Learning curve of mini-right vertical infra-axillary thoracotomy for pediatric atrial septal defect repair: a CUSUM-based analysis

Purpose: Mini–right vertical infra-axillary thoracotomy (MRVIAT) is a minimally invasive technique used for pediatric atrial septal defect (ASD) repair, but its learning curve has not been clearly quantified. This study evaluated the learning curve of MRVIAT using cumulative sum (CUSUM) analysis.Materials and Methods: This single-center retrospective study included 75 consecutive pediatric patients who underwent isolated ASD repair via MRVIAT between 2015 and 2020. CUSUM analysis of total operative time, cardiopulmonary bypass (CPB) time, and aortic cross-clamp time was performed to identify learning phases. Multivariable linear regression and segmented regression analyses were used to validate the effect of cumulative surgical experience and confirm potential breakpoints in the learning curve.Results: Operative performance improved progressively across learning phases. Total operative time decreased significantly (126.8 ± 16.2 min vs. 103.9 ± 11.1 min vs. 91.8 ± 2.7 min). Case order remained independently associated with shorter operative time (β = −0.62 minutes per case). Segmented regression confirmed an inflection point around case 22 and performance stabilization after approximately 35–40 cases..Conclusion: The learning curve of MRVIAT for pediatric ASD repair demonstrates rapid early improvement followed by stabilization. These thresholds should be interpreted as an individual learning curve rather than a universally generalizable benchmark.