a sensing system configured to sense a cardiac signal following a pacing pulse delivered to a heart; and

a processor coupled to the sensing system, the processor configured to (a) provide at least one detection window (b) detect a feature of the cardiac signal, the detected feature being disposed at a location relative to the detection window, (c) compare the detected feature to the detection window, (d) determine a direction of change for the detection window based on a comparison of the detected feature to the detection window, and (e) modify the detection window using a first adjustment coefficient associated with a preferred direction of change in response to the direction of change corresponding to the preferred direction and modify the detection window using a second adjustment coefficient associated with a second direction in response to the direction of change corresponding to the second direction, wherein the first coefficient provides a more aggressive modification of the detection window than the second coefficient.