Safety and Effectiveness of Left Bundle Branch Pacing in Patients With Cardiac Dysfunction and AV Block

Inclusion Criteria: * Above 18 years old * Agree to participate in trial and sign informed consent * NYHA cardiac function class I-III * LVEF\<50% * Second or complete atrioventricular block with pacing indication or ventricular pacing dependent with ventricular pacing percentage \>40% * Patients who are willing to take the de-novo implant or device replacement or upgrade. Exclusion Criteria: * Life expectancy \<1 year * Patients with severe tricuspid valvular disease1 or who have undergone mechanical valve or bioprosthetic valve surgery * Acute myocardial infarction within 1 month * Women of childbearing age who are pregnant or becoming pregnant during the study period * Severe liver and kidney dysfunction2 * Have been enrolled in another clinical studies that may interferes with the current trial objectives * Evidence of severe pulmonary hypertension (PASP\>70mmHg) * Evidence of hypertrophic cardiomyopathy which shall affect the prognosis of patients. * The investigator believes that subject's physical condition is not suitable for participation in the trial