AKT Chau, BHY Chung, KS Lun, YF Cheung, TC Yung

Abstract

Purpose: This study reports the clinical experience and midterm outcomes of transcatheter closure of secundum atrial septal defect with the Amplatzer septal occluder in children. Methods: From April 1998 to June 2002, 41 children (male = 14) with a median age of 11.0 years (range = 3.2-18.9 years) and median weight of 31.5 kg (range = 13.5-65 kg) underwent transcatheter closure of secundum atrial septal defect using the Amplatzer Septal Occluder after a detailed pre-implantation evaluation. The procedures were performed under general anaesthesia with fluoroscopic guidance and transesophageal echocardiographic monitoring. The size of the device deployed was determined by the balloon-stretched diameter of the defect. Patients were followed for any residual shunts and possible complications. Results: The mean diameter of atrial septal defect measured by transesophageal echocardiography was 14.3±4.1 mm and 19.2±4.7 mm by balloon-stretched diameter. The mean device diameter was 19.2±4.7 mm (range = 11-30 mm). The mean fluoroscopy time was 17.3 minutes (range = 7.4 to 30 minutes) and the mean procedure time was 100 minutes (range = 35-190 minutes). All devices were successfully deployed. Two patients developed transient atrioventricular dissociation with spontaneous recovery. Complete closure rate at 24 hours, one week, one, 6 and 12 months were 83% [90% confidence limit (CL): 73-91%], 93% (90% CL: 84-97%), 95% (90% CL: 81-96%) and 97% (90% CL: 91-99%), respectively. The mean follow-up period was 46.5?8.6 months (range = 10.7-86.6 months). All devices were in stable position with no late complications. Conclusions: Transcatheter closure of atrial septal defect using the Amplatzer Septal Occluder is safe and effective in children. The midterm results are excellent. However, long-term follow-up is needed to ascertain the absence of possible late complications.

目的：本研究總結了經心導管手術方法，使用 Amplatzer ASD 閉合器治療兒童繼發孔 ASD 損的臨床經驗及治療結果的中期報告。方法：本研究包括了 1998 年 4 月至 2002 年 6 月期間，在本院治療的 41 例兒童（男：14 例，女：27 例），平均年齡 11.0 歲（範圍 3.2 歲至 18.9 歲），平均體重 31.5 公斤（範圍 13.5-65 公斤）。所有病兒先進行詳細的術前評估，而後經心導管手術方法，置入 Amplatzer ASD 閉合器治療繼發孔 ASD。所有手術都是在全身麻醉後，以 X-光及食道超聲波指引下進行的。根據球囊測量方法選擇閉合器。隨訪時主要對殘餘漏孔及併發症進行評估。結果：以食道超聲波評估 ASD 直徑平均為 14.3±4.1 毫米，而球囊測量方法結果為 19.2±4.7 毫米。所使用的閉合器直徑平均為 19.2±4.7 毫米（範圍 11-30 毫米）。手術中 X-光暴露時間為 17.3 分鐘(範圍 7.4-30 分鐘），平均手術時間 100 分鐘（範圍 35-190 分鐘）。全部手術過程順利。2 例患者曾出現一過性房室傳導阻滯，很短時間即自行恢復。缺孔的完全閉合率在 24 小時，1 週，1 月，6 月及12 月分別為 83%（90% 可信度範圍 73-91%）；93%（90% 可信度範圍 84-97%）；95%（90% 可信度範圍 81-96%)及 97%（90% 可信度範圍 91-99%）。平均隨訪期為 46.5±18.6 個月(範圍 10.7-86.6 月)，隨訪結果顯示無一例發生延遲性併發症。所置入的所有閉合器都很穩固。結論：經心導管方法置入 Amplatzer ASD 閉合器治療兒童的 ASD 是一種安全而有效的治療方法。

Introduction

Surgical repair of secundum atrial septal defect (ASD) has long been proven to be a safe procedure with low mortality.¹ However, morbidity related to cardiopulmonary bypass, post-pericardiotomy syndrome, arrhythmias, long duration of hospitalisation and permanent sternotomy scar^2,3 can occur. Furthermore, cardiopulmonary bypass that is required in surgical closure may lead to adverse neuro-developmental consequences in young children.⁴ Therefore, transcatheter closure of ASD has become a viable and attractive alternative to surgery.

A variety of devices have been developed and tested for their efficacy for more than two decades.^5-16 Variable degree of success has been reported previously. Limitations in their use included the need for large delivery systems, complicated implantation techniques, inability to reposition or recapture the device, frequent structural failure like metal frame fracture, local damage to intra-cardiac structures and dislodgement resulting in embolisation.

The Amplatzer septal occluder (ASO) is a self-expanding double-disc device with a central connection waist to stent the atrial septal defect. Preliminary human experience regarding its safety and efficiency in closing ASD has been very encouraging.^17-19 In the present study, we sought to report the mid-term results of transcatheter closure of secundum ASD with the ASO in children.

