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Echocardiologists' role in the deployment of the Amplatzer Atrial Septal Occluder device in adults
Echocardiologists’ Role in the Deployment of the Amplatzer Atrial Septal Occluder Device in Adults Jennifer C. Cooke, MBBS, FRACP, John S. Gelman, MBBS, FRACP, and Richard W. Harper, FRACP, FACC, Clayton, Victoria, Australia
Use of the Amplatzer Septal Occluder device to close selected secundum atrial septal defects is ever-increasing. This article illustrates the central role of the echocardiologist before, during, and after per-
I n the adult population, atrial septal defect (ASD) is second only to bicuspid aortic valve as the most common congenital heart lesion, constituting 22% of adult congenital heart disease.1 Ostium secundum defects make up 70% to 80% of all ASDs. Because of the ease with which the interatrial septum can be approached through the venous system, attempts at percatheter secundum ASD closure with devices have occurred for over 25 years. The percutaneous approach has several advantages over surgery, including the lack of a sternotomy and scar, avoiding cardiopulmonary bypass, and having a shorter hospital stay. In some patients, a general anaesthetic potentially may not be required with the percatheter method.This may be of particular importance in the elderly with other comorbidities. The first successful device closure of an ASD was performed in 1974 by King and Mills.2 However, deployment of early devices was hampered by large introducing sheaths, cumbersome deployment techniques, difficult device retrieval and repositioning, and device embolization. Early device fatigue and fracture resulted in acute and subacute cardiac perforation with some device designs. An innovative modern development has been the introduction of the Amplatzer Septal Occluder (ASO). This device comprises two flat disks of woven nitinol wires connected by a cylindrical waist, the diameter of which dictates the device size. From the Centre for Heart and Chest Research, Monash Medical Centre, Clayton, Victoria, Australia. Reprint requests: Dr Jennifer Cooke, Mater Adult Hospital, Raymond Terrace, South Brisbane 4101, Australia. Copyright © 2001 by the American Society of Echocardiography. 0894-7317/2001/$35.00 + 0 27/1/113364 doi:10.1067/mje.2001.113364
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catheter closure with the Amplatzer Septal Occluder device. Figures, diagrams, and tables detail each stage of the evaluation, procedure, and postprocedural assessment. (J Am Soc Echocardiogr 2001;14:588-94.)
Because the waist stents or plugs the defect completely, it is a self-centering device. Its two major advantages are the ease with which it can be repositioned and its ability to effectively close larger ASDs. With clamp-type, non–self-centering devices, the disk size required is at least twice the defect size, limiting the ability of these devices to close large defects.With the Amplatzer device, the left atrial disk has a radius only 7 mm greater than the waist of the device (and thus the defect) and the right atrial disk is slightly smaller, being only 5 mm larger than the defect. Thus less rim is required around the defect to safely attempt closure compared with earlier devices. Furthermore, the flexibility of the device and lack of sharp edges means that cardiac perforation is no longer a significant risk. Compared with other closure devices, the ASO device has been shown to close appropriately selected secundum ASDs with a higher occlusion rate, decreased fluoroscopy times, and a wider range of ASD sizes.3-7 With ever-increasing use of the Amplatzer device, the increasing confidence in its ease of deployment has even led to its deployment under echocardiographic guidance alone, without radiography.8 Thus it seems an appropriate time to reflect on the role of the echocardiologist in the patient with ASD before, during, and after ASO device deployment.
BEFORE PROCEDURE Transesophageal echocardiography (TEE) has an integral role before percutaneous device deployment. Most obvious is its role in establishing the initial diagnosis of an ASD of the secundum type, determining its size, and whether single or multiple. The
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Figure 1 Transesophageal echocardiogram of biatrial view (106°) showing flow from right upper pulmonary vein into left atrium and left-to-right shunt across atrial septal defect.
atrial septum is assessed for fenestrations and whether it is aneursymal. TEE provides further anatomic detail including the presence of other associated lesions such as mitral valve prolapse and anomalous pulmonary venous drainage. The relation of the secundum ASD to adjacent cardiac structures is particularly important before device implantation because the left atrial disk has a radius 7 mm larger than the central core. Specifically, the distance of the defect from the mitral valve and right upper pulmonary vein should be at least 7 mm from the margin of the ASD for insertion of the ASO device. Although initially it was recommended that the orifice of the coronary sinus should also be at least 7 mm from the defect, experience has shown that slightly smaller distances should not be seen as precluding attempted ASO device closure. Defects exceeding 40 mm cannot be closed with current Amplatzer devices. Defect Location and Echocardiographic Views To measure the distance of the defect from the mitral valve, the mid-esophageal 4-chamber view at 0° to 20° is generally used. To view the coronary sinus requires a low esophageal position, near or at the gastro-esophageal junction at 0°, where the coronary sinus will be seen from the right of the monitor screen. Obtaining both the lower end of the ASD and the coronary sinus in the same frame is often challenging, and this measured distance is often the most difficult to obtain. Finally, the distance between the ASD to right upper pulmonary vein is best obtained from the biatrial view at 90° to 110°, with some clockwise rotation and use of color flow mapping
(Figure 1). Importantly, the entire rim of the defect should be visualized to ensure a stable platform for device deployment. Unlike other devices, a small rim (<7 mm) in the region of the aortic root is not a contraindication to deployment6 because this device can capably “spread-eagle” to embrace the aortic root, as the result of its rounded, flexible design. The most difficult secundum defect to both assess and close in our experience is a large defect located inferoposteriorly. Although it is reasonable to attempt device closure of large defects in this region, the operator must be aware of the decreased likelihood of success. For monitoring during the procedure, the views most useful are illustrated in Figures 2 through 4. They are the mid-esophageal 4-chamber view at 0°, the short-axis view at 45° to 60°, and the biatrial long-axis view at 90° to 110°. These are listed as a guide only because views and angles should be optimized for each case.
