Review: Atrial Septal Defects

When and How Should Atrial Septal Defects Be Closed in Adults?

P. Syamasundar Rao, MD
P. Syamasundar Rao, MD
From the Division of Pediatric Cardiology, Department of Pediatrics, University of Texas-Houston Medical School/Memorial Hermann Children’s Hospital, Houston, Texas. *Presented in part at the Concepts in Contemporary Cardiology, Houston, Texas, April, 2006. Address for correspondence: P. Syamasundar Rao, MD, Professor and Director, Division of Pediatric Cardiology, UT-Houston Medical School, 6431 Fannin, Suite 3.132, Houston, TX 77030. E-mail: P.Syamasundar.Rao@uth.tmc.edu

__________________________________
ABSTRACT: In this review, evidence is presented to indicate that hemodynamically significant (right ventricular volume overload) atrial septal defects (ASDs) in adults should be transcatheter occluded, irrespective of symptomatology. While surgical closure is safe and effective, device closure carries less morbidity. Several devices have been investigated over the last few decades, but at the present time, only two devices, namely, the Amplatzer and the Helex, have received FDA approval; the former is useful in most defects, while the latter is useful in small- and medium-sized defects. A detailed description of Amplatzer device implantation is presented. Finally, approaches to occlude ASDs with complex anatomy are reviewed.

J INVASIVE CARDIOL 2009;21:76–82

____________________________________
The most common types of defects in the atrial septum are ostium secundum, ostium primum, sinus venosus and patent foramen ovale. Ostium primum and sinus venosus defects require surgical intervention because of associated defects (cleft in the mitral valve causing mitral regurgitation in the ostium primum defects and partial anomalous pulmonary venous connection in sinus venosus defects). The considerations for closure of a patent foramen ovale (PFO), namely, presumed paradoxical embolism, platypnea-orthodeoxia syndrome, migraine, decompression illness and others, are completely different than those for the closure of ostium secundum atrial septal defects (ASDs). In this review, only ostium secundum ASDs in adult subjects will be discussed. Some authorities opine that closure of ASDs in adult subjects is not necessary if they are not symptomatic. Some early studies were interpreted to show no major benefit if surgical closure was performed in adulthood.1–3 Based on more recent analysis, it would appear that ASDs should be closed when they are identified. The purpose of this review is to present evidence to support the argument that ASDs in adults should be closed. The methods of transcatheter closure in adults is reviewed, as are the approaches to occlude complex forms of ASDs.

