New Pediatric Version of Balloon-Assisted Technique for Atrial Septal Defect Closure Using Self-Centering Devices: Relation to Interatrial Septal Thickness

Abstract: Aim. Some difficult atrial septal defect (ASD) cases with deficient rims or large defects may require specific maneuvers to facilitate transcatheter occlusion of these defects with self-centering devices. In our center, we developed a modification of balloon-assisted technique (BAT) for difficult ASDs to assist proper positioning of the device. Our aim was to demonstrate the efficiency of ASD closure with self-centering devices in children and to present the results of the new pediatric version of BAT (PBAT) in young children and its relation to the interatrial septal thickness. Methods and Results. Over 2 years, a total of 65 patients with ASD secundum were referred for closure, from which 50 cases were deemed suitable for transcatheter closure by transthoracic echocardiography during precatheter evaluation. Ten difficult defects required assisted techniques; 6 of these were successfully closed using the PBAT with a small-sized valvuloplasty balloon. The cut-off levels for needing an assistance technique in pediatric patients were age >5 years, ASD >16 mm, and  weight >22 kg. The interatrial septal thickness was thinner in young ASD patients. Conclusion. The PBAT was needed to optimize device closure in difficult cases, especially in large defects without rim deficiency. This technique is easy to learn and results in quick and simple device closure.

J INVASIVE CARDIOL 2015;27(11):510-515

Key words: balloon-assisted technique, atrial rims, difficult ASD closure

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Atrial septal defect (ASD) is a common form of congenital heart disease, accounting for nearly 5%-10% of all congenital cardiac defects in children.¹ Closure of these defects is generally indicated in children to prevent the development of congestive heart failure and pulmonary hypertension. These defects can also cause failure to thrive or arrhythmias later in life.^2,3 Surgical closure is considered a safe and effective procedure for all ASD types, with very low mortality (0%-3%).^4,5 However, percutaneous ASD occlusion is now widely accepted as an alternative in correctly selected patients.^6,7 Individual centers are increasingly reporting percutaneous ASD occlusion in smaller patients with larger defects.^8,9

In some difficult cases with deficient rims or large defects, other methods involving specific maneuvers or assistive tools have been described to facilitate the occlusion of these defects with self-centering devices.^10-13

Agmon and colleagues have reported that the interatrial septum (IAS) increases in thickness by 12.6% per 10 years of age post childhood (95% confidence interval [CI], 9.0%-16.4%) adjusting for sex and body surface area (BSA), and increases by 7.0% per 0.1 m² BSA (95% CI, 5.0%-9.2%) adjusting for age and sex. They concluded that IAS thickening is an age-associated process.¹⁴

In our center, we have developed a modification of the balloon-assisted technique (BAT) for children with difficult ASDs for use when other techniques have failed to assist with proper positioning of the device. This new technique does not involve overstretching of the comparatively thinner IAS, which might result in overstretching or tears in the thinner septum. Use of this new modification at our center has been so successful that it is now considered the simplest maneuver to use directly in difficult ASDs in children.

Accordingly, this work was planned: (1) to demonstrate the efficiency of ASD closure with self-centering devices in children; and (2) to present the results of the new pediatric version of balloon-assisted technique (PBAT) in young children and its relation to IAS thickness.

Methods

The study population included 65 consecutive patients diagnosed at our institution with secundum IAS defect from October 1, 2011 to September 30, 2013. In this prospective study, 50 cases were referred to the cath lab that were deemed suitable for transcatheter closure by transthoracic echocardiography. Only 15 cases were referred directly to surgery and were considered unsuitable for transcatheter closure (single defect, too large for occlusion with the available devices in 11 cases; multiple ASDs unsuitable for interventional closure in 1 case; and defect close to the superior vena cava, inferior vena cava, pulmonary veins, coronary sinus, or atrioventricular [AV] valves in 3 cases).¹⁵

The cases for transcatheter closure had mostly isolated ASD secundum or ASD secundum and patent ductus arteriosus (PDA) suitable for closure at the same session. One case had associated pulmonary valve stenosis that was ballooned during the same session.

