Small unrepaired atrial septal defects display impaired exercise capacity compared with healthy peers.

Adult patients with a diagnosis of small, unrepaired atrial septal defect have significantly impaired exercise capacity when compared to healthy controls. The impairment was present even if, by the time of assessment, the defect had closed spontaneously. The pathophysiological mechanisms behind the impaired exercise capacity demonstrated in these patients remain unexplained and will be a target for future work.