Percutaneous Occlusion of Complex Atrial Septal Defects

Since the pioneering investigations by King, Rashkind and their colleagues^1–6 in mid 1970s of percutaneous device occlusion of secundum atrial septal defects (ASDs), a number of other investigators have designed and tested other devices as reviewed elsewhere.^7,8 The interventional cardiologist has therefore, lots of devices to choose from. But the selection of one device over the other is difficult because of lack of prospective randomized clinical trials.^9,10 Such trials involving all the eligible devices is necessary to provide accurate information on usefulness of the devices. The present medical, ethical, regulatory and economic considerations are unlikely to result in such clinical trials. Therefore, the choice of the device has to be based on results of large cohorts of implantations of individual devices, sponsored by the manufacturer of the devices. Detailed review of independently conducted clinical trials revealed similar results with regard to the feasibility, safety and effectiveness of all devices.^11,12 Considerations with regard to the size of the delivery system, ease of device placement, cost, and availability also enter into the selection of devices. Some devices have advantages with some aspects and other with another. Some of the devices have been discontinued and others modified and redesigned.^7–11 At the present time, only one device, the Amplatzer Septal Occluder (ASO), is approved for general clinical use by the Food and Drug Administration (FDA). A number of other devices are in FDA-approved (under Investigational Device Exemption) clinical trials with local IRB supervision. These devices, to the best of our knowledge, are CardioSeal/StarFlex, COD (centering-on-demand) buttoned device, Helex device and transcatheter patch.^11,12 Despite the confusion because of multiple devices and their modified versions as well as their clinical trials, percutaneous device closure of secundum ASD has gone a long way to become a standard of care in most patients during the last quarter of a century. However, this has opened new frontiers and brought new challenges that kept stimulating researchers and clinicians to develop new techniques and/or tools to perfect current technique and solve difficult challenges. One of such challenges is device closure of secundum ASD with complex anatomy. In the preceding paper, Pedra and his associate¹³ evaluate the results of percutaneous occlusion of complex ASDs. During an approximately six-year period ending July 2003, attempts to percutaneously occlude ASDs were undertaken in 143 patients. Of these, 40 (28%) were judged to have “complex anatomy.” The complex anatomy was arbitrarily defined as ASDs with stretched diameters larger than 26 mm with a deficient (10 mm) atrial septum (N=4). Device occlusion was unsuccessful in 5 (12.5%) patients; these patients had large defects with either deficient anterior rim or a floppy posterior rim. The remaining 35 patients had Amplatzer (N=31) or Helex (N=4) devices implanted. Immediately following the procedure, there was complete occlusion in 63% patients and 89% were shown to have complete occlusion at mean follow-up of 18 months. The authors conclude that percutaneous closure of complex ASDs is feasible, safe and effective although larger defects with deficient anterior rim and floppy posterior septum may not be suitable candidates for percutaneous closure.

