Background The current technique used in severe mitral regurgitation in children can occasionally lead to residual regurgitation. To address this issue, the posterior annulus elevation technique was developed to enhance coaptation and reduce residual lesions. This study aims to evaluate the effectiveness of this technique in reducing residual regurgitation during mitral valve repair in children. Methods A total of 64 patients aged <18 years old undergoing mitral valve repair were randomized into two groups: the intervention (with posterior annulus elevation) group and the control group, which underwent conventional repair techniques. Various parameters, including coaptation area, residual mitral regurgitation, clinical outcomes, metabolic, and hemolytic markers, were measured on days 0, 5, 2 weeks, and 3 months after surgery. Results The intervention group (n = 32) showed a significant reduction in residual …