Signal evaluation method for detecting QRS complexes in electrocardiogram signals

• US 20020058878A1
• Filed: 03/12/2001
• Published: 05/16/2002
• Est. Priority Date: 03/10/2000
• Status: Active Grant

• Current Assignee: Biotronik Mess-Und Therapiegeraete GmbH & Company Ingenieurbuero Berlin (Biotronik SE & Company KG)
• Original Assignee: Biotronik Mess-Und Therapiegeraete GmbH & Company Ingenieurbuero Berlin (Biotronik SE & Company KG)
• Inventors: Kohler, Bert-Uwe, Orglmeister, Reinhold
• Granted Patent: US 6,625,484 B2
• Time in Patent Office: Days
• US Class Current: 600/521
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/346 Analysis of electrocardiograms
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A signal evaluation method for detecting QRS complexes in electrocardiogram signals incorporates the following process steps:

sampling of the signal (4) and conversion to discrete signal values (x(n)) in chronological order,

determining the sign of each signal value (x(n)),

continuous checking of the signs of consecutive signal values (x(n)) for the presence of a zero crossing between two consecutive signal values (x(n)),

determining the number (D(n)) of zero crossings in a defined segment (N) of the consecutive signal values (x(n)), and

comparing the determined number of zero crossings (D(n)) to a defined threshold value, wherein an undershoot of the threshold value signifying the presence of a QRS complex (5, 6, 7) in the defined segment of the signal curve (4).

FIG. 2

Claims

1. A signal evaluation method for detecting QRS complexes in electrocardiogram (ECG) signals (4), comprising the following process steps:

sampling of the signals (4) and conversion to discrete signal values (x(n)) in chronological order,

determining the sign of each signal value (x_f(n)),

continuous checking of the signs of consecutive signal values (x_f(n)) for a presence of a zero crossing between two consecutive signal values (x_f(n)),

determining a number (D(n)) of zero crossings in a defined segment (N) of the consecutive signal values (x_f(n)), and

comparing the determined number of zero crossings (D(n)) to a defined threshold value, wherein an undershoot of the threshold value is significant for a presence of a QRS complex (5, 6, 7) in a defined segment of the signal curve (4).

2. A signal evaluation method according to claim 1, wherein after the sampling, the ECG signal values (x(n)) are subjected to a high-pass filtering.

3. A signal evaluation method according to claim 1, wherein after the sampling, the ECG signal values (x(n)) are subjected to a band-pass filtering (BP).

4. A signal evaluation method according to claim 3, wherein the lower and upper pass frequencies (f_g1, f_g2) of the band pass filtering (BP) are approximately 18 Hz and 27 Hz, respectively.

5. A signal evaluation method according to claim 1, wherein the signal values (x_f(n)) are squared prior to checking them for zero crossings and determining the number of zero crossings (D(n)), while maintaining their respective signs.

6. A signal evaluation method according to claim 3, wherein a high-frequency overlay signal (b(n)) with an amplitude (K(n)) that is low in comparison to an amplitude of the QRS complex (5, 6, 7) is added to the band-pass filtered and squared ECG signal (x_fq(n)) prior to the sampling.

7. A signal evaluation method according to claim 6, wherein a value of the amplitude (K(n)) of the high-frequency overlay signal (b(n)) is adaptively determined from a flowing detection of the average of the band-pass filtered and squared signal values (x_fq(n)) over a defined averaging period (P).

8. A signal evaluation method according to claim 5, wherein the addition of the high-frequency overlay signal (b(n)) is paused when a QRS complex (5, 6, 7) is detected.

9. A signal evaluation method according to claim 1, wherein the threshold value of the number of zero crossings signifying a QRS complex (5, 6, 7) is variably adjusted as an adaptive threshold from quantiles of a frequency distribution (f(m)) of the number of zero crossings itself.

10. A signal evaluation method according to claim 4, wherein a maximum of the band-pass filtered and squared signal values (x_fq(n)) is determined in a search interval around a starting point of a QRS complex (5, 6, 7) to determine the time of an occurrence of the R spike (5).

11. A signal evaluation method according to claim 1, wherein an estimated useful signal strength (P_QRS) and an estimated interfering signal strength (P_Noise) are determined from the signal values (x_fq(n)) and a detection strength (DS) signifying the presence of at least one of an interference signal and useful signal is determined from same.