In the international project "Common Standards for Quantitative Electrocardiography" (CSE), diagnostic results of different computer programs for the interpretation of the electrocardiogram (ECG) and of the vectorcardiogram (VCG) were combined, and it was shown that the "combined program" performs better than each program separately. Because the program MEANS (Modular ECG Analysis System) comprises 2 different classification programs--one for the ECG, the other for the VCG--this allowed investigation of whether the combined interpretations would yield a better diagnostic result than either one separately. This approach requires that a VCG always be recorded in addition to the ECG. To circumvent this complication, the VCG was reconstructed from the simultaneously recorded ECG leads. This reconstructed VCG was then interpreted by the VCG classification program, whereupon the diagnostic interpretations of the ECG and the reconstructed VCG were combined. For the validation, the CSE database of documented ECGs and VCGs (n = 1,220) was used. The combination of the ECG and VCG interpretations yielded a better diagnostic result than each interpretation program separately (total accuracy 74.2% (ECG + VCG) vs 69.8% (ECG) and 70.2% (VCG), p less than 0.001 in both cases). The results for the reconstructed VCG (total accuracy 70.5%) are comparable to those for the ECG and the VCG (p greater than 0.10 in both cases). The performance of the combined interpretations of ECG and reconstructed VCG (total accuracy 73.6%) is approximately the same as that of the combined ECG and VCG (p greater than 0.10). Thus, the performance of an ECG computer program can be improved by incorporating both ECG and VCG classificatory knowledge, using only the ECG itself.

In an international collaborative project aimed at producing common standards for quantitative electrocardiography, a standard communications protocol (SCP-ECG) was developed for computerized electrocardiography. The protocol consisted of standards for the interchange, encoding, and storage of digital ECG data. The work was performed in three distinct, but closely related, work-packages and in close collaboration with representatives from 13 manufacturers of computerized electrocardiographs from all over the world. The objectives and results of SCP-ECG are briefly described in this paper.

The objective of this study is to assess the performance of patient-specific segment-specific (PSSS) synthesis in QRST complexes using CAVIAR, a new method of the serial comparison for electrocardiograms and vectorcardiograms. A collection of 250 multi-lead recordings from the Common Standards for Quantitative Electrocardiography (CSE) diagnostic pilot study is employed. QRS and ST-T segments are independently synthesized using the PSSS algorithm so that the mean-squared error between the original and estimated waveforms is minimized. CAVIAR compares the recorded and synthesized QRS and ST-T segments and calculates the mean-quadratic deviation as a measure of error. The results of this study indicate that estimated QRS complexes are good representatives of their recorded counterparts, and the integrity of the spatial information is maintained by the PSSS synthesis process. Analysis of the ST-T segments suggests that the deviations between recorded and synthesized waveforms are considerably greater than those associated with the QRS complexes. The poorer performance of the ST-T segments is attributed to magnitude normalization of the spatial loops, low-voltage passages, and noise interference. Using the mean-quadratic deviation and CAVIAR as methods of performance assessment, this study indicates that the PSSS-synthesis algorithm accurately maintains the signal information within the 12-lead electrocardiogram.

A new method is presented, different from usual methods, for the discussion of the results of computer ECG measurement programs, based on a new graphical evaluation method. The proposed "scatter-graphs" both highlight the main program results and facilitate the comparison between various wave-recognition algorithms. They allow the distinction between the reliability of an algorithm, which is its capacity to provide a maximum of measurements with a minimum amount of errors, and its precision, i.e., the standard deviation of the differences between its point estimates and the reference. The method proves to be a powerful tool for the discussion of individual, as well as the median program results in CSE Measurement Study. It allows to highlight limitations induced in performance assessment by the variability of the reference itself, and to state that the median program is at least as close to the "Gold Standard" as the median of the referees.

Computer processing of electrocardiograms (ECGs) has over the last 15 years increased rapidly. Still, there are at present no standards for computer ECG interpretation. Different techniques are used not only for measurement and interpretation, but also for transmission and storage of data. In order to fill these gaps, a large international project, sponsored by the European Commission, was launched in 1980 to develop "Common Standards for Quantitative Electrocardiography (CSE)". The main objective of the first CSE study was to reduce the wide variation in wave measurements currently obtained by ECG computer programs. The second study was started in 1985 and aimed at the assessment and improvement of diagnostic classification of ECG interpretation programs. To this end reference libraries of well documented ECGs have been developed and comprehensive reviewing schemes devised for the visual and computer analysis of ECGs. This task was performed by a board of cardiologists in a Delphi review process, and by 9 VCG and 10 standard 12-lead programs developed by university research groups and by industry. A third action was started in June 1989 to harmonize acquisition, encoding, interchange and storing of digital ECG data. The action thus performed have become internationally recognized milestones for the standardization of quantitative electrocardiography.

