ObjectiveTo study the safety of right vertical infra-axillary thoracotomy (RVIAT) in the repair of ventricular septal defect (VSD) and the optimal age for RVIAT.MethodsBetween June 2014 and June 2018, 441 children underwent VSD repair via RVIAT in our hospital. According to the age, they were divided into four groups: a 4 months to 1 year old group (R1 group, n=123), a 1-2 years old group (R2 group, n=106), a 2-5 years old group (R3 group, n=166), a >5 years old group (R4 group, n=46). The clinical effects of the patients were compared.ResultsAll the operations were successfully performed and no serious complication was found in all groups. No statistical difference was observed in the operation time, blood loss during operation, thoracic drainage 24 h after operation among groups (P>0.05). The cardiopulmonary bypass time, aortic cross-blocking time and ICU stay time in the R1 and R2 groups were longer than those in the R3 and R4 groups (P<0.05). In the R1 group, the postoperative ventilating time and postoperative hospital stay time were longer, and the blood transfusion volume was more than those in the R3 and R4 groups (P<0.05). The incidence of postoperative complications was higher in the R4 group than that in the R1 and R3 groups (P<0.05).ConclusionVSD repair via RVIAT may be more effective in children >2 years old, and 2-5 years old may be the optimal age.