Percutaneous PFO closure represents a standard secondary prevention strategy for cryptogenic ischemic stroke. However, interventional cardiologists often encounter persistent interatrial communications during routine post-procedural surveillance. Moreover, moderate to large residual shunts correlate directly with recurrent cerebrovascular events. Therefore, complete endothelialization and anatomical sealing remain paramount clinical goals. Although device technology has evolved, comparative evidence evaluating distinct transcatheter platforms remains limited. Consequently, a multicenter study from the CAHAL network provides timely insights into device performance.

Clinical Significance of Residual Shunt in Percutaneous PFO Closure

Residual interatrial defects after structural intervention compromise secondary stroke prevention. In particular, right-to-left shunting allows paradoxical emboli to bypass pulmonary capillary filtration, thereby reaching the cerebral circulation. Clinical studies consistently demonstrate that small, trivial residual shunts rarely increase recurrent thromboembolic events. In contrast, moderate to large residual leaks markedly elevate long-term stroke hazards. Therefore, interventional teams must meticulously evaluate procedural success and post-implantation integrity. Furthermore, clinicians often deliberate over whether device selection alters the likelihood of achieving complete mechanical seal. The Amplatzer PFO Occluder utilizes a double-disc nitinol mesh with polyester fabric, which promotes rapid thrombosis and tissue ingrowth. Conversely, the Occlutech Figulla Flex II device features a flexible delivery mechanism and a single-hub left atrial disc. This distinct design minimizes foreign material within the left atrium while enhancing conformability against uneven septal tissue. Despite these structural distinctions, robust clinical trials comparing their mid-term residual shunt rates have remained sparse. Consequently, cardiologists have relied heavily on institutional preference and individual defect anatomy rather than direct comparative efficacy data.

Design and Methodology of the CAHAL Cohort Study

To address this knowledge gap, investigators analyzed real-world outcomes across two tertiary referral centers in the Netherlands. Specifically, the CAHAL registry evaluated patients undergoing transcatheter closure between 2018 and 2024 at Amsterdam UMC and Leiden UMC. The researchers included 413 consecutive adults who underwent successful structural intervention with either an Amplatzer or an Occlutech device. Overall, the cohort exhibited a mean age of 45.8 years, and 51.6% of participants were male. In total, 279 individuals received an Amplatzer device, whereas 134 patients received an Occlutech occluder. The clinical teams assessed shunt presence at six months of follow-up using standardized bubble contrast transthoracic or transesophageal echocardiography. Furthermore, the primary outcome focused on the prevalence of moderate or large residual right-to-left shunts. To prevent confounding, the investigators performed a rigorous sensitivity analysis using inverse probability of treatment weighting. This statistical adjustment thoroughly accounted for critical baseline variables, including patient age, sex, smoking history, baseline shunt severity, device size, and the presence of an atrial septal aneurysm. Thus, this methodology provided a balanced comparison between both commercial devices.

Six-Month Outcomes: Amplatzer Versus Occlutech Devices

The primary analysis revealed intriguing crude differences between the two study cohorts. Specifically, 22.2% of patients receiving an Amplatzer device displayed a moderate or large residual shunt at six months. In comparison, only 14.9% of patients in the Occlutech group exhibited residual shunts of similar magnitude. However, this absolute numerical variation did not achieve statistical significance in unadjusted testing. Furthermore, the sensitivity analysis confirmed that device choice was not independently associated with incomplete mechanical closure. After applying inverse probability weighting, the odds ratio for residual shunting with the Occlutech device was 0.71 with a wide 95% confidence interval spanning from 0.39 to 1.28. Consequently, the multivariable model demonstrated comparable closure efficacy across both technologies. In addition, the findings highlight that imperfect endothelization occurs in a notable subset of patients regardless of hardware selection. Therefore, routine six-month echocardiographic surveillance remains indispensable for detecting silent persistent pathways. Clinicians must recognize that anatomical closure represents a dynamic biologic process rather than an instantaneous physical barrier.

