Time transformation of local activation times

• US 10,357,168 B2
• Filed: 03/07/2016
• Issued: 07/23/2019
• Est. Priority Date: 03/07/2016
• Status: Active Grant

• Current Assignee: APN Health, LLC
• Original Assignee: APN Health, LLC
• Inventors: Brodnick, Donald, Sra, Jasbir
• Primary Examiner(s): Abreau, Michael J D
• Application Number:
  US15/062,697
• Publication Number:
  US 20170251942A1
• Time in Patent Office: 1,233 Days
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

An automatic method of determining local activation time (LAT) from at least three multi-channel cardiac electrogram signals including a mapping channel and a plurality of reference channels. The method comprises (a) storing the cardiac channel signals, (b) using the mapping-channel signal 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 three multi-channel cardiac electrogram signals from a patient, such signals including a mapping channel and a plurality of reference channels, the method carried out during a medical procedure and comprising:

capturing, digitizing, and storing the cardiac channel signals;

using the mapping-channel signal 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,

thereby to reduce the duration of the medical procedure.

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 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.

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

5. The automatic LAT-determining method of claim 4 wherein computing a signal characteristic of a signal includes computing the frequency content of the signal.

6. The automatic LAT-determining method of claim 5 wherein computing the frequency content of the signal includes computing a fast Fourier transform for a predetermined time period of the signal.

7. The automatic LAT-determining method of claim 6 wherein the signal is segmented into a plurality of time-overlapping segment signals.

8. The automatic LAT-determining method of claim 7 wherein weightings are applied to each of the segment signals.

9. The automatic LAT-determining method of claim 8 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.

10. The automatic LAT-determining method of claim 9 wherein the computed signal characteristic is the first moment of the signal power determined from the fast Fourier transform of the signal.

11. The automatic LAT-determining method of claim 6 wherein the computed signal characteristic is the first moment of the signal power determined from the fast Fourier transform.

12. The automatic LAT-determining method of claim 5 wherein computing the frequency content of the signal includes computing a Haar transform for a predetermined time period of the signal.

13. The automatic LAT-determining method of claim 12 wherein the signal is segmented into a plurality of substantially-sequential segment signals.

14. The automatic LAT-determining method of claim 13 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.

15. The automatic LAT-determining method of claim 14 wherein the computed signal characteristic is the first moment of the signal power determined from the frequency-selective aggregate magnitudes.

16. The automatic LAT-determining method of claim 12 wherein the computed signal characteristic is the first moment of the signal power determined from the computed Haar transform.

17. The automatic LAT-determining method of claim 5 wherein computing the frequency content of the signal includes computing a Fourier transform for a predetermined time period of the signal.

18. The automatic LAT-determining method of claim 4 further including selecting the second reference-channel signal from channels which have not lost timing stability.

19. The automatic LAT-determining method of claim 18 wherein selecting the second reference-channel signal from channels which have not lost timing stability includes computing signal quality.

20. The automatic LAT-determining method of claim 4 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.

21. The automatic LAT-determining method of claim 4 wherein the computed signal characteristic is the maximum signal amplitude minus the minimum signal amplitude within a predetermined time period of the signal.

22. 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.

23. The automatic LAT-determining method of claim 22 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).

24. 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.

25. The automatic LAT-determining method of claim 24 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).

26. 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.

27. The automatic LAT-determining method of claim 26 wherein the average is computed over a predetermined number of times.