Automatic programming of rate-adaptive therapy via activity monitoring

• US 8,538,526 B2
• Filed: 12/16/2010
• Issued: 09/17/2013
• Est. Priority Date: 12/17/2009
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Stahmann, Jeffrey E., Querimit, Michael A., Hopper, Donald L., Larson, Brian Ralph, Emerson, Paul F., O'Brien, Daniel
• Primary Examiner(s): Bertram, Eric D.
• Application Number:
  US12/970,613
• Publication Number:
  US 20110152963A1
• Time in Patent Office: 1,006 Days
• Field of Search: 607/19, 607/20
• US Class Current: 607/20
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/37264 Changing the program; Upgrading firmware

Abstract

A rate-adaptive pacemaker and a method for its operation in which the response factor for a minute ventilation sensor or other type of exertion level sensor is automatically set during a parameter adjustment mode that utilizes an activity level measurement to determine when the patient is at a target activity level with which is associated an appropriate target pacing rate. In a preferred embodiment, the target activity level corresponds to casual walking (e.g., 2 mph at a 4% grade) with a target pacing rate selected as appropriate for that level of activity in the individual patient.

Claims

1. A pacemaker, comprising:

pacing circuitry for generating pacing pulses to be delivered to one or more atrial or ventricular sites;

a minute ventilation sensor for measuring minute ventilation (MV);

an activity level sensor for measuring activity level; and

,

a controller for controlling the delivery of pacing pulses in accordance with a programmed mode, wherein the controller is further programmed to;

deliver pacing pulses at a rate determined by a rate-adaptive algorithm as a function of the sensed minute ventilation, termed the sensor-indicated rate (SIR);

compute the sensor-indicated rate by mapping a measured ventilation value equaling a specified baseline minute ventilation value (BMV) to a specified minimum pacing rate, termed the lower rate limit (LRL), and mapping a measured minute ventilation value greater than the baseline minute ventilation value to a pacing rate calculated as the LRL added to the amount by which the measured minute ventilation value exceeds the baseline minute ventilation value multiplied by a rate response factor; and

,

enter a parameter adjustment mode for calculating the value of the rate response factor by;

     1) monitoring the measured activity level,

     2) when the measured activity level is maintained within a specified target activity level range for a specified length of time, measuring a corresponding target minute ventilation value (TMV), and

     3) calculating the rate response factor (RF) as;

RF=(THR−

LRL)/(TMV−

BMV)

where the target heart rate THR is a specified value corresponding to a desired pacing rate for the target activity level range and wherein the target activity level range is selected such that the TMV is less than a minute ventilation value that is mapped by the rate-adaptive algorithm to a maximum sensor-indicated rate.

2. The pacemaker of claim 1 wherein the target activity level range corresponds to the activity level of a casual walk.

3. The pacemaker of claim 1 wherein the specified length of time for the target activity level to be maintained is two minutes or greater.

4. The pacemaker of claim 1 wherein the controller is further programmed to calculate the sensor-indicated rate as function of both the measured ventilation value and the measured activity level using separate response factors.

5. The pacemaker of claim 1 wherein the controller is programmed to calculate the sensor-indicated rate according to a dual-slope rate response curve having separate response factors for lower and higher minute ventilation values.

6. The pacemaker of claim 1 wherein the controller is further programmed to increase and/or decrease the target activity level according to a predetermined sequence if the target activity level is not reached within a specified time period.

7. The pacemaker of claim 1 wherein the minute ventilation sensor is a transthoracic impedance sensor and the measured minute ventilation is an ohmic impedance signal related to true minute ventilation value by appropriate scaling.

8. The pacemaker of claim 1 wherein the controller is programmed to enter the parameter adjustment mode upon receiving a telemetry command to do so.

9. The pacemaker of claim 1 wherein the controller is programmed to enter the parameter adjustment mode at periodic intervals.

10. The pacemaker of claim 1 wherein the controller is programmed to enter the parameter adjustment mode in response to a detected condition which causes a recalibration of the baseline minute ventilation value (BMV).

11. The pacemaker of claim 1 wherein the detected condition which causes a recalibration of the baseline minute ventilation value (BMV) is a change of lead vectors used to measure thoracic impedance.

12. The pacemaker of claim 1 wherein the detected condition which causes a recalibration of the baseline minute ventilation value (BMV) is a warm reset of the pacemaker.

13. The pacemaker of claim 1 wherein the detected condition which causes a recalibration of the baseline minute ventilation value (BMV) is a shut off and turn on of the minute ventilation sensor due to a tachyarrhythmia episode.

14. The pacemaker of claim 1 wherein the activity level sensor is an accelerometer.