See Pedra, et al. on pages 117–122

This is a well-written paper and the authors deserve congratulations for their diligent work in a complex group of ASD patients. Although other investigators addressed this issue,^14–17 this work is a valuable addition on this topic. Taking into consideration the incidence of complex anatomy of secundum ASD, the total number of studied cases looks reasonable. However, breaking down this number into several subtypes of complex anatomy resulted in subgroups with only 1 or 2 patients, which makes it difficult to draw solid conclusions on certain types of complex anatomy that these authors reported. The reported experience is confined mostly to the ASO and does not study how other devices would have handled the same complex anatomy. There are many forms of complex anatomy of secundum ASD. Pondar et al.¹⁸ described the morphological variations of secundum ASDs in their series of 190 patients who underwent transcatheter or surgical repair. Their findings showed centrally placed defects in 24% of cases, 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 inferior anterior (IA), superior posterior (SP) and coronary sinus rims to be 1% each. Large defects. One complex anatomy of ASD is simply the size of the defect even with adequate rims. A large ASD was defined by Pedra et al. as an ASD with a stretched diameter > 26 mm. A similar definition was used by most other workers in this field. Although it seems like a simple problem, the questions would be how large a device could be used to close such a defect, whether or not the left atrium would accommodate such device and whether such a large device would encroach on other intra-cardiac structures (e.g., mitral valve) or obstruct blood flow (e.g., vena cavae or pulmonary veins). As pointed out recently,17 large defects are likely to be associated with deficient posterior-inferior rim, which makes the device implantation even more difficult. Deficient anterosuperior rim. Deficient anterosuperior rim is frequently encountered with large ASDs and indeed in our own personal experience most patients we attempt to occlude with various devices were found to have deficient anterior superior rim. Other investigators^15,18,19 had similar experiences. In a study recently reported by Varma et al.,¹⁶ it is the deficient inferior rim that was found to be associated with unsuccessful Amplatzer implantations. With deficient anterior rim, the disks of the Amplatzer straddle the ascending aorta. With other double disk devices the left atrial disk sits on the back of aorta. Initial reports of erosion of the aortic wall by the ASO with development of aorta-to-right atrium²⁰ or aorta-to-left atrium²¹ fistulae led to the recommendation of over-sizing (i.e. using a device size 4 mm larger than the measured stretched diameter) the implanted device in large defects with deficient anterior superior rim to ensure the device disks straddle and remain flared around the ascending aorta to prevent discrete areas of pressure where erosion may occur. When over-sizing the device, care has to be taken not to interfere with surrounding intra-cardiac structures. However, the difficulty in deploying the ASO in patients with deficient anterior superior rim is that the left atrial disk tends to become perpendicular to the atrial septum leading to prolapse of the left disk into the right atrium, representing a challenging difficulty. To overcome such difficulties several techniques have been proposed. Deployment of the left disk of the device in the right upper or left upper pulmonary vein followed by release of the waist and the right atrial disk while simultaneously withdrawing the deployed left atrial disk against the atrial septum^{14–16,19,22} has been successfully used. 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 overcome the prolapse of the left disk into the right atrium.^16,17,23 Another technique is the use of a specially designed sheath (Hausdorf sheath; Cook, Bloomington, Indiana) with two curves at the end to help align the left atrial disk parallel to the septum.^16,24 Supporting/holding the left atrial disk with the tip of a reinforced dilator to prevent prolapse into the right atrium is another method recently used successfully.²⁴Multiple or fenestrated defects. These represent another complex anatomy of the ASD which may be successfully closed using different techniques or devices. Carano et al.²⁵ 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. Szkutnik et al.²⁶ reported a technique, which has been used in many institutions and that is using a single ASO device deployed in the larger defect to occlude two or more smaller defects. In their series, a smaller defect less than 7 mm distance from the larger defect had a 100% closure rate at one-month follow-up. Deploying the device in the larger defect may decrease the distance between the two defects or even compress the smaller defect. They found that if the distance between the two defects is > 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 device^27,28 or the new Amplatzer Cribriform device.²⁹ If the smaller defect is hemodynamically significant, but is far from the other defect (> 7 mm) two devices should be used.²⁶ This is the approach used by Pedra et al.¹³ and we agree with such an approach of closure of two distant defects with two separate devices; closing the smaller defect followed by closure of larger defect. After verifying good position of both devices, release of smaller device should precede the release of larger device. Echocardiographic evaluation while occluding the larger defect with a balloon is helpful in deciding on the use of two devices. Deficient posteroinferior rim. Closure of a large ASD with deficient or absent posterio-inferior (PI) rim continues to be a real challenge. Insufficient number of cases with deficient PI rim reported in most series makes it even more difficult to have a solid consensus. Pedra et al.¹³ mentioned one case with deficient anterior rim and a floppy, thin and hyper mobile posterior rim that was not a good candidate for device closure. Du et al.¹⁴ reported 23 patients with deficient rims, of which 3 patients had deficient inferior or posterior rims. Two patients had 2 mm of posterior rim and the third had a 4 mm posterior rim. These 3 patients were successfully closed. Yet, the number of cases is too small to make a generalized conclusion. Lack of detailed anatomical description of the deficient rims and surrounding rims and defects in most reported studies adds to difficulty in drawing useful conclusions. Mathewson et al.¹⁷ defined absent PI rim as a rim 17 Aneurysmal atrial septum. Septal aneurysms with single or multiple defects represent a different kind of complex anatomy of the ASD. Such anatomy is better dealt with devices that don’t rely on stenting mechanism within the defect to achieve stabilization in the septum. Patch or double disc type of 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 aneurismal septum may however require a large ASO device or may not be amenable for ASO closure. Closing two small but distant defects within an aneurismal atrial septum may effectively close both defects but carry a higher risk of later development of thrombus formation.³⁰ We have successfully closed defects associated with atrial septal aneurysms with hybrid buttoned devices by compressing the aneurysm between the occluder and the square shaped counter-occluder.³¹ In conclusion, most cases of complex anatomy of secundum atrial septal defects can be closed successfully either by using traditional or special techniques or devices. Defects with deficient or absent posteroinferior rim continue to form a challenging task for most interventional cardiologists.