Improved alignment method in ECG signal averaging: application to late potentials detection

The purpose of this study is to obtain the ventricular late activity from the surface ECG. The signal is measured by means of a two-channel electrocardiographic system: a low-gain amplifier for the reference ECG acquisition and a low-noise, high-gain amplifier for the late potential. The selected bipolar leads are a standard limb lead for reference and a special precordial lead for high amplification. A comparative analysis of three temporal alignment methods in the signal averaging has been performed: double level (DL), position of normalized integrals (NI) in coincidence, and matched filtering (MF). Results obtained by signal averaging from patients with documented ventricular tachycardia and volunteers without evidence of heart disease are presented. The influence of the bipolar precordial lead position and the selected bandwidth of the filters has also been evaluated. The MF and NI methods allow the estimation of higher magnitude and higher frequency components than the DL method. The MF method works better than the NI method for some ECG signal methodologies. The results show that there is not late activity over 300 Hz; the basis components are mainly in the narrow band of 100-150 Hz