PROCEDURE Although some patients will tolerate the procedure under topical pharyngeal anesthetic and sedation only, it has been our practice to use general anesthesia to ensure patient comfort and optimal airway control. A full description of the interventional aspect of the procedure is well described in the articles by Fischer et al6 and Masura et al.7 As alluded to earlier, there are now published reports of ASO device deployment being fully performed under echocardiographic guidance only, without the need
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Figure 2 Four-chamber transesophageal echocardiographic image (0°).
Figure 3 Short-axis transesophageal echocardiographic image (42°).
for fluoroscopy.8 With the defect and both atria optimally imaged (generally by both the short-axis and biatrial views), it may be feasible to guide the proceduralists during guide wire placement across the ASD and into the left atrium and confirm its position there.The sizing balloon is then passed up over the guide wire and into the left atrium; again, this can be readily confirmed on TEE. It is important to confirm that the sizing balloon is well placed in the left atrium, free of the mitral valve, before its inflation to prevent any inadvertent valve obstruction. Sizing the Defect The task of accurately sizing the defect is very important when using the ASO because the defect size directly determines the device size. Although the device can be retrieved and changed if an inappropriate device size is initially chosen, this is not with-
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Figure 4 Biatrial transesophageal echocardiographic image (94°).
out the considerable expense of using another ASO. Thus it is essential that precise determination of the defect size be undertaken before choosing a device for use. The balloon-stretched diameter of the defect remains the gold standard for determining the defect size.A spherical balloon is inflated in the left atrium and then gently pulled back against the ASD. It is progressively deflated such that it can just be pulled through the defect and into the right atrium.This is done under both TEE and fluoroscopic guidance, with particular attention paid to the demonstration that the balloon at this size successfully occludes the defect such that no residual shunt is visible on color Doppler TEE. Measuring the diameter of the inflated balloon across the defect either by caliper or Mmode has proved highly accurate and reliable in our laboratory for estimating the device size required. The firmly inflated balloon is then reinflated after removal from the patient, and size is confirmed with a sizing plate. It is likely that the firm, spherical nature of this balloon distorts oval defects into a more rounded shape as it passes through the defect, which is likely to be replicated by the Amplatzer device itself. As reported in the literature6,9,10 and as noted in our own experience,11 TEE may underestimate the size of the ASD, as determined by the stretched balloon diameter.The possible explanations for this are several. First, the defects are often oval in shape; therefore a thorough search for the plane with the maximal diameter must occur. Second, with increasing right atrial size caused by the interatrial shunt, the plane of the interatrial septum can become distorted and displaced, sometimes making it difficult to accurately image both edges of the defect in the
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Figure 5 Transesophageal echocardiographic image in 4chamber view demonstrating pliable tissue margin to atrial septal defect and nearby firm rim.
Figure 6 “Cobrahead malformation” caused by twisting of left atrial disk and waist as seen in biatrial view (103°).
one plane, particularly with a large ASD. Third, 3dimensional TEE has demonstrated that the size and shape of the defect appears to change during the cardiac cycle.9,12,13 Last, the tissue margin of the defect may be composed of pliable, almost aneurysmal tissue, which is readily pushed aside by both the sizing balloon and the waist of the occluder device. On occasions, a thicker, less mobile tissue rim is nearby, and this will become the margin when the inflated balloon compresses the weaker, more pliable tissue. In reality, this will be the firm platform against which the device will be secured. Although measuring the defect size to the thicker, less mobile tissue rim may be helpful,TEE is likely to underestimate defect size, and the proceduralists should be advised accordingly. The example in Figure 5 shows a thin, pliable rim of tissue to one side of the defect.The ASD diameter on echocardiography was 20 mm; however, measuring to the adjacent firm rim, the likely platform for the device, the estimated “defect size” was 29 mm. Correspondingly, the stretched balloon diameter in this patient was 30 mm. Another balloon technique has also been used that uses a compressible cylindrical balloon that is inflated across the defect, causing a waisting of the central portion as the defect rim indents it. With the use of quantitative cine or echo calipers, the diameter of the waist is then measured.Although this technique will minimize the chance of inadvertent septostomy, there is a tendency for the balloon to “melon seed” into either atria during inflation. In addition to the technical challenge of using this balloon and its increased expense compared with the spherical balloon, there are some potential areas of concern in using it as a sizing technique. First, the cine camera should be on plane with the interatrial septum to
give clear delineation of the margins and prevent the larger adjacent parts of the balloon obscuring the waist and thus accurate measurement. Second, it is possible that this indentible balloon may not always waist in a spherical shape but rather assume the oval shape of many defects, particularly if they have a firm rim. If this is the case, then only when the largest diameter is strictly cranio-caudal in direction will it truly estimate the full size of the defect. Device Deployment After the exacting task of sizing the defect and thus the device to be used, the procedure quickly gathers pace.The delivery catheter is passed over the guide wire and into the left atrium, as confirmed on TEE. It is important to be sure that the catheter tip is free in the body of the left atrium before releasing the left atrial disk so as not to entrap it in the left atrial appendage, the mitral valve, or its apparatus.Another less common but potentially important hazard is entanglement of the catheter in a Chiari network,14 as occurred early in our experience. Guide wires and catheters must be scrutinized for thrombus and fibrin deposition, particularly when in the left atrium. It must be ensured that the deployed disk “unfolds” properly, such that it attains an almost flat shape. If the device twists on loading into the catheter or if the delivery catheter is advanced too far into the left atrium, the left atrial disk may catch against the left atrial free wall or appendage, resulting in a twisting of the waist and a “cobrahead malformation” of the disk15 (Figure 6). On echocardiography, this is first recognized by the disk not attaining its streamlined flat profile. Although this malformation may resolve on withdrawal of the device into the body of the left atrium, if this is not successful, then removal from
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Figure 8 Successful deployment of atrial septal occluder device with both disks flat and parallel, as seen in biatrial view (99°).