Evidence in Favor of Closing ASDs in Adults

Rosas et al4 followed 200 patients > 40 years of age (49 ± 9 years) for a period ranging from 2 to 22 years and found that 37 (18.5%) had major events: 7 developed heart failure, 5 suddenly died, 13 had severe pulmonary infection, 5 developed embolism, 4 had a stroke and 3 had miscellaneous complications; 51% had dyspnea. Predictors of complications were age at presentation, elevated pulmonary artery pressures and O2 saturations 6 They examined 179 patients > 40 years of age; 84 patients underwent surgical closure and 95 patients did not have surgery. Both groups were followed for 10 years. The 10-year survival rate was 95% in the surgery group and 84% in the no-surgery group. Surgery also appears to have prevented deterioration of the patients’ NYHA functional class. The authors concluded that surgical repair of ASDs in adult subjects increases long-term survival and decreases functional deterioration when compared to medical therapy. Cardiac function following ASD closure was evaluated by Salehian et al.7 Twenty-five patients at a mean age of 46 years were studied prior to and 3 months (mean) after device closure of their ASD. Their right ventricular myocardial performance index (MPI) improved from 0.35 ± 0.14 to 0.28 ± 0.09 (p = 0.004), while their left ventricular MPI improved from 0.37 ± 0.12 to 0.31 ± 0.11 (p = 0.04) (Figure 1). The lack of improvement of the right ventricular MPI following surgical closure8 is attributed to the adverse effects of cardiopulmonary bypass on ventricular function. They concluded that ASD closure improves cardiac function. Functional capacity following ASD closure was studied by Brochu et al.9 They evaluated 37 patients (mean age, 49 years) with a Qp:Qs ratio of 2:1. The VO2 maximum was measured prior to and 6 months after ASD closure and was found to be improved (23 ± 6 vs. 27 ± 7; p Surgical vs. Transcatheter Closure Although surgical closure of ASDs is safe and effective with low mortality,10–12 the morbidity associated with sternotomy/ thoracotomy is unavoidable. Consequently, substantial efforts have been made by the cardiology community to develop a nonsurgical, catheter-based method of ASD occlusion. Since the initial description in the mid-1970s by King and Mills and associates13–15 of an ASD occlusion device, a number of other devices, including Rashkind’s devices (hooked and double-umbrella), the Clamshell occluder, the buttoned device, Pavnik’s mono-disc device, the modified Rashkind’s patent ductus arteriosus umbrella device, the ASDOS (atrial septal defect occluding system), the Das Angel Wing device, the Amplatzer septal occluder, the CardioSeal and StarFlex devices, the Centering-on-Demand buttoned device, the Helex device, the transcatheter patch and others (Figures 3–5), have been studied and reviewed elsewhere.16,17 Other devices in clinical trials include the PFM, bioabsorbable NMT, the Occlutech and Solysafe devices and the Heart R Septal Occluder (manufactured in China). Most studies comparing surgical vs. device closure suggest similar effectiveness,18,19 but device closure is less invasive, requires no cardiopulmonary bypass, has less complications (10 vs. 31%), requires shorter hospital stays (1 vs. 4.3 days), and is less expensive ($11,000 USD vs. $21,000 USD).20 The device closure techniques have proven to be safe, cost-effective and favorably compare with surgical closure.18-21 Transcatheter closure of ASDs using various devices22 is now an established practice in most cardiac centers.

Device Closure

Many devices are available to the interventional cardiologist, but selection of a particular device becomes difficult because of the lack of randomized clinical trial data. A few studies 23–26 attempted to compare the results of several devices when they became available, but these studies are neither randomized nor blinded and are unlikely to shed any more light than the single-center device studies. With existing economical, ethical and medical considerations, it is not possible to conduct a prospective randomized clinical trial utilizing all the eligible devices. For this reason, selection of the device may have to be based on the results of clinical trials conducted separately by the inventor or manufacturer of the device. A careful comparison27–30 of implantation feasibility (ratio of implantations versus patients taken to the catheterization laboratory with the intent to occlude), percent of device dislodgements/misplacement/embolization, percent of patients with effective occlusion and reintervention-free rates during follow up, tabulated elsewhere,29,30 reveal that these are similar and comparable for most, if not all, devices. In addition to the feasibility, safety and effectiveness data, the availability, cost, size of the delivery sheath and other factors may have to be considered in the selection of the device. Of the devices listed above, some were discontinued because of the problems identified during the study of the respective devices. At present, the Amplatzer (AGA Medical Corp., Golden Valley, Minnesota) and Helex (W.L. Gore, Flagstaff, Arizona) are the only devices approved by the U.S. Food and Drug Administration (FDA) for general clinical use to close ASDs. Several other devices are currently in clinical trials. At present, the Amplatzer septal occluder is the most commonly used ASD closure device worldwide. The feasibility, safety and efficacy of device occlusion is based on the self-expandable, retrievable and re-positionable design of the device.31 Even very large defects can be closed successfully with the Amplatzer device using a variety of techniques.32,33 In this review, device occlusion with Amplatzer device will be described.

