Comparison of the Effectiveness and Safety of Single Versus Dual Occluders for the Closure of Multiple Atrial Septal Defects

Abstract: Background. The purpose of this study was to compare the effectiveness and safety of a single vs dual occluders in the treatment of multiple atrial septal defects (ASDs). Methods. We retrospectively reviewed the records of patients with multiple ASDs treated with single or dual Amplatzer septal occluders from January 2010 to March 2013. Data extracted from the medical records included patient demographic information, ASD sizes, distance between the defects, preprocedure and postprocedure echocardiographic parameters, and treatment-related complications. Treatment success was defined as the occluder stably fixed without shunting, and no effects to other heart structures. Results. Sixty-four patients were included. There were no significant differences between the two groups with respect to age, weight, gender, larger ASD diameter, smaller ASD diameter, and echocardiographic parameters before treatment. Successful closure was achieved in all patients in the single-occluder group regardless of whether the distance between defects was ≥7 mm or <7 mm, and in all patients in the dual-occluder group. Residual shunting after surgery and residual leakage after 1-year follow-up were significantly more common in the dual-occluder group compared with the single-occluder group (residual shunting: 31% vs 8%, respectively; P=.02 and residual leakage: 19% vs 2%, respectively; P=.04). No procedure-related complications occurred in either group. Conclusions. Single and dual occluders are both safe and effective for the repair of multiple ASDs; however, the risk of residual shunt is greater with dual occluders. 

J INVASIVE CARDIOL 2015;27(6):E90-E97

Key words: atrial septal defect, multiple atrial septal defects, occluder, Amplatzer, device closure

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Since King first described transcatheter atrial septal defect (ASD) closure in 1976, the technique has matured and has been shown as effective as surgical repair, with a similar complication rate, lower procedural morbidity, and shorter length of hospital stay.^1-11 While transcatheter closure has become the procedure of choice for the repair of single ASDs and patent foramen ovale (PFO), the use of transcatheter closure for the management of multiple interatrial defects is somewhat in its infancy and has only recently been investigated. Although results from case reports and case series^12-16 and some larger studies^2,6,16-19 have provided encouraging results, many questions remain unanswered. For example, it is not known if transcatheter closure of multiple defects is associated with higher complication rates and when a single occluder or more than one occluder is necessary.

Thus, the purpose of this study was to compare the effectiveness and safety of single vs dual occluders in the treatment of multiple ASDs.  

Methods

The records of patients treated from January 2010 to March 2013 at the first affiliated hospital of Xi’ An Jiaotong University with a diagnosis of multiple ASDs eligible for treatment with a single or dual occluder were retrospectively reviewed. Patients with chronic diseases, such as pulmonary artery hypertension and structural heart disease, other than ASDs were excluded. In addition, patients with preoperative arrhythmias or a prior history of arrhythmias (transient or persistent) were excluded so that results such as the occurrence of postoperative arrhythmia and occluder-related thrombosis were not influenced by prior conditions. Detection of paroxysmal atrial premature beats, transient paroxysmal atrial fibrillation, atrial flutter, or atrial tachycardia and sinus rhythm that was restored spontaneously on 24-hour Holter monitoring was considered a transient atrial arrhythmia. The presence of the aforementioned atrial arrhythmia for >24 hours in a single form or a mixed form and sinus rhythm was not restored spontaneously, or frequent atrial premature beats lasting for more than 24 hours were present was considered a persistent atrial arrhythmia. 

Transthoracic echocardiography (TTE) was routinely used for the diagnosis of ASDs (Figure 1).²⁰ In cases in which the edges of the defect could not be precisely determined to ensure adequate fixation of the occluder, or the impact of the occluders on intracardiac structures could not be evaluated, transesophageal echocardiography (TEE) was performed. 

The study was approved by the IRB of the First Affiliated Hospital of Xi’an Jiaotong University. Due to the retrospective nature of the study, written informed consent was waived. All patients had provided written consent for the procedures performed. 

