William Harvey was the first scientist to describe the heart as consisting of separate right- and left-sided circulations. Our understanding of the heart’s anatomy and physiology has grown significantly since this landmark discovery in 1628. Today, we recognise not only the importance of these separate systems, but also the specific tissue that divides them. Our growing understanding of the inter-atrial septum has allowed us to identify defects within this structure and develop effective percutaneous devices for closure of these defects in the adult patient. This article discusses the formation of a patent foramen ovale (PFO) and atrial septal defect (ASD). In addition, we describe the medical illnesses caused by these defects and summarise the indications and risks related to percutaneous closure of these defects. We also report the most up-to-date transcatheter therapeutic options for closure of these common congenital defects in the adult patient.