Protocol for ASD Closure

Diagnosis and indications. Following clinical and echocardiographic diagnosis of moderate-to-large ostium secundum ASDs, a consideration for transcatheter closure should be given. Because of poor echo windows, most adult subjects require transesophageal echocardiography (TEE) to confirm the diagnosis, to quantify the ASD size and to define the septal rims. The reasons for closure of ASDs in children include the prevention of pulmonary vascular obstructive disease in adulthood, prevention of arrhythmias and prevention of symptoms later in life. The indications for closure in children are an echocardiographic finding of right ventricular volume overloading and/or catheterization findings of a pulmonary-to-systemic flow ratio (Qp:Qs) > 1.5:1.0, which are essentially carried over to adult subjects. Consent and catheterization. Informed consent is obtained and cardiac catheterization is performed during the same session as transcatheter ASD closure. Percutaneous right-heart catheterization is undertaken to confirm the clinical and echocardiographic diagnosis, with particular attention to exclude partial anomalous pulmonary venous return. A left atrial cineangiogram is performed in a left axial oblique view (300 degree LAO and 300 degree cranial), with the catheter positioned in the right upper pulmonary vein at its junction with the left atrium. While I routinely perform this angiogram, other operators do not. Next, transesophageal echocardiography (TEE) or intracardiac echocardiography (ICE)34 is undertaken to measure the size of the ASD, visualize the entry of all pulmonary veins into the left atrium and to examine the atrial septal rims. Balloon sizing. Static balloon-sizing of the ASD using NuMED PTS (NuMED, Inc., Hopkinton, New York) or AGA Amplatzer sizing balloons used to be done routinely. The balloon is inflated until the color-flow stops or a small waist is seen; it should not be overinflated. During balloon occlusion, color Doppler evaluation of the atrial septum to rule out additional atrial defects is carried out. Recent studies suggest that there is no need to routinely balloon-size the ASD. At the present, we do not routinely balloon-size the defect. Instead, we measure the defect size using only the thick portions of the septal rims, eliminating the thin and frail portions. These data are used to select the size of the device to be implanted. If there is a discrepancy between the various modes of measurement of an ASD, balloon-sizing is performed. Device implantation. The device is implanted under both echocardiographic and fluoroscopic guidance. An Amplatzer Septal Occluder, 1–2 mm larger than the TTE or ICE estimated size of the ASD or stretched diameter (balloon-sizing, if performed) of the ASD is selected. A delivery sheath accommodating the selected device is positioned in the left upper pulmonary vein, taking appropriate precautions to avoid inadvertent air entry into the system. The device is screwed onto the delivery cable, and is loosened by unscrewing by one turn and drawn into the loader sheath under saline. The device is deposited into the delivery sheath while flushing the loader sheath continuously with saline to prevent inadvertent air entry into the system. The device is then advanced under fluoroscopic guidance to the left atrium by advancing the delivery cable. The entire system is withdrawn so that the left atrial disc is against the left atrial side of the atrial septum. Once it is determined to be in a good position (by TEE or ICE), the tip of the sheath is withdrawn into the ASD so that the waist of the device is across the defect. The right atrial component of the device is released in the right atrium. TEE/ICE is then performed to confirm that the device components are on either side of the atrial septum, to ensure that there is no interference with AV valves and venous (pulmonary and systemic) return, and to document any residual shunting. A “Minnesota” wiggle is performed to ensure that there is no device dislodgement. The delivery wire is then unscrewed and the device released. Cinefluoroscopy of the device and TEE/ICE are performed to confirm the position of the device, as detailed above. The catheters and sheaths are then removed. Heparin is administered to keep the activated clotting time (ACT) > 250 seconds. One dose of antibiotic (usually cefazolin sodium) is administered in the catheterization laboratory followed by 2 more doses over the next 12 hours. Aspirin 3–5 mg/kg/day p.o. for 6 months is prescribed. Some cardiologists administer clopidogrel 75 mg/day for the first 2–3 months after device implantation. Restriction from high-intensity physical activity for 3 months is recommended. Reevaluation 1, 6 and 12 months after the procedure and 1–5 years thereafter is suggested.

