Patent ID: 7392087
Filing Date: 2008-06-24
Classification: A61N

Abstract:
1. A method for automatically adjusting a sensing threshold in a cardiac rhythm management device, comprising: sensing a ventricular electrogram signal via a ventricular sensing channel and detecting an r-wave when the sensed ventricular signal exceeds a ventricular sensing threshold; sensing an atrial electrogram signal via an atrial sensing channel and detecting a p-wave when the sensed atrial signal exceeds an atrial sensing threshold; adjusting the atrial sensing threshold for a current cardiac cycle, wherein the adjustment results in a decrease of the atrial sensing threshold if no p-wave is detected and no atrial pace is delivered during the current cardiac cycle unless the adjusted atrial sensing threshold would then be below a minimum value or unless a noise level of the atrial sensing channel has increased by a specified; and, adjusting the atrial sensing threshold based upon detection of noise during a refractory period by measuring the amplitude of p-waves, setting the atrial sensing threshold to a previous atrial sensing threshold value within a noise measurement window that occurs during the refractory period, measuring the amplitudes of atrial electrogram signals that exceed the atrial sensing threshold during the noise measurement window, computing a current atrial noise level N(t) based upon the measured amplitudes, and adjusting the atrial sensing threshold based upon the measured amplitude of a detected p-wave and the current noise level.