Many pacemaker patients have cardiac conduction system disease and thus need ventricular pacing. Traditional ventricular pacing causes ventricular dyssynchrony that in turn causes cardiac contraction dysfunction. CRT pacing provides better ventricular synchronization, but not the optimal, especially in patients with narrow QRS. CRT non-response rate is at 30%. His bundle pacing utilizes naturel His bundle-Purkinjie system to provide optimal physiological pacing. But many pacing-indicated patients have abnormal His bundle-Purkinje system, thus His bundle pacing cannot provide optimal pacing in patients with abnormal cardiac conduction system. Moreover, the pacing threshold is high during His bundle pacing. More recently, left bundle branch pacing is proposed. However, LBBP will generate right bundle branch block pattern, another kind of weak ventricular synchronization. Thus, the investigators propose to excite the left and right bundle branches area simultaneously to normalize ventricular synchronization. The purpose of this study is to explore the electrocardiogram (ECG) characteristics of simultaneous stimulation of right and left bundle branches area.