ECGSYN generates a synthesized ECG signal with usersettable mean heart rate, number of beats, sampling frequency, waveform morphology (P, Q, R, S, and T timing, amplitude,and duration), standard deviation of the RR interval, and LF/HF ratio (a measure of the relative contributions of the low and high frequency components of the RR time series to total heart rate variability). Using a model based on three coupled ordinary differential equations, ECGSYN reproduces many of the features of the human ECG, including beattobeat variation in morphology and timing, respiratory sinus arrhythmia, QT dependence on heart rate, and Rpeak amplitude modulation. The output of ECGSYN may be employed to assess biomedical signal processing techniques which are used to compute clinical statistics from the ECG.
ECGSYN was contributed to PhysioNet by Patrick McSharry from the Department of Engineering Science, University of Oxford, and by Gari Clifford of the Laboratory for Computational Physiology at MIT. Three implementations are available:
 A version for Matlab and Octave (sources)
 A version in C (sources; readytorun binaries for GNU/Linux, Solaris, and MSWindows are also available)
 A Java applet by Mauricio Villarroel of the Universidad Católica Boliviana (click here to run the applet in your web browser; the Java sources are also available)
The algorithms used by ECGSYN are described in
McSharry PE, Clifford GD, Tarassenko L, Smith L. A dynamical model for generating synthetic electrocardiogram signals. IEEE Transactions on Biomedical Engineering 50(3): 289294; March 2003.
Current implementations of ECGSYN allow the user to modify the morphology of the PQRST cycle, which was not a feature of the original ECGSYN described in the paper. The angle of each attractor (P, Q, R, S and T) around the limit cycle is set by ti (initially, [70 15 0 15 100]*pi/180). Their positions above or below the z=0 plane are set by bi and the widths of the waveform components are given by ai. Since ti=0 defines the placement of the Rpeak, the ordering of each element of ti, ai and bi is [P Q R S T]. The bi and the ti are stretched by the square root of the reciprocal mean RR interval, as suggested by Bazett's (empirical) formula relating the QT interval to the heart rate. This transformation does not cancel out the reduction of the interattractor angular distance that arises 'naturally' from augmented heart rates in this model.
Of related interest is ECGwaveGen, a Matlab/Octave application that generates (nonrealistic) ECGlike test waveforms with welldefined characteristics as specified in ANSI/AAMI EC13:1992 (American National Standard: Cardiac Monitors, Heart Rate Meters, and Alarms).
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PhysioNet is supported by the National Institute of General Medical Sciences (NIGMS) and the National Institute of Biomedical Imaging and Bioengineering (NIBIB) under NIH grant number 2R01GM10498709.
