Commentary

Quest for the Ideal ASD/PFO Closure Device Continues…

Duraisamy Balaguru, MD and P. Syamasundar Rao, MD
Duraisamy Balaguru, MD and P. Syamasundar Rao, MD

Several devices have been developed over the past four decades for transcatheter occlusion of atrial septal defects (ASD) and patent foramen ovale (PFO) starting with the first reported success in the mid-1970s by King, Mills and their associates.1–3 Transcatheter closure of ASD or PFO has been well established over the past several years with several device options — two in the U.S. and more in other countries. Therefore, any novel device has to prove its worth in two ways: performance at least similar to currently available devices, and additional advantage over existing devices. The future of percutaneous closure in children and adults will consist of refinement of existing device technology and inventing new and different shapes or anchoring methodologies. The Occlutech® devices represent a refinement of technology rather than a radical departure from existing device technology. In the current issue, Krizanic et al4 report the results of a safety and feasibility study in human subjects using a novel set of devices, Occlutech® Figulla PFO and ASD occluders (Occlutech GmbH, Jena, Germany). The device description resembles the Amplatzer septal occluder (AGA Medical Corp., Plymouth, Minnesota), but with some differences as discussed below. The authors enrolled 41 adult patients with PFO or ASD and successfully closed the defects in all patients without any significant complications. One death that occurred 9 days after implantation was reportedly unrelated to the device, but was secondary to a second myocardial infarction. The majority of the patients (27/41) had a PFO. Only 11 patients had an ASD. The relationship of the disc-to-waist diameters is similar to the Amplatzer septal occluder. However, the investigators did not specify the criteria based on the length of the septal rims around the defect to determine suitability for transcatheter closure. Follow up was available for 138 patients (27 PFOs and 11 ASDs) up to 180 days, and the results are comparable to the performance of other well-established devices.5,6 Krizanic et al address important issues in the ongoing development of ASD and PFO closure devices and should be congratulated for their efforts. The authors claim several advantages to the design of the Occlutech device and include: 1) half the bulk of the left atrial (LA) disc; 2) lack of a central pin in the LA disc; 3) a self-centering mechanism for PFO device; and 4) the ability to assess device position without the tension from delivery cable prior to release of the device. The authors claim that a reduction in the bulk of the LA disc is an advantage in that the single-layer LA disc will be less thrombogenic than a bulkier device such as the Amplatzer occluder. The authors also suggest that the lack of a central pin in the LA disc will make the device less thrombogenic. While single case reports of thrombus formation have been published, 7–9 single and multi-institutional studies of the Amplatzer septal occluder have not revealed concerning rates of thrombus formation. A clinical study published in 200410 does not support the notion that the bulk of the device will lead to more thrombus formation. This study involved 1,000 consecutive patients who underwent closure of either a secundum ASD or a PFO and had transesophageal echocardiography (TEE) at 4 weeks and 6 months after device implantation. The Amplatzer septal occluder had a lower incidence of thrombus formation when compared to other devices involved in the study, namely, the Rashkind, Buttoned device, ASDOS, CardioSEAL (NMT Medical, Inc., Boston, Massachusetts), StarFLEX (NMT Medical), PFO-Star (Cardia Inc., Burnsville, Minnesota) and Helex (W.L. Gore & Associates, Flagstaff, Arizona). Given the low incidence of thrombus formation with the Amplatzer septal occluder, the presumed superiority of the Occlutech device with regard to reduced thrombus formation awaits confirmation in future studies. Self-centering and the ability to assess device position during deployment without tension from the delivery cable — prior to releasing the device — are stated advantages and are desirable. One additional advantage may be the ability to have a 45° angle between the septum and delivery cable. Exclusion of patients 11–13 a deficient superior vena caval rim may result in residual shunts14 and a deficient aortic rim may be responsible for late perforations.15,16 What is an ideal ASD/PFO device? 1) Simple and user-friendly deployment; 2) Ability to readjust the device position during deployment; 3) Stable upon release; 4) Fits the ASD or PFO appropriately;17 5) No long-term complications such as device displacement or dislodgement, thrombus formation, perforation or endocarditis; and 6) Bioabsorbable. In view of the reports of erosion or perforation of the atrial wall by the device, it would be prudent to have a device that is confined to the true atrial septum so that if an erosion were to occur, it would be confined to the “true” atrial septum17 and would not involve extravasation of blood with its attendant serious consequences. However, the limitations are such that all existing transcatheter devices need a portion of the atrial septum beyond the defect to hold on to for stability. Alternatively, the anchoring or “hold” for the device should not be 4–7 mm long, as is required with many of the devices. One alternative idea is use of a patch, without any metallic components that could cause erosion. Sideris’ patch device has such a feature.18,19 However, that device has not come into routine clinical use in the U.S. and has not been tested as extensively as other devices. A disadvantage of Sideris’ patch device is the need for “holding” the patch in place using a balloon. However, recently, a rapid deployment procedure reportedly has been developed for this device.20 The feasibility and safety of such a patch device remain to be seen. From the perspective of tissue healing and lifelong risk, a bioabsorbable device will be of help. Even though there is a recent report of a device with bioabsorbable patch material, 21 it still has a stainless steel metal framework, but this is a step in the right direction. Anatomists would claim that the atrial septum consists of the true atrial septum, which is the part of the atrial septum that can be removed without exiting the cavities of the heart in the process, and the rest of the atrial septum, a mere infolding of the walls of the right and left atrial myocardium sandwiching the adventitial tissue.17 Most of the true septum is confined to the oval fossa and the anterior rim of the fossa ovalis. A greater understanding of the clinical anatomy of the atrial septum and its surrounding structures should be forthcoming with the advent of 3-dimensional (3D) echocardiography, computed tomographic (CT) scans and cardiac magnetic resonance imaging (MRI) that allow for real-time visualization of atrial septum and its surrounding structures in any given patient when closure of an ASD or a PFO is contemplated. A patient gets referred for evaluation of transcatheter closure of an ASD. He or she undergoes 3D echocardiography, CT or MRI. A virtual model of the patient’s heart — specifically of the atrial septum — is obtained. This gets sent to a laboratory where a custom-made device that takes into account the rims of the defect and the relationship to the structures around the ASD is manufactured. The device is going to interact with these elements, after all! This device arrives in 2 weeks and is placed using a transcatheter technique. Such days may not be far off.

