REVIEW Different patent foramen ovale closure techniques in varying anatomies Technological developments in recent years have made percutaneous patent foramen ovale (PFO) closure a feasible and safe treatment option. Procedural competency demands a thorough understanding on the variations of PFO anatomy, which can broadly be classified into PFO with minimal tunnel, PFO with long tunnel and PFO associated with atrial septal aneurysm. Each of these subtypes requires different techniques to achieve successful PFO closure and it is unlikely that a single ‘ideal’ device will be suitable for all subtypes. Recognizing the potential problems associated with bulky metallic devices, current developments are focused on a minimalistic approach to PFO closure with reduced foreign material left on the inter-atrial septum. With further refinements, these novel technologies will likely take up a major role in the treatment of PFO-related diseases in the future. † KEYWORDS: Amplatzer® n anatomy n atrial septal aneurysm n long tunnel Ryan Ko , n morphology n patent foramen ovale n PFO closure n PFO closure device n RSTA flex® Nicola E Walker & Michael J Mullen †Author for correspondence: A patent foramen ovale (PFO) can be found in anatomy pertinent to successful device clo- Adult Congenital Heart Disease up to a quarter of the general population [1]. In sure [10]. A PFO is a persistent inter-atrial com- Unit, Royal Brompton Hospital, recent years, this remnant of the fetal circula- munication that resembles a trapdoor; the thin London, SW3 6NP, UK tory system has been implicated in a number and compliant septum primum is analogous to Tel.: +44 207 351 8600 of pathological states, including cryptogenic the door closing against the foramen ovale on the Fax: +44 207 351 8513 strokes, transient ischemic attacks, migraine septum secundum. A PFO is anatomically dif- [email protected] with auras, decompression sickness and severe ferentiated from a secundum atrial septal defect refractory hypoxemia [2–5]. (ASD) by a complete coverage of the foramen Developments in medical engineering over ovale [11], which effectively separates the two the past decade have made percutaneous trans- atriums under normal physiological conditions. catheter closure of PFO a feasible and safe treat- Right-to-left shunting can therefore only occur ment option. In experienced centers, this is a when right atrial pressure exceeds left atrial pres- very low-risk procedure that can be carried out sure, as in the release phase of a valsalva maneuver. with a short procedural time [6]. Because of The entrance of a PFO from the right atrium this favorable risk–benefit ratio, catheterization is an oblique, slit-like defect on the anterior– laboratories worldwide have seen an increase in superior margin of the foramen ovale. This the number of transcatheter PFO closures being opens into a curvilinear tunnel-like gap, walled performed [7]. between the septum primum on the left side Numerous devices are now available with a and the septum secundum on the right. Finally high procedural success rate and reported closure exiting into the left atrium via the remnant of rates of up to 94% at 1 year [8,9]. Manufacturers the foramen secundum in close proximity to the continue to improve their devices in order to anterior atrial wall and the aortic root. This entry simplify the technical requirements and allow and exit pattern of the PFO tunnel is fitting to wider adoption. However, successful closure of the fetal circulation in utero where oxygenated PFO depends on an understanding of the vari- inferior vena cava blood is streamed directly into ability of the anatomy of PFO and surrounding the left atrium. Based on this topography, varia- structures, as well as selecting the appropriate tions in PFO anatomy can arise from different device and technique of closure. degrees of overlapping of the foramen ovale, as well as the mobility of the septum primum. PFO anatomy In patients, a number of variations of this An in-depth knowledge on the embryological complex anatomy may be found: first, PFO development of the atrial septum is necessary with minimal tunnels. This is due to minimal in order to better understand the varying PFO overlapping by the septum primum, analogous 10.2217/ICA.09.36 © 2010 Future Medicine Ltd Interv. Cardiol. (2010) 2(1), 85–95 ISSN 1755-5302 85 REVIEW Ko, Walker & Mullen to a better-fitted trapdoor against the doorframe. device (St Jude Medical, Inc., MN, USA) and The openings on either side of the atrium are the Gore HELEX® Septal occluder (WL Gore therefore geometrically closer together (FIGURE 1). and Associates, AZ, USA). The newer genera- Second, PFO with long tunnels. This is due tion STARflex® and BioSTAR® devices (NMT to extensive overlapping by the septum primum, Medical Inc., MA, USA), as well as the Solysafe® giving rise to a long tunnel-like gap between septal occluder (Swissimplant AG, Switzerland) the septum secundum and septum primum. have self-centering features in their design, which The entrance and exit of this type of PFO are may help in