Final answer:
An unexpected postoperative finding with atrial septal defect repair is paradoxical interventricular septal motion.
Step-by-step explanation:
An unexpected postoperative finding with atrial septal defect repair is C. Paradoxical interventricular septal motion.
During atrial septal defect (ASD) repair, the abnormal opening in the atrial septum is closed. However, in some cases, there can be a paradoxical motion of the interventricular septum after the repair. This means that the interventricular septum, which separates the left and right ventricles of the heart, moves in the opposite direction than it should during the cardiac cycle.
This abnormal motion can lead to decreased ventricular function and other complications.