Staged Acclimatization in a Failing Fontan by AFR in AFR: Ever-Decreasing Circles.

We describe serial implantation of atrial flow regulator (AFR) devices in the Fontan fenestration of a 4-year-old patient. Initially, the fenestration size was decreased using a 6/5 AFR, resulting in improved saturations and hemodynamics. One year later, further improvement was achieved by placing a 4/10 AFR inside the original device. (Level of Difficulty: Advanced.).