Preintervention protocol. All patients had a physical examination. Laboratory studies included complete blood counts, prothrombin time, prothrombin concentration, partial thromboplastin time, and international normalized ratio to exclude bleeding disorders. A standard 12-lead electrocardiography (ECG) and transthoracic echocardiography (TTE) were also performed. Informed written consent was obtained from the child’s legal guardian. Transesophageal echocardiography (TEE) was performed under general anesthesia in the cath lab immediately prior to the intervention. TTE and TEE included multiple views to assess the ASD position, diameter, single or multiple rim adequacy, and relation to adjacent cardiac structures. The rim was classified as either adequate (>4 mm) or inadequate in case of deficiency (≤4 mm) around the ASD for the coronary sinus rim, the inferior vena cava (toward the inferior vena cava), the AV rim (toward the AV valves), the superior vena cava (toward the superior vena cava) rim,¹⁶ and the posterior rim (posteriorly between the superior and inferior vena cava rims). Because it is well demonstrated that deficiency in the anterior rim toward the aorta does not influence the success rate for transcatheter ASD closure,¹⁷ we considered the anterior rim as inadequate only when it was <2 mm or totally absent. 

The thickness of the IAS depends on the part at which it is measured; therefore, we chose to standardize our measurements. Thickness was measured in the plane visualizing the fossa ovalis, which was equivalent to the bicaval view by TEE at the region of constant thickness. For patients in sinus rhythm, the thickness was measured at the frame demonstrating maximum thickening of the IAS. We also measured the AV rim thickness.¹⁸

Occluding devices. Amplatzer septal occluder (ASO; St. Jude Medical, Inc) and Occlutech devices (Figulla-N and Figulla Flex; Occlutech International) were used.

Standard interventional procedure. All cases were performed under general anesthesia. Transcatheter closure was performed using venous access through the femoral vein and TEE guidance in children according to protocols published previously.^6,11 Patients received 50-100 U/kg of heparin (maximum, 5000 U) and antibiotic prophylaxis (cefotaxim 50 mg/kg). Balloon sizing of the defect was performed for large (>20 mm) or complex defects with the Meditech balloon (Boston Scientific) or with the Amplatzer sizing balloon II (St. Jude Medical, Inc). Before and after release of the device, positioning and relationships with cardiac structures were studied on TEE. In cases with large defect, additional TTE views were performed. The presence of a residual shunt was documented when color-flow imaging showed a left-to-right shunt across the IAS. Shunting was defined as trivial (<1 mm jet width), small (1-2 mm), moderate (2-4 mm), or large (>4 mm).^19,20 Patients were considered to have successful ASD closure if they had no residual shunt as assessed by color-flow imaging.²¹

Techniques used to close difficult ASDs with deficient rims. The pulmonary-vein technique was utilized in 2 cases.¹⁰ The Hausdorf-Sheath technique was utilized in 1 case.¹² The sizing-balloon assisted technique was not used in any cases.²² The modified sizing-balloon assisted technique (SBAT) was attempted in 1 failed case. Briefly, the sizing balloon is inflated in the IAS or even in the left atrium in order to use it as a rim to anchor the device. Then, the left atrial disk is delivered just outside a superior pulmonary vein rather than in the left atrium. The Amplatzer device was fully deployed while the balloon was inflated. Once the Amplatzer device was fully delivered with the inflated balloon between the left and right atrial disks, the balloon was slowly deflated.²³

The PBAT was utilized in 6 cases. This technique can be used in difficult pediatric cases, especially when the device keeps slipping into the right atrium, or when the sizing balloon is not already used. A small-sized (8 x 2 mm or 10 x 2 mm) valvuloplasty balloon, such as the Zmed II (NuMED), Wanda (Boston Scientific), or Powerflex (Cordis Corporation), which are readily available in the cath lab, can be introduced from another femoral vein line. The balloon is advanced through the ASD over a wire lodged in the left upper pulmonary vein or left lower pulmonary vein, and is inflated following deployment of the left atrial disc in the left atrium just beneath the pulmonary vein in cases with big left atrium (Figures 1A and 1B) and within the pulmonary vein in most pediatric cases, which have small left atrium compared with dilated right atrium (Figures 1C and 1D). The device waist is deployed slowly and the balloon is deflated simultaneously by the second operator in harmony (in order to not overstretch the delicate IAS). The right atrial disc is sequentially opened on the right atrial side. Then, the device and the partially inflated balloon are pulled nearer to the septum to align with the defect (Figures 1E and 1F). Complete deflation of the balloon is done before pulling it out of the way. Finally, the left atrial disc flips in place nicely, with the device sandwiching the IAS (Figures 1G and 1H).

