Method and apparatus for detection and monitoring of T-wave alternans

• US 20060116592A1
• Filed: 07/21/2005
• Published: 06/01/2006
• Est. Priority Date: 12/01/2004
• Status: Abandoned Application

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Gillberg, Jeffrey M., Zhou, Xiaohong, Mullen, Thomas J., Stadler, Robert W.
• Application Number:
  US11/186,552
• Publication Number:
  US 20060116592A1
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/355 Detecting T-waves
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/37258 Alerting the patient

Abstract

A system and method are provided for assessing T-wave alternans (TWA) using cardiac EGM signals received from implanted electrodes. A T-wave signal parameter is measured from signals received by an automatic gain control sense amplifier. A TWA measurement is computed from a beat-by-beat comparison of T-wave parameter measurements or using frequency spectrum techniques. The TWA measurement magnitude and measurement conditions are used in detecting a clinically important TWA. TWA assessment further includes discriminating concordant and discordant TWA in a multi-vector TWA assessment, and determining the association of a TWA measurement with QRS alternans, mechanical alternans, and other physiological events. A prediction of a pathological cardiac event is made in response to a TWA assessment. A response to a cardiac event prediction is provided.

Claims

1. A method of determining a cardiac event in a medical device, comprising:

acquiring a cardiac EGM signal from implanted electrodes;

defining a T-wave measurement window to be applied to the EGM signals relative to each cardiac cycle;

measuring a T-wave parameter within the T-wave measurement window for a plurality of cardiac cycles to generates a plurality of measured T-wave signals;

determining a T-wave alternans consistency in response to the plurality of measured T-wave signals; and

determining whether a T-wave signal of the plurality of measured T-wave signals is greater than a predetermined threshold.

2. The method of claim 1, wherein the predetermined threshold corresponds to a range between approximately 30 uV and 50 uV.

3. The method of claim 1, wherein the predetermined threshold is approximately equal to 36 uV.

4. The method of claim 1, wherein determining a T-wave alternans consistency comprises:

generating a matrix of the measured T-wave signals;

computing a T-wave alternans measurement from the generated matrix; and

determining the T-wave alternans consistency in response to the computed T-wave alternans measurement.

5. The method of claim 1, wherein acquiring the cardiac EGM signal comprises automatically adjusting a sense amplifier gain responsive to a voltage amplitude measured during a T-wave signal.

6. The method of claim 1, wherein defining the T-wave measurement window comprises measuring any of a QRS width, an S-T interval duration and a Q-T interval duration.

7. The method of claim 1, wherein the measured T-wave parameter is a T-wave signal voltage amplitude.

8. The method of claim 4, wherein generating a matrix of the T-wave parameter measurements, comprises:

labeling consecutive T-waves in an alternating “

A-B-A-B”

pattern, and

storing the T-wave parameter measurements made for the plurality of cardiac cycles according to the “

A”

or “

B”

label of the respective T-wave for which the T-wave parameter measurement was made.

9. The method of claim 8, wherein determining the T-wave alternans consistency comprises computing a difference between the “

A”

labeled T-wave parameter measurements and the “

B”

labeled T-wave parameter measurements.

10. The method of claim 1, wherein determining the T-wave alternans consistency comprises one of determining a frequency of phase reversals in differences computed between consecutive pairs of measured T-wave signals of the plurality of measured T-wave signals, determining the frequency of premature contractions in the acquired cardiac EGM signal, determining an effect of a respiration signal on the plurality of measured T-wave signals, and determining a frequency of T-wave signal artifacts in the acquired cardiac EGM signal.

11. The method of claim 1, further comprising:

measuring a heart rate associated with the plurality of measured T-wave signals; and

comparing the heart rate to a predetermined heart rate threshold.

12. The method of claim 1, further comprising:

determining a cardiac event in response to the determining a T-wave alternans consistency the determining whether a T-wave signal of the plurality of measured T-wave signals is greater than the predetermined threshold; and

performing one of controlling a preventative therapy and generating an alarm.

13. The method of claim 12 wherein controlling a preventive therapy corresponds to one of delivering overdrive pacing, delivering neurostimulation, delivering a drug, deactivating delivery of a therapy, controlling delivery of an extra systolic stimulation therapy, and adjusting a therapy delivery control parameter.

14. The method of claim 1, further comprising:

sensing a physiological signal;

determining a correlation between the physiological signal and the measurement of T-wave alternans.

15. A medical device, comprising:

a plurality of electrodes adapted for implantation in a patient'"'"'s body for sensing cardiac EGM signals to sense a plurality of T-wave signals during a plurality of cardiac cycles; and

a microprocessor determining a T-wave alternans consistency in response to the plurality of T-wave signals and determining whether a T-wave signal of the plurality of T-wave signals is greater than a predetermined threshold.

16. The medical device of claim 15, wherein the predetermined threshold corresponds to a range between approximately 30 uV and 50 uV.

17. The medical device claim 15, wherein the predetermined threshold is approximately equal to 36 uV.