Complex Atrial Septal Defects

Centrally-placed secundum ASDs are found in only 24% of cases.35 In a detailed review of 190 patients who underwent transcatheter or surgical repair, Pondar and associates35 showed deficient superior anterior (SA) rim in 42%, deficient inferior posterior (IP) rim in 10%, perforated aneurysm of the atrial septum in 8%, multiple defects in 7%, deficient inferior anterior (IA) and superior anterior (SA) rims in 3%, deficient inferior posterior and posterior rims in 2%, and deficient IA, superior posterior (SP) and coronary sinus rims in 1% each. In the study by Pedra and his associates,36 complex ASDs were present in 40 (28%) of 143 patients. The complex anatomy was arbitrarily defined as: ASDs with stretched diameters > 26 mm with a deficient ( 7 mm (n = 8), fenestrated atrial septum (n = 5) or redundant and hypermobile (> 10 mm) atrial septum (n = 4). Issues related to complex ASD anatomy will be reviewed here. Large defects. A large ASD was defined by Pedra et al36 as one with a stretched diameter > 26 mm, and a similar definition has been used by most other operators in this field. Although it appeared to be a simple problem, there were questions about how large a device could be used to close such defects, whether the left atrium could accommodate such a device, and whether such a large device would encroach on other intracardiac structures (e.g., atrioventricular valves) or obstruct blood flow (e.g., vena cavae or pulmonary veins). Large defects are likely to be associated with a deficient posterior-inferior rim,37 rendering device implantation even more difficult. Deficient anterosuperior rim. A deficient anterosuperior rim is frequently encountered with large ASDs and, indeed, in our center’s experience, most ASDs we have attempted to occlude with various devices were found to have a deficient anterosuperior rim. Other investigators35,38,39 have had similar experiences. In a study reported by Varma et al,40 a deficient inferior rim was found to be associated with unsuccessful Amplatzer implantations. With a deficient anterosuperior rim, the discs of the Amplatzer straddle the ascending aorta. With other double-disc devices, the left atrial disc sits on the back of the aorta. Initial reports of erosion of the aortic wall by the ASO, with development of aorta-to-right atrium41 or aorta-to-left atrium42 fistulae, led to the recommendation of oversizing the device (i.e., using a device size 4 mm larger than the measured stretched diameter) in large defects with a deficient anterosuperior rim to ensure the device discs straddle and remain flared around the ascending aorta to prevent discrete areas of pressure where erosion may occur. When oversizing the device, care must be taken not to interfere with surrounding intracardiac structures. In addition, one must be cognizant of potential problems associated with the use of large devices. Device migration/erosion of the aorta during follow up43,44 was observed in 37 out of 35,000 Amplatzer implants, i.e., 0.11% (1 in 1,000). In the U.S., 18 out of 15,900 implants, i.e., 0.12% (1 in 1,000) developed such complications. Review of data by the Review Board and AGA Medical suggested that device erosion is related to oversizing of the device (Figure 6). They recommend against using a device size > 1.5 times the TEE/ICE diameter of the ASD. However, the difficulty in deploying the Amplatzer device in patients with a deficient anterosuperior rim is that the left atrial disc tends to become perpendicular to the atrial septum, leading to prolapse of the left disc into the right atrium. To overcome such a challenge, several techniques have been proposed and reviewed elsewhere.32,33 Deployment of the left disc of the device in the right upper or left upper pulmonary vein, followed by release of the waist and the right atrial disc while simultaneously withdrawing the deployed left atrial disc against the atrial septum,19,38-40,45 has been successfully done. Heat-bending the distal delivery sheath 360 degrees plus cutting off the tip of the sheath ≥ 45 degrees toward its inner circumference is another technique