Transcatheter patent foramen ovale closure: review and choice of devices

The foramen ovale is an essential part of the fetal circulation, allowing right-to-left shunt of oxygenated blood derived from the umbilical vein to bypass the nonfunctional lungs in utero. It is formed by the septum primum and septum secundum. After birth, owing to an increase in the left atrial pressure and a decrease in the right atrial pressure, the septum primum is pushed against the thicker septum secundum from the left atrial side, resulting in closure of this foramen ovale. However, in a significant proportion of individuals, the foramen ovale remains patent. On autopsy studies, a patent foramen ovale (PFO) has been identified in 27% of individuals [1,2]. Such post-mortem ‘probe patency’ may be an overestimate of the prevalence of a PFO under physiologic conditions in the general population, as transesophageal echocardiographic studies have found a PFO to be present in approximately 10–15% of individuals [3,4]. Owing to its high prevalence, a PFO is mostly considered to be a benign, incidental finding. However, several conditions have been found to be associated with a PFO. Those conditions include cryptogenic stroke or transient ischemic attack (TIA), decompression sickness in divers, platypnea–orthodeoxia syndrome, high altitude pulmonary edema and migraine headaches [5–11]. The mechanism by which a PFO is believed to be related to those disease states is secondary to the resulting right-to-left shunt. This shunting allows passage of blood low in oxygen content, vasoactive substances or corpuscular material such as thrombi into the systemic circulation, potentially causing hypoxemia, migraine or strokes. Closure of a PFO in the right context may allow attenuation of symptoms of hypoxemia or recurrence of strokes or migraine headaches. This article briefly reviews the data supporting transcatheter PFO closure in a variety of clinical scenarios, understanding that the majority of data are available in patients with cryptogenic stroke or TIA. We will then provide an overview of the different devices available for PFO closure with a focus on device specifics that are important to the interventionalist when choosing a device for transcatheter PFO closure.