Atrial septal defect (ASD) and patent foramen ovale (PFO) are the most common congenital heart diseases in adults.1,2 Treatment typically involves sealing the defect, which can be achieved through either a percutaneous or surgical approach, depending on clinical and anatomical features. Most cases are treated percutaneously using an atrial septal occluder (ASO), a double-disc device designed to appose the interatrial septum on both sides of the defect.
Accessing the left atrium in patients with an ASO can be challenging and requires careful planning. This scenario is expected to become more frequent due to the increasing availability of mitral valve transcatheter therapies, which require a transseptal approach. Additionally, patients with an ASO have a higher risk of developing AF and may require left atrial access for procedures such as pulmonary vein isolation (PVI) or left atrial appendage occlusion (LAAO).3,4
The larger ASO devices used to treat ASD represent the most significant obstacle to left atrial access. However, transseptal puncture (TSP) can often be performed at the device’s rim (typically caudal), with fluoroscopic guidance using the device as a marker in the left anterior oblique projection.
The approach to TSP in patients with an ASO is not well established, but given the growing need for procedural guidance in this complex setting, this review aims to describe procedural planning and steps; provide a literature review on TSP in different clinical scenarios and associated complications; and propose a comprehensive treatment algorithm.
Procedural Planning
ASO devices pose a challenge for TSP, making preoperative imaging essential for a safe and effective procedure. Preprocedural transoesophageal echocardiography (TOE) and cardiac CT are mandatory for effective procedural planning. CT scans with orthogonal reconstructions offer detailed visualisation of the septum and its fluoroscopic landmarks. 3D reconstructions further enhance anatomical rendering and procedural planning. However, device-related artifacts may limit this approach. Thus, multimodality imaging – combining CT and echocardiography – is crucial for identifying the optimal puncture site.5 TSP can be performed through either the native interatrial septum or the ASO device. Left atrium access via the native septum is preferred when the fossa ovalis is large enough to accommodate the puncture site and the sheath outside the ASO (Figure 1 ).6 A trans-device approach is required in a minority of cases, typically in patients with large ASOs and insufficient native septal rims (Figure 2 ).6
Given the anatomical variations and imaging challenges, understanding the mechanical and structural properties of each occluder device is essential. The Amplatzer septal occluder (Abbott) consists of a double-disc nitinol mesh with Dacron patches, offering good stability but requiring greater force during TSP. The GORE CARDIOFORM septal occluder (Gore Medical), featuring a soft, petal-like design made of expanded polytetrafluoroethylene mounted on a nitinol wire frame, presents a thinner, more elastic profile. This design may facilitate puncture but can pose challenges in maintaining sheath stability. The Occlutech Figulla device (Occlutech) features a nitinol frame with a titanium oxide-coated surface and an ultra-thin polyethylene patch, promoting early endothelialisation and providing a balance between flexibility and support during the procedure.
Although structural differences among devices can influence puncture feasibility and technique, current data remain limited. Therefore, a detailed description of device-specific puncture techniques is not yet possible.
Technical Aspects of Transseptal Puncture in Patients with Atrial Septal Occluder
TSP is a well-described procedure, but unique considerations apply in the presence of an ASO.5
After femoral vein puncture, an 8.5 Fr transseptal sheath and dilator (fixed-curve or steerable) are advanced over a 0.032/0.035" wire to the superior vena cava under fluoroscopic (anteroposterior projection [AP]) and TOE (bicaval view) guidance. The sheath is then gently withdrawn to the designated puncture site under TOE or intracardiac echocardiography (ICE) monitoring.
A transseptal Brockenbrough needle (BRK, St Jude Medical) is inserted into the dilator and advanced under fluoroscopic guidance, ensuring it does not extend beyond the sheath tip. To minimise friction, the BRK needle should be advanced with its stylet inside until it is approximately 4 cm from the tip. A nearly perpendicular puncture angle to the ASO plane is preferred to reduce friction.5 If puncture is difficult, a radiofrequency needle or electrosurgical cautery can facilitate septal crossing without excessive force (Figure 2 ).
