A system and method for determining atrial arrhythmia burden is provided. Consecutive sets of parametric data regularly obtained from an implantable medical device through remote interrogation are centrally maintained. An atrial arrhythmia burden is determined. A cumulative atrial tachyarrhythmia (AT) duration is identified for each atrial arrhythmia episode recorded in the parametric data over a fixed look back period. One of an AT mode switch time and maximum atrial tachyarrhythmia AT duration are evaluated respectively subject to the duration between the consecutive sets being of sufficient length and a change having occurred to the maximum AT duration.