Pacemaker with diagnostic intrinsic beat search

A method of performing an intrinsic heart beat search in an implantable medical device while delivering pacing therapy to a patient's heart, the method comprising:

• identifying a reduced pacing rate representing a reduction relative to a therapy based pacing rate;
• pacing a ventricle of the patient's heart for a period of time at the reduced pacing rate using a plurality of pacing pulses but where one or more of the plurality of pacing pulses may be inhibited by a corresponding sensed intrinsic beat;
• recording one or more items, the one or more items comprising one or more of:
• a beat type for each beat, wherein the beat type comprises an intrinsic beat or a paced beat;
• a beat rate, wherein the beat rate represents the rate at which the beats occur;
• a beat rate variability, wherein the beat rate variability represents the rate variability at which the beats occur;
• and
• an egram;
• determine if there are sustained intrinsic beats at the reduced pacing rate, wherein there is a determination of sustained intrinsic beats when at least 80 percent of the beats are intrinsic beats;
• repeating the pacing, recording and determining steps using different reduced pacing rates;
• in response to determining that there are sustained intrinsic beats, pacing the ventricle of the patient's heart at the therapy based pacing rate.

A method of regulating cardiac activity following a procedure that may temporarily impair a cardiac conduction system within a patient's heart, the method comprising:

• pacing the patient's heart at a starting pacing rate;
• instigating an intrinsic heart beat search algorithm comprising:
• pacing at a reduced rate for a period of time;
• capturing electrical signals representative of cardiac electrical activity while pacing at the reduced rate in order to determine a presence or absence of sustained intrinsic heart beats, wherein there is a determination of sustained intrinsic beats when at least 80 percent of the beats are intrinsic beats;
• pacing at a further reduced rate for a period of time if sustained intrinsic heart beats are not detected;
• returning to pacing at the starting pacing rate if sustained intrinsic heart beats are detected;
• continuing to reduce the pacing rate and capturing electrical signals while pacing at the further reduced pacing rate in order to determine a presence or absence of sustained intrinsic heart beats until sustained intrinsic heart beats are detected or until a lower search rate limit is reached.