This study is designed to assess the clinical outcomes of Left-Ventricular (LV) fusion pacing compared to Bi-Ventricular (BV) pacing, also known as Cardiac Resynchronization Therapy (CRT), in Chinese Heart Failure (HF) population. Specifically, the study will assess the changes of cardiac function of each group through 3-month follow up/ 6-month follow up compared with original outcomes before aCRT (adaptive Cardiac Resynchronization Therapy) implantation. Secondly, the study will assess whether parameters of aCRT that were tested in Western population are relevant to parameters of Chinese HF patients.

Traditional dual-chamber pacemakers usually utilize pacing at right atrium (RA) and right ventricle (RV). But many clinical studies have proved that permanent RV pacing could cause ventricular desynchronization in electrical activation and mechanical movement, also may lead to atrial fibrillation and cardiac failure in the long term. Cardiac Resynchronization Therapy (CRT) can overcome the ventricular desynchrony caused by permanent RV pacing, through pacing both left and right ventricles. But the cost of CRT device is usually expensive in emerging markets like in China. Recently, a few clinical studies have demonstrated that LV-fusion pacing (without RV pacing) using adaptive CRT feature provides better clinical outcomes than RV pacing, and also equivalent clinical improvements compared to conventional CRT pacing. However, it is unknown whether similar results can be duplicated in Chinese population as the clinical profile of Chinese CRT populations is different from that of Western CRT population.

This study is designed to assess the clinical outcomes of Left-Ventricular (LV) fusion pacing compared to Bi-Ventricular (BV) pacing in Chinese Heart Failure population. Specifically, the study will assess the changes of cardiac function of each group through 3-month follow up/ 6-month follow up compared with original outcomes before aCRT implantation. Secondly, the study will assess whether parameters of aCRT that were tested in Western population are relevant to parameters of Chinese HF patients.

CRT-indicated heart failure patients who meet the Inclusion & Exclusion criteria will be enrolled voluntarily in this study. No intervention will be assigned to enrolled patients. CRT therapy will be assigned according to the Guideline (ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure 2012). Left-Ventricular (LV) fusion pacing or Bi-Ventricular (BV) pacing mode, both included in CRT therapy, will be applied upon physicians' judgment based on the Guideline and patients' specific situations. Both pacing modes, as well as all the clinical assessments in this study, are routine cares in clinical practice.

The study will enroll up to 30 subjects in each group (LV pacing group and BV pacing group) that meet the indication for CRT therapy, and also the Inclusion & Exclusion criteria. Consented subjects will receive CRT therapy and two follow-ups in the following 3 and 6 months.

Inclusion Criteria:

• Age between 18~80
• Life expectancy > 1 year
• Sign Informed Consent
• CRT-indicated
• NYHA (New York Heart Association) class II and III
• PR (term in Electrocardiograph) interval < 200 ms
• ECG (Electrocardiograph) LBBB (left bundle branch block)

Exclusion Criteria:

• Patient with severe liver or kidney dysfunction
• CRT-contraindication
• CRT-upgraded
• Persistent AF (atrial fibrillation)
• AV block (atrioventricular block)
• RBBB (right bundle branch block)
• Valvular Disease
• LV threshold ≥ 3.5 volt
• Patient is unwilling to sign the informed consent
• Patient is pregnant or has pregnancy intention in the study duration
• Patient has a medical condition that would limit study participation
• Patient is enrolled in a concurrent study that may affect the outcome of this study