Automatic control of the sensing threshold for monitoring cardiac rhythm in a implantable device

摘要

An improved automatic sensing threshold control for cardiac rhythm detection in an implantable device. The improvement includes setting the sensing threshold according to the amplitude of both sensed signals corresponding to cardiac activity and sensed noise, for setting the threshold substantially below the sensed signal amplitude, but above the noise amplitude. The invention provides absolute refractory periods after pacing or sensing, followed by a retriggerable noise refractory period. Following sensing the device sets the sensing threshold to approximately one-fourth of the measured amplitude, and then increases the threshold when it detects noise.