Effects of VALsartan On atRIAl Mitral Regurgitation

The goal of this clinical trial is to learn whether valsartan can slow the progression of atrial functional mitral regurgitation (AFMR) in adults with preserved left ventricular ejection fraction. The study will also evaluate the safety and tolerability of valsartan in this population.

The main questions it aims to answer are:

* Does treatment with valsartan reduce the progression of atrial functional mitral regurgitation compared with placebo? * Does valsartan have favorable effects on mitral valve leaflet remodeling and related cardiac structure and function? * Is valsartan safe and well tolerated in patients with atrial functional mitral regurgitation who do not currently require angiotensin-converting enzyme inhibitors or angiotensin receptor blockers?

Researchers will compare valsartan to a placebo (a look-alike substance with no active drug) to see if valsartan reduces the progression of atrial functional mitral regurgitation and improves clinical and imaging outcomes.

Participants will:

* Take valsartan or placebo twice daily for 12 months, with dose adjustments based on blood pressure, kidney function, and tolerance * Undergo 3D echocardiography at baseline, 6 months, and 12 months * Complete a 6-minute walk test at baseline and 12 months * Complete the Kansas City Cardiomyopathy Questionnaire (KCCQ) at baseline, 6 months, and 12 months * Undergo 24-hour ambulatory blood pressure monitoring at 1 month * Have regular safety monitoring, including phone follow-up at 7 days, blood tests at 1 month, and blood pressure checks after dose adjustments