A A PILLAI, V BALASUBRAMANIAN Deficient antero-superior rims Deficient posterior or postero-inferior rims Techniques Employed for Complex ASD Device Closure Pulmonary vein deployment technique Left atrial roof deployment technique Wahab technique/dilator-assisted technique Complications of Transcatheter Device Closure Management of device embolization Transcatheter closure of atrial septal defects (ASDs) has become standard therapy in the management of most of ostium secundum ASDs. It can be safely performed with excellent results when appropriate techniques are used. Most ASDs (25–75%) are centrally located and closure of the defects is straightforward. But a considerable percentage has complex anatomy which is challenging to close percutaneously. ASDs that are difficult to close percutaneously may be large, have deficient rims, be aneurysmal or have multiple fenestrated defects. These defects are termed ‘complex’ ASDs.1 In a study by Pedra et al., complex ASDs were defined as ASD with complex anatomy such as the presence of large ASDs (stretched diameter more than 26 mm); ASDs associated with deficient rims (≤4 mm) at anterior, inferior or posterior portion; two separate ASDs within the septum; multifenestrated ASDs; ASDs with floppy redundant and hypermobile septum (excursion ≥10 mm) considered to be aneurysmal or combination of these. The success of complex ASD closure mainly relies on proper pre-procedural imaging techniques.2 Morphology of atrial septum is paramount in any closure of complex ASDs. Complex anatomy, especially sinusoidal defects and fenestrated defects, needs careful assessment prior to the procedure. Large ASDs even with adequate rims are complex ASDs. ASDs with stretched diameter larger than 26 mm are considered to be large. Although closure would appear to be a simple procedure, the size of device to be used to close such defects remains to be determined. There are other issues, such as whether the left atrium would accommodate large discs fear of impingement of the device on adjacent structures such as the aorta pulmonary veins causing obstruction, mitral valve and vena cava. Large defects are associated with deficient rims, which make device closure still challenging. An adequate rim is 7 mm or larger. A deficient rim is less than 3 mm. Inadequate rims are between 3 and 5 mm. To close the ASDs the operator should have thorough knowledge of atrial septal rims and adjoining structures. With minor modification to the classification proposed by Shrivastava and Radhakrishnan, Amin et al. has as in Figure 11.1 suggested3 Aortic rim—rim adjacent to aortic valve SVC (superior vena cava) rim—rim adjacent to SVC Superior rim—rim between aortic rim and SVC rim Posterior rim—rim opposite to aortic rim IVC (inferior vena cava) rim—rim adjacent to IVC Atrioventricular rim—rim adjacent to AV valve. Figure 11.1 Classification of atrial septal rims. Illustration depicts different rims of ostium secundum ASDs. CS: coronary sinus, RUPV: right upper pulmonary vein, SVC: superior vena cava, IVC: inferior vena cava. (Illustration by Saranya Gousy.) Deficient antero-superior rims are associated with large ASDs. In our centre largest ASDs had deficient antero-superior rims. The main problem with a deficient antero-superior rim is that during the transcatheter closure there is the problem of straddling the left atrial disc on the aorta, which can lead to erosion of the device. Initial reports of device erosion have led to use of oversizing the device by 4 mm more than the stretched diameter so that the device remains flared to prevent any discrete area of pressure on aorta where erosion may occur. The other frequent problem is that larger the LA disc, the more perpendicular it lies to the septal defect and may prolapse into the RA. So modified techniques have been developed, such as the Hausdorf sheath technique which uses a specially designed sheath with two curves which helps in aligning the disc parallel to the septum during deployment. Closure of large ASDs with posterior rim is real challenge. As the difference in the radial length between right and left disc is 3 mm, deficient rims will not allow the ASD device to be stable. This leads to complications such as device embolization and impingement of the device on adjacent structures. Multiple ASDs account for 13% of all of secundum ASDs. They are complex defects that may be successfully closed by more than one device. If the distance between two defects is less than 7 mm, closing the larger defect will close the smaller defects too. If the distance is more than 7 mm, then echocardiographic evaluation with balloon occlusion of larger defects will help in deciding whether to use two devices.7 If the smaller defect is significant it should be closed prior to closing the larger defect as shown in Figure 11.2. Figure 11.2 TEE images showing device closure in fenestrated ASDs (a, b) and balloon assistance for closing multiple ASDs (c–e). Large defects have septal excursions of more than 10 mm, which are termed septal aneurysms and make device closure quite challenging. Double disc devices such as the Helex buttoned device or the Amplatzer cribriform device are appropriate choices. Zomara et al. successfully closed defects associated with large septal aneurysms with buttoned devices by compressing the aneurismal tissue between occluder and counteroccluder. Balloon sizing of large ASDs is a useful method as most ASDs are not circular. They are oval in shape, and selecting the correct size is challenging. Some of the sizing balloons available are from companies like NUmed, Amplatzer and Cocoon.2 Usually they are available in 18-, 24-, 34-mm sizes only. These balloons are compliant and soft so they can stretch and increase the size of the defect and falsify the actual defect size. Some operators do not use this method for fear of complications. Amin et al. have recommended the stop-flow technique when balloon sizing is done. In this method, the sizing balloon is kept across the ASD and inflated with saline contrast mixture; colour Doppler echo confirms the disappearance of the shunt. This is followed by deflation until the shunt reappears and then inflation just till the shunt disappears. This is the stop-flow diameter of the ASD. A device equal to or 2 mm larger than the stop-flow diameter is usually chosen. This is difficult in cases of malaligned septum and in small children with larger defects as it can obstruct the inflow portion and lead to hypotension. Transcatheter closure of complex ASDs is usually challenging. Some modified techniques are available based on the operator’s choice and experience in using those methods. In the case of complex ASDs, the spectrum of anatomic variation is high, and this may challenge the success of the procedure and sometimes complicate the transcatheter closure and pose a risk of device embolization. Understanding the morphological anatomy is the basis of the transcatheter closure success.3 The size of the defect, location and boundaries or margins of the defect have to be clearly understood by imaging before attempting the closure. A large ostium secundum ASD of more than 20 mm in a child and more than 30 mm in an adult is always a concern because these are the defects which have deficient margins; these always require some modification from routine technique, and defects more than 40 mm require a custom-made device and have a higher risk of failure. Rims are defined with standard descriptions. A deficient rim is one which is less than 5 mm. The rims measured also do not tell the real strength with which the device is being held. The following rims, shown in Figure 11.3, must be looked at in detail before the procedure: The antero-superior rim or the Aortic rim The antero-inferior rim or the AV valve rim The postero-superior rim or the SVC rim The postero-inferior rim or the IVC rim The true posterior/RUPV rim.
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Transcatheter closure of complex and large ASDs
LARGE DEFECTS
Deficient septal rims
Deficient antero-superior rims
Deficient posterior or postero-inferior rims
Multiple or fenestrated discs
Atrial septal aneurysm
BALLOON SIZING THE DEFECT
TECHNIQUES EMPLOYED FOR COMPLEX ASD DEVICE CLOSURE
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