Rate-adaptive pacemaker with compensation for long-term variations in average exertion level

• US 7,155,280 B2
• Filed: 11/01/2002
• Issued: 12/26/2006
• Est. Priority Date: 11/01/2002
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Harris, Zoe, Ni, Quan, Daum, Douglas R.
• Primary Examiner(s): Evanisko, George R.
• Assistant Examiner(s): ALTER, ALYSSA MARGO
• Application Number:
  US10/286,379
• Publication Number:
  US 20040088016A1
• Time in Patent Office: 1,516 Days
• Field of Search: 607 17- 27
• US Class Current: 607/19
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

A rate-adaptive pacemaker is disclosed in which a sensor-indicated rate is calculated by adding a function of the measured exertion level to a programmed lower rate limit. In the case where the function of the measured exertion level is the difference between a short-term average and a long-term average of the measured exertion level, the lower rate limit is modulated as a function of the long-term average of the measured exertion level and maximum and minimum values of the long-term average of the measured exertion level during a defined extended time period.

Claims

1. A cardiac pacemaker, comprising:

a pacing channel for delivering pacing pulses to a heart;

an exertion level sensor for measuring a patient'"'"'s exertion level;

a controller for controlling the delivery of pacing pulses through the pacing channel in accordance with a programmed mode, wherein the controller is programmed to pace a heart chamber in a demand mode at a sensor-indicated rate equal to a lower rate limit plus a function of the measured exertion level multiplied by a rate-response factor;

wherein the controller is further programmed to compute the function of the measured exertion level as the amount, if any, by which a short-term average of the measured exertion level exceeds a long-term average of the measured exertion level; and

,

wherein the controller is further programmed to modulate the lower rate limit as a function of the long-term average of the measured exertion level and the maximum and minimum values of the long-term average of the measured exertion level during a defined extended time period, wherein the controller is programmed to modulate the lower rate limit according to the following formula;

LRL=LRL_min+(LRL_max−

LRL_min)*(EXL_lta−

EXL_ltaMin)/(EXL_ltaMax−

EXL_ltaMin)

where LRL is the lower rate limit to be used by the pacemaker, LRL_min and LRL_max are programmed minimum and maximum values, respectively, for the LRL, EXL_lta is the long-term average of the measured exertion level, EXL_ltaMin is the minimum value of EXL_lta during the defined extended time period, and EXL_ltaMax is the maximum value of EXL_lta during the defined extended time period.

2. The pacemaker of claim 1 wherein the controller is programmed such that the defined extended time period is 24 hours, the long-term average of the measured exertion level is computed over a period of 2 hours, and the short-term average of the measured exertion level is computed over a period of 30 seconds.

3. The pacemaker of claim 1 wherein the exertion level sensor is a minute ventilation sensor for measuring a patient'"'"'s minute ventilation.

4. The pacemaker of the claim 1 wherein the exertion level sensor is a minute ventilation sensor for measuring minute ventilation in a patient.

5. The pacemaker of claim 4 wherein the controller is programmed such that the defined extended time period is 24 hours, the long-term and short-term averages of the measured exertion level are computed over periods of 2 hours and 30 seconds, respectively, and the controller is programmed to modulate the lower rate limit according to the following formula:

LRL=LRL_min+(LRL_max−

LRL_min)*(MV_2h−

MV_2hMin)/(MV_2hMax−

MV_2hMin)

where LRL is the lower rate limit to be used by the pacemaker, LRL_min and LRL_max are programmed minimum and maximum values, respectively, for the LRL, MV_2h is the 2 hour average of the measured minute ventilation, MV_2hMin is the minimum value of MV_2h during the 24 hour time period, and MV_2hMax is the maximum value of MV_2h during the 24 hour time period.

6. The method of claim 1 wherein the measured exertion level is a patient'"'"'s minute ventilation.

7. The method of claim 6 wherein the defined extended time period is 24 hours, the long-term and short-term averages of the measured exertion level are computed over periods of 2 hours and 30 seconds, respectively, and the lower rate limit is modulated according to the following formula:

LRL=LRL_min+(LRL_max−

LRL_min)*(MV_2h−

MV_2hMin)/(MV_2hMax−

MV_2hMin)

where LRL is the lower rate limit to be used by the pacemaker, LRL_min and LRL_max are programmed minimum and maximum values, respectively, for the LRL, MV_2h is the 2 hour average of the measured minute ventilation, MV_2hMin is the minimum value of MV_2h during the 24 hour time period, and MV_2hMax is the maximum value of MV_2h during the 24 hour time period.

8. A method for operating a cardiac pacemaker, comprising:

delivering pacing pulses to a heart chamber in a demand mode at a sensor-indicated rate equal to a lower rate limit plus a function of a measured exertion level multiplied by a rate-response factor;

computing the function of the measured exertion level as the amount, if any, by which a short-term average of the measured exertion level exceeds a long-term average of the measured exertion level; and

,

modulating the lower rate limit as a function of the long-term average of the measured exertion level and maximum and minimum values of the long-term average of the measured exertion level during a defined extended time period, wherein the lower rate limit is modulated according to the following formula;

LRL=LRL_min+(LRL_max−

LRL_min)*(EXL_lta−

EXL_ltaMin)/(EXL_ltaMax−

EXL_ltaMin)

where LRL is the lower rate limit to be used by the pacemaker, LRL_min and LRL_max are programmed minimum and maximum values, respectively, for the LRL, EXL_lta is the long-term average of the measured exertion level, EXL_ltaMin is the minimum value of EXL_lta during the defined extended time period, and EXL_ltaMax is the maximum value of EXL_lta during the defined extended time period.

9. The method of claim 8 wherein the defined extended time period is 24 hours, the long-term average of the measured exertion level is computed over a period of 2 hours, and the short-term average of the measured exertion level is computed over a period of 30 seconds.

10. The method of claim 8 wherein the measured exertion level is a patient'"'"'s minute ventilation.