proposed to help avoid prolapsing of the left disc into the right atrium.37,40,46 Another technique involves the use of a specially-designed sheath (Hausdorf Sheath; Cook Inc., Bloomington, Indiana) with two curves at the end to help align the left atrial disc parallel to the septum.36,40,43,47 Supporting/holding the left atrial disc with the tip of a reinforced dilator48 or sizing-balloon catheter49 to prevent prolapse into the right atrium are other methods that have been recently employed with success. Kutty at al50 cut the sheath to create a straight catheter with a side hole, the so-called SSH modification, and were successful in positioning the device in 120 of 122 (98.4%) patients in contradistinction to successful deployment of the device in 14 of 18 (78%) patients with the use of a standard Amplatzer delivery sheath. The interventional cardiologist should consider all options reviewed above, including SSH modification, and select the method that is most likely to result in successful implantation of the device. Multiple or fenestrated defects. These types of ASDs may be successfully closed using different techniques or devices. Carano et al51 reported the use of balloon atrial septostomy to create a single large defect that could then be closed with a single large ASO device. We are not in favor of using such a technique, however. Szkutnik et al52 reported the use of a single ASO device deployed in the larger defect to occlude two or more smaller defects. In their series, a smaller defect 7 mm, a residual left-to-right shunt will persist. Other methods for closure of multiple defects with a single device include using a single CardioSeal device53,54 or the new Amplatzer Cribriform device.55 If the smaller defect is hemodynamically significant, but is far from the other defect (> 7 mm), two devices should be used. After verifying good positioning of both devices, release of the smaller device should precede release of the larger device. We have used both the two-device technique and the Cribriform device with good success. Deficient posteroinferior rim. Closure of a large ASD with a deficient or absent posteroinferior (PI) rim continues to be a real challenge. The insufficient number of cases with a deficient PI rim reported in most series makes it even more difficult to form a solid consensus. Pedra et al36 mentioned 1 case with a deficient anterior rim and a floppy, thin and hypermobile posterior rim that was not a good candidate for device closure. Du et al19 reported 23 patients with deficient rims, of which 3 patients had deficient inferior or posterior rims. Two patients had a 2 mm posterior rim, and the third had a 4 mm posterior rim. These 3 patients underwent successful closure procedures. The number of cases is too small, however, to make a generalized conclusion. Mathewson et al37 defined an absent PI rim as one measuring 37 Aneurysmal atrial septum. Septal aneurysms with single or multiple defects represent a different kind of complex anatomy of the ASD. Such anatomy is better treated with devices that do not rely on a stenting mechanism within the defect to achieve stabilization in the septum. Patch or double-disc-type devices such as the COD buttoned device, the Helex, the CardioSeal or the more recent Amplatzer Cribriform, are more appropriate choices to close such defects. A large defect within an aneurysmal septum may, however, require a large Amplatzer device or may not be amenable to Amplatzer closure. Closing two small but distant defects within an aneurysmal atrial septum may effectively close both defects, but carries a higher risk of later development of thrombus formation.56 We have successfully closed defects associated with atrial septal aneurysms with hybrid buttoned devices (Figure 7) by compressing the aneurysm between the occluder and the square-shaped counter-occluder.57 In conclusion, most cases of complex anatomy of secundum ASDs can be closed successfully either by using traditional or special techniques or devices. Defects with a deficient or absent PI rim continue to be a challenging task for most interventional cardiologists.

