Comparative roles of the atrial septal aneurysm versus patent foramen ovale in systemic embolization with inferences from neonatal studies.

Patent foramen ovale (PFO) and atrial septal aneurysm (ASA) have a significant statistical relation to ischemic strokes in adults. We reviewed their prevalence in 106 echocardiograms of neonates. Although all normal neonates have PFO, only 4% had ASA. From fetal and neonatal echocardiograms, we conclude that ASAs are more likely to be caused by inadequate size of the PFO, but the ASA can act as a funnel, enhancing the chances of paradoxic embolization in the presence of a PFO. There is no convincing evidence that an ASA alone causes strokes in adults; the confounder is probably atrial fibrillation.