Multi-channel cardiac measurements

• US 8,768,440 B1
• Filed: 05/06/2013
• Issued: 07/01/2014
• Est. Priority Date: 03/15/2013
• 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:
  US13/888,070
• Time in Patent Office: 421 Days
• Field of Search: 600/509
• US Class Current: 600/509
• CPC Class Codes: A61B 2505/05 Surgical care
• CPC Class Codes: A61B 2562/04 Arrangements of multiple sensors of the same type
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence

Abstract

An automatic method of determining local activation time (LAT) in multi-channel cardiac electrogram signals including at least two cardiac channels, one of the cardiac channels being a mapping channel and another cardiac channel being a reference channel, the method comprising: (a) estimating a cycle length CL in the reference channel; (b) determining a mapping-channel fiducial time t_M in the mapping channel signal; (c) determining a plurality of reference-channel fiducial times t_R; (d) computing adjusted reference-channel fiducial times t_RA by adding or subtracting multiples of cycle length CL to each time t_R such that each time t_RA is within a time window of length CL surrounding mapping-channel fiducial time t_M; (e) computing a single final reference-channel fiducial time t_RF from the plurality of adjusted reference-channel fiducial times t_RA; and (f) computing the LAT as t_M minus t_RF.

Claims

1. An automatic method of determining local activation time (LAT) in multi-channel cardiac electrogram signals including at least two cardiac channels, one of the cardiac channels being a mapping channel and another cardiac channel being a reference channel, the method comprising:

(a) estimating a cycle length CL in the reference channel;

(b) determining a mapping-channel fiducial time t_M in the mapping channel signal;

(c) determining a plurality of reference-channel fiducial times t_R;

(d) computing adjusted reference-channel fiducial times t_RA by adding or subtracting multiples of cycle length CL to each time t_R such that each time t_RA is within a time window of length CL surrounding mapping-channel fiducial time t_M;

(e) computing a single final reference-channel fiducial time t from the plurality of adjusted reference-channel fiducial times t_RA; and

(f) computing the LAT as t_M minus t_RF.

2. The automatic LAT-determination method of claim 1 wherein the time window of length CL surrounding t_M spans ±

CL/2 of t_M.

3. The automatic LAT-determination method of claim 1 wherein the adjusted reference-channel fiducial times t_RA used to compute final reference-channel fiducial time t are a subset of the plurality of adjusted reference-channel fiducial times t_RA.

4. The automatic LAT-determination method of claim 3 wherein computing a single final reference-channel fiducial time t_RF comprises the steps of:

computing an average av_RA of the subset;

including av_RA in the subset; and

setting the final reference-channel fiducial time t to the median of the subset.

5. The automatic LAT-determination method of claim 4 wherein the median of the subset is the set-member median.

6. The automatic LAT-determination method of claim 1 wherein the adjusted fiducial times t_RA are a set of adjusted fiducial times and computing a single final reference-channel fiducial time t_RF comprises the steps of:

computing an average av_RA of the set;

including av_RA in the set; and

setting the final reference-channel fiducial time t to the median of the set.

7. The automatic LAT-determination method of claim 6 wherein the median of the set is the set-member median.

8. The automatic LAT-determination method of claim 1 wherein the mapping-channel fiducial time t_M is at a time of maximum negative velocity of the mapping-channel signal.

9. The automatic LAT-determination method of claim 1 wherein the reference-channel fiducial times t_R are at times of maximum negative velocity of the reference-channel signal.

10. The automatic LAT-determination method of claim 1 further including repeating steps (a) through (f) to generate a plurality of LAT values and displaying the plurality of LAT values as an LAT map.

11. The automatic LAT-determination method of claim 1 wherein computing a single final reference-channel fiducial time t_RF from the plurality of adjusted reference-channel fiducial times t_RA includes ordering the plurality of adjusted reference-channel fiducial times t_RA and using a subset of times t_RA to compute final reference-channel fiducial time t_RF.

12. The automatic LAT-determination method of claim 11 wherein the subset of times t_RA is the interquartile set of times t_RA.

13. The automatic LAT-determination method of claim 12 wherein the final reference-channel fiducial time t_RF is the median of the set.

14. The automatic LAT-determination method of claim 13 wherein the median of the interquartile set is the set-member median.

15. The automatic LAT-determination method of claim 1 further including computing a confidence interval for the determined LAT.

16. The automatic LAT-determination method of claim 15 wherein computing an LAT confidence interval comprises:

computing an intermediate LAT value as LAT=t_M−

t_RA for each of the plurality of adjusted reference-channel fiducial times t_RA, the intermediate LAT values comprising a set of values;

selecting the highest and lowest intermediate LAT values in the set; and

computing the confidence interval as ±

a fraction of the difference between the highest and lowest intermediate LAT values.

17. The automatic LAT-determination method of claim 16 wherein the fraction of the difference is one-half.

18. The automatic LAT-determination method of claim 16 wherein the set is a subset of the intermediate LAT values.

19. The automatic LAT-determination method of claim 18 wherein the fraction of the difference is one-half.

20. The automatic LAT-determination method of claim 1 wherein estimating a cycle length CL in the reference channel comprises:

digitizing the reference-channel signal over a first preset time window;

filtering the reference-channel signal to generate a reference-channel absolute-value velocity signal;

autocorrelating the reference-channel absolute-value velocity signal; and

selecting a peak value of the autocorrelation and setting the cycle length CL as the lag at the peak.

21. The automatic LAT-determination method of claim 20 further including determining a CL confidence interval by setting a lag value L2 as the lag at a second autocorrelation peak near twice CL and setting the CL confidence interval at ±

(L2−

2CL).