Performance degradation of the coherent averaging technique by a molding effect

In coherent averaging of the ECG, the authors show that when temporal alignment is performed by matched filtering, the signal-to-noise ratio (SNR) improvement can reach a stable limit after a certain number of averaged events. The source of this degradation lies in the noise that can be contained in the template of the matched filter. This effect depends on the SNR and the morphology of the signal, and it can be reduced by a multipass averaging procedure or by a temporal updating technique.