Figure 7 Malalignment of atrial septal occluder device lying perpendicular to defect plane. This was not recognized on fluoroscopy.
the patient to allow untwisting of the device may be necessary. After successful opening of the left atrial disk and waist, they should be positioned against the interatrial septum before release of the right atrial disk. If the left atrial disk is pulled back against a large defect before the waist is expanded, part of the disk edge may prolapse into the right atrium. Incorrect device position will therefore occur during deployment. Similarly, if the released left atrial disk and waist are not sufficiently retracted back against the ASD before right atrial disk deployment, prolapse of the right atrial disk into the left atrium may occur. If prolapse of either disk occurs, withdrawal of the disks into the sheath and redeployment should be undertaken. It is only the Amplatzer device that allows this degree of retrieval and redeployment permitting multiple attempts without damaging the device. With large defects, the device may be initially orientated perpendicular to the defect, and this malalignment may persist even when the waist is pulled into the defect.This may not be appreciated on fluoroscopy but is readily recognized with TEE (Figure 7). To correct this problem, it may be necessary to rotate or reshape the delivery sheath or even to insert a gentle curve on the delivery cable. TEE is used to confirm that the disks lay to either
side of the ASD/septum and have assumed the desired profile. Note that the right atrial disk will not fully flatten until completely released. Nonetheless, the defect should be adequately stented and plugged by the device at this stage to allow assessment of any residual shunt. It is important to minimize any tension on the cable attached to the right atrial disk at this stage to allow the disk to flatten before assessing the residual shunt. The design of the Amplatzer device, with its mesh of nitinol wires and inner core of polyester fabric, will at this stage inevitably have small amounts of flow through the center of the device. Often a trivial shunt on color flow mapping is also seen around the edge of the device, which frequently disappears on full release of the device, when its proper conformation is obtained.Any residual shunt more significant than this will need to be thoroughly delineated and discussed with the proceduralists because device retrieval and replacement with a larger device is still possible at this stage. At this time, a quick scan is done to ensure that the device is not interfering with the mitral valve, coronary sinus, and right upper pulmonary vein flow.The proceduralist will then perform the “Minnesota wiggle”7 by gently tugging on the delivery catheter still attached to the right atrial disk to ensure that the device, straddling the ASD, is stable in position (Figure 8). On release, it is wise to quickly reassess the residual shunt before withdrawing the TEE probe. Occasionally, transient inferior ST elevation will be noted on electrocardiographic monitoring during the procedure.This is thought to be caused by minor embolization, usually of air from the catheters, to the right coronary artery. The TEE is ideally placed for
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assessment and monitoring of any associated inferior regional wall motion abnormalities.
AFTER PROCEDURE Transthoracic echocardiography is usually performed serially after device implantation; most often at day 1, 1 month, and 3 to 6 months after the procedure. The aim is to check the device position, its relation to other structures (especially the mitral valve), residual shunt (which usually diminishes and disappears in the majority of cases11,16), and device structural integrity. Pulmonary artery pressure and right heart size and function are also noted. Some centers, including our own, also routinely perform a follow-up TEE to more accurately assess for residual shunt.With several reports now of early thrombus formation on other types of ASD devices17-19 and one report of an infected device secondary to septicemia,20 TEE may be required for a broad range of indications; thus familiarity with the device appearance over time as it endothelializes will be necessary.
EMERGING ROLES With rapid developments in the field of 3D echocardiography, it will not be long before this technology is standard in many labs. Although there are reports demonstrating the superiority of 3D TEE in imaging the closure devices, especially when abnormally placed,9 the literature has revealed conflicting results9,10 as to the ability of 3D TEE to provide a more accurate sizing method for device implantation. In our own experience, 3D TEE does help appreciate the ASD morphology and surrounding rim but remains dependent on adequate 2D TEE image acquisition and gating. Inferoposterior defects remain a challenge. Processing time for reconstruction has been another difficulty, although this is rapidly improving. This article has concentrated on use of the Amplatzer device to close a single defect. However, closure of multiple defects may also be accomplished by one of two methods. First, when the defects are separated by an adequate distance, a device can be deployed for each defect.The smaller diameter of the ASO compared with its predecessors makes this device particularly well suited for use in this way. With increasing experience, many centers will now deploy multiple devices where necessary. Second, in placing a device to close a large defect,
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Table 1 Evaluation, procedure, and postprocedural assessment Preprocedure Define ASD location Define ASD size Define ASD number; look for fenestrations Delineate ASD rim -Is it firm or pliable? -Is it deficient at any point, eg, inferoposteriorly? -Atrial septal aneurysm? Look for associated defects (MVP, APVD) Measure distance from ASD to MV, CS, RUPV Intraprocedural Confirm guide wire in LA Confirm sizing balloon free in LA before inflation Confirm inflated balloon closes the defect Confirm delivery catheter in body of LA Ensure adequate deployment and positioning of LA disk Guide positioning during waist and RA disk deployment Watch for deployment difficulties -Cobrahead malformation -Chiari network entanglement -Thrombus on catheters Assess adequacy of occlusion Review device relation to MV, CS, RUPV Check position stability during “Minnesota wiggle” Document degree of residual shunt through and around device Postprocedural Check device position Check device structural integrity Assess residual shunt Monitor changes in right heart chambers Check relation to other structures (MV, RUPV) Look for potential complications: thrombus, infection ASD, Atrial septal defect; MV, mitral valve; CS, coronary sinus; RUPV, right upper pulmonary vein; APVD, anomalous pulmonary venous drainage; LA, left atrium; RA, right atrium.
small nearby defects or fenestrations may be covered by the disk margins. Similarly, atrial septal aneurysms are often associated with multiple small fenestrations. In this situation, use of a patent foramen ovale occluder device that has a small waist but large disk radius is ideal. By choosing the most centrally placed defect, the large disks will cover a sizeable surrounding area, often fully covering all defects and the aneurysmal portion of the interatrial septum with a stable device position achieved.TEE imaging plays an essential role in guiding the proceduralist in these more complex cases.
