Body position and activity sensor

A pacing system that is implantable within the body of a patient and provides one or more signals that are indicative of movement of the patient, the system comprising:

• a sensor adapted for implantation in the body of a patient in a fixed orientation with respect to the body so that movement of the body results in corresponding movement of the sensor that includes an enclosure having a first surface with a central electrode extending in a first direction into a cavity defined by the enclosure and at least two peripheral electrodes that extend from the first surface in the first direction in the cavity wherein the at least two peripheral electrodes are planar in configuration with an inner surface that is curved so that each point on the inner surface is substantially the same distance from the central electrode, and wherein the central electrode and the at least two peripheral electrodes are mounted on the first surface within the enclosure;
• an electrolytic solution positioned within the enclosure wherein movement of the electrolytic solution results in variations in the quantity of electrolytic solution positioned between the central electrode and the at least two peripheral electrodes;
• a central electrode lead that is connected to the central electrode and extends out of the first surface of the enclosure in a second direction;
• at least two peripheral electrode leads that are connected to the at least two peripheral electrodes and extend out of the first surface of the enclosure in the second direction;
• a mounting plate that defines a planar surface that receives the central electrode lead and the at least two peripheral electrode leads;
• a driving circuit that provides an electrical signal to the central electrode;
• a sensing circuit that senses an orientation signal in response to the driving circuit providing the electrical signal wherein the orientation signal is representative of the orientation of the sensor;
• and
• a pacemaker controller for controlling the delivery of pacing impulses delivered to a heart of the patient that receives the orientation signal from the sensing circuit and uses said orientation signal to adjust the delivery of pacing impulses to the heart of the patient.

An implantable sensor for detecting body position and body movement, the sensor comprising:

• an elongated central electrode having a terminal portion;
• at least two side electrodes having a length, an inner surface and a radius of curvature so that a uniform distance is maintained between the central electrode and the inner surface of the side electrodes, each of the side electrode having at terminal portion;
• a cylindrical enclosure defining a generally cylindrical cavity and having an open end, a sealed end and a central axis, the cylindrical enclosure being adapted for implantation in a patient;
• mounting means, dimensioned to fit within the open end of cylindrical enclosure, for mounting the at least two side electrodes so as to be coaxial about the central electrode and extending in a direction substantially parallel to the central axis of the cylindrical enclosure, the mounting means including means for hermetically sealing the open end so that the terminal portions of each electrode extends to an exterior side of the mounting means;
• and
• an electrolytic solution positioned in the cavity such that when the sensor is implanted within a patient, movement of the sensor about the central axis of the cylindrical enclosure results in variations in the quantity of electrolytic solution positioned between the central electrode and the side electrodes so that when an electrical signal is applied to the central electrode, a signal is produced which is indicative of one of body position or body movement of the patient;
• whereby the curvature of the side electrodes and the uniform distance to the central electrode minimizes corrosion and plating of the electrodes.