Patent ID: 6112119
Filing Date: 2000-08-29
Classification: A61N

Abstract:
A method for automatically adjusting a present gain/threshold parameter value of an input sense amplifier for use in an implantable medical device which operates said input sense amplifier to receive and, responsive to electrical activity of sufficient intensity that can be called sufficient senses, determine senses of event specific pulses of electrical activity native to a body into which said device is designed for implantation, and from said sufficient senses said amplifier produces a sense amplifier output, said method comprising:determining adjustments to be made to said input sense amplifier present gain/threshold parameter value based on current values of at least two indicator means for monitoring sense amplifier output, determining a condition and producing a signal output,keeping track of said current values for said at least two indicator means, a first of said at least two being a Long Time Few Sense (LTFS) indicator means for monitoring sense amplifier output, determining a condition relating to LTFS, and producing a signal output from said LTFS condition determination and a second of said at least two being a Long Term Average (LTA) indicator means for monitoring sense amplifier output, determining a condition relating to LTA, and producing a signal output from said LTA condition determination, said keeping track steps comprising:tracking said at least two indicator means from each input sense amplifier output by,operating said LTFS indicator means to (a) monitor said input sense amplifier output to determine whether said LTFS indicator means has received an insufficient number of senses in a tracked period immediately preceding any given sense amplifier output and (b) if said LTFS indicator means has determined a condition of having received such insufficient number of senses, generating an LTFS output signal representative of said condition,operating said LTA indicator means, to monitor said input sense amplifier for a valid sense output signal, and to count and maintain an LTA count of said valid sense output signals, wherein when a sufficient number of said valid senses has been counted said LTA count is deemed sufficient and, then resetting the LTA count and adjusting an LTA signal value based on comparing a last LTA signal value to said present sense amplifier gain/threshold parameter value, but only adjusting said LTA signal value if there is an LTFS output signal present when said LTA count is deemed sufficient.