CONCLUSIONS Since King and Mills first described percatheter ASD closure more than 25 years ago, the quest for a reliable, user-friendly, easy-to-deploy device has continued. In the ASO, we appear to have such a device.The
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exponential explosion in its use is testament to the confidence that proceduralists have in its dependability and utility. However, deployment of this device requires a team approach, with equal involvement of both the proceduralist and echocardiologist. With increasing numbers of cardiac centers now embarking on this procedure, it is essential that echocardiologists are fully familiar with the procedure, both the interventional aspects as well as the echocardiographic requirements. Similarly, it is beneficial for the proceduralist to have a sound working knowledge of the echocardiographic aspects of the procedure at each stage: preprocedural, intraprocedural, and postprocedural (as listed in Table 1). The cornerstone to successful deployment is good communication and an understanding of each other’s roles. We hope that this article lays a foundation for the development of this understanding and knowledge.
REFERENCES 1. Fuster V, Brandenburg RO, McGoon DC, Giuliani ER. Clinical approach and management of congenital heart disease in the adolescent and adult. Cardiovasc Clin 1980;10:161-97. 2. King TD, Mills NL. Nonoperative closure of atrial septal defects. Surgery 1974;75:383-8. 3. Walsh KP, Tofeig M, Kitchiner DJ, Peart I, Arnold R. Comparison of the Sideris and Amplatzer Septal Occlusion devices. Am J Cardiol 1999;83:33-6. 4. Berger F, Ewert P, Bjornstad PG, Dahnert I, Krings G, BrillaAustenat I, et al. Transcatheter closure as standard treatment for most interatrial defects: experience in 200 patients treated with the Amplatzer Septal Occluder. Cardiol Young 1999;9: 468-73. 5. Chan KC, Godman MJ, Walsh K, Wilson N, Redington A, Gibbs JL. Transcatheter closure of atrial septal defect and interatrial communications with a new self-expanding nitinol double disc device (Amplatzer Septal Occluder): multicentre UK experience. Heart 1999;82:300-6. 6. Fischer G, Kamer HH, Stieh J, Harding P, Jung O. Transcatheter closure of secundum atrial defects with the new selfcentering Amplatzer Septal Occluder. Eur Heart J 1999;20: 541-9. 7. Masura J, Gavosa P, Formanek A, Hijazi Z. Transcatheter closure of secundum atrial septal defects using the new selfcentering Amplatzer Septal Occluder: initial human experience. Cathet Cardiovasc Diagn 1997;42:388-93.
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8. Ewert P, Daehnert I, Berger F, Kaestner A, Krings G, Vogel M, et al. Transcatheter closure of atrial septal defects under echocardiographic guidance without x-ray: initial experiences. Cardiol Young 1999;9:136-40. 9. Magni G, Hijazi MD, Pandian NG, Delabays A, Sugeng L, Laskari C, et al. Two- and three-dimensional echocardiography in patient selection and assessment of atrial septal defect closure by the new DAS-Angel wings device. Circulation 1997;96:1722-8. 10. Maeno YV, Benson LN, Boutin C. Impact of dynamic 3D transoesophageal echocardiography in the assessment of atrial septal defects and occlusion by the double-umbrella device. Cardiol Young 1998:8:368-78. 11. Cooke JC, Gelman JS, Menahem S, Hardas SP, Harper RW. Early Australian experience with the Amplatzer Atrial Septal Occluder device in adults [abstract]. Aust N Z J Med 2000;30:174. 12. Acar P, Saliba Z, Bonhoeffer P, Aggoun Y, Bonnet D, Sidi D, et al. Influence of atrial septal defect anatomy in patient selection and assessment of closure with the Cardioseal device. Eur Heart J 2000;21:573-81. 13. Franke A, Kuhl HP, Rulands D, Jansen C, Erena C, Grabitz RG, et al. Quantitative analysis of the morphology of secundum type atrial septal defects and their dynamic change using transesophageal three-dimensional echocardiography. Circulation 1997;96:II-323-7. 14. Cooke JC, Gelman JS, Harper RW. Chiari network entanglement and herniation into the left atrium by an atrial septal defect occluder device. J Am Soc Echocardiogr 1999;12:6013. 15. Cooke JC, Gelman JS, Harper RW. Cobrahead malformation of the Amplatzer Septal Occluder Device: an avoidable complication of percutaneous ASD closure. Catheter Cardiovasc Intervent 2001;52:83-5. 16. Thanaopoulos BD, Laskari CV, Tsaousis GS, Zarayelyan A, Vekiou A, Papadopoulos GS. Closure of atrial septal defects with the Amplatzer Septal Occluder Device: preliminary results. J Am Coll Cardiol 1998;31:1110-6. 17. Cooke JC, Gelman JS, Menahem S, Harper RW. Thrombus on an ASD closure device: a call for caution. Heart Lung Circulation 2000;9:30-1. 18. Sievert H, Babic UU, Hausdorf G, Schneider M, Hopp HW, Pfeiffer D, et al. Transcatheter closure of atrial septal defect and patent foramen ovale with ASDOD device (a multi-institutional European trial). Am J Cardiol 1998;82:1405-13. 19. Gastmann O, Werner GS, Babic UU, Figulla HR. Thrombus formation on transcatheter ASD occluder device in a patient with coagulation factor XII deficiency. Cathet Cardiovasc Diagn 1998;43:81-3. 20. Wilkinson JL, Goh TH. Early clinical experience with use of “Amplatzer Septal Occluder” device of atrial septal defect. Cardiol Young 1998;8:295-302.
