IMMEDIATE AND DAY-TO-DAY REPRODUCIBILITY OF THE SIGNAL-AVERAGED ELECTROCARDIOGRAM IN PATIENTS WITH CORONARY-ARTERY DISEASE

The purpose of this study was to prospectively evaluate the immediate (5 minutes) and short-term (1 day) reproducibility of the signal-avera ged electrocardiogram (SAECG) in patients with coronary artery disease . A total of 59 consecutive patients with coronary artery disease (50 male, 9 female, mean age 59 +/- 13 years) were included, Analysis was performed using a commercially available system with high-pass filters of 25, 40, and 80 Hz without any change in electrode position. The fo llowing time-domain parameters were measured: (1) total filtered QRS d uration; (2) duration of high-frequency low-amplitude signals (HFLA); and (3) root-mean-square voltage of She terminal 40 ms of the QRS comp lex (RMS40). Correlation between pairs of measurements was excellent, ranging from 0.91-0.99 for QRS and HFLA duration, and from 0.83-0.98 f or RMS40 value. However, the range of differences was wide for all par ameters, especially at 25 and 80 Hz, revealing marked individual varia tions in selected cases. The immediate reproducibility of an initially normal SAECG was 95% at 25 Hz, 100% at 40 Hz, and 81% at 80 Iii; figu res for an initially abnormal SAECG were 89%, 91%, and 93%, respective ly, and the coefficient of agreement kappa was highest at 40 Hz than a t 25 or 80 Hz. Discordant results were most frequently observed in pat ients with borderline values, or in cases with nonsimilar residual noi se levels. In conclusion the immediate and day-to-day reproducibility of the SAECG is excellent in patients with chronic stable coronary art ery disease. However, individual variations are observed in selected c ases, leading to modification in interpretation of the result. For thi s reason, individual reproducibility should be considered before evalu ating the effect of any therapeutic intervention on the SAECG, especia lly in patients with borderline values of the quantitative parameters of the SAECG.