Cardiac pacemaker with hystersis behavior

A 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 a rate of change of MAVG of successive intrinsic escape intervals;
• B. comparing MAVG to a first predetermined limit SL1;
• C. comparing a last intrinsic escape interval RRN to the lower rate hysteresis interval (LRHI);
• and
• D. stimulating at the lower rate hysteresis (LRH) and gradually incrementing a 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.

A method of pacing the heat including the steps:

• 1) sensing electrical depolarizations within a heart chamber,
• 2) making a determination based on sensed depolarizations in said chamber of the intrinsic heart rate,
• 3) comparing the current intrinsic heart rate with previously sensed intrinsic heart rate to determine whether a rapid drop in heart rate of a predetermined size has occurred,
• 4) on the discovery of a rapid drop in heart rate of said predetermined size, pacing at predetermined rates higher than a lower pacing rate.

A heart stimulator comprising:

• pulse generator means for generating and emitting stimulation pulses to a heart at a rate;
• detector means for sensing events in said heart, including spontaneous heartbeats;
• and
• control means, connected to said pulse generator means and to said detector means, for controlling the emission of stimulation pulses by said pulse generator means for causing the emission of a stimulation pulse if a spontaneous heartbeat rate as sensed by said detector means drops below a defined lower rate within a predetermined period and for causing said pulse generator means, when said spontaneous heartbeat rate falls below said defined lower rate within said period, to emit said stimulation pulses at rates faster than said defined lower rate.