The quest for optimal electrocardiography. Task Force II: Quality of electrocardiographic records

Standardization in Performing and Interpreting Electrocardiograms

Excellence in recording and interpretation of electrocardiogram (ECG) is a necessity for optimal electrocardiography. This includes data to properly interpret the ECG, including data on age, gender, cardiovascular diagnosis, medications, abnormal laboratory findings (eg, data on electrolytes), and the indications for the electrocardiogram. The ECG needs to be performed by a qualified technician and interpreted by an experienced physician.

Matrix of regularity for improving the quality of ECGs

The 12-lead electrocardiography (ECG) is the gold standard for diagnosis of abnormalities of the heart. However, the ECG is susceptible to artifacts, which may lead to wrong diagnosis and thus mistreatment. It is a clinical challenge of great significance differentiating ECG artifacts from patterns of diseases. We propose a computational framework, called the matrix of regularity, to evaluate the quality of ECGs. The matrix of regularity is a novel mechanism to fuse results from multiple tests of signal quality. Moreover, this method can produce a continuous grade, which can more accurately represent the quality of an ECG. When tested on a dataset from the Computing in Cardiology/PhysioNet Challenge 2011, the algorithm achieves up to 95% accuracy. The area under the receiver operating characteristic curve is 0.97. The developed framework and computer program have the potential to improve the quality of ECGs collected using conventional and portable devices.

Recommendations for the standardization and interpretation of the electrocardiogram: part I: the electrocardiogram and its technology a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society endorsed by the International Society for Computerized Electrocardiology

This statement examines the relation of the resting ECG to its technology. Its purpose is to foster understanding of how the modern ECG is derived and displayed and to establish standards that will improve the accuracy and usefulness of the ECG in practice. Derivation of representative waveforms and measurements based on global intervals are described. Special emphasis is placed on digital signal acquisition and computer-based signal processing, which provide automated measurements that lead to computer-generated diagnostic statements. Lead placement, recording methods, and waveform presentation are reviewed. Throughout the statement, recommendations for ECG standards are placed in context of the clinical implications of evolving ECG technology.

Recommendations for the Standardization and Interpretation of the Electrocardiogram

This statement examines the relation of the resting ECG to its technology. Its purpose is to foster understanding of how the modern ECG is derived and displayed and to establish standards that will improve the accuracy and usefulness of the ECG in practice. Derivation of representative waveforms and measurements based on global intervals are described. Special emphasis is placed on digital signal acquisition and computer-based signal processing, which provide automated measurements that lead to computer-generated diagnostic statements. Lead placement, recording methods, and waveform presentation are reviewed. Throughout the statement, recommendations for ECG standards are placed in context of the clinical implications of evolving ECG technology.

Recommendations for the standardization and interpretation of the electrocardiogram. Part I: The electrocardiogram and its technology. A scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society

This statement examines the relation of the resting ECG to its technology. Its purpose is to foster understanding of how the modern ECG is derived and displayed and to establish standards that will improve the accuracy and usefulness of the ECG in practice. Derivation of representative waveforms and measurements based on global intervals are described. Special emphasis is placed on digital signal acquisition and computer-based signal processing, which provide automated measurements that lead to computer-generated diagnostic statements. Lead placement, recording methods, and waveform presentation are reviewed. Throughout the statement, recommendations for ECG standards are placed in context of the clinical implications of evolving ECG technology.

Results of the performance testing of purpose-built and PC-based electrocardiographs using a simple evaluation procedure

This paper presents the results of the evaluation testing of six 12-lead electrocardiographs, three purpose-built instruments and three of the recently introduced personal computer-based type (PC-based). As for PC-based electrocardiographs, three examples of the MRT systems, two examples of the 300 Hz CardioScope model and one prototype of the 1200 Hz CardioScope were examined but only results for one representative example of each are given here. It was of particular interest to compare the performance advantages and limitations of the PC-based electrocardiographs with that of instruments currently in use. A test procedure was developed that can be used by a medical technical department to evaluate an electrocardiograph before making a purchase decision. The procedure includes tests of frequency response, sampling rate, 50 Hz filter attenuation, gain and common mode rejection ratio (CMRR) plus tests based upon simulated electrocardiograms (ECGs). The procedure takes account of the AHA and ECRI recommendations for electrocardiograph checks and can be completed in less than two hours. The only equipment required being an ECG simulator and a signal generator. The results of this work show that purpose-built electrocardiographs meet all normal performance requirements, whereas the PC-based types, whilst having the potential to at least equal these requirements, currently exhibit software and hardware related problems.