Anatomical Complexity and Predictors of Incomplete Closure

Anatomical complexities often influence procedural outcomes far more aggressively than device brand alone. For instance, the presence of an atrial septal aneurysm creates hypermobile tissue margins that complicate secure disc apposition. In such settings, oversized devices may inadvertently stretch surrounding fossa ovalis tissue, thereby creating peripheral gaps. Moreover, long-tunnel morphologies and prominent Eustachian valves frequently alter the delivery angle during sheath deployment. Consequently, the device may seat obliquely, which delays tissue endothelialization and perpetuates micro-channels. The CAHAL study adjusted for these critical baseline features, confirming that device diameter and anatomical variance contribute substantially to residual shunts. Interventional cardiologists must therefore prioritize high-resolution pre-procedural imaging to evaluate septum primum thickness and tunnel trajectory. Similarly, careful device sizing prevents excessive radial force while ensuring complete rim coverage. When clinicians match device characteristics to distinct patient anatomy, they dramatically reduce the risk of incomplete closure. Thus, meticulous operator planning remains the chief determinant of long-term interatrial sealing.

Clinical Implications for Practice in Indian Healthcare Settings

These comparative findings offer valuable practical guidance for cardiologists operating in India and resource-diverse healthcare environments. In India, transcatheter closure has expanded rapidly as secondary prevention following juvenile or cryptogenic stroke. However, economic factors and device availability often govern device selection across public and private hospitals. Because the CAHAL trial demonstrates clinical equivalence between Amplatzer and Occlutech platforms, operators can confidently select either technology based on availability and cost-effectiveness. In addition, healthcare centers must establish standardized post-closure imaging protocols. Specifically, practitioners should perform agitated saline contrast echocardiography with provocative maneuvers at six months. If a moderate or large residual shunt persists, clinicians should maintain antiplatelet therapy and closely monitor for paradoxical embolism. Furthermore, patient compliance with medical management remains vital during the initial endothelialization phase. Ultimately, institutional quality improves when cath labs combine meticulous device sizing with systematic follow-up pathways. This dual approach ensures optimal neurological protection for young stroke survivors.

Frequently Asked Questions

Why is detecting a residual shunt clinically significant after PFO closure?

Detecting a residual shunt is essential because persistent right-to-left interatrial communication allows venous thrombi to bypass pulmonary filtration. Consequently, moderate to large residual shunts maintain a persistent risk of recurrent ischemic stroke. While trivial micro-shunts rarely cause clinical harm, larger leaks indicate incomplete mechanical sealing or delayed endothelialization. Therefore, clinicians must identify these defects early to optimize secondary antiplatelet therapy and prevent recurrent thromboembolic events effectively.

Did the CAHAL study demonstrate any superiority between Amplatzer and Occlutech?

No, the CAHAL registry demonstrated no statistically significant difference in residual shunt rates between the Amplatzer and Occlutech devices. Although the unadjusted data showed slightly lower shunt rates for Occlutech, rigorous inverse probability weighting yielded an adjusted odds ratio of 0.71 with a non-significant p-value of 0.25. Consequently, interventional cardiologists can view both occluders as equally effective options for achieving anatomical interatrial closure in clinical practice.

How should clinicians monitor patients for residual shunts after transcatheter closure?

Clinicians should perform standardized transthoracic or transesophageal echocardiography combined with agitated saline contrast bubble studies at six months post-procedure. Specifically, imaging specialists must administer bubble injections during rest and forceful Valsalva maneuvers to unmask latent right-to-left shunting. If moderate or large shunting persists, cardiologists typically prolong dual or single antiplatelet therapy, reassess defect morphology, and monitor the patient diligently for any recurrent neurological symptoms.

Disclaimer: This content is for informational and educational purposes only. It is not intended to substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for specific medical guidance. Refer to the latest local and national guidelines for clinical practice.

References

1. Nieuwendijk JD et al. Residual Shunt at 6 Months Follow-up After Percutaneous Patent Foramen Ovale Closure in CAHAL: A Comparison of Occlutech and Amplatzer. Catheter Cardiovasc Interv. 2026 Nov 01. doi: 10.1002/ccd.70963. PMID: 42967338.

2. Pristipino C, Sievert H, D'Ascenzo F, et al. European position paper on the management of patients with patent foramen ovale. General approach and left circulation thromboembolism. Eur Heart J. 2019;40(38):3182-3195.

3. Saver JL, Carroll JD, Thaler DE, et al. Long-Term Outcomes of Patent Foramen Ovale Closure or Medical Therapy after Stroke. N Engl J Med. 2017;377(11):1022-1032.