Summary and Conclusions

ASDs in adult subjects should be closed at presentation, electively, irrespective of their age and symptoms. The Amplatzer device appears to be the best available option at present. Careful attention to the details of the technique is mandatory to achieve a successful outcome.

References

1. Ward C. Secundum atrial septal defect: Routine surgical treatment is not of proven benefit. Br Heart J 1994;71:219–223. 2. Gatzoulis MA, Redington AN, Somerville J, et al. Should atrial septal defects in adults be closed? Ann Thorac Surg 1996;61:657–659. 3. Webb G. Do patients over 40 years of age benefit from closure of an atrial septal defect? Heart 2001;85:249–250. 4. Rosas M, Attie F, Sandoval J, et al. Atrial septal defect in adults ≥ 40 years old: Negative impact of low arterial oxygen saturation. Int J Cardiol 2004;93:145–155. 5. Horvath KA, Burke RP, Collins JJ Jr, Cohn LH. Surgical treatment of adult atrial septal defect: Early and long-term results. J Am Coll Cardiol 1991;20:1156–1159. 6. Konstantinides S, Geibel A, Olschewski M, et al. A comparison of surgical and medical therapy for atrial septal defects in adults. N Engl J Med 1995;333:469–473. 7. Salehian O, Horlik E, Schwermann M, et al. Improvement in cardiac form and function after transcatheter closure of secundum atrial septal defects. J Am Coll Cardiol 2005;45:499–504. 8. Eidem BW, O’Leary PW, Tei C, Seward JB. Usefulness of the myocardial performance index for assessing right ventricular function in congenital heart disease. Am J Cardiol 2000;86:654–658. 9. Brochu MC, Baril JF, et al. Improvement in exercise capacity in asymptomatic and mildly symptomatic adults after atrial septal defect percutaneous closure. Circulation 2002;106:1821–1826. 10. Murphy JG, Gersh BJ, McGoon MD, et al. Long-term outcome after surgical repair of isolated atrial septal defect. New Engl J Med 1990;323:1645–1650. 11. Galal MO, Wobst A, Halees Z, et al. Perioperative complications following surgical closure of atrial septal defect type II in 232 patients — A baseline study. Eur Heart J 1994;15:1381–1383. 12. Pastorek JS, Allen HD, Davis JT. Current outcomes of surgical closure of secundum atrial septal defect. Am J 1994;74:75–77. 13. King TD, Mills NL. Nonoperative closure of atrial septal defects. Surgery 1974;75:383–388. 14. Mills NL, King TD. Nonoperative closure of left-to-right shunts. J Thorac Cardiovasc Surg 1976;72:371–378. 15. King TD, Thompson SL, Steiner C, et al. Secundum atrial septal defect: Nonoperative closure during cardiac catheterization. JAMA 1976;235:2506–2509. 16. Chopra PS, Rao PS. History of the development of atrial septal occlusion devices. Current Intervent Cardiol Reports 2000;2:63–69. 17. Rao PS. History of atrial septal occlusion devices. 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. 1–9. 18. Berger F, Vogel M, Alexi-Meskishvili V, Lange PE. Comparison of results and complications of surgical and Amplatzer device closure of atrial septal defects. J Thorac Cardiovasc Surg 1999;118:674–678. 19. Du ZD, Hijazi ZM, Kleinman CS, et al. Comparison between transcatheter and surgical closure of secundum atrial septal defect in children and adults: Results of multicenter nonrandomized trial. J Am Coll Cardiol 2002;39:1836–1844. 20. Kim JJ, Hijazi ZM. Clinical outcomes and costs of Amplatzer transcatheter closure as compared with surgical closure of ostium secondum atrial septal defects. Med Science Monitor 2002;12:CR787–791. 21. Bettencourt N, Salome N, Carneiro F, et al. Atrial septal closure in adults: Surgery versus Amplatzer — Comparison of results. Rev Port Cardiol 2003;22:1203–1211. 22. Rao PS. Catheter closure of atrial septal defects. J Invasive Cardiol 2003;15:398–400. 23. Walsh KP, Tofeig M, Kitchiner DJ, et al. Comparison of the Sideris and Amplatzer septal occlusion devices. Am J Cardiol 1999;83:933–936. 24. Formigari R, Santoro G, Rosetti L, et al. Comparison of three different atrial septal defect occluding devices. Am J Cardiol 1998;82:690–692. 