Maggie has been going through a lot during the past couple of episodes, especially since her faith in her own abilities have been shattered since her cousin died on her operating table. Elliot Calhoun's return to the hospital does nothing to help that. He comes in for a fourth aortic valve replacement, with Maggie having done the previous three surgeries, right after his wife gives birth to their baby boy.
Already shaken by the very thought of going in solo, Maggie calls in Teddy to assist during surgery, but as soon as she feels secure and the other surgeon leaves the operating room, Elliot's heart stops. There's the possibility that it may start back up sometime in the future, but the situation causes Maggie to question herself and she resigns immediately after.