This is a prospective, single-site, non-randomized, acute feasibility clinical study. The purpose of this study is to explore the electrocardiogram (ECG) characteristics of simultaneous stimulation of right and left bundle branches area.

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.

Inclusion Criteria:

• Aged from 18 to 80 years old
• Subjects who are willing to provide Informed Consent
• Subjects who have pacing indications or indications for CRT, and will receive pacemaker or CRT therapy

Exclusion Criteria:

• Subjects who have contra-indications for pacing therapy or CRT
• CRT up-graded subjects
• Ventricular hypertrophy
• Subjects who have medical conditions that would limit study participation
• Subjects who are pregnant or have a plan for pregnancy during the study
• Subjects who are not willing to provide Informed Consent

This study will enroll subjects who have pacing indications or indications for CRT.