25. Sievert H, Koppeler P, Rux S, et al. Percutaneous closure of 176 interatrial defects in adults with different occlusion devices — 6 years experience [abstract]. J Am Coll Cardiol 1999;33:519A. 26. Keppeir P, Rux S, Dirko J, et al. Transcatheter closure of 100 patent foramina ovalia in patients with unexplained stroke and suspected paradoxic embolism: A comparison of five different devices [abstract]. Europ Heart J 1999;20:196. 27. Rao PS. Closure devices for atrial septal defect: Which one to chose? Indian Heart J 1998;50:379–383. 28. Rao PS. Transcatheter closure of atrial septal defects: Are we there yet? J Am Coll Cardiol 1998;31:1117–1119. 29. Rao PS. Summary and comparison of atrial septal defect closure devices. Current Intervent Cardiol Reports 2000;2:367–376. 30. Rao PS. Comparative summary of atrial septal defect occlusion devices. 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. 91–101. 31. Hamdan MA, Cao Q, Hijazi ZM. Amplatzer septal occluder. In: Rao PS, Kern MJ (Eds). Catheter Based Devices for Treatment of Noncoronary Cardiovascular Disease in Adults and Children. Philadelphia: Lippincott, William & Wilkins. 2003, pp. 51–59. 32. Nagm AM, Rao PS. Percutaneous occlusion of complex atrial septal defects . J Invasive Cardiol 2004;16:123–125. 33. Rao PS. Techniques for closure of large atrial septal defects. Catheter Cardiovasc Interv 2007;70:329–330. 34. Hijazi ZM, Wang Z, Cao QL, et al. Transcatheter closure of atrial septal defects and patent foramen ovale under intracardiac echocardiographic guidance: Feasibility and comparison with transesophageal echocardiography. Catheter Cardiovasc Interv 2001;52:194–199. 35. Pondar T, Martanovič P, Gavora P, Masura J. Morphological variations of secundum — Type atrial septal defects: Feasibility for percutaneous closure using Amplatzer septal occluders. Catheter Cardiovasc Interv 2001;53:386–391. 36. Pedra CAC, Pedra SRF, Esteves CSA, et al. Transcatheter closure of secundum atrial septal defects with complex anatomy. J Invasive Cardiol 2004;16:117–122. 37. 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 Echocardiogr 2004;17:62–69. 38. Berger F, Ewert P, Abdul-Khalid H, et al. Percutaneous closure of large atrial septal defects with the Amplatzer septal occluder: Technical overkill or recommedable alternative treatment. J Intervent Cardiol 2001;14:63–67. 39. Chessa M, Carminati M, Buetera G, et al. Early and late complications associated with transcatheter occlusion of secundum atrial septal defect. J Am Coll Cardiol 2002;39:1061–1065. 40. Varma C, Benson LN, Silversides C, et al. Outcome and alternative techniques for device closure of large secundum atrial septal defect. Catheter Cardiovasc Interv 2004;61:131–139. 41. Chun DS, Turrentine MW, Moustapha A, Hoyer MH. Development of aorta-to-right atrial fistula following closure of secundum atrial septal defect using the Amplatzer septal occluder. Catheter Cardiovasc Interv 2003;58:246–251. 42. Aggoun Y, Gallet B, Acar P, et al. Perforation of the aorta after percutaneous closure of an atrial septal defect with an Amplatzer prosthesis with acute severe hemolysis. Arch Mal Coeur Vaiss 2002;95:479–482. 43. 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;63:491–502. 44. AGA Medical Technical Note, January 2006:1–4. 45. Harper RW, Mottram PM, McGaw DJ. Closure of secundum atrial septal defects with the Amplatzer septal occluder device: Techniques and problems. Catheter Cardiovasc Interv 2002;57:508–524. 46. Cooke JC, Gelman JS, Harper RW. Echocardiographic role in the deployment of the Amplatzer septal occluder device in adults. J Am Society of Echocardiogr 2001;14:588–594. 47. Staniloae CS, El-Khally Z, Ibrahim R, et al. Percutaneous closure of secundum atrial septal defects in adults – A single-center experience with Amplatzer septal occluder. J Invasive Cardiol 2003;15:393–397. 48. Abdul Wahab H, Bairam AR, Cao Q, Hijazi ZM. Novel technique to prevent prolapse of the Amplatzer septal occluder through large atrial septal defect. Catheter Cardiovasc Interv 2003;60:543–545. 49. Dalvi BV, Pinto RJ, Gupta A. New technique for device closure of large atrial septal defects. Catheter Cardiovasc Interv 2005;64:102–107. 50. Kutty S, Asnes JD, Srinath G, et al. Use of a straight, side-hole delivery sheath for improved delivery of Amplatzer ASD occluder. Catheter Cardiovasc Interv 2007;69:15–20. 51. Carano N, Hagler DJ, Agnetti A, Squarcia U. Device closure o