LVSP Based CRT vs. RVAP Based CRT

Inclusion Criteria: 1\. Chronic heart failure, LVEF ≤35% after at least 3 months of guideline-optimized drug therapy, NYHA class II-IV with complete left bundle branch block (QRSd≥130 ms), OR Atrioventricular block with LVEF ≤ 50% with the indication of cardiac pacing; 3. Age between 18 and 90 years old; 4. The expected survival period is greater than 12 months; 5. Signed the informed consent form for the study. Exclusion Criteria: 1. Previous mechanical tricuspid valve replacement. 2. Previous pacemaker or other devices implanted and for device replacement or upgrading for this time. 3. Patients have a history of unstable angina, acute myocardial infarction, CABG, and PCI surgery within three months. 4. Persistent atrial fibrillation without AV block, the proportion of biventricular pacing is not expected to less than 95%. 5. Patients participated in any of the other studies at the same time, which may confound the results of this study. 6. Pregnancy, planning to become pregnant. 8\. Patients with a history of heart transplantation.