R. Degani

A reference data base for multilead electrocardiographic computer measurement programs

In an effort to standardize and evaluate the performance of electrocardiographic computer measurement programs, a 15 lead reference library has been developed based on simultaneously recorded standard 12 lead and orthogonal XYZ lead data. A set of 250 electrocardiograms (ECGs) with selected abnormalities was analyzed by a group of five referee cardiologists and 11 different 12 lead and 6 XYZ computer programs. Attention was focused on the exact determination of the onsets and offsets of P, QRS and T waves. The referees performed their task on highly amplified, selected complexes from the library in a two round process. Median results of the referees coincided best with the median derived from all programs. An analysis of stability proved that the combined program median was a robust reference. However, some individual program results were widely divergent. Paired t tests demonstrated earlier onset for P and QRS (p less than 0.001), as well as later offset for P and T waves in the median 12 lead than in the XYZ results. Significant differences also existed among results obtained by programs analyzing all standard ECG leads at one time, the so-called multilead programs, and those obtained by the conventional standard three lead analysis programs. As a consequence, the derived P, PR, QRS and QT interval measurements varied quite widely among the various programs. Significant differences were also observed among measurements of Q, R and S duration. Some programs showed Q waves that were on the average 6 ms (p less than 0.001) longer than those of others. This may significantly influence diagnostic performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the performance of electrocardiographic computer programs with the use of a reference data base.

To allow an exchange of measurements and criteria between different electrocardiographic (ECG) computer programs, an international cooperative project has been initiated aimed at standardization of computer-derived ECG measurements. To this end an ECG reference library of 250 ECGs with selected abnormalities was established and a comprehensive reviewing scheme was devised for the visual determination of the onsets and offsets of P, QRS, and T waves. This task was performed by a group of cardiologists on highly amplified, selected complexes from the library of ECGs. With use of a modified Delphi approach, individual outlying point estimates were eliminated in four successive rounds. In this way final referee estimates were obtained that proved to be highly reproducible and precise. This reference data base was used to study measurement results obtained with nine vectorcardiographic and 10 standard 12-lead ECG analysis programs. The medians of program determinations of P, QRS, and T wave onsets and offsets were close to the final referee estimates. However, an important variability could be demonstrated between measurements from individual programs and mean differences from the referee estimates amounted to 10 msec for QRS for certain programs. In addition, the variances of all programs with respect to the referee point estimates were variable. Some programs proved to be more accurate and stable when the data from high- vs low-noise recordings were analyzed. Average Q wave durations calculated from ECGs for which programs agreed on the presence of a Q or QS wave differed by more than 8 msec in several program-to-program comparisons. Such differences may have important consequences with respect to diagnostic performance. Various factors that might explain these differences have been determined. The present study demonstrates that to allow an exchange of results and diagnostic criteria between different ECG computer programs, definitions, minimum wave requirements, and measurement procedures urgently need to be standardized.

Compression and encoding of ECG data within the European standard communications protocol

The European Community has launched a project to develop a standard communications protocol for computerized electrocardiography (SCP-ECG). Within this project, compression and encoding of ECG data for transmission and storage has been investigated. A compression scheme with well-specified error limits was developed. Compression ratios for resting ECGs achieved by this method are as high as 20. The reconstruction root mean square (RMS) error can be maintained below 10 mu V. The method provides fully reproducible measurements and allows reliable visual rhythm analysis of the reconstructed ECG. For verification of errors introduced by compression and decomposition a standard test data set from the CSE database has been specified. For digital transmission a general protocol (SCP-Protocol) has been defined which allows communication between ECG carts and hospital information systems.<<ETX>>

Comparison of diagnostic results of ECG computer programs and cardiologists

In the European concerted action Common Standards for Quantitative Electrocardiography (CSE) results of nine electrocardiography (ECG) and 6 vector cardiography (VCG) computer programs have been compared with a true diagnosis based on ECG-independent evidence, as well as to the results obtained by eight cardiologists who read the ECGs and five who read the VCGs. Results obtained in 1220 cases are presented. Assessment of the diagnostic performance of computer programs and of cardiologists against ECG-independent validated data was the primary objective. However, also testing against the readings of a group of cardiologists was performed to assess the clinical acceptability of the computer program results. The study shows that programs with the best performance reached almost equal levels to the best cardiologists. The study also shows that all can still be improved for one or more diagnostic categories, whereas some require general improvement.<<ETX>>

Common Standards for Quantitative Electrocardiography : The CSE Pilot Study

A four year concerted action project has been started in the European Communities (EC) with the aim of “Common Standards for Quantitative Electrocardiography” (CSE Project). Standards for computer derived ECG measurements are urgently required because more and more quantitative diagnostic ECG criteria are now being derived by ECG computer programs and in view of the existing differences, first of all with respect to time measurements of present computer programs.

A standard communications protocol for computerized electrocardiography

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.

Development Of A Standard Communications Protocol For The Exchange And The Storage Of Digital ECGs

In the SCP-ECG Project (AIM #1015) a standard communications protocol has been developed for computerized electrocardiography, consisting of standards and recommendations for the interchange, encoding and storage of digital ECG data. The work has been performed in three distinct, but closely related workpackages in close collaboration with representatives from academia and industry from all over the world. The objectives and results obtainedso far are described in the present paper.