Use of the Amplatzer Septal Occluder device to close selected secundum atrial septal defects is ever-increasing. This article illustrates the central role of the echocardiologist before, during, and after per-
I n the adult population, atrial septal defect (ASD) is second only to bicuspid aortic valve as the most common congenital heart lesion, constituting 22% of adult congenital heart disease.1 Ostium secundum defects make up 70% to 80% of all ASDs. Because of the ease with which the interatrial septum can be approached through the venous system, attempts at percatheter secundum ASD closure with devices have occurred for over 25 years. The percutaneous approach has several advantages over surgery, including the lack of a sternotomy and scar, avoiding cardiopulmonary bypass, and having a shorter hospital stay. In some patients, a general anaesthetic potentially may not be required with the percatheter method.This may be of particular importance in the elderly with other comorbidities. The first successful device closure of an ASD was performed in 1974 by King and Mills.2 However, deployment of early devices was hampered by large introducing sheaths, cumbersome deployment techniques, difficult device retrieval and repositioning, and device embolization. Early device fatigue and fracture resulted in acute and subacute cardiac perforation with some device designs. An innovative modern development has been the introduction of the Amplatzer Septal Occluder (ASO). This device comprises two flat disks of woven nitinol wires connected by a cylindrical waist, the diameter of which dictates the device size. From the Centre for Heart and Chest Research, Monash Medical Centre, Clayton, Victoria, Australia. Reprint requests: Dr Jennifer Cooke, Mater Adult Hospital, Raymond Terrace, South Brisbane 4101, Australia. Copyright © 2001 by the American Society of Echocardiography. 0894-7317/2001/$35.00 + 0 27/1/113364 doi:10.1067/mje.2001.113364
588
catheter closure with the Amplatzer Septal Occluder device. Figures, diagrams, and tables detail each stage of the evaluation, procedure, and postprocedural assessment. (J Am Soc Echocardiogr 2001;14:588-94.)
Because the waist stents or plugs the defect completely, it is a self-centering device. Its two major advantages are the ease with which it can be repositioned and its ability to effectively close larger ASDs. With clamp-type, non–self-centering devices, the disk size required is at least twice the defect size, limiting the ability of these devices to close large defects.With the Amplatzer device, the left atrial disk has a radius only 7 mm greater than the waist of the device (and thus the defect) and the right atrial disk is slightly smaller, being only 5 mm larger than the defect. Thus less rim is required around the defect to safely attempt closure compared with earlier devices. Furthermore, the flexibility of the device and lack of sharp edges means that cardiac perforation is no longer a significant risk. Compared with other closure devices, the ASO device has been shown to close appropriately selected secundum ASDs with a higher occlusion rate, decreased fluoroscopy times, and a wider range of ASD sizes.3-7 With ever-increasing use of the Amplatzer device, the increasing confidence in its ease of deployment has even led to its deployment under echocardiographic guidance alone, without radiography.8 Thus it seems an appropriate time to reflect on the role of the echocardiologist in the patient with ASD before, during, and after ASO device deployment.
BEFORE PROCEDURE Transesophageal echocardiography (TEE) has an integral role before percutaneous device deployment. Most obvious is its role in establishing the initial diagnosis of an ASD of the secundum type, determining its size, and whether single or multiple. The
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Figure 1 Transesophageal echocardiogram of biatrial view (106°) showing flow from right upper pulmonary vein into left atrium and left-to-right shunt across atrial septal defect.
atrial septum is assessed for fenestrations and whether it is aneursymal. TEE provides further anatomic detail including the presence of other associated lesions such as mitral valve prolapse and anomalous pulmonary venous drainage. The relation of the secundum ASD to adjacent cardiac structures is particularly important before device implantation because the left atrial disk has a radius 7 mm larger than the central core. Specifically, the distance of the defect from the mitral valve and right upper pulmonary vein should be at least 7 mm from the margin of the ASD for insertion of the ASO device. Although initially it was recommended that the orifice of the coronary sinus should also be at least 7 mm from the defect, experience has shown that slightly smaller distances should not be seen as precluding attempted ASO device closure. Defects exceeding 40 mm cannot be closed with current Amplatzer devices. Defect Location and Echocardiographic Views To measure the distance of the defect from the mitral valve, the mid-esophageal 4-chamber view at 0° to 20° is generally used. To view the coronary sinus requires a low esophageal position, near or at the gastro-esophageal junction at 0°, where the coronary sinus will be seen from the right of the monitor screen. Obtaining both the lower end of the ASD and the coronary sinus in the same frame is often challenging, and this measured distance is often the most difficult to obtain. Finally, the distance between the ASD to right upper pulmonary vein is best obtained from the biatrial view at 90° to 110°, with some clockwise rotation and use of color flow mapping
(Figure 1). Importantly, the entire rim of the defect should be visualized to ensure a stable platform for device deployment. Unlike other devices, a small rim (<7 mm) in the region of the aortic root is not a contraindication to deployment6 because this device can capably “spread-eagle” to embrace the aortic root, as the result of its rounded, flexible design. The most difficult secundum defect to both assess and close in our experience is a large defect located inferoposteriorly. Although it is reasonable to attempt device closure of large defects in this region, the operator must be aware of the decreased likelihood of success. For monitoring during the procedure, the views most useful are illustrated in Figures 2 through 4. They are the mid-esophageal 4-chamber view at 0°, the short-axis view at 45° to 60°, and the biatrial long-axis view at 90° to 110°. These are listed as a guide only because views and angles should be optimized for each case.
