From Mayo clinic (Mair DD et al. Surgical repair of Ebstein's anomaly:Selection of patients, early and late operative results. Circ 1985;72:II70-II76)
1) NYHA III or IV
2) NYHA I and II, but with CT ratio 0.65 or more.
3) Significant cyanosis (80% or less; Hb 16g% or more)
4) Paradoxical embolism
5) Intractable arrhythmia (even though arrhythmia will not be altered by surgery, but it will be better tolerated after surgery)
Indications for surgery in infants with cyanosis and CHF are less clear. Should be individualized.
Also, see other posting on Neonatal Ebstein's Anomaly Management.