Heart rate variability as an indicator of exercise capacity

• US 20010037069A1
• Filed: 06/25/2001
• Published: 11/01/2001
• Est. Priority Date: 06/08/1998
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Spinelli, Julio C., Carlson, Gerrard M., Kadhiresan, Veerichetty A.
• Granted Patent: US 6,529,772 B2
• Time in Patent Office: Days
• US Class Current: 600/510
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/222 combined with detection or measurement of physiological parameters, e.g. heart rate
• 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 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/36592 controlled by the heart rate variability

Abstract

Based upon patient studies indices a high degree of correlation was found between HRV and VO2_max, i.e., the patient'"'"'s exercise capacity. Based on this finding, a pacing therapy optimization protocol for treating patients with CHF has been devised. The protocol involves first pacing the patient'"'"'s heart with a pacemaker programmed to operate in a first mode for a predetermined time period and then collecting electrogram data from which a HRV index is derived. The mode is then changed and the steps repeated until all possible modes have been utilized. At that time, a determination is made as to which of the modes is associated with the largest HRV index and the pacemaker is then programmed to function in that mode. Alternatively, the method of the present invention can be applied to changes in drug therapy instead of or in combination with pacing therapy. By the plotting the HRV index computed in the manner described, the efficacy of a change in therapy on patient exercise capacity can be assessed.

Claims

1. A method of indirectly assessing a patient'"'"'s maximum oxygen update (VO2_MAX) comprising the steps of:

(a) sensing and recording RR intervals from ECG waveform of a patient over a 24-hour period;

(b) determining from the recording the average length of R-to-R intervals in 288 five-minute intervals; and

(c) computing the standard deviation of the 288 averages determined in step (b) to create a HRV index correlating with VO2_MAX for the patient.

4. The method as in any one of claims 1-3 wherein the mode of cardiac therapy comprises a mode of electrical cardiac stimulation.

5. The method as in any one of claims 1-3 wherein the mode of cardiac therapy comprises a mode of drug applications.

6. The method as in any one of claims 1-3 and further including the step of creating a plot of the HRV index at fixed predetermined time intervals.

2. A method of assessing the efficacy of a given mode of cardiac therapy on a patient'"'"'s exercise capacity, comprising the steps of:

(a) applying cardiac therapy to the patient'"'"'s heart in accordance with said given mode;

(b) recording ECG waveforms from the patient over a first predetermined time period;

(c) measuring the average length of R-to-R intervals in said waveforms during a plurality of predetermined segments of the first predetermined time period;

(d) computing the standard deviation of the plurality of said segment averages to create a HRV index;

(e) repeating steps (b)-(d) at a time subsequent to said first predetermined time; and

(f) comparing the HRV index computed in step (d) associated with ECG waveforms recorded at said first predetermined time with the HRV index computed in step (d) associated with the ECG waveforms recorded at said subsequent time to determine whether the given mode of therapy improves or degrades the patient'"'"'s exercise capacity.

3. The method of

claim 2

and further including the step of:

(g) changing the mode of cardiac therapy so as to cause an increase in the HRV index computed in step (d) associated with the ECG waveforms recorded at said subsequent time over the HRV index computed in step (d) associated with the ECG waveforms recorded at said first time.

7. A method of optimizing a mode of therapy applied to a patient, comprising the steps of:

(a) measuring and recording ECG waveforms over a predetermined time interval at a first point in time;

(b) computing from said ECG waveforms the absolute value of the difference in the length of successive RR intervals;

(c) plotting a two-dimensional histogram of the values computed in step (b) vs. RR intervals;

(d) measuring the area subtended by the plot of step (c) as an indicator of a patient'"'"'s exercise capacity;

(e) subsequently changing the mode of therapy applied to the patient;

(f) repeating steps (a) through (d) at a later time;

(g) plotting a value of the area measured in step (d) at the first point in time and at the later time to display trends in the patient'"'"'s exercise capacity;

(h) comparing the area measured in step (d) at the first point in time to the area measured in step (d) at the later time to assess which area is the greater; and

(i) adjusting the mode of therapy to increase the patient'"'"'s exercise capacity.