Dapagliflozin Effect on FunctiOnal Mitral Regurgitation and Myocardial Fibrosis (DEFORM)

Inclusion Criteria: 1. Agree to get enrolled; 2. Age 18-90 years old, gender is not limited; 3. More than moderated FMR ( EROA by echocardiography ≥0.2cm2) , and LVEF more than 40%; 4. The structure of mitral valve leaflets and chordae is normal; 5. GDMT for FMR has been taken orally for more than 2 weeks, and the dose has not been adjusted for more than 2 weeks (If there is no contraindication, the drugs includes β blockers, the renin-angiotensin system inhibitors \[Angiotensin-Converting Enzyme Inhibitors/Angiotensin Receptor Blockers/angiotensin receptor neprilysin inhibitor\], aldosterone receptor antagonists), and for the last 2 weeks no intravenous drug for heart failure were used. Exclusion Criteria: 1. Have indication for dapagliflozin; 2. Angioedema, or allergic to dapagliflozin; 3. Already taking Dapagliflozin or other SGLT2 inhibitors; 4. Primary mitral valve structural damage, such as rheumatic heart disease, mitral valve prolapse; 5. Non-dialysis patients with estimated glomerular filtration rate\<30ml/min/1.73m2; 6. Dialysis patients; 7. Acute myocardial infarction, acute myocarditis, or percutaneous transluminal coronary intervention, coronary artery bypass grafting and other vascular reconstruction operations have occurred within 3 months; 8. Those who plan to take vascular reconstruction, cardiac resynchronization therapy, percutaneous mitral valve repair, surgical valve repair or replacement within 3 months after enrollment; 9. Complications of obvious aortic valve disease (more than moderate stenosis or more than moderate regurgitation); 10. Thyroid function combined with hyperthyroidism has not returned to normal; 11. Pregnant and lactating women.