Method and apparatus for detecting loss of capture

A cardiac pacing device, comprising:

• means for delivering cardiac pacing pulses to a chamber of a patient's heart at a first pulse amplitude in a demand pacing mode;
• means for measuring a first series of intervals between successive events of the chamber, including sensed and paced events;
• means for determining whether the first measured series of intervals meets a stability criterion;
• means responsive to the first measured series of intervals failing to meet the stability criterion, for determining whether the first measured series of intervals includes an interval between a delivered pacing pulse and a sensed event that is less than a defined duration;
• means responsive to the interval between a delivered pacing pulse and a sensed event being less than the defined duration, for delivering cardiac pacing pulses to the chamber of a patient's heart at a second pulse amplitude in a demand pacing mode;
• means for measuring a second series of intervals between successive events of the chamber, including sensed and paced events;
• means for determining whether the second measured series of intervals meets the stability criterion.

A non-transitory medium comprising instructions for determining stability of a patient's intrinsic rhythm in a cardiac pacing device, comprising instructions for:

• delivering cardiac pacing pulses to a chamber of a patient's heart at a first pulse amplitude in a demand pacing mode;
• measuring a first series of intervals between successive events of the chamber, including sensed and paced events;
• determining whether the first measured series of intervals meets a stability criterion;
• responsive to the first measured series of intervals failing to meet the stability criterion, determining whether the first measured series of intervals includes an interval between a delivered pacing pulse and a sensed event that is less than a defined duration;
• responsive to the interval between a delivered pacing pulse and a sensed event being less than the defined duration, delivering cardiac pacing pulses to the chamber of a patient's heart at a second pulse amplitude in a demand pacing mode;
• and
• measuring a second series of intervals between successive events of the chamber, including sensed and paced events;
• determining whether the second measured series of intervals meets the stability criterion.