Rate responsive pacemaker adapted to adjust lower rate limit according to monitored patient blood temperature

• US 5,814,087 A
• Filed: 12/18/1996
• Issued: 09/29/1998
• Est. Priority Date: 12/18/1996
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Renirie, Alexis C. M.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/768,604
• Time in Patent Office: 650 Days
• Field of Search: 607/17, 607/18, 607/21
• US Class Current: 607/21
• CPC Class Codes: A61N 1/3655 controlled by body or blood temperature
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

A rate responsive pacemaker is provided having the capability of automatically adjusting the lower rate limit (LRL) for sleep, or nighttime. The pacemaker has a temperature sensor for determining patient blood temperature, and processes patient blood temperature data to obtain an average daily low value of nighttime blood temperature. The pacemaker monitors blood temperature to determine a drop below a threshold which is coupled to the average daily low value, as well as when the rate of temperature change exceeds a predetermined limit, these two coincident conditions suggesting onset of nighttime and/or sleep. Lower rate limit is decremented, preferably by a predetermined amount at onset of nighttime, and is automatically incremented when patient blood temperature and/or time of day indicate the end of nighttime.

Claims

1. A rate responsive pacemaker, having a controllable pulse generator for delivering pacing pulses, rate means for sensing at least one parameter containing information indicative of desired pacing rate and control means for controlling said pulse generator to deliver pacing pulses at a rate which is a function of said at least one parameter, said control means further comprising limit means for limiting rate pacing adjustment between a low rate limit (LRL) and an upper rate limit (URL), and having LRL means for adjusting said LRL, said LRL means having

a temperature sensor for determining patient blood temperature,

measure means for determining from said patient blood temperature a measure of the daily low value of said blood temperature,

means for determining a threshold temperature at a predetermined relation to said measure of daily low value,

comparison means for continually comparing said blood temperature with said threshold, and up/down adjusting means for adjusting said LRL as a function of said comparison.

2. The pacing system as described in claim 1, wherein said measure means comprises means for determining patient average daily low blood temperature.

3. The pacing system as described in claim 1, wherein said measure means comprises means for storing low temperature values over a predetermined number of days, and averaging means for cyclically determining an average daily low temperature.

4. The pacing system as described in claim 1, comprising change means for determining incremental change in blood temperature over a predetermined increment of time, and means for enabling said LRL adjustment only when said incremental temperature change over said increment of time exceeds a predetermined value.

5. The pacing system as described in claim 1, comprising means for adjusting said threshold in coupled relation to said measure of average daily low value.

6. The pacing system as described in claim 1, comprising timing means for tracking the time of day, and means for enabling said LRL adjustment downward only during a predetermined range of time during a given day.

7. The system as described in claim 1, wherein said adjusting means comprises means for adjusting said LRL downward by a predetermined increment when said blood temperature falls below said threshold.

8. The system as described in claim 1 comprising means operative after said LRL has been adjusted downward for determining when said LRL is to be readjusted upward, and for re-adjusting said LRL upward in response to a said upward determination.

9. The system as described in claim 8, wherein said upward means comprises a nighttime clock for timing out a predetermined night time duration.

10. A rate responsive pacemaker system, having a controllable pulse generator for producing and delivering pace pulses, rate means for sensing at least one parameter containing information indicative of desired pacing rate and control means for controlling the rate of delivery of pace pulses as a function of said at least one parameter, said control means further comprising limit means for limiting rate pacing adjustment to rates above a low rate limit (LRL), and having LRL means for adjusting said LRL, said LRL means further comprising:

a temperature sensor for determining patient blood temperature,

threshold means for setting a low blood temperature threshold, said threshold means comprises low temperature means for determining patient daily average low blood temperature;

temperature rate means for determining a measure of the rate of drop of patient blood temperature,

determining means for determining the occurrence when patient blood temperature has fallen below said temperature threshold and said rate of drop has exceeded a predetermined rate, and

initiating means for initiating a drop of LRL to a lower LRL when a said occurrence is determined.

11. The system as described in claim 10, wherein said LRL means comprises upward adjustment means for adjusting said LRL upward upon the occurrence of predetermined conditions while at a said lower LRL.

12. The system as described in claim 11, wherein said upward adjustment means comprises a clock for timing out a time interval corresponding to a nighttime rest interval.

13. The system as described in claim 10, wherein said low temperature means comprises means for substantially continuously updating said daily average low blood temperature.

14. The system as described in claim 13, comprising means for setting said threshold above said updated daily average low blood temperature.

15. The system as described in claim 10, further comprising clock means for determining nighttime, and said initiating means being inhibited from initiating a drop in LRL except during nighttime.