PROCEDURE Although some patients will tolerate the procedure under topical pharyngeal anesthetic and sedation only, it has been our practice to use general anesthesia to ensure patient comfort and optimal airway control. A full description of the interventional aspect of the procedure is well described in the articles by Fischer et al6 and Masura et al.7 As alluded to earlier, there are now published reports of ASO device deployment being fully performed under echocardiographic guidance only, without the need
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Figure 2 Four-chamber transesophageal echocardiographic image (0°).
Figure 3 Short-axis transesophageal echocardiographic image (42°).
for fluoroscopy.8 With the defect and both atria optimally imaged (generally by both the short-axis and biatrial views), it may be feasible to guide the proceduralists during guide wire placement across the ASD and into the left atrium and confirm its position there.The sizing balloon is then passed up over the guide wire and into the left atrium; again, this can be readily confirmed on TEE. It is important to confirm that the sizing balloon is well placed in the left atrium, free of the mitral valve, before its inflation to prevent any inadvertent valve obstruction. Sizing the Defect The task of accurately sizing the defect is very important when using the ASO because the defect size directly determines the device size. Although the device can be retrieved and changed if an inappropriate device size is initially chosen, this is not with-
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Figure 4 Biatrial transesophageal echocardiographic image (94°).
out the considerable expense of using another ASO. Thus it is essential that precise determination of the defect size be undertaken before choosing a device for use. The balloon-stretched diameter of the defect remains the gold standard for determining the defect size.A spherical balloon is inflated in the left atrium and then gently pulled back against the ASD. It is progressively deflated such that it can just be pulled through the defect and into the right atrium.This is done under both TEE and fluoroscopic guidance, with particular attention paid to the demonstration that the balloon at this size successfully occludes the defect such that no residual shunt is visible on color Doppler TEE. Measuring the diameter of the inflated balloon across the defect either by caliper or Mmode has proved highly accurate and reliable in our laboratory for estimating the device size required. The firmly inflated balloon is then reinflated after removal from the patient, and size is confirmed with a sizing plate. It is likely that the firm, spherical nature of this balloon distorts oval defects into a more rounded shape as it passes through the defect, which is likely to be replicated by the Amplatzer device itself. As reported in the literature6,9,10 and as noted in our own experience,11 TEE may underestimate the size of the ASD, as determined by the stretched balloon diameter.The possible explanations for this are several. First, the defects are often oval in shape; therefore a thorough search for the plane with the maximal diameter must occur. Second, with increasing right atrial size caused by the interatrial shunt, the plane of the interatrial septum can become distorted and displaced, sometimes making it difficult to accurately image both edges of the defect in the
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Figure 5 Transesophageal echocardiographic image in 4chamber view demonstrating pliable tissue margin to atrial septal defect and nearby firm rim.
Figure 6 “Cobrahead malformation” caused by twisting of left atrial disk and waist as seen in biatrial view (103°).
one plane, particularly with a large ASD. Third, 3dimensional TEE has demonstrated that the size and shape of the defect appears to change during the cardiac cycle.9,12,13 Last, the tissue margin of the defect may be composed of pliable, almost aneurysmal tissue, which is readily pushed aside by both the sizing balloon and the waist of the occluder device. On occasions, a thicker, less mobile tissue rim is nearby, and this will become the margin when the inflated balloon compresses the weaker, more pliable tissue. In reality, this will be the firm platform against which the device will be secured. Although measuring the defect size to the thicker, less mobile tissue rim may be helpful,TEE is likely to underestimate defect size, and the proceduralists should be advised accordingly. The example in Figure 5 shows a thin, pliable rim of tissue to one side of the defect.The ASD diameter on echocardiography was 20 mm; however, measuring to the adjacent firm rim, the likely platform for the device, the estimated “defect size” was 29 mm. Correspondingly, the stretched balloon diameter in this patient was 30 mm. Another balloon technique has also been used that uses a compressible cylindrical balloon that is inflated across the defect, causing a waisting of the central portion as the defect rim indents it. With the use of quantitative cine or echo calipers, the diameter of the waist is then measured.Although this technique will minimize the chance of inadvertent septostomy, there is a tendency for the balloon to “melon seed” into either atria during inflation. In addition to the technical challenge of using this balloon and its increased expense compared with the spherical balloon, there are some potential areas of concern in using it as a sizing technique. First, the cine camera should be on plane with the interatrial septum to
give clear delineation of the margins and prevent the larger adjacent parts of the balloon obscuring the waist and thus accurate measurement. Second, it is possible that this indentible balloon may not always waist in a spherical shape but rather assume the oval shape of many defects, particularly if they have a firm rim. If this is the case, then only when the largest diameter is strictly cranio-caudal in direction will it truly estimate the full size of the defect. Device Deployment After the exacting task of sizing the defect and thus the device to be used, the procedure quickly gathers pace.The delivery catheter is passed over the guide wire and into the left atrium, as confirmed on TEE. It is important to be sure that the catheter tip is free in the body of the left atrium before releasing the left atrial disk so as not to entrap it in the left atrial appendage, the mitral valve, or its apparatus.Another less common but potentially important hazard is entanglement of the catheter in a Chiari network,14 as occurred early in our experience. Guide wires and catheters must be scrutinized for thrombus and fibrin deposition, particularly when in the left atrium. It must be ensured that the deployed disk “unfolds” properly, such that it attains an almost flat shape. If the device twists on loading into the catheter or if the delivery catheter is advanced too far into the left atrium, the left atrial disk may catch against the left atrial free wall or appendage, resulting in a twisting of the waist and a “cobrahead malformation” of the disk15 (Figure 6). On echocardiography, this is first recognized by the disk not attaining its streamlined flat profile. Although this malformation may resolve on withdrawal of the device into the body of the left atrium, if this is not successful, then removal from
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Figure 8 Successful deployment of atrial septal occluder device with both disks flat and parallel, as seen in biatrial view (99°).
