Objectives: The study is to establish the sinus node dysfunction (SND) and atrial fibrillation (AF) of canine model induced by rapid pacing in the atrium for observing changes of electrophysiological characteristics: atrail effective refractory period (AERP), AERP discrete, atrial activity sequence, atrial activity time and the incidence of secondary AF, the restoration process of AERP, exploring the relationship between the reoccurrence and maintenance of AF and atrial electrical remodeling. To investigate...