This technique is easy and uses readily available balloons, and can be used for deficient anterior, superior, or posterior rims in children.

Follow-Up. All patients underwent plain chest x-ray and TTE examination the day after ASD closure, before discharge to verify the position of the occluding device and the absence of thrombus formation. Any complications during and after the intervention were recorded.

Preexisting antifailure treatment prior to the procedure was maintained and weaned according to clinical and echocardiographic findings during follow-up. In addition, all patients were given acetylsalicylic acid 5 mg/kg/day after the procedure and for 6 months following transcatheter closure.

Patients were subsequently evaluated by clinical examination, ECG, and TTE at 1 week, 1 month, and 6 months after the procedure. Complications related to the device implantation were noted at each visit.

Statistical analysis. The Statistical Package for Social Science version 15.0 (SPSS, Inc) was used for analysis of data. The Student’s t-test was used for analysis of quantitative data, while the Mann-Whitney (non-parametric) U-test was used for analysis of quantitative non-symmetrically distributed data. The Chi-square test was used for analysis of qualitative data. The receiver operating characteristic curve was used to determine the cut-off of patient age, ASD size, and patient weight with the best sensitivity and specificity.

Results

Over 2 years, a total of 65 consecutive patients with ASD presented to our institution. Fifteen patients (23%) were referred to surgery after TTE due to large ASDs with multiple deficient/flimsy rims, especially of the inferior vena cava, and multiple large ASDs. Thus 50/65 patients (77%) were technically eligible for transcatheter closure. Four cases (6%) were excluded and referred to surgery after TEE: 2 cases had posterior rim marked deficiency and 2 cases had flimsy thin inferior vena cava rim. In those cases, the procedure would have been very challenging and potentially dangerous, with an increased risk for device embolization and/or erosion. 

In total, 20 ASD cases (31%) were referred to surgery over the 2 years. In this cohort of young patients, 45 patients (69%) were successfully closed in the cath lab, with 97.8% success rate over this period, which was mainly due to the meticulous selection of patients (Figure 2).

In our study, transcatheter closure was attempted in 50 patients, where 19 patients exhibited rim deficiency, ie, deficient superior-posterior rim (n = 5), deficient inferior vena cava rim (n = 6), borderline inferior-posterior rim deficiency of 3 or 4 mm (n = 2), and aortic rim <2 mm or totally absent (n = 8). 

Mean patient age was 5.4 ± 3.1 years (range, 8 months to 15 years). Mean weight was 18.45 ± 8.9 kg (range, 7.6-59 kg. All cases had evidence of right-sided volume overload. One case had severe right ventricular failure and pericardial effusion; this patient was on antifailure medication prior to the procedure, which was continued for a few weeks after closure. None of our cases had systolic pulmonary artery pressure more than half systemic pressure, and mean Qp/Qs assessed during catheterization was 1.9 ± 2.24 (Table 1). Atrial septal rim thickness was evaluated by TEE. Mean superior vena cava rim thickness was 2.52 ± 0.92 mm (range, 1.1-4.5 mm) and mean inferior vena cava rim thickness was 2.48 ± 0.71 mm (range, 1.2-4.0 mm) (Table 1); IAS thickness was then compared between those closed with versus without the use of assisted techniques (Table 2).

Thirty-six of 45 cases (55% of the total group) who underwent transcatheter closure were performed with the classical technique, whereas 10 cases (15%) needed assisting techniques. The second group were significantly older in age (P=.01) and their ASD size by TEE was significantly larger (P=.02) (Table 3), which accordingly required placement of significantly larger devices (P=.02). However, we did not find statistically significant differences in rim thickness or ASD size indices (Table 2). 