Figure 7 Malalignment of atrial septal occluder device lying perpendicular to defect plane. This was not recognized on fluoroscopy.
the patient to allow untwisting of the device may be necessary. After successful opening of the left atrial disk and waist, they should be positioned against the interatrial septum before release of the right atrial disk. If the left atrial disk is pulled back against a large defect before the waist is expanded, part of the disk edge may prolapse into the right atrium. Incorrect device position will therefore occur during deployment. Similarly, if the released left atrial disk and waist are not sufficiently retracted back against the ASD before right atrial disk deployment, prolapse of the right atrial disk into the left atrium may occur. If prolapse of either disk occurs, withdrawal of the disks into the sheath and redeployment should be undertaken. It is only the Amplatzer device that allows this degree of retrieval and redeployment permitting multiple attempts without damaging the device. With large defects, the device may be initially orientated perpendicular to the defect, and this malalignment may persist even when the waist is pulled into the defect.This may not be appreciated on fluoroscopy but is readily recognized with TEE (Figure 7). To correct this problem, it may be necessary to rotate or reshape the delivery sheath or even to insert a gentle curve on the delivery cable. TEE is used to confirm that the disks lay to either
side of the ASD/septum and have assumed the desired profile. Note that the right atrial disk will not fully flatten until completely released. Nonetheless, the defect should be adequately stented and plugged by the device at this stage to allow assessment of any residual shunt. It is important to minimize any tension on the cable attached to the right atrial disk at this stage to allow the disk to flatten before assessing the residual shunt. The design of the Amplatzer device, with its mesh of nitinol wires and inner core of polyester fabric, will at this stage inevitably have small amounts of flow through the center of the device. Often a trivial shunt on color flow mapping is also seen around the edge of the device, which frequently disappears on full release of the device, when its proper conformation is obtained.Any residual shunt more significant than this will need to be thoroughly delineated and discussed with the proceduralists because device retrieval and replacement with a larger device is still possible at this stage. At this time, a quick scan is done to ensure that the device is not interfering with the mitral valve, coronary sinus, and right upper pulmonary vein flow.The proceduralist will then perform the “Minnesota wiggle”7 by gently tugging on the delivery catheter still attached to the right atrial disk to ensure that the device, straddling the ASD, is stable in position (Figure 8). On release, it is wise to quickly reassess the residual shunt before withdrawing the TEE probe. Occasionally, transient inferior ST elevation will be noted on electrocardiographic monitoring during the procedure.This is thought to be caused by minor embolization, usually of air from the catheters, to the right coronary artery. The TEE is ideally placed for
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assessment and monitoring of any associated inferior regional wall motion abnormalities.
AFTER PROCEDURE Transthoracic echocardiography is usually performed serially after device implantation; most often at day 1, 1 month, and 3 to 6 months after the procedure. The aim is to check the device position, its relation to other structures (especially the mitral valve), residual shunt (which usually diminishes and disappears in the majority of cases11,16), and device structural integrity. Pulmonary artery pressure and right heart size and function are also noted. Some centers, including our own, also routinely perform a follow-up TEE to more accurately assess for residual shunt.With several reports now of early thrombus formation on other types of ASD devices17-19 and one report of an infected device secondary to septicemia,20 TEE may be required for a broad range of indications; thus familiarity with the device appearance over time as it endothelializes will be necessary.
EMERGING ROLES With rapid developments in the field of 3D echocardiography, it will not be long before this technology is standard in many labs. Although there are reports demonstrating the superiority of 3D TEE in imaging the closure devices, especially when abnormally placed,9 the literature has revealed conflicting results9,10 as to the ability of 3D TEE to provide a more accurate sizing method for device implantation. In our own experience, 3D TEE does help appreciate the ASD morphology and surrounding rim but remains dependent on adequate 2D TEE image acquisition and gating. Inferoposterior defects remain a challenge. Processing time for reconstruction has been another difficulty, although this is rapidly improving. This article has concentrated on use of the Amplatzer device to close a single defect. However, closure of multiple defects may also be accomplished by one of two methods. First, when the defects are separated by an adequate distance, a device can be deployed for each defect.The smaller diameter of the ASO compared with its predecessors makes this device particularly well suited for use in this way. With increasing experience, many centers will now deploy multiple devices where necessary. Second, in placing a device to close a large defect,
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Table 1 Evaluation, procedure, and postprocedural assessment Preprocedure Define ASD location Define ASD size Define ASD number; look for fenestrations Delineate ASD rim -Is it firm or pliable? -Is it deficient at any point, eg, inferoposteriorly? -Atrial septal aneurysm? Look for associated defects (MVP, APVD) Measure distance from ASD to MV, CS, RUPV Intraprocedural Confirm guide wire in LA Confirm sizing balloon free in LA before inflation Confirm inflated balloon closes the defect Confirm delivery catheter in body of LA Ensure adequate deployment and positioning of LA disk Guide positioning during waist and RA disk deployment Watch for deployment difficulties -Cobrahead malformation -Chiari network entanglement -Thrombus on catheters Assess adequacy of occlusion Review device relation to MV, CS, RUPV Check position stability during “Minnesota wiggle” Document degree of residual shunt through and around device Postprocedural Check device position Check device structural integrity Assess residual shunt Monitor changes in right heart chambers Check relation to other structures (MV, RUPV) Look for potential complications: thrombus, infection ASD, Atrial septal defect; MV, mitral valve; CS, coronary sinus; RUPV, right upper pulmonary vein; APVD, anomalous pulmonary venous drainage; LA, left atrium; RA, right atrium.
small nearby defects or fenestrations may be covered by the disk margins. Similarly, atrial septal aneurysms are often associated with multiple small fenestrations. In this situation, use of a patent foramen ovale occluder device that has a small waist but large disk radius is ideal. By choosing the most centrally placed defect, the large disks will cover a sizeable surrounding area, often fully covering all defects and the aneurysmal portion of the interatrial septum with a stable device position achieved.TEE imaging plays an essential role in guiding the proceduralist in these more complex cases.