Occluder. There were no specific restrictions on the use of an occluder to treat ASD patients. The Amplatzer septal occluder and delivery system (AGA Medical Corporation) was used for all patients, and has been described in detail.²¹ Multiple device sizes are available, and the size chosen should be based on the maximum ASD defect determined by TTE or TEE. Generally, the size of the occluder should be 4-6 mm greater than the maximum ASD diameter in adults, and 2-4 mm in children.    

Occluder placement. Single occluder implantation. Under general or local anesthesia, the catheter sheath was routinely placed via the right femoral vein. Under fluoroscopic guidance, the long exchange guidewire was passed through the large ASD aperture until it reached the left upper pulmonary vein. A catheter sheath of corresponding diameter was then inserted into the left atrium along the exchange guidewire so that its distal end was located at the center of the left atrium. Then, the occluder was inserted into the left atrium via the catheter sheath, and the left atrial side disc, connecting portion, and right atrial side disc were expanded in turn, making certain that the portion connecting the two discs was centered in the ASD. TTE was used to confirm that fixation of the occluder was adequate, no obvious residual shunt was present, and the function of the surrounding structures was not affected. The knob at the end of the carrier was then rotated counterclockwise to release the occluder, and all delivery devices were withdrawn.

Double occluder implantation. Under general or local anesthesia, catheter sheaths were routinely placed via the left and right femoral veins. Under fluoroscopic guidance, the long exchange guidewires were inserted through the two ASD apertures until they reached the left and right upper pulmonary veins, respectively. The catheter sheaths were then inserted along the 2 guidewires. The larger occluder was then inserted via the catheter sheath in the large aperture, and the smaller occluder was inserted via the catheter sheath in the smaller aperture. First, the left atrial side disc of the large occluder was released and expanded, and then the left atrial side disc of the small occluder was released, followed by the release of the right atrial side disc of the large occluder and the right atrial side disc of the small occluder. During the closure procedure, TTE multislice continuous scanning (parasternal short axis view, parasternal four-chamber view, subxiphoid two-atria view) was used to determine the fenestration(s) the guidewires passed through. If TTE was not adequate, then TEE was used. TTE was also used to confirm that fixation of the occluders was adequate, no obvious residual shunt was present, and the function of surrounding structures was not affected. The two occluders may partially overlap (overlap method), or not overlap (parallel implantation). Representative images of the overlap and parallel implantation methods are shown in Figures 2 and 3.

The use of a single or double occluder was based on the diameter of the ASD, number of ASDs, the space between the apertures, the shunt volume, and physician discretion. The most important factor, however, was the space between the defects, as described by Zhu.²² If the distance between defects was ≤7 mm, a single occluder was chosen that was large enough to cover the edges of the defect. If the distance between defects was >7 mm, and if the defect was small, a larger occluder was tried first. If the defects could not be completely covered (resulting in a shunt), two occluders were used. Cases in which one or two occluders were judged to not be adequate were not repaired by this approach and were treated surgically. 

For all procedures, an intraoperative intravenous injection of 2000-5000 U heparin was administered based on patient weight. Postoperatively, antibiotics were given intravenously for 3 days to prevent infection and low-molecular-weight heparin (LMWH) 100 U/kg was administered by subcutaneous injection twice a day for 3 days. Aspirin 5 mg/kg/day was given orally for 6 months. Electrocardiogram (ECG), 24-hour Holter monitoring, and echocardiography were performed at 24 hours, at 1, 3, and 6 months, and at 1 year postoperatively. Patients were routinely discharged 1 week after the procedure. 

Data collection and outcome measures. Data extracted from the medical records included patient demographic information, size of the ASDs, distance between the defects, and echocardiographic parameters before and after the procedure, including left atrial diameter, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, ejection fraction, right ventricular end-diastolic diameter, pulmonary artery diameter, and pulmonary artery systolic pressure. Treatment-related complications were also recorded. Successful closure of the ASD was defined as x-ray and TTE showing the occluder covering the edge of the defect, no residual shunt, no mitral or tricuspid regurgitation, no adverse effects on the coronary sinus, and no atrioventricular block identified on ECG monitoring. An arrhythmia lasting for >24 hours after the procedure was considered a persistent arrhythmia.