seating of the device during deploy- t herefore further away from each other (FIGURE 2). ment. The general implantation techniques are Finally, PFO associated with atrial septal similar across different devices and will not be aneurysm (ASA). This is due to a redundant further described in this article. and highly mobile septum primum that has A number of studies focusing on individual been defined in different echocardiographic devices have been published, each reporting their studies as a septal excursion of at least 10 mm own procedural success and closure rates [8,14,15]. during the cardiorespiratory cycle [12,13]. ASA However, there is not yet a direct head-to-head can also exist alone or in association with single comparison between different devices with refer- or m ultifenestrated secundum ASDs (FIGURE 3). ence to specific anatomical subtypes [16]. With It is also possible for PFOs to coexist with operators’ own experience and preference aside, multiple small secundum ASDs. These multi- it is likely that different devices will work equally fenestrated PFOs represent a distinctive entity well if they are correctly placed and matched from an interventional perspective, as they to their best-suited PFO anatomy. This reiter- require closure of both the PFO and the ASD ates the need to appreciate individual patient’s to effectively prevent residual shunts. anatomical variations and to tailor each device closure strategy based on these findings. PFO closure devices By contrast, selecting an appropriate device The objective of any PFO closure device is to size is often based on operators’ intuition. hold the septum primum against the septum Various methods using sizing balloon or echo- secundum; effectively keeping the trapdoor shut. cardiographic measurements have been proposed Secondary closure then occurs when the device is to standardize the device size selection process, fully endothelialized and becomes incorporated but none have been widely accepted [17]. In some within the atrial septum; sealing off any residual centers, a single ‘work-horse’ size and device is shunts. Commonly used PFO closure devices used successfully for almost all PFO closures, predominantly consist of a double disc design removing the sizing issue altogether [18]. with a connecting waist and rely on appositional Despite the lack of a standardized protocol on forces between the two atrial discs to effect clo- device size selection, it is well recognized that sure. Examples are the Amplatzer® PFO occluder inappropriate device size will result in both early (AGA Medical, MN, USA), the CardioSEAL® and late complications. Deployment of an over- (NMT Medical Inc., MA, USA), the Premere™ sized device can lead to poor final positioning LA RA Figure 1. Patent foramen ovale with minimal tunnel. (A) Trans-esophageal echocardiogram (short axis) showing a patent foreman ovale with minimal tunnel (white arrow). (B) Sizing balloon inflated within a patent foreman ovale with short tunnel morphology (black arrow). LA: Left atrium; RA: Right atrium. 86 Interv. Cardiol. (2010) 2(1) future science group Different patent foramen ovale closure techniques in varying anatomies REVIEW LA SP SS SS RA Figure 2. Patent foramen ovale with long tunnel. (A) Trans-esophageal echocardiogram (bi-caval view) showing a patent foreman ovale with long tunnel morphology (solid arrows). Note the extensive overlapping of the SP over the SS. (B) Fluoroscopic imaging at straight LAO 50°. Contrast injection through the delivery sheath showing the long tunnel morphology (dotted arrow). (C) Successful deployment of the Premere™ patent foreman ovale closure device (St Jude Medical, Inc., MN, USA) in this patent foreman ovale with long tunnel morphology. LA: Left atrium; RA: Right atrium; SP: Septum primum; SS: Septum secundum. and encroachment on the aortic root. This can size of the PFO and the septal anatomy. Finally, lead to wall erosion and cardiac perforation as intraprocedural echocardiographic monitoring reported in [19]. An undersized device increases can help avoid trapping surrounding struc- the risk of early device embolization as well as tures such as prominent Eustachian valves or recurrent neurological events from inadequate Chiari networks, and help to assess the degree PFO closure and persistent residual shunts [20]. of anchorage in difficult cases, such as with large In our practice, a compliant sizing balloon atrial septal aneurysm and the early detection of together with periprocedural echocardiographic periprocedural complications [21]. guidance (either trans-esophageal or intra- cardiac) is used in every patient during PFO PFO with minimal tunnel device closure. Although slightly more labori- This is the most favorable type of PFO anatomy ous, this arrangement offers several advantages. from an interventional perspective for two rea- First, the sizing balloon allows for a fluoroscopic sons. First, minimal overlapping of the septum estimation of the length of the tunnel as well primum over the foramen ovale means only a as a roadmap for the subsequent intervention.