CONCLUSIONS Since King and Mills first described percatheter ASD closure more than 25 years ago, the quest for a reliable, user-friendly, easy-to-deploy device has continued. In the ASO, we appear to have such a device.The
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exponential explosion in its use is testament to the confidence that proceduralists have in its dependability and utility. However, deployment of this device requires a team approach, with equal involvement of both the proceduralist and echocardiologist. With increasing numbers of cardiac centers now embarking on this procedure, it is essential that echocardiologists are fully familiar with the procedure, both the interventional aspects as well as the echocardiographic requirements. Similarly, it is beneficial for the proceduralist to have a sound working knowledge of the echocardiographic aspects of the procedure at each stage: preprocedural, intraprocedural, and postprocedural (as listed in Table 1). The cornerstone to successful deployment is good communication and an understanding of each other’s roles. We hope that this article lays a foundation for the development of this understanding and knowledge.
REFERENCES 1. Fuster V, Brandenburg RO, McGoon DC, Giuliani ER. Clinical approach and management of congenital heart disease in the adolescent and adult. Cardiovasc Clin 1980;10:161-97. 2. King TD, Mills NL. Nonoperative closure of atrial septal defects. Surgery 1974;75:383-8. 3. Walsh KP, Tofeig M, Kitchiner DJ, Peart I, Arnold R. Comparison of the Sideris and Amplatzer Septal Occlusion devices. Am J Cardiol 1999;83:33-6. 4. Berger F, Ewert P, Bjornstad PG, Dahnert I, Krings G, BrillaAustenat I, et al. Transcatheter closure as standard treatment for most interatrial defects: experience in 200 patients treated with the Amplatzer Septal Occluder. Cardiol Young 1999;9: 468-73. 5. Chan KC, Godman MJ, Walsh K, Wilson N, Redington A, Gibbs JL. Transcatheter closure of atrial septal defect and interatrial communications with a new self-expanding nitinol double disc device (Amplatzer Septal Occluder): multicentre UK experience. Heart 1999;82:300-6. 6. Fischer G, Kamer HH, Stieh J, Harding P, Jung O. Transcatheter closure of secundum atrial defects with the new selfcentering Amplatzer Septal Occluder. Eur Heart J 1999;20: 541-9. 7. Masura J, Gavosa P, Formanek A, Hijazi Z. Transcatheter closure of secundum atrial septal defects using the new selfcentering Amplatzer Septal Occluder: initial human experience. Cathet Cardiovasc Diagn 1997;42:388-93.
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8. Ewert P, Daehnert I, Berger F, Kaestner A, Krings G, Vogel M, et al. Transcatheter closure of atrial septal defects under echocardiographic guidance without x-ray: initial experiences. Cardiol Young 1999;9:136-40. 9. Magni G, Hijazi MD, Pandian NG, Delabays A, Sugeng L, Laskari C, et al. Two- and three-dimensional echocardiography in patient selection and assessment of atrial septal defect closure by the new DAS-Angel wings device. Circulation 1997;96:1722-8. 10. Maeno YV, Benson LN, Boutin C. Impact of dynamic 3D transoesophageal echocardiography in the assessment of atrial septal defects and occlusion by the double-umbrella device. Cardiol Young 1998:8:368-78. 11. Cooke JC, Gelman JS, Menahem S, Hardas SP, Harper RW. Early Australian experience with the Amplatzer Atrial Septal Occluder device in adults [abstract]. Aust N Z J Med 2000;30:174. 12. Acar P, Saliba Z, Bonhoeffer P, Aggoun Y, Bonnet D, Sidi D, et al. Influence of atrial septal defect anatomy in patient selection and assessment of closure with the Cardioseal device. Eur Heart J 2000;21:573-81. 13. Franke A, Kuhl HP, Rulands D, Jansen C, Erena C, Grabitz RG, et al. Quantitative analysis of the morphology of secundum type atrial septal defects and their dynamic change using transesophageal three-dimensional echocardiography. Circulation 1997;96:II-323-7. 14. Cooke JC, Gelman JS, Harper RW. Chiari network entanglement and herniation into the left atrium by an atrial septal defect occluder device. J Am Soc Echocardiogr 1999;12:6013. 15. Cooke JC, Gelman JS, Harper RW. Cobrahead malformation of the Amplatzer Septal Occluder Device: an avoidable complication of percutaneous ASD closure. Catheter Cardiovasc Intervent 2001;52:83-5. 16. Thanaopoulos BD, Laskari CV, Tsaousis GS, Zarayelyan A, Vekiou A, Papadopoulos GS. Closure of atrial septal defects with the Amplatzer Septal Occluder Device: preliminary results. J Am Coll Cardiol 1998;31:1110-6. 17. Cooke JC, Gelman JS, Menahem S, Harper RW. Thrombus on an ASD closure device: a call for caution. Heart Lung Circulation 2000;9:30-1. 18. Sievert H, Babic UU, Hausdorf G, Schneider M, Hopp HW, Pfeiffer D, et al. Transcatheter closure of atrial septal defect and patent foramen ovale with ASDOD device (a multi-institutional European trial). Am J Cardiol 1998;82:1405-13. 19. Gastmann O, Werner GS, Babic UU, Figulla HR. Thrombus formation on transcatheter ASD occluder device in a patient with coagulation factor XII deficiency. Cathet Cardiovasc Diagn 1998;43:81-3. 20. Wilkinson JL, Goh TH. Early clinical experience with use of “Amplatzer Septal Occluder” device of atrial septal defect. Cardiol Young 1998;8:295-302.