Automatic adjustment of pacing parameters based on intracardiac impedance measurements

The selection of the parameters used for rate control is determined not only by technical feasibility, but also by patient considerations. Technical feasibility considerations include long-term stability and reliability of the sensor, as well as susceptibility to interference. The patient considerations relate to the patient's physical state, including the various physiological and pathologic conditions. The rate response must be in proportion to circulatory demand. The specificity of the rate response is of particular importance for the patient with low cardiac reserve. The development of future pacemakers aims at providing additional patient benefits, with a reduction of the effort associated with initial parameter selection and patient follow-up. This will be achieved by utilizing a better understanding of the integration of the control mechanisms for the entire cardiovascular system under physiological and pathological conditions. To support the development of the future pacemakers, we must utilize realistic multiparametric models of the cardiovascular system. These models will assist the evaluation of potential algorithms for integrating multisensor signals into a single pacing rate. The parameterization and validation of these models are important issues to be addressed. Intracardiac impedance measurements in conjunction with microprocessor controlled signal processing and improved lead technology provide a great variety of practical applications for physiological control of the pacing rate and the automatic adjustment of pacemaker parameters. The concepts of an "intelligent" pacemaker capable of automatic control in response to changes in the pacing requirements under a variety of physiological and clinical conditions are presented.