Assessing ECG signal quality on a coronary care unit

Poor electrocardiograph (ECG) signal quality is associated with an increase in the number of false alarms, may degrade diagnostic information, and can increase the workload for coronary care unit (CCU) or other intensive care staff. It is important therefore to establish simple quantitative measures that can be used to demonstrate signal quality problems. In this study, a fixed-gain diagnostic bandwidth ECG from patients in a single CCU bed was monitored continuously for 10 weeks and measures which could relate to quality were calculated. These measures were the number of times the ECG exceeded a preset limit (out-of-range events, +/-4 mV) and the frequency content of the ECG plus superimposed noise in six different bandwidths (0.05-0.25, 0.25-10, 10-20, 20-48, 48-52, and 52-100 Hz). A computer-based data collection system calculated a 10 s average for each of the measures and logged these to memory. Following the data collection phase, good-quality baseline levels for the seven measures were calculated for each of the days studied and compared with levels during the evening-night (6 pm-6 am), which were in turn compared with levels during the day-time (6 am-6 pm). All measures were significantly lower (p < 0.001) for the selected good-quality ECGs compared with those recorded during the night, with low frequency, lower ECG bandwidth, and out-of-range events producing the greatest differences. Night-time noise levels were lower than day-time levels, and the largest reductions were found in the rate of out-of-range events (19.8 to 9.3 h-1) (p < 0.02), and low-frequency content less than 0.25 Hz (70 to 56 microV) (p < 0.01). Significant reductions during the night were also found in the lower ECG bandwidth 0.25-10 Hz (111 to 98 microV) (p < 0.01). No significant changes were found in the higher frequencies. We conclude that the low-frequency content and rate of out-of-range events are easy to obtain and could be used as measures for evaluating signal quality.

Automated electrocardiogram analysis: the state of the art

The overwhelming number of electrocardiograms (ECGs) now recorded routinely has prompted the development of computer analysis which in turn has benefited electrocardiography with important technological advances. All automated ECG analysis systems adopt a similar approach: a measurement program and a program that interprets the clinical significance of these measurements along with a rhythm analysis algorithm. Measurement, selection and classification of parameters vary according to the program used. Data compression is applied to the signal to reduce processing time and allow long-term storage. Diagnostic accuracy, however, is not greatly improved over that of experienced cardiologists. Programs studied using a validated data bank provided by an international group of cardiologists show a variability not only in parameter measurement but also in diagnostic statement and in the way in which such statements are expressed. Recommendations for measurement standards have been made to fulfil the need for exchange of diagnostic criteria. No recommendations concerning the selection of parameters have been proposed, and so new parameters or combinations of parameters can be introduced with the ultimate aim of increased diagnostic performance.

Signal quality of resting electrocardiograms

Artifact may cause errors of technical origin when ECGs are interpreted by automatic methods. Baseline shift and high-frequency noise content of minimal and typical length ECG records from pediatric and adult populations were measured to allow prediction of both the likelihood of interpretation errors of technical origin and the number of reacquistions needed to obtain an artifact-free record. Ages of the 708 subjects in this study ranged from 2 weeks to 27 years. When a baseline shift of 0.25 mv (exceeded in 7% of the R-R intervals in the database) or a noise content greater than 15 muv RMS (exceeded in 6% of the R-R intervals in the database) within six seconds of three simultaneous leads was declared an unacceptable artifact, then 68% of the records from 0-4 year olds and 31% of the records from adults (greater than 19 years), were rejected on the basis of technical quality. These failure rates mean that, on the average, 3.1 tries would be needed to obtain an artifact-free record from 0-4 year olds; 1.4 tries would be needed for adults. If acquisition is done interactively, the measurement time for a 6-second, 3-lead group would be increased by 13 seconds for 0-4 years olds and by three seconds for adults in order to assure adequate signal quality for computer-assisted analysis.

Future of computerised electrocardiography

The advent of computerised electrocardiography has been of prime importance for the storage and retrieval of data, but none of the available systems is of universal application for analysis of patterns. Future needs require hierarchical systems of increasing degrees of complexity, depending on the source of requests, and there should be appropriate provision for review by cardiologists before the final report is issued.