What is a foramen ovale?A foramen ovale (FO) is an anatomical structure allowing communication between the right and the left atrium. Differently from an atrial septal defect which is a hole in the atrial septum, the FO is a tunnel running from right to left between the septum secundum, on the right side, and the septum primum on the left side ( Figure 1).The width and length of the tunnel can be widely different from case to case, depending on the degree of separation and overlapping of the two septa. The septum primum, which is the thinner of the two septa, can be redundant and mobile forming an atrial septal aneurysm and it can harbor one or more fenestrations creating additional communications between the atria. The septum secundum, which is not a real septum but an infolding of the atrial wall filled with fat tissue, can vary in thickness, depending on the amount of fat, up to more than 10 mm (lipomatous hypertrophy). Therefore, the anatomical features of the FO are consistently variable and additional anatomical structures such as a redundant Eustachian valve or a Chiari network, can further add to the complexity of its anatomy. The FO is essential for fetal life allowing the oxygenated blood coming from the placenta via the inferior vena cava to cross the atrial septum reaching the left ventricle and ascending aorta to mainly supply the brain; the well-developed Eustachian valve of the fetus plays a crucial role by directing the blood from the inferior vena cava to the entrance of the FO on the right side of the septum.After birth, respiration lowers the pulmonary vascular resistances increasing the pulmonary blood flow and the blood inflow into the left atrium which, in turn, increases left atrial pressure forcing the septum primum against the septum secundum and functionally closing the FO. With time, the two septa become fused to each other, anatomically sealing the FO. This sealing process does not occur in many people leaving a patent foramen ovale (PFO) in around 25%-30% of the general population as shown by autopsy findings and echocardiographic reports.
ABSTRACTThe foramen ovale (FO) is an anatomical structure normally present in the fetus, which can persist in up to 25%-30% of the general population after birth. Normally it does not cause any harm but it has been associated with different pathological conditions; the more frequently encountered in clinical practice is an ischemic stroke or transient ischemic attack without any recognizable cause. However, a causal link between the cerebrovascular event and a right to left shunt through the FO is hard to demonstrate in most cases and which is the best treatment for secondary prevention is still a matter of debate with antithrombotic therapy or transcatheter closure of the FO as possible options. No definitive evidence of which is the most effective treatment is actually available so that a careful evaluation of each single patient is mandatory in order to select who will probably benefit the most from the interventional treatment as opposed to wh...