Computation of the signal averaged ECG

Successive QRS complexes meeting a predetermined coefficient of similarity are aligned (within the window indicated by dashed lines) on an ongoing basis. Their rolling arithmetic mean is computed until a predetermined noise threshold is achieved (shown as the typical criterion of the standard deviation of the TP segment <1 microvolts). The QRS complex is then filtered and analyzed for late potentials, defined when the filtered QRS duration is >114 milliseconds, root mean square (RMS) voltage in the terminal 40 milliseconds is <20 microvolts, and low amplitude signal (LAS) duration (the terminal signal duration from 40 mV to isopotential) is >38 milliseconds.