Methods

Patients

From April 1998 to June 2002, 41 consecutive children (14 male, 27 female) with secundum ASD underwent transcatheter closure of ASD with the ASO at a median age of 11.0 years (range = 3.2-18.9 years). The median weight was 31.5 kg (range = 13.5-65.0 kg). Five patients (12%) were young children aged 3-5 years old.

All patients underwent clinical, electrocardiographic, radiographic and echocardiographic evaluation. Transthoracic echocardiography was performed in all patients and if the echocardiographic window was not satisfactory, a transesophageal echocardiogram (TEE) would be performed either before the procedure or during cardiac catheterisation. Details of echocardiographic evaluation had been reported previously from our institution.²⁰ Briefly, the morphologic characteristics of the ASD including its diameter, location, shape, the width of surrounding septal margins, length of atrial septum and relationship of the defect to adjacent important vessels and heart valves were evaluated.

The indications for transcatheter closure was the same as that for surgical closure, i.e., evidence of significant left to right shunting causing volume overloading of the right heart as evidenced by dilation of the right atrium and right ventricle on transthoracic or transesophageal echocardiography. The inclusion criteria were (i) age >=3 years old, (ii) isolated or closely separated ASDs, (iii) clinical evidence of significant left-to-right shunt, (iv) a width of septal margin of >=5 mm at the superior / inferior caval veins, tricuspid / mitral valve and right pulmonary veins and (v) the atrial septum is expected to be able to accommodate the whole device.

Exclusion criteria were (i) age < 3 years, (ii) multiple or fenestrated ASD, (iii) insufficient septal margins around the ASD, (iv) other associated cardiac abnormalities that may require surgery, and (v) patients with primum or sinus venosus type of ASD. Written informed consents were obtained from patients or parents before the procedure.

The Device

Details of the device have been described previously.^17-19 The ASO is a self-expanding, double-disc device made of 0.004 to 0.006 inch nitinol wires. The left and right atrial discs are connected by a central waist that is used to stent and thereby close the ASD. The diameter of waist is the diameter of the device. Polyester patches are sewn inside the device to induce thrombosis (Figure 1).

(a) Side-view of the occluder showing the larger left atrial disc on the left connected to the smaller right atrial disc on the right by a central waist.	(b) Frontal view of the occluder.	(c) Side-view of the occluder screwed onto a delivery cable.
Figure 1 Amplatzer septal occluder.

The Procedure

The procedure was performed under general anaesthesia with fluoroscopic and transesophageal echocardiographic guidance. Routine right heart catheterisation was performed to obtain haemodynamic data and contrast injection was done in the right upper pulmonary vein to profile the ASD. TEE was performed to evaluate the morphological characteristics of ASD. A balloon-stretched diameter (BSD) was obtained with an Amplatzer sizing balloon. The size of the device was chosen to be equal to the BSD. Standard technique of implantation which had been described earlier^18,19 was used. In brief, after loading of the ASO on a delivery cable, the device was passed through a French 7-10 sheath that was placed in the left atrium. The left atrial disc was deployed in the left atrium and pulled gently against the atrial septum. While maintaining some traction on the delivery cable, the connecting waist was deployed at the ASD, followed by the right atrial disc (see Figure 2). The process was monitored by fluoroscopy and TEE to ensure optimal device position and that the function of heart valves or blood flow in major vessels were not affected. Stability of the device was checked by pulling and pushing the device and if the position was satisfactory, the device was released through a microscrew system. A right atrial contrast injection and TEE were repeated after release of device to detect residual shunting. Patients were discharged the next day after clinical, radiographic and transthoracic echocardiographic evaluations to check device position and residual shunting.

 

(a) Angiogram in the right upper pulmonary vein profiling a moderate-sized secundum ASD (arrows).	(b) Deployment of the left and right atrial discs with the central waist stenting the ASD.
(c) Fluoroscopic appearance of the occluder after release.	(d) Contrast injection in RA showing good device position and no residual shunt through the device.
Abbreviations : ASD = atrial septal defect; RA = right atrium
Figure 2 Transcatheter occlusion of secundum-typed atrial septal defect with the Amplatzer septal occluder.

Follow-up

All patients received anti-platelet dose of aspirin (3-5 mg/kg daily) for 6 months to prevent thromboembolism. They were reviewed at 1 week, 1, 6, 12 months and thereafter at 6 to 12 monthly intervals. Besides clinical examination, chest radiographs were taken to check device position and fracture. Electrocardiograms were repeated to detect evidence of cardiac arrhythmias. Transthoracic echocardiography was used to assess residual shunt, device position, heart valve functions and obstruction to blood flow in caval and pulmonary veins. Other possible late complications were also noted.

Statistical Analysis

Data are expressed as mean±SD. Median values and ranges were given where appropriate. Complete closure rate of ASD were expressed as percentage of total. The Kaplan Meier method was used to analyse the prevalence of residual shunt with time.

