Time transformation of local activation times

• US 9,314,179 B1
• Filed: 09/25/2014
• Issued: 04/19/2016
• Est. Priority Date: 09/25/2014
• Status: Active Grant

• Current Assignee: APN Health, LLC
• Original Assignee: APN Health, LLC
• Inventors: Brodnick, Donald, Sra, Jasbir
• Primary Examiner(s): Wieland, Robert N
• Application Number:
  US14/497,162
• Publication Number:
  US 20160089048A1
• Time in Patent Office: 572 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/333 Recording apparatus specially adapted therefor
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7257 using Fourier transforms

Abstract

An automatic method of determining local activation time (LAT) from at least four multi-channel cardiac electrogram signals including a ventricular channel, a mapping channel and a plurality of reference channels. The method comprises (a) storing the cardiac channel signals, (b) using the ventricular and mapping channel signals and a first reference channel signal to compute LAT values at a plurality of mapping-channel locations, (c) monitoring the timing stability of the first reference channel signal, and (d) if the timing stability of the monitored signal falls below a stability standard, using the signal of a second reference channel to determine LAT values. Substantial loss of LAT values is avoided in spite of loss of timing stability.

Claims

1. An automatic method of determining local activation time (LAT) from at least four multi-channel cardiac electrogram signals including a ventricular channel, a mapping channel and a plurality of reference channels, the method comprising:

storing the cardiac channel signals;

using the ventricular and mapping channel signals and a first reference channel signal to compute LAT values at a plurality of mapping-channel locations;

monitoring the timing stability of the first reference channel signal; and

if the timing stability of the monitored signal falls below a timing-stability standard, using a second reference channel signal to determine LAT values and avoid substantial loss of LAT values in spite of loss of timing stability.

2. The automatic LAT-determining method of claim 1 further including computing one or more timing offsets using pairs of the plurality of reference channel signals, a timing offset being LAT_K(J), the local activation time of a reference channel J based on a reference channel K and used to transform an LAT value based on reference channel J to an LAT value based on reference channel K.

3. The automatic LAT-determining method of claim 2 wherein using the second reference channel signal to determine LAT values includes transforming future LAT values such that they are based on the first reference channel.

4. The automatic LAT-determining method of claim 3 wherein:

LAT₂(M) is a future LAT value of mapping channel M based on the second reference channel; and

future transformed values LAT₁(M) of mapping channel M based on the first reference channel are equal to a timing offset LAT₁(2) plus LAT₂(M).

5. The automatic LAT-determining method of claim 2 wherein using the second reference channel signal to determine LAT values includes transforming past LAT values such that they are based on the second reference channel.

6. The automatic LAT-determining method of claim 5 wherein:

LAT₁(M) is a past LAT value of mapping channel M based on the first reference channel; and

past transformed values LAT₂(M) of mapping channel M based on the second reference channel are equal to a timing offset LAT₂(1) plus LAT₁(M).

7. The automatic LAT-determining method of claim 2 wherein the one or more timing offsets are computed at a plurality of times, and the value of each timing offset is replaced with its average over the plurality of times.

8. The automatic LAT-determining method of claim 7 wherein the average is computed over a predetermined number of times.

9. The automatic LAT-determining method of claim 2 wherein monitoring the timing stability of the first reference channel signal includes monitoring multiple timing offsets LAT₁(X) where X represents the channels with which timing offsets with the first reference channel are computed.

10. The automatic LAT-determining method of claim 9 further including computing a signal characteristic for the plurality of reference channels and determining therefrom which one or more channels among these reference channels has/have not lost timing stability.

11. The automatic LAT-determining method of claim 10 further including selecting the second reference channel signal from channels which have not lost timing stability.

12. The automatic LAT-determining method of claim 11 wherein selecting the second reference channel signal from channels which have not lost timing stability includes computing signal quality.

13. The automatic LAT-determining method of claim 10 wherein computing a signal characteristic of a signal includes computing the frequency content of the signal.

14. The automatic LAT-determining method of claim 13 wherein computing the frequency content of the signal includes computing a Fourier transform for a predetermined time period of the signal.

15. The automatic LAT-determining method of claim 13 wherein computing the frequency content of the signal includes computing a fast Fourier transform for a predetermined time period of the signal.

16. The automatic LAT-determining method of claim 15 wherein the computed signal characteristic is the first moment of the signal power determined from the fast Fourier transform.

17. The automatic LAT-determining method of claim 15 wherein the signal is segmented into a plurality of time-overlapping segment signals.

18. The automatic LAT-determining method of claim 17 wherein weightings are applied to each of the segment signals.

19. The automatic LAT-determining method of claim 18 wherein computing the fast Fourier transform of the signal includes (a) computing a signal-segment fast Fourier transform for each segment signal and (b) averaging each such signal-segment fast Fourier transform to form the fast Fourier transform of the signal.

20. The automatic LAT-determining method of claim 19 wherein the computed signal characteristic is the first moment of the signal power determined from the fast Fourier transform of the signal.

21. The automatic LAT-determining method of claim 13 wherein computing the frequency content of the signal includes computing a Haar transform for a predetermined time period of the signal.

22. The automatic LAT-determining method of claim 21 wherein the computed signal characteristic is the first moment of the signal power determined from the computed Haar transform.

23. The automatic LAT-determining method of claim 21 wherein the signal is segmented into a plurality of substantially-sequential segment signals.

24. The automatic LAT-determining method of claim 23 wherein computing the Haar transform of the signal includes (a) computing Haar transform coefficients for each segment signal, (b) computing absolute values of the coefficients, (c) computing a set of frequency-selective aggregate magnitudes for each segment signal by summing signal-segment Haar transform coefficients having like time scales, and (d) averaging the sets of frequency-selective aggregate magnitudes to form a single set of frequency-selective aggregate magnitudes for the signal.

25. The automatic LAT-determining method of claim 24 wherein the computed signal characteristic is the first moment of the signal power determined from the frequency-selective aggregate magnitudes.

26. The automatic LAT-determining method of claim 10 wherein the computed signal characteristic is the fraction of time within a predetermined time period of the signal at which the absolute value of signal velocity is above a predetermined threshold.

27. The automatic LAT-determining method of claim 10 wherein the computed signal characteristic is the maximum signal amplitude minus the minimum signal amplitude within a predetermined time period of the signal.