Extreme exercise dislike of a toddler due to a patent foramen ovale.

A 5-year-old girl presented with chronic fatigue and extreme exercise intolerance. After countless doctor visits, investigations, and hospital admissions, striking desaturation during exercise test pointed to a cardiovascular problem. Desaturation as a result of right-to-left shunting through a patent foramen ovale during upright exercise was hypothesised. A cardiac catheterisation confirmed the presence of an unusually cranially located patent foramen ovale; the defect was subsequently closed. Physical re-evaluation 6 weeks later showed spectacular physical and mental improvement and stabile saturation during exercise.