Retrograde atrial sensing for identifying sub-threshold atrial pacing

Abstract

Methods and systems for delivering a pacing pulse to an atrium during a cardiac cycle. A retrograde P-wave may be identified during the cardiac cycle, indicative of sub-threshold atrial pacing. Delivery of the pacing pulse to the atrium may be adjusted in a subsequent cardiac cycle in response to identifying the retrograde P-wave. Adjusting delivery of the pacing pulse may involve initiating an atrial capture threshold test, temporarily increasing one or both of the pacing pulse amplitude and pulse width, and/or re-evaluating one or both of the pacing pulse amplitude and pulse width. Adjusting delivery of the pacing pulse may also involve altering the timing of a scheduled atrial capture threshold test. During an atrial capture threshold test, a retrograde P-wave template may be generated in response to atrial non-capture sensed during the atrial capture threshold test, and used to identify subsequent retrograde P-waves.