An important feature of an ECG analysis program is its ability to provide reliable measurements under various operating conditions, e.g., on noise-free and noisy ECGs. Therefore, within the European cooperative project "Common Standards For Quantitative Electrocardiography" (CSE), the accuracy and stability of ECG measurements obtained by several computer programs has been compared. To investigate the stability of measurements two sets of 10 ECGs with and without seven different high- and low-frequency types of noise--altogether 160 electrocardiograms and 160 vectorcardiograms--have been analyzed by eight electrocardiographic and five vectorcardiographic computer programs. The stability of measurement was tested with respect to results obtained for the noise-free recordings. In a previous paper, the influence of noise on wave boundary recognition has been reported. In the present paper, the effect of noise on amplitude measurements and on problems of waveform definitions within the QRS complex are described. The results indicate that programs analyzing an averaged beat exhibit less variability than programs which measure every complex or a selected beat. Comparability and stability of measurements could be improved if a standardized procedure for amplitude references were to be introduced. In addition, the stability of QRS waveform labelling could be improved if waveforms' minimum amplitude and duration were to be validated against the noise level which itself should be determined by a standardized procedure.

The authors describe an extension of McNemar's test that can be used to compare diagnostic performance when multiple statements are obtained from computer analysis or visual interpretation of the ECG. If two or more diagnostic statements are made, by definition only one can be correct for the cases in the CSE pilot database, which were selected for single, clinically well documented, abnormalities. If one statement stood out from others as being made with the highest degree of certainty, that was accepted as the single interpretation, right or wrong. However, when two or more statements were made with the same degree of certainty and only one statement was correct, then in the previous application of McNemar's test that interpretation was given credit for being correct. In the extension of the method presented in this article, such an interpretation is given partial credit for the one correct statement and partial discredit for any incorrect statement, thereby reporting the results more properly in the sensitivity and specificity statistics for the different diagnostic categories.

As a measure for performance of ECG computer programs, systematic noise tests have been performed within the European project Common Standards For Quantitative Electrocardiography. Ten original and ten artificial VCG and ECG records (the artificial records were constructed from one beat of the original ones) without and with added noise were processed by eight ECG programs and by five VCG programs. Three lowpass filtered high frequency noise levels, line frequency noise and three baseline noise levels were added to the original records. The processing results for the noise-free and for the noisy records have been analyzed in the CSE coordinating center. Results presented in this study refer to the amplitude differences obtained after comparison of results from noise-free and noisy ECG records. Increasing high frequency noise results in overestimation of peak amplitudes and increased variability of measurements.

The development of a data base is described which can be used as common reference for ECG computer programs analyzing 12 or 15 simultaneously recorded leads. This data base is an extension of the 3-lead CSE reference library, described previously.

The use of computers for the interpretation of the resting electrocardiogram (ECG) is critically reviewed. After a short description of the motives for the application of computers in this field, the processes that are sequentially executed in an ECG data processing system are critically analyzed, i.e., the acquisition and transmission of signals; the wave recognition and measurement phase; the parameter extraction, rhythm analysis, and classification phases; and, finally, the reporting of results as well as serial comparison. Emphasis is given on the evaluation and standardization of measurement and interpretation results of various ECG computer programs, based on the experience of the author as project leader of the International Cooperative Project "Common Standards for Quantitative Electrocardiography" (CSE). An extensive list of references is provided.

In an international project investigators from 21 institutes are trying to establish a common reference library and evaluation methods for testing the diagnostic performance of various ECG computer programs using ECG independent clinical information. Preliminary results indicate that the classification accuracy of different programs varies widely.

We present a new graphical evaluation method aimed at displaying the main characteristics of computer ECG measurement program results. The proposed graphs provide information on the number of rejected measurements and gross program errors, and on the precision of the results, i.e. the scatter of the differences between fiducial point estimates given by the programs and the reference. 'Scatter-graphs' concerning P, QRS and T wave boundary recognition from the programs participating in the European Concerted Action on 'Common Standards for Quantitative Electrocardiography (C.S.E.)' are analysed and discussed (10 standard 12-lead ECG programs and 9 Vectorcardiographic (VCG) programs from 10 European, 5 American and 1 Japanese Centers). The method proved to be a powerful tool for a direct and global qualitative comparison of the efficiency of the algorithms elaborated by the program developers, and allowed some of the strategies adopted in these programs to be highlighted.