Er. Valverde et al., INFLUENCE OF FILTERING TECHNIQUES ON THE TIME-DOMAIN ANALYSIS OF SIGNAL-AVERAGED P-WAVE ELECTROCARDIOGRAM, Journal of cardiovascular electrophysiology, 9(3), 1998, pp. 253-260
Differences in P Wave Filtering Techniques, Introduction: The advent o
f signal-averaged ECG (SAECG) systems for P wave analysis has made it
important to determine if the use of different filtering techniques in
these systems is diagnostically equivalent. Methods and Results: Thre
e different high-pass filtering techniques and two cutoff frequency va
lues were used: 29- and 40-Hz Butterworth bidirectional filter (BB29,
BB40), 29- and 40-Hz Butterworth unidirectional filter (UB29, UB40), a
nd 29- and 40-Hz least mean square filter (LMS29, LMS40). Normal healt
hy volunteers (n = 36) and patients with documented paroxysmal atrial
fibrillation (n = 23) were analyzed, A custom-built SAECG system and s
tandard bipolar orthogonal leads were used, Noise was reduced to < 0.3
mu V. P wave total duration, root mean square voltage of the terminal
20, 30, and 40 msec of the filtered vector magnitude, and the area un
der the curve between the onset and offset of averaged unfiltered and
filtered P wave vector magnitude were analyzed, Only the duration of t
he P wave showed statistically significant differences between groups,
being longer in the PAF group for all filters and cutoff frequencies
studied, A bias increment of similar to 20 msec was detected in unidir
ectional and least mean square filters as compared to the bidirectiona
l filter, Sensitivity, specificity, and predictive accuracy were > 70%
for all filters; the BB40 filter yielded the best performance. Conclu
sion: The normality limits derived from one filter cannot be applied d
irectly to recordings obtained from the other filters, Critical limits
must be established individually for different software settings.