Results

All procedures including those in the five young children were successful. The mean pulmonary to systemic flow ratio (Qp/Qs) was 2.7±1.2. The mean diameter of the ASD was 14.3±4.1 mm by TEE and 19.2±4.7 mm by BSD. The device diameter was 19.2±4.7 mm (range = 11-30 mm). The mean fluoroscopy time was 17.3 minutes (range = 7.4-30 minutes) whereas the mean procedure time was 100 minutes (range = 35-190 minutes). One patient had two closely separated ASDs that were closed with one device. Two patients developed transient atrioventricular dissociation with a slow junctional rhythm after deployment but before release of the device. Spontaneous recovery to sinus rhythm occurred within 10 minutes in both patients and the devices were released. No other immediate complications such as device embolisation were encountered.

Complete immediate closure of ASD was achieved in 27 patients (67%) and this increased to 34 patients [83%, 90% confidence limit (CL): 73-91%] at 24 hours. On follow-up, the complete closure rate was further increased to 93% (90% CL: 84-97%), 95% (90% CL: 81-96%) and 97% (90% CL: 91-99%) at 1, 6 and 12 months, respectively (Figure 3). Only one adolescent patient was found to have a small residual shunt (< 2 mm in diameter on colour Doppler) at 12 months and as her transthoracic echocardiographic window became unsatisfactory, she was awaiting a TEE for confirmation of complete closure on further follow-up.

Figure 3 Prevalence of residual shunt after transcatheter occlusion of ASD with the Amplatzer septal occluder.

Follow-up

All patients completed follow-ups. The mean follow-up period was 46.5±18.6 months (range = 10.7-86.6 months). All devices were in stable position and there were no late complications like device embolisation, thromboembolism, pericardial effusion, cardiac perforation, infective endocarditis, cardiac arrhythmias, mitral or tricuspid valvar regurgitation or obstruction of blood flow in the caval and pulmonary veins. The two patients who developed transient atrioventricular dissociation during implantation of ASO had normal electrocardiograms during follow-up.

Discussion

The ASO is one of the most frequently used devices to close ASD and has been proven to be highly effective and safe in the short-term. Previous reports have confirmed that transcatheter closure of ASD with the ASO not only achieved a comparable efficacy and safety with that of surgical closure but has an additional advantage of causing less complications, requiring a shorter hospital stay and avoidance of a permanent scar.^21,22 The present study showed an excellent mid-term outcome of percutaneous transcatheter closure of secundum-type of ASD using the ASO. The complete closure rate of 97% at mid-term follow-up was comparable to other reports.²³ It also showed that neither death nor major complications occurred up to mid-term follow-up, further confirming the effectiveness and safety of the procedure. Excellent long-term outcome was demonstrated in a recent report.²⁴ In our study, results of the procedure in five young children aged 3 to 5 years old was encouraging and by the time of writing this manuscript, the procedure has been extended to children as young as two years of age at our institution. Similar success of applying transcatheter closure of ASD in young children has also been reported in recent years.²⁵ To date, the use of ASO for transcatheter closure of ASD had become standard treatment in many centres where only patients not suitable for this form of treatment were sent for surgical closure. It has been estimated that 70-80% of secundum ASDs are occludable.²⁴

While mid-term outcomes are encouraging, there remain concerns on some long-term issues such as late device embolisation, thromboembolism, cardiac perforations, arrhythmias, mitral or tricuspid regurgitation, and obstruction to blood flow in caval or pulmonary veins.

Device embolisation, a well-known early complication that is commonly due to evaluation error or use of an undersized ASO, can usually be avoided. Late device embolisation due to the use of an undersized ASO for an oval shaped ASD has been reported.²⁶ Transesophageal echocardiographic monitoring has an important role in preventing this complication.

The incidence of thromboembolism after device closure of ASD was fortunately low.^27,28 Maintaining patients on aspirin for 6 months would reduce the risk of such a complication before complete endothelialization of the device. However, small and clinically silent thrombi may still be undetected even examining with TEE. In our study, we did not encounter any thromboembolic events.

Cardiac perforation and haemopericardium causing cardiac tamponade, a potentially life-threatening complication, has been reported to occur from several weeks to 8 months after the procedure.²⁹ It is due to late erosions, occurring at the anterosuperior or retroaortic portion of the atrial wall, and more commonly on the left atrial side of the septum. It is unclear whether this is related to a large implanted device. We think that on oversized device should be avoided in young children.

Two of our patients developed transient atrioventricular heart block with a slow junctional rhythm after deployment but before release of the ASO. Spontaneous recovery was observed within 10 minutes and the devices could be released. Should the atrioventricular block persisted, the devices would have to be retrieved. These two patients had no recurrence of cardiac arrhythmias on follow-up. So far, most of the reported cardiac arrhythmias that occur during or early after the procedure improved spontaneously or resolved on follow-up with no recurrence.^24,30

In our study, we did not encounter obstruction to blood flow in the caval and pulmonary vein or dysfunction of the mitral and tricuspid valves although these complications had been reported.²⁹ Careful patient evaluation and selection of an ASO of appropriate size were important factors to avoid these complications.

Conclusions

Our study confirmed that percutaneous transcatheter closure of ASD with the ASO was safe and effective. Mid-term results are excellent. The procedure can be performed safely in young children. Careful and detailed patient evaluation and selection of an ASO of appropriate size are important factors for success and avoidance of complications. However, long-term, large scale follow-up is necessary to ascertain absence of possible late complications.

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