Implantable medical device responsive to heart rate variability analysis

• US 20020072683A1
• Filed: 10/15/2001
• Published: 06/13/2002
• Est. Priority Date: 12/11/1995
• Status: Active Grant

• Current Assignee: Andre G. Routh, David Prutchi, Edward A. Schroeppel
• Original Assignee: Andre G. Routh, David Prutchi, Edward A. Schroeppel
• Inventors: Schroeppel, Edward A., Prutchi, David, Routh, Andre G.
• Granted Patent: US 6,571,121 B2
• Time in Patent Office: Days
• US Class Current: 600/515
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/36592 controlled by the heart rate variability
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

A method and apparatus for evaluating heart rate variability of the heart of a person in order to forecast a cardiac event A cardiac stimulator receives heart beat signals from the heart and determines a measurement of heart rate variability based on statistical data derived from the heart beat signals and sensing data derived from a sensor. This measurement of heart rate variability is compared with previously stored heart rate variability zones defining normal and abnormal heart rate variability. These zones are modifiable after the occurrence of a cardiac event. Once a cardiac event is detected, a pathway is computed which extends from a generally normal heart rate variability condition to an abnormal heart rate variability condition. Subsequent measurements of heart rate variability are compared with this pathway. Selective therapy regimes are initiated depending on the measurement of heart rate variability.

Claims

1. A method for evaluating heart rate variability of the heart of a patient, comprising the steps of:

receiving a plurality of heart beat signals from said heart for each of a plurality of epochs;

computing a measurement of heart rate variability for each of said epochs;

defining an abnormal heart rate variability zone to include a first measurement of heart rate variability from a corresponding first epoch if said heart exhibits a cardiac anomaly during said first epoch; and

comparing said abnormal heart rate variability zone with said measurements of heart rate variability occurring after said first epoch.

2. The method of claim 1 further comprising the step of modifying said abnormal heart rate variability zone to further include a series of successive measurements of heart rate variability occurring before and leading to said first epoch.

3. The method of claim 2 further comprising the steps of:

creating a pathway along said series of successive measurements;

modifying said abnormal heart rate variability zone to include said pathway; and

comparing said modified abnormal heart rate variability zone with said measurements of heart rate variability occurring after said first-epoch.

4. The method of claim 3 in which said pathway is expanded to include a tolerance zone.

5. The method of claim 4 in which said tolerance zone expands said pathway about fifteen percent.

6. The method of claim 1 in which said heart beat signals for said first epoch and said first measurement of heart rate variability are stored in permanent memory if said heart of said patient exhibits said cardiac anomaly.

7. The method of claim 1 further comprising the step of modifying said abnormal heart rate variability zone if said heart of said patient exhibits another cardiac anomaly after said first epoch.

8. The method of claim 1 in which said measurements of heart rate variability occurring after said first epoch are stored in permanent memory when said measurements of heart rate variability are within said abnormal heart rate variability zone.

9. The method of claim 1 further comprising the step of expanding said first measurement of heart rate variability to include a tolerance zone.

10. The method of claim 1 in which said cardiac anomaly is an abnormal fluctuation of sinus rhythm of said heart beat signals.

11. The method of claim 1 in which said cardiac anomaly is one of arrhythmia, dysrhythmia, fibrillation, tachycardia, bradycardia, flutter, myocardial infarction, and heart disease.

12. The method of claim 1 in which said step of computing said measurement of heart rate variability further comprises the step of computing one of mean absolute deviation, standard deviation, measure of central tendency, and range.

14. The method of claim 13 further comprising the steps of:

receiving a second series of heart beat signals from the heart of said patient during a second time period occurring after said first time period;

computing said second heart beat signals into a second measurement of heart rate variability; and

comparing said second measurement of heart rate variability with said modified abnormal heart rate variability zone if said patient exhibits said cardiac anomaly during said first time period, otherwise comparing said second measurement of heart rate variability with said abnormal heart rate variability zone.

15. The method of claim 14 further comprising the step of further modifying said modified abnormal heart rate variability zone to include said second measurement of heart rate variability if the heart of said patient exhibits another cardiac anomaly during said second time period.

16. The method of claim 13 further comprising the steps of:

defining said abnormal heart rate variability zone to include a plurality of abnormal heart rate variability subzones;

designating a therapy regime for each of said subzones;

comparing said first measurement of heart rate variability with each of said subzones; and

initiating one of said therapy regimes if one of said subzones includes said first measurement of heart rate variability.

17. The method of claim 13 in which said first measurement of heart rate variability is derived from statistical data derived from said heart beat signals and sensing data derived from sensor measurements.

18. The method of claim 17 in which:

said statistical data includes one of a measure of central tendency and a measure of deviation; and

said sensor measures one of;

evoked QT intervals, respiration, stroke volume, central venous oxygen saturation, right ventricular pressure, blood pressure, impedance, muscle noise, acceleration, activity, temperature, blood pH, and adrenaline.

19. The method of claim 13 in which said cardiac anomaly is an abnormal fluctuation of sinus rhythm of said heart beat signals.

20. The method of claim 13 further comprising the steps of:

storing in memory said abnormal heart rate variability zone;

modifying said abnormal heart rate variability zone to include said first measurement of heart rate variability when said first measurement of heart rate variability is outside limits of said abnormal heart rate variability zone; and

storing in memory said modified abnormal heart rate variability zone.

13. A method for evaluating cardiac sinus rhythm of a patient, comprising the steps of:

defining an abnormal heart rate variability zone for said patient;

receiving a first series of heart beat signals from the heart of said patient during a first time period;

computing said heart beat signals into a first measurement of heart rate variability;

comparing said first measurement of heart rate variability with said abnormal heart rate variability zone; and

modifying said abnormal heart rate variability zone to include said first measurement of heart rate variability if the heart of said patient exhibits a cardiac anomaly during said first time period.