We calculated the cut-off points for using assisted techniques (including BAT) to be age >5 years, ASD size >16.4 mm, and weight >22 kg (Tables 4 and 5). 

Neither the ASD indices nor the device indices were found to be associated with higher risk for using assisted techniques.

Discussion

ASDs termed difficult to close by percutaneous approach include the closure of ASDs in childhood. Some of these are large and others have deficient rims or aneurysmal IAS.¹⁶ The complexity of the difficult ASDs in children includes the fact that IAS thickness is significantly lesser than in adults.¹⁴ We attempted to adapt one or more of the different published technical modifications and assisted techniques^10,12,22,23 and ultimately developed a newer technique to help close these challenging ASDs, aiming to facilitate successful treatment. 

The findings in our paper, despite the small numbers, indicate that transcatheter closure of large defects in children (ASD >16 mm) or weight >22 kg is noticeably associated with the use of assisted techniques, including all cases that needed either SBAT or PBAT, with a statistically significant difference between those who needed assisted techniques vs those not needing any assisted techniques. These guiding cut-off points may help the operator to anticipate the need for assisted techniques and prepare for a second venous access. This will also save time and reduce exposure (especially in pediatric patients) from repeated unsuccessful device deployment attempts. In Kammache et al’s report on the modified SBAT, the authors were able to close large ASDs (up to 41.5 mm), and could successfully position the ASO device in all studied cases, except for a 5.6 kg infant in whom SBAT was not attempted.²³ Earlier, Hijazi and Cao reported the use of the Judkin’s right coronary guiding catheter, with its curve that enabled the authors to align the left atrial disc against the septum in a child with posterior rim deficiency.¹⁹ Others reported the need for BAT using the sizing balloon in large defects, but without differentiating between children and adults.²⁹ Ten patients in our group needed one form or another of assisted technique (21.7%); these cases had relatively larger ASDs with one or two deficient rims.

Our study showed that patients <5 years of age with large ASDs with two or more deficient rims were preferably referred to surgery. Patients undergoing transcatheter closure were usually older, with mean age 5.44 ± 3.1 years, and exhibited smaller and more often single ASDs.^6,20,23-26 This explains why we had older patients (>5 years) requiring the assisted techniques. However, this can’t be generalized due to the limited number of patients in this cohort (21.7%) who required assisted techniques. Transcatheter closure was attempted in 46 patients, with a single-rim deficiency (superior-inferior, inferior vena cava, or posterior-inferior) in 13 cases. While 6 patients had more than one rim deficiency, they were all successfully closed. Three of these patients were closed using the pediatric version of BAT, whereas 2 patients were closed using the pulmonary-vein technique and 1 patient was closed without specific techniques after several attempts. Contrary to our results, Butera et al¹⁹ did not recommend transcatheter closure in cases with deficiency of any rim other than the anterior-superior, yet Amin et al recently challenged this by reporting that aortic rim deficiency or absence is a risk factor for erosion over the long-term follow-up.²⁷

Dalvi et al, who reported on a modified SBAT success in 300 consecutive patients,⁹ found it safe and effective, with some limitations especially in children <15 kg, which represents almost all of our patients. A number of other methods and techniques have been attempted to prevent ASO device misalignment, especially when the defect was large and had insufficient anterior-superior rim.^30,31 Deployment in the left or right pulmonary vein was used in 2 cases, but extreme caution was required to avoid injury to the pulmonary vein, and the need for an experienced operator who could perform the swift withdrawing maneuver and deploy both discs simultaneously limited the use of this technique over the 2-year study. Alternatively, some operators have used a curved sheath (Cook Hausdorf, Judkin’s right).^12,19 At our center, we have limited access to the Hausdorf, and it is not readily available on the shelf in different sizes. The second drawback is that it adds to the cost of the procedure significantly in our country. Thus, we are only adding the cost of the small balloon (which is one-quarter the price of the Hausdorf sheath), especially since we use the same short sheath we used before exchanging it with the long sheath, as well as the same wire. The experienced operators at our center would try the pulmonary-vein technique first before reaching for the second venous line, although an additional femoral venous access seems acceptable. The technical efficiency and potential complications due to the other techniques have not been reported to give us the ability to compare.

