Mitral Valve Anomalies in Transposition of the Great Arteries.

OBJECTIVESTo describe the mitral valve (MV) anomalies found in patients with transposition of the great arteries (TGA), the surgical procedures performed, and the fate of the abnormal MV.METHODSFrom 1990 to 2020, 52 patients out of 1590 TGA {S, D, D} patients (3.3%) undergoing biventricular repair were identified with abnormal MV. Anomalies were a mitral cleft (n = 46 [88%], ejection/outflow tract in 40 and as atrioventricular septal defect [AVSD]-type in 6) and/or anomalies of the subvalvular apparatus (60%). A ventricular septal defect was present in 88.5% and pulmonary stenosis in 17.3%.RESULTSThe main surgical procedure was an arterial switch operation (90.4%). Overall survival was 92.3% at 1 year and 88.3% at 20 years with a mean follow-up of 11.2 years. Ten patients (19.2%) had a concomitant mitral procedure at initial surgery: cleft/indentation closure alone in 4, isolated subvalvular/annuloplasty repair in 1, and combined cleft closure plus subvalvular procedures in 5; 4 had a preoperative grade ≥2 mitral regurgitation (MR). None of these patients have required subsequent MV surgery during follow-up. Another 6 patients required late MV surgery for MR (n = 4) and/or for left ventricular outflow tract obstruction (LVOTO) due to accessory MV material or a narrowed subaortic pathway. None had undergone a mitral procedure at initial repair. All 6 underwent cleft closure, with LVOTO relief in 3 (abnormal chordae attachments resection in 2 and fibromuscular stenosis without MV subvalvular apparatus' anomalies in 1). One patient required redo MV surgery for MV replacement. Freedom from late MV surgery in the overall cohort was 97.9% at 1 year, 93.7% at 5 years, and 82.8% at 20 years.CONCLUSIONSThe most frequent MV anomalies in TGA are anterior clefts and subvalvular abnormalities. Mortality and reoperation rates are much higher than in the other subtypes of TGA. Mitral repair at initial surgery should be considered only in cases of significant regurgitation or obstruction due to subvalvular apparatus' anomalies. Late MV procedure, for a limited proportion of patients, involves cleft closure and LVOTO relief.KEYWORDSarterial switch, mitral cleft, mitral valve, mitral valve repair, reoperation, transposition of the great arteries© The Author(s) 2026. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.