The Senning repair is one of two "atrial switch" procedures used to functionally correct transposition of the great arteries (the other being the Mustard repair). 

The two share a similar fundamental principle.  Systemic blood flow is redirected away from the RV and toward the LV.  Essentially "two wrongs make a right."

The main adverse effect of these atrial switch procedures is arrhythmia.  During creation of the baffle and redirected atrial flow, the sinoatrial node is often injured. The Senning repair has a lower rate of arrhythmia than the Mustard repair, but the arterial switch procedure is now preferred to correct transposition, partly to avoid this complication.