References

1. King TD, Mills NL. Nonoperative closure of atrial septal defects. Surgery 1974;75:383–388.

2. Mills NL, King TD. Nonoperative closure of left-to-right shunts. J Thorac Cardiovasc Surg 1976;72:371–378.

3. King TD, Thompson SL, Steiner C, et al. Secundum atrial septal defect: Nonoperative closure during cardiac catheterization. J Am Med Assoc 1976;235:2506–2509.

4. Krizanic F, Sievert H, Pfeiffer D, et al. The Occlutech Figulla PFO and ASD occluder: A new nitinol wire mesh device for closure of atrial septal defects. J Invasive Cardiol 2010;22:182–187.

5. Rao PS. Summary and comparison of atrial septal defect closure devices. Current Intervent Cardiol Reports 2000;2:367–376.

6. Rao PS. Comparative summary of atrial septal defect occlusion devices. In Rao PS, Kern MJ (eds). Catheter Based Devices for Treatment of Noncoronary Cardiovascular Disease in Adults and Children. Philadelphia: Lippincott, Williams & Wilkins. 2003, pp. 91–101.

7. Willcoxson FE, Thomson JD, Gibbs JL. Successful treatment of left atrial disk thrombus on an Amplatzer atrial septal defect occluder with abciximab and heparin. Heart 2004;90:e30.

8. Acar P, Aggoun Y, Abdel-Massih T. Images in cardiology: Thrombus after transcatheter closure of ASD with an Amplatzer septal occluder assessed by three-dimensional echocardiographic reconstruction. Heart 2002;88:52.

9. Cetta F, Arruda MJ, Graham LC. Large left atrial thrombus formation despite warfarin therapy after device closure of a patent foramen ovale. Catheter Cardiovasc Intervent 2003;59:396–398.

10. Krumsdor U, Ostermayer S, Billinger K, et al. Incidence and clinical course of thrombus formation on atrial septal defect and patent foramen ovale closure devices in 1000 consecutive patients. J Am Coll Cardiol 2004;43:302–309.

11. Nagm AM, Rao PS. Percutaneous occlusion of complex atrial septal defects (Editorial). J Invasive Cardiol 2004;16:123–125.

12. Mathewson JW, Bichell D, Rothman A, Ing FF. Absent posteroinferior and anterosuperior atrial septal defect rims: Factors affecting nonsurgical closure of large secundum defects using the Amplatzer occluder. J Am Soc Echocardio 2004;17:62–69.

13. Rao PS, Techniques for closure of large atrial septal defects. Catheter Cardiovasc Intervent 2007;70:329–330.

14. Balaguru D, Anderson RH, Rosenthal GL, et al. Predictors of residual defects following closure of defects of the oval fossa using the Amplatzer device: Echocardiography recapitulates morphometry. Cardiol Young 2003;13:352–360.

15. Divekar A, Gaamangwe T, Shaikh N, et al. Cardiac perforation after device closure of atrial septal defects with the Amplatzer septal occluder. J Am Coll Cardiol 2005;45:1213–1218

16. Amin Z, Hijazi ZM, Bass JL, et al. Erosion of Amplatzer septal occluder device after closure of secundum atrial septal defect: Review of registry of complications and recommendations to minimize future risk. Catheter Cardiovasc Interv 2004;63:496–502.

17. Martins J, Anderson, R.H. The anatomy of interatrial communications — What does the interventionist need to know? Cardiol Young 2000;10:464-473.

18. Zamora R, Rao PS, Sideris EB. Buttoned device for atrial septal defect occlusion. Current Intervent Cardiol Reports 2000;2:167–176.

19. Sideris EB. Wireless devices for the occlusion of atrial septal defects. In: Rao PS, Kern MJ (eds). Catheter-Based Devices in the Treatment of Non-coronary Cardiovascular Disease in Adults and Children. Philadelphia: Lippincott, William & Wilkins. 2003, pp. 79–84.

20. Sideris EB. Personal communication. January 2010.

21. Jux C, Bertram H, Wohlsein P, et al. Interventional atrial septal defect closure using a totally bioabsorbable occluder matrix. Development and preclinical evaluation of the BioSTAR device. J Am Coll Cardiol 2006;48:161–169.

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From the Department of Pediatrics, Division of Pediatric Cardiology, The University of Texas-Houston Medical School/Children’s Memorial Hermann Hospital, Houston, Texas. The authors report no conflicts of interest regarding the content herein. Address for correspondence: P. Syamasundar Rao, MD, Professor of Pediatrics and Medicine, University of Texas-Houston Medical School, 6410 Fannin, UTPB 425. Houston, TX 7 7030. E-mail: P.Syamasundar.Rao@uth.tmc.edu