The number of heart failure with mildly reduced or preserved ejection fraction gradually increases. SGLT2-i has been shown to reduce the risk of hospitalization for heart failure and cardiovascular death among patients with chronic heart failure and a left ventricular ejection fraction of 40% or more . However,its effect on the function on left atrium in heart failure with mildly reduced or preserved ejection fraction is still unknown.

Heart failure with mildly reduced or preserved ejection fraction has become an important part of heart failure, the proportion is also gradually increased .Atrial fibrillation , as a common arrhythmia disease, is often caused by heart failure and aggravates the process of heart failure. It has been documented that in patients with heart failure and an ejection fraction more than 40%, it may have a higher incidence of atrial fibrillation.Heart failure and atrial fibrillation together increase the risk of stroke, hospitalization for heart failure, and all-cause death from heart failure.

SGLT-2 inhibitor (SGLT-2i) is a new metabolic drug, through a variety of mechanisms on cardiac metabolism, has been shown to reduce the risk of death and rehospitalization, and improve the health of patients with heart failure.But the effect on preventing arrhythmia in patients with heart failure is still unclear. Some studies have shown that SGLT-2i reduces the left atrial volume index and the left ventricular diastolic volume index compared with placebo and some have proved that the indicators of the function of left atrium, such as peak atrial longitudinal strain (PALS), peak atrial contraction strain (PACS), can effectively predict the occurrence of atrial fibrillation. The purpose of this study is to apply empagliflozin (a class of SGLT-2i) in heart failure patients with mildly reduced or preserved ejection fraction to measure the changes in the function of left atrium and thus verify its prevention and control effect on atrial fibrillation.

Inclusion Criteria:

• Age ≥ 18 years old, BMI18.5-27.9kg/m²
• Meet the definition of chronic heart failure and an ejection fraction of 40% or more (according to 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure)
• Elevated NT-proBNP levels of more than 300 pg/mL
• Signed and dated written informed consent form

Exclusion Criteria:

• Myocardial infarction,coronary artery bypass graft surgery, or other major cardiovascular surgery within 30 days after enrollment
• Percutaneous coronary intervention ,coronary artery bypass graft surgery,cardiac resynchronization therapy, implantable cardioverter defibrillatoror or other cardiac surgeries within 90 days prior to enrollment
• Atrial fibrillation or flutter
• SGLT-2i using within 90 days prior to enrollment
• Cardiomyopathy based on infiltrative diseases (e.g. amyloidosis), accumulation diseases (e.g. haemochromatosis, Fabry disease),cardiomyopathy with reversible causes (e.g. stress cardiomyopathy), or known pericardial constriction
• Acute decompensated heart failure.
• Moderate to severe valvular stenosis or regurgitation
• Symptomatic hypotension with systolic pressure ≤ 90mmHg or uncontrolled hypertension using drugs with systolic blood pressure of ≥180 mmHg at randomization
• Sever infectious diseases(e.g. Severe myocarditis, severe pneumonia, and severe urinary tract infection)
• Chronic pulmonary disease requiring home oxygen, oral corticosteroid therapy or hospitalization for exacerbation within 12 months
• Other significant co-morbid conditions(impaired renal function( an estimated glomerular filtration rate of <20 mL/min/1.73 m2), hepatic failure, malignant tumors, severe hematologic diseases, etc.)
• Major surgery performed within 90 days prior to enrollment or major scheduled elective surgery within 90 days after enrollment(major according to the investigator's assessment,such as gastrointestinal surgery that might interfere with trial medication absorption or malignant tumors surgery)
• Type 1 diabetes or history of ketoacidosis
• Pregnancy
• Completion within 90 days of a trial of another drug study. Receipt of any investigative treatment other than the study medications for this trial