A dual chamber pacemaker system is provided having an improved Wenckebach response for optimizing tracking of atrial signals having rates within a rate range above the normal tracking range, i.e., in a designated Wenckebach range. When an atrial sense occurs in the Wenckebach range, the AV delay is extended up to a predetermined maximum extension to enable delivery of a ventricular pulse at the ventricular upper rate limit (dynamic tracking limit). When the AV delay would have to be extended beyond the maximum extension in order to pace the ventricle at the dynamic tracking limit, the next ventricular stimulus is delivered asynchronously at an escape interval greater than the escape interval corresponding to the dynamic tracking limit, e.g., at a predetermined lower pacing limit.