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1. (WO1993016756) PACEMAKER A CARACTERISTIQUE D'HYSTERESIS ADAPTABLE
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What is claimed is:
1. In a pacemaker having a programmable lower rate and upper rate, a programmable lower hysteresis rate (LRH) corresponding to a lower rate hysteresis interval (LRHI), and a programmable intermediate pacing rate (IR) the
improvement comprising:
A. means for measuring the rate of change MAVG of
successive cardiac intrinsic escape intervals;
B. means for comparing MAVG to a first predefined
limit SL1;
C. means for comparing the last intrinsic escape
interval to the lower rate hysteresis interval
(LRHI); and
D. means for stimulating at the lower rate hysteresis (LRH) and for gradually incrementing the pacing
rate until it reaches the intermediate pacing rate (IR) if the last intrinsic escape interval is
longer than the lower rate hysteresis interval
(LRHI) and if said MAVG is greater than SL1.

2. The pacemaker according to claim 1 further
including:
A. time counter means for maintaining continuous
pacing at the intermediate rate (IR) for a
predefined period of time; and B. means for allowing gradual decay of the pacing
rate after said selected period of time has
lapsed.

3. The pacemaker according to claim 1, wherein said means for measuring the rate of change MAVG includes:
A. means for measuring intervals between two
successive ventricular depolarizations (RR
intervals); and
B. means for averaging the rate of change MAVG of
said successive RR intervals.

4. The pacemaker according to claim 3, wherein said means for averaging the rate of change of said RR intervals includes:
A. means for calculating the difference D between two successive RR intervals;
B. means for comparing the value of said difference D to a predetermined reference value;
C. means for storing those values of D which are
greater than said reference value;
D. means for calculating the sum M of N stored values of D, wherein N is a predetermined positive
integer; and
E. means for setting MAVG equal to M .

5. The pacemaker according to claim 4, wherein said means for averaging MAVG includes means for averaging the values of D greater than said reference value over a
predefined period of time.

6. The pacemaker according to claim 5, wherein said reference value is zero, and wherein only positive values of D are stored and added.

7. The pacemaker according to claim 3, further includes means for comparing MAVG to a second predetermined limit SL2 having a value greater than that of SL1.

8. The pacemaker according to claim 7, wherein said means for stimulating gradually increments the pacing rate until it reaches the intermediate pacing rate (IR), if the last intrinsic escape interval RRN is longer than LRHI, and if MAVG is greater than or equal to SL1 but less than or equal to SL2.

9. The pacemaker according to claim 4, wherein N is set equal to six beats.

10. The pacemaker according to claim 2, wherein said selected programmable time is set equal to five minutes.

11. The pacemaker according to claim 3, further including means for inhibiting stimulation if MAVG is less than SL1, and if the last intrinsic escape interval RRN is less than or equal to LRHI.

12. The pacemaker according to claim 11, further including means for stimulating at the lower rate if MAVG is less than SL1, and if the RRN interval will be greater than LRHI.

13. The pacemaker according to claim 7, further including means for inhibiting stimulation if MAVG is greater than SL2, and if the RRN interval is less than or equal to LRHI.

14. The pacemaker according to claim 13, further including means for stimulating at the lower rate if MAVG is greater than SL2, and if the RRN interval will be longer than LRHI.

15. The pacemaker according to claim 13, further including:
A. means for inhibiting stimulation if MAVG is
greater than SL2, and if the RRN interval is less than or equal to LRH; and B. means for stimulating at the lower rate if MAVG is greater than SL2, and if the RRN interval will be
longer than LRHI.

16. Method for pacing with a pacemaker having a programmable lower rate and upper rate, a programmable lower hysteresis rate (LRH) corresponding to a lower rate
hysteresis interval (LRHI), and a programmable intermediate pacing rate (IR), the pacing method comprising the steps of:

A. measuring the rate of change MAVG of successive
intrinsic escape intervals;
B. comparing MAVG to a first predetermined limit SL1;

C. comparing said last intrinsic escape interval to
the lower rate hysteresis interval (LRHI); and
D. stimulating at the lower rate hysteresis (LRH) and gradually incrementing the pacing rate until it
reaches the intermediate pacing rate (IR) if the
RRN interval will be longer than the lower rate
hysteresis interval (LRHI) and if said MAVG is
greater than SL1.

17. The pacing method according to claim 16 further including the steps of:
A. maintaining continuous pacing at the intermediate rate (IR) for a predefined period of time; and B. allowing gradual decay of the pacing rate after
said selected period of time has lapsed.

18. The pacing method according to claim 17, wherein said step of measuring the rate of change MAVG includes:
A. measuring intervals between two successive
ventricular depolarizations (RR intervals); and
B. averaging the rate of change MAVG of said
successive RR intervals;

19. The pacing method according to claim 18, wherein said step of averaging the rate of change of said RR intervals includes:
A. calculating the difference D between two
successive RR intervals;
B. comparing the value of said difference D to a
predetermined reference value;
C. storing those values of D which are greater than said reference value;
D. calculating the sum M of N stored values of D,
wherein N is a predetermined positive integer; an E. setting MAVG equal to .

20. The pacing method according to claim 19, further including the step comparing MAVG to a second predetermined limit SL2 having a value greater than that of SL1.

21. The pacing method according to claim 20, wherein said step of stimulating includes gradually incrementing the pacing rate until it reaches the intermediate pacing rate (IR), if the RRN interval will be longer than LRHI, and if MAVG is greater than or equal to SL, but less than or equal to SL2.

22. The pacing method according to claim 18, further including:
A. the step of inhibiting stimulation if MAVG is less than SL1, and if the last sensed RR interval is
less than or equal to LRHI;
B. the step of stimulating at the lower rate if MAVG is less than SL1, and if the RRN interval will be
longer than LRHI;
C. the step of inhibiting stimulation if MAVG is
greater than SL2, and if the RRN interval is less
than or equal to LRHI; and
D. the step of stimulating at the lower rate if MAVG is greater than SL2, and if the RRN interval will
be longer than LRHI.