Apparatus and method for optimizing cardiac performance by determining the optimal timing interval from an accelerometer signal

A cardiac stimulating apparatus functioning in a rate adaptive preset pacing mode, and programmed to optimize cardiac performance of a patient's heart, comprising:

• a) a dual chamber cardiac pacer and leads coupled to said cardiac pacer for sensing atrial and ventricular events of a patient's heart and for stimulating preselected chambers of the heart, and further including a cardiac cycle means for identifying cardiac cycles of the patient's heart;
• b) a cardiac electrogram coupled to said cardiac pacer for identifying R--R intervals of the patient's heart;
• c) an accelerometer contained within a housing of said cardiac pacer and coupled to a microprocessor based controller of said cardiac pacer, said accelerometer having a filter wherein said accelerometer transmits to the cardiac pacer a waveform having various features associated with mechanical movement events within an atrium and mechanical movement events within a ventricle;
• and
• d) said microprocessor based controller including feature means for identifying pre-selected features of the waveform transmitted by the accelerometer, respiratory means coupled to said cardiac pacer for identifying complete respiratory cycles, means for corresponding both the R--R interval identified by the cardiac electrogram and the respiratory cycles identified by the respiratory means with the features identified by the feature means, and analyzing means for analyzing identified features over corresponding R--R intervals and respiratory cycles, wherein the identified features are analyzed and compared by said microprocessor over a preselected number of at least one of R--R intervals and respiratory cycles for a plurality of preselected timing intervals, said timing intervals being a time between at least one of intrinsic and paced stimulations of pre-selected chambers of the heart, to thereby determine an optimum timing interval.

A method for optimizing the timing interval of an implantable cardiac pacer between intrinsic and paced stimulations of pre-selected chambers of a patient's heart, said pacer being of the type having a microprocessor-based controller having memory, a pulse generator, and an accelerometer for sensing mechanical atrial and ventricular events contained therein, said method comprising the steps of:

• a) pacing a patient's heart with the implantable cardiac pacer, wherein the cardiac pacer has a preset pacing mode, identifies cardiac cycles of the patient's heart and controls a timing interval between at least one of intrinsic and paced stimulations of preselected chambers of the heart;
• b) setting the timing interval of the implantable cardiac pacer to a first value of a predetermined set of timing interval values;
• c) receiving a signal from the accelerometer;
• d) coupling a cardiac electrogram to the implantable cardiac pacer to identify R--R intervals of the patient's heart;
• e) identifying pre-selected features from the signal, and storing data associated with identified features of the signal received from the accelerometer for a plurality of R--R intervals in the memory of the microprocessor-based controller;
• f) calculating from the identified features, characteristic values of the identified features of the signal;
• g) selecting a new timing interval value from the predetermined set of timing interval values;
• h) repeating steps c-g until all the timing interval values of the predetermined set of timing interval values have been used;
• i) analyzing and comparing the calculated characteristic values for each timing interval value of the predetermined set of timing interval values, to determine an optimum timing interval value;
• and
• j) setting the timing interval of the implantable cardiac pacer to the determined optimum timing interval value.