How do the Mustard repair and Senning repair differ?
The Mustard repair uses artificial material to circle the caval orifices and splits the subtricuspid isthmus. The Senning repair accomplishes the same "atrial switch" but uses the right atrial free wall and atrial septal flap to correct flow.
How is the Senning repair formed?
The atrial wall is cut near the level of the tricuspid valve, creating a flap/baffle. The flap of the atrial septum is then sutured to the anterior lip of the orifices of the left pulmonary veins. This separates the pulmonary and systemic venous channels.
Axial sequence demonstrating a Senning repair for transposition of the great arteries. Instead of switching the circulation at the level of the arteries (arterial switch procedure), the circulation is switched at the level of the atria.
Note how the aorta arises anteriorly (as with transposition) and how the right ventricle has become thicker and trabeculated, assuming the morphology of the left ventricle.
Oxygenated blood flow (red arrow); deoxygenated blood flow from the SVC and IVC (blue arrow). The green arrow points to the baffle formed from the right atrial free wall and atrial septal flap.