Why Is This Study Important? The heart has valves that help control blood flow. Aortic regurgitation (AR) is a condition where one of these valves (the aortic valve) doesn't close properly, causing blood to leak back into the heart. Over time, this makes the heart work harder and grow larger (remodeling) to keep up. Many patients with severe AR need valve replacement surgery to fix this problem. After surgery, the heart doesn't have to work as hard, and over time, it can shrink back to a healthier size (reverse remodeling). However, doctors don't know if medications can help speed up or improve this healing process. This study aims to find out if a common blood pressure medication, losartan, can help the heart recover better after surgery. What Do the Investigators Already Know? Doctors often prescribe medications like ACE inhibitors, angiotensin receptor blockers (ARBs), beta-blockers, and spironolactone to people with heart failure because these drugs help the heart function better and prevent worsening disease. However, these medications haven't been studied in people with valve disease because most major research studies excluded patients with valve problems. Even though there is not strong evidence, many doctors prescribe these medications after valve surgery, assuming they might be helpful. But is that really the case? That's the question this study hopes to answer. What Is This Study About? This study will test whether losartan, a medication often used for high blood pressure, can help hearts recover better after aortic valve replacement surgery. The researchers will compare two groups of patients: * One group will take losartan (50 mg per day) after surgery. * The other group will take a placebo (a pill with no active medication). By comparing these two groups, the study will determine whether losartan helps the heart shrink back to a normal size faster and function better after surgery. How Will the Study Work? Who? 60 patients with severe AR who are having aortic valve replacement surgery. How? Patients will be randomly placed into one of the two groups (losartan or placebo). For how long? Patients will be followed for one year after surgery. What Will Be Measured? Doctors will check patients four times: before surgery, and 1 month, 3 months, and 12 months after surgery. At each visit, the investigators will measure: * NT-proBNP levels: A blood test that tells us how much strain the heart is under. Lower levels mean the heart is recovering well. * Echocardiogram: An ultrasound of the heart to check its size and function. * 6-minute walk test: To see if patients feel stronger and can exercise better. * Quality of life survey: To understand how patients feel physically and emotionally. * Kidney function and electrolyte levels: To check for medication side effects. Why Is This Study Exciting? This is the first study to test whether a medication can help the heart heal better after valve surgery. If losartan proves beneficial, it could change how doctors treat patients after surgery and lead to better recovery, stronger hearts, and healthier lives. Many people with aortic regurgitation have to wait until their symptoms get worse before patients can have surgery. If this study finds that medication can speed up healing, it could help doctors treat valve disease more effectively and improve long-term outcomes for patients. What Happens Next? If losartan is found to be helpful, this study could lead to larger research trials and, eventually, new treatment guidelines for people who have had aortic valve surgery. If it doesn't help, doctors will know not to prescribe it unnecessarily, preventing unnecessary side effects and costs for patients. Either way, the results will help improve care for people with heart valve disease. By participating in this study, patients are helping researchers discover new ways to improve heart health and recovery after surgery.