Mitral valve (MV) anomalies can be associated with transposition of the great arteries (TGA), but their influence on the choice of the surgical technique and the outcomes after anatomical repair, mainly mitral regurgitation (MR) and LVOT obstruction, have rarely been addressed.

Our study objectives are to describe the MV anomalies found in patients with TGA, the different surgical procedures performed and the fate of the anomalous MV.

From 1990 to 2020, 52 patients out of 1590 (3.3%) were identified. Main MV anomalies were a mitral cleft (88%) and anomalies of the subvalvular apparatus (60%) such as abnormal chordae attachments (16/52, 30.8%), straddling (6/52, 11.5%), accessory tissue (7/52, 13.5%) or an abnormal papillary muscle (4/52, 7.7%). The mitral cleft was described as anterior (ejection/outflow tract) in 40 and as AVSD-type in 6. A ventricular septal defect (VSD) was associated in 88.5% (58% outlet) (Figure 1).

Main surgical procedure performed at repair was the arterial switch operation (ASO) (n=47, 90.4%). Two patients (3.8%) underwent a Bex-Nikaidoh procedure, 2 (3.8%) a half turned truncal rotation and 1 (1.9%) a “reparation à l’étage ventriculaire” (REV) procedure. Overall survival was 90% at 1 year and 88% at 10 and 20 years during a mean follow-up period of 9.5 years. Ten patients (19.2%) had a concomitant mitral procedure at repair (cleft closure in 7, procedure on the subvalvular apparatus in 6), of which 4 had a preoperative grade ≥ 2 MR. Five patients required reoperation for MR and/or for left ventricle outflow tract obstruction (LVOTO), none of them had previously undergone a mitral procedure at repair. All five underwent cleft closure, with LVOTO relief in 3. Freedom from MV reoperation was 96% at 1 year, 93% at 5 years, and 84.5% at 20 years.

Main MV anomalies in TGA are the presence of an anterior cleft and abnormalities of the subvalvular apparatus, frequently associated with an outlet VSD. Mortality and reoperation rates are higher than in the other subtypes of TGA. Mitral repair at initial surgery should be considered only in cases of MR or LVOTO. Reoperation involves cleft closure and LVOTO relief. No MV replacement was required.