Changes of signal-averaged ECG in normal subjects after one year

Repeated signal-averaged electrocardiograms (SA ECG) were recorded twice with a mean interval of 13 months in 11 healthy volunteers in order to acquire basic information on long-term changes of SA ECG. After one year the duration of filtered QRS remains the most stable parameter of SA ECG on the contrary to parameters describing end of fQRS--i.e. both HFLA and RMS. Moreover fQRS seems to have better specificity in comparison to HFLA and RMS. An estimation of significant long-term changes in individual parameters of SA ECG was obtained. According to our results, only changes in QRS +/- 13 ms, fQRS +/- 8 ms, HFLA +/- 22 ms and RMS +/- 17 microV should be considered significant when found in a long-term follow-up of patients with a heart disease.