This prospective, multicenter cohort study aims to evaluate the outcomes of surgical repair for pediatric mitral regurgitation (MR) in China. From March 2020 to December 2024, consecutive patients younger than 14 years who underwent mitral valve repair at eight representative congenital heart disease centers were enrolled. Eligible patients were those with at least moderate MR on preoperative echocardiography and no prior mitral valve surgery. Patients with uncorrectable concomitant cardiac anomalies, moderate or greater mitral stenosis, ischemic MR, severe leaflet dysplasia, connective tissue disorders (e.g., Barlow, Marfan), cardiomyopathies, or single-ventricle physiology were excluded.

The primary endpoint is a composite of all-cause mortality, reoperation for cardiovascular causes, or recurrence of moderate-or-severe MR during follow-up. Secondary endpoints include perioperative outcomes such as postoperative hospital stay, intensive care unit stay, mechanical ventilation time, and hospitalization cost.

This study is designed to provide high-quality prospective evidence on the safety, durability, and predictors of surgical repair for pediatric MR in a contemporary, real-world, multicenter setting. The findings may inform surgical decision-making and postoperative management strategies for this rare but challenging population.

Inclusion Criteria:

• Age < 14 years
• No prior mitral valve surgery
• Preoperative echocardiography demonstrating moderate or severe mitral regurgitation

Exclusion Criteria:

• Concomitant cardiac malformations unable to be corrected simultaneously
• Moderate or severe mitral stenosis
• Ischemic mitral regurgitation
• Severe leaflet dysplasia precluding adequate coaptation
• Connective tissue disorders(e.g., Barlow's disease, Marfan syndrome)
• Any type of cardiomyopathy
• Single ventricle physiology or common atrioventricular valve

Children younger than 14 years with moderate or greater mitral regurgitation undergoing surgical repair at eight representative congenital heart disease centers in China. Eligible patients must not have undergone prior mitral valve surgery and must meet the predefined inclusion and exclusion criteria. The study aims to prospectively evaluate surgical outcomes, durability, and predictors of repair from March 2020 to December 2024, with follow-up completed through September 2025.

The data underlying this article cannot be shared publicly for the privacy of individuals that participated in the study.