Under TOE and fluoroscopic guidance (AP or right anterior oblique projection), the needle is advanced to the left atrium, followed by the dilator and sheath. Crossing the septum with the sheath can be challenging, particularly when puncturing the ASO. As a first step, the transseptal needle can be withdrawn and reshaped to a larger curve, adjusting the puncture angle to make the needle nearly vertical to the device plane. This adjustment provides better support for advancing the system. The Amplatzer nitinol mesh (Abbott) can exert elastic retraction after TSP. These devices are theoretically less compressive at the periphery, and a TSP distant from the central hub may improve catheter manoeuvrability for procedures such as pulmonary vein isolation.7
If the external sheath cannot be advanced through the device, a sequential balloon dilation technique should be considered. Using a 0.014" guidewire positioned in the left pulmonary vein, coronary and/or peripheral balloons can be advanced to the interatrial septum, and multiple dilations can be performed.
Balloon dilation of the interatrial septum can also facilitate catheter manipulation; however, this may be insufficient in TSP through an ASO due to device mesh retraction. In this scenario, balloon-assisted tracking may be employed. This technique involves advancing a peripheral balloon over a stiff 0.035" guidewire, alternating inflations and deflations while gradually advancing the sheath. This method creates a pathway within the device mesh, allowing access to the left atrium. The process is performed under continuous monitoring and the position of the sheath tip in the left atrium should be confirmed using TOE or ICE. Upon completing the procedure and removing the catheter, reassessment of the interatrial septum and ASO is essential to rule out residual shunts or pericardial effusion.8–10
Clinical Scenarios
Access to the left atrium is required for a wide range of interventions on left-sided structures, including the pulmonary veins, left atrial appendage, and mitral valve. Pulmonary vein isolation, left atrial appendage occlusion, and mitral interventions are the most performed procedures requiring a site-specific transseptal puncture; herein, we provide an overview of this specific clinical setting.
Transcatheter Pulmonary Veins Isolation
The largest experience with TSP in patients with ASO involves AF treatment and PVI. The pulmonary veins are located posteriorly in the left atrium, making an adequate TSP crucial for accessing all surfaces and ensuring a satisfactory ablation. There are three main approaches to PVI: radiofrequency ablation, cryoablation, and pulse field ablation.
Radiofrequency ablation can be performed either through an anterior TSP, which allows for better manoeuvrability of the sheaths and catheters, or through a posterior access, typically preferred for better alignment with the right pulmonary veins.11,12
Cryoablation and pulsed field ablation are preferably achieved through a more anterior crossing of the intra-atrial septum. Overall, an anterior TSP is required for different types of pulmonary vein ablation and the puncture should accommodate a sheath up to 14 Fr.13,14
In 2011, Santangeli et al. documented TSP safety in 39 ASO patients undergoing PVI.10 TSP was achieved through the native septum in 35 patients and through the device in four patients with an oversized device compared to the interatrial septum.10 Subsequent studies confirmed the feasibility and safety of TSP in ASO patients, with native septum access being the most commonly used approach. Compared to native septal puncture, device puncture is a more demanding procedure requiring longer procedural time and advanced techniques, such as balloon-assisted tracking (Supplementary Table 1 ).
Li et al. proposed an algorithm for TSP through ASO in patients with devices ≥26 mm, though this cut-off was based on fluoroscopic guidance.15 Sang et al. proposed a larger cut-off (>28 mm) but also documented a case of native septum puncture in a patient with a 32 mm ASO using TOE guidance.8 This finding underscores the importance of tailored procedural planning and accurate imaging guidance.
