Left Ventricular Myocardial Work for Predicting Response to CRT

Healthy Adults Group Inclusion Criteria: * Participants must meet all of the following criteria to be enrolled: 1. Of Han Chinese ethnicity 2. Aged 18-79 years 3. Normal blood pressure (\< 140/90 mmHg) 4. Normal fasting blood glucose 5. Normal blood lipid levels (triglycerides, total cholesterol, low-density lipoprotein, high-density lipoprotein) 6. Normal complete blood count results (hemoglobin concentration, white blood cell count, red blood cell count, platelet count) 7. Normal liver and renal function (alanine transaminase \< 2× upper limit of normal; normal creatinine and blood urea nitrogen) 8. Normal electrocardiogram results (occasional atrial premature beats may be enrolled at the investigator's discretion) 9. No structural heart disease and normal cardiac function confirmed by echocardiography Exclusion Criteria: Participants will be excluded if they meet any of the following criteria: 1. Clinically significant cardiac valve regurgitation (≥ mild severity) 2. Respiratory diseases: acute or chronic respiratory disorders 3. Endocrine diseases: thyroid disease, diabetes mellitus, hyperaldosteronism, pheochromocytoma, etc. 4. Abnormal liver function (alanine transaminase \> 2× upper limit of normal), abnormal renal function (elevated creatinine beyond normal range), or dyslipidemia (elevated triglycerides, total cholesterol, low-density lipoprotein, or high-density lipoprotein) 5. Other systemic diseases: anemia, malignancy, connective tissue disease, large artery/peripheral vascular diseases (aortic dilation, aortic dissection, coarctation of the aorta, Takayasu arteritis, atherosclerosis), etc. 6. Pregnant or lactating women 7. Professional athletes 8. Poor-quality ultrasound images that cannot support parameter measurement and analysis Heart failure patients with LBBB who are scheduled for CRT treatment Group Inclusion criteria: 1. LVEF ≤ 35% 2. QRS ≥ 150ms; LBBB 3. At least 3 months of optimal drug therapy before implantation Exclusion Criteria: 1. Suffering from connective tissue diseases such as systemic lupus erythematosus, polymyositis, and rheumatoid arthritis; 2. Having a history of blood diseases and severe systemic diseases such as infections; 3. Those who cannot cooperate with the examinations. Patients with LBBB who have preserved LVEF Group Inclusion criteria: 1. LVEF≥53% 2. LBBB Exclusion Criteria: 1. Suffering from connective tissue diseases such as systemic lupus erythematosus, polymyositis, and rheumatoid arthritis; 2. Having a history of blood diseases and severe systemic diseases such as infections; 3. Those who cannot cooperate with the examinations. Patients with reduced LVEF but without LBBB Group Inclusion criteria: 1. LVEF ≤ 35% 2. non-LBBB Exclusion Criteria: 1. Suffering from connective tissue diseases such as systemic lupus erythematosus, polymyositis, and rheumatoid arthritis; 2. Having a history of blood diseases and severe systemic diseases such as infections; 3. Those who cannot cooperate with the examinations.