1. A method for monitoring atrial stretch, for use by an implanted system including a chronically implanted cardiac device and at least one chronically implanted lead, the method comprising: (a) for each of a plurality of periods of time during which the atrium is paced to provoke an atrial evoked response (a.1) obtaining, using the chronically implanted cardiac device and the at least one chronically implanted lead, an atrial intracardiac electrogram (IEGM) indicative of atrial electrical activity of a patient's heart during the period of time; and (a.2) determining based on the atrial IEGM and storing information about at least one atrial evoked response metric indicative of atrial electrical activity during the period of time; (b) detecting, based on the stored information, a change in the at least one atrial evoked response metric over time; and (c) monitoring atrial stretch based on the detected change in the at least one atrial evoked response metric over time.