To minimise risks, it is preferable to reduce sheath manipulation or even fix its location and orientation while manoeuvring only the catheter. Sang et al. recommended a single-catheter technique to reduce complications, prevent device compression, and avoid interference from a second sheath during mapping.8
Left Atrial Appendage Occlusion
The left atrial appendage (LAA) typically has an anterior orientation. For an effective LAAO, a coaxial device positioning is crucial to achieve complete sealing. A posterior TSP generally provides optimal sheath orientation. For commonly used devices, a mid-septal to slightly inferior TSP is preferable.5 However, newer steerable devices, such as the WATCHMAN TruSteer (Boston Scientific), may expand the range of suitable septal puncture sites. Data on LAAO and TSP in patients with ASO are limited to case reports and case series. Gloekler et al. described a successful LAAO through a 24 mm Amplatzer septal occluder (36 mm disc) using fluoroscopic guidance alone.16 The device was perforated in the lower part of the left disc, and an Amulet 22 mm device was effectively deployed. The residual septal hole was closed with an 8 mm ASO, and at the 3-month follow-up, all three devices were well-seated and thrombus-free. Other reports confirm the feasibility and safety of LAAO in ASO patients, with sheath sizes reaching up to 14 Fr and left atrial access primarily achieved through the native septum (Supplementary Table 2 ).17–20
Mitral Valve Interventions
The TSP location for mitral valve interventions, particularly transcatheter edge-to-edge repair (TEER), is typically superior and posterior. Higher TSP positions are required for more medial jets.11 Mitral interventions generally necessitate larger sheaths (up to 24 Fr), making a well-placed TSP essential for procedural success. Villablanca et al. were the first to report an Amplatzer septal occluder (20 mm) puncture for a mitral TEER. Multiple balloon dilations with a 10 mm balloon were required, but the procedure was successfully completed without complications.21 Other case reports highlight the feasibility of mitral TEER in ASO patients, either through the native septum or device puncture.22,23 In these cases, iatrogenic septal defects were initially left untreated, with reports of spontaneous closure within 1 year. However, in one case, closure was required 1 month after the index procedure due to worsening heart failure.23 Overall, TSP through an ASO appears feasible and safe, but the available literature is limited to case reports and case series (Supplementary Table 3 ).
Complications
TSP is a complex procedure with a major complications rate of 1–2%, including pericardial tamponade, cerebral stroke, air embolism and residual iatrogenic shunt.24,25 Despite the perceived higher risk of TSP in ASO patients, few periprocedural complications have been reported; however, publication bias must be considered. Notably, no reports of device migrations have been published, supporting the recommendation that a 6-month interval between ASO placement and subsequent puncture is a safe timeframe.
Guo et al. reported a case of aortic puncture, without adverse consequences, and no cases of pericardial tamponade have been documented in patients undergoing TSP through an ASO.6 Saluveer et al. described a case of sheath displacement to the right atrium and entrapment of a PENTARAY mapping catheter (Biosense Webster) through an Occlutech device requiring surgical removal.26
Studies on patients undergoing pulmonary vein isolation have shown no residual shunts at the 3-month follow-up.9,10,15 Literature suggests that residual shunts are more common with larger transseptal sheaths.27 The structure of the ASO may also influence post-TSP adaptations, with more elastic, branched devices like the Amplatzer differing from more linear, open-structured devices like GORE or Ultrasept (Cardia). While the optimal timing for closure remains unclear, a conservative approach is generally favoured unless significant symptoms or severe shunt are present.27
Treatment Algorithm
Although rare, the presence of ASO in the interatrial septum represents a unique challenge. Cross-sectional imaging provides insights into the device margins and remaining fossa ovalis area for TSP. Reports document successful TSP across most commercially available ASO devices, including specific considerations for GORE and Amplatzer.15,28
The optimal approach depends on multiple factors, including device type and size. PFO closure devices are typically smaller than ASO devices. The device dimension should be compared with the interatrial septum, particularly the fossa ovalis. For devices up to 26–28 mm, a native septum puncture is generally possible. Multimodality imaging, including CT, TOE, and/or ICE, is essential. If a device puncture is necessary, appropriate escalation of TSP methodology is crucial, requiring in-depth knowledge of available techniques to overcome procedural challenges. A tailored approach is mandatory, considering atrial anatomy, device type, and the planned intervention.
Conclusion
TSP can be safely and effectively performed in patients with ASO. Pre-procedural planning and assessment of the relative dimensions of the occluder device compared to the interatrial septum and fossa ovalis are fundamental in determining whether trans-device access is necessary.