<qa>  What is the atrial effective refractory period?1. Paroxysmal AF group: The p-wave duration, P wave dispersion and P wave amplitude are detected before and 24 hours after procedure.The atrial effective refractory period, refractory period dispersion, frequency adaptation and atrial conduction time were tested before and after procedure. Detect atrial electromechanical conduction time in the tissue doppler before and 1 week after procedure. 