The 1 failed case in this series was a patient with a large ASD, absent aortic rim, and deficient 4 mm AV rim. The ASD was assessed with a sizing balloon that was also used to assist device deployment and the thin IAS was markedly stretched using the modified BAT; after deployment, the ASD was overstretched and the device slipped repeatedly into the right atrium. The device was subsequently retrieved and the patient was sent to surgery. Six patients had their device successfully deployed using the proposed new technique for children, with no failures. Its simplicity made other operators from our center eager to learn it and apply it in their difficult cases.

In this study, the IAS thickness of different rims were lesser than previously published ranges.³² This difference can be explained by the fact that those patients had ASDs and were young in age. Agmon et al¹⁴ found that age and BSA were significantly associated with IAS thickness (median, 6 mm; range, 2-17 mm). IAS thickness increased by 12.6% per 10 years of age (95% CI, 9.0%-16.4%) adjusting for sex and BSA, and increased by 7.0% per 0.1 m² BSA (CI, 5.0%-9.2%) adjusting for age and sex. They reported that age, sex, and BSA are responsible for 22.5% of the variability in IAS thickness. They concluded that IAS thickening is an age-associated process. Similarly, in 1995, Galzerano et al¹⁸ demonstrated that IAS thickness increases by age; no correlation exists between IAS thinning and age. They noted that at the time of ventricular end-systolic phase, the IAS thickness ranged from 4-13 mm (mean, 6.7 ± 1.9 mm). On the other hand, Schwinger et al³² reviewed the results of 119 TEE studies to examine the effect of age. They found that the thickness correlated weakly with the age of the patient. In the present work, we could not reach any significant difference between the patients who needed assisting techniques and those who did not. 

To our knowledge, this is the first paper to consider the delicacy and fragility of the IAS in pediatric interventions that involve the IAS in the form of stretchability due to high elasticity or tearing of the thin IAS. Although the results showed a weak relation to IAS thickness, studying a larger number of patients might help prove the concept of weaker IAS in childhood.

Our study is the first to report the need for targeted assisted techniques for the pediatric age group during device placement. Six patients in an unselected patient population required a special method of implantation to optimize transcatheter closure of ostium secundum ASDs. The new PBAT had no specific procedural complications associated with its use in our experience. This technique provides equal efficiency and safety.

In our practice, we have abandoned all other techniques used to stabilize the left atrial disk, because we found the new PBAT to be easier and more efficient.

Conclusion

The vast majority of ASDs are amenable to transcatheter closure, with a high procedural success rate. The pediatric version of BAT was needed to optimize device closure in 13% of cases, especially in large defects without rim deficiency. This technique is easy to learn and makes device closure quick and simple.

The cut-off levels established by this work that mark the need for an assisting technique in pediatric patients were age >5 years, ASD >16 mm, and weight >22 kg. The IAS thickness was thinner in young ASD patients. 

Study limitations. This study was limited by the small group of patients. This is also a short-term (2-year) study, and long-term follow-up might detect late complications.

Acknowledgment. The authors thank Prof Hala Agha and Dr Hayat Nassar. We also acknowledge the entire cath lab team at Cairo University Children’s Hospital. The support of Prof Ziyad Hijazi and his encouragement to write this work is highly appreciated.

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From the Department of Pediatrics, Pediatric Cardiology Division, Cairo University, Egypt.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted October 17, 2014, provisional acceptance given December 8, 2014, final version accepted January 26, 2015.

Address for correspondence:  Prof. Sonia A. El Saiedi, MD, Department of Pediatrics, Division of Pediatric Cardiology, Cairo University, 2 Ali Basha Ibrahim Street, Mounira, 5 Kasr Al Ainy St, Cairo, Egypt. Email: myheartclinic@windowslive.com