Statistical analysis. Continuous variables were presented as means and standard deviations with independent t-test used to compare differences between two groups. Categorical variables were presented as counts and percentages with chi-square test or Fisher’s exact test used to compare differences between two groups. Due to the repeated measurements of heart functions, a linear mixed model was performed to investigate the effect of groups (denoted as group effect), test times (denoted as time effect), and their interaction (denoted as group × time effect). When the main effects or interactions were found to be significant, the Bonferroni method was used to control the type-I error rate during post hoc multiple comparisons. Statistical analyses were performed with SAS software version 9.2 (SAS Institute, Inc). A 2-tailed P<.05 indicated statistical significance.

Results

Patient characteristics. A total of 64 patients with porous-type ASDs were included in the analysis. A single occluder was used in 48 patients and dual occluders were used in 16 patients. Representative color blood-flow echocardiography from a patient with multiple ASDs is shown in Figure 1.

The baseline characteristics of patients who received single and double occluders are shown in Table 1, and there were no significant differences between the two groups (P>.05 for all). However, the mean distance between apertures was significantly greater in patients who received a double occluder compared with those who received a single occluder (11.06 mm vs 5.19 mm, respectively, P<.001). 

Successful ASD closure was achieved in all patients in both groups, and there were no cases of cardiac death, occluder dislodgment, cardiac perforation, pericardial effusion, major bleeding, hemolysis, and thromboembolism. There were no significant differences between single-occluder and dual-occluder groups with respect to postoperative atrial arrhythmias (2% vs 12%; respectively) and advanced atrioventricular block (2% vs 0%, respectively) (P>.05 for both). Residual shunting was significantly more common in the dual-occluder group compared with the single-occluder group (31% vs 8%, respectively; P=.02). 

The mean follow-up duration of the single and double occluder groups was 324 ± 136 days and 293 ± 97 days, respectively (P=.40). There were no cases of death, embolization, erosion, aortic regurgitation, pericardial effusion, thrombus formation, permanent atrial arrhythmia, infective endocarditis, residual neurological sequelae, or migraine. During follow-up, residual leakage was significantly more common in the dual-occluder group vs the single-occluder group (19% vs 2%, respectively; P=.04). There were no differences in the occurrence of transient or permanent atrial arrhythmias between the single-occluder and dual-occluder groups (transient: 0% vs 12%, respectively; permanent: 0% vs 0%; P>.05 for both). 

Preoperative and postoperative heart function. Heart function before and after surgery in patients who received either single or dual occluders is shown in Table 2. In patients in both groups, the mean right ventricular end-diastolic diameter after surgery was significantly lower than before surgery (single occluder: 24.02 mm after surgery vs 28.13 mm before surgery [P<.001]; double occluder: 23.25 mm after surgery vs 28.81 mm before surgery [P=.01]). In patients who received a single occluder, the mean pulmonary artery systolic pressure was significantly lower after surgery (31.92 mm Hg after surgery vs 41.23 mm Hg before surgery P<.001). 

Patients who received a single occluder based on distance between defects. The baseline characteristics of patients who received a single occluder based on distance between defects of ≥7 mm and <7 mm are shown in Table 3. The mean diameter of the smaller ASD was significantly greater in patients with a distance between defects ≥7 mm compared with patients with a distance <7 mm (7.27 mm vs 5.81 mm, respectively; P=.04). There were no significant differences in other baseline characteristics between the two groups (P>.05 for all).

Successful closure was achieved regardless of the distance between defects, and no complications were seen. There were no significant differences between the ≥7 mm and <7 mm groups in postoperative residual shunting (18% vs 5%, respectively), atrial arrhythmias (0% vs 3%, respectively), and advanced atrioventricular block (P>.05 for all). The mean follow-up duration of the ≥7 mm and <7 mm groups was 314 ± 116 days and 327 ± 142 days, respectively (P=.79). During the follow-up period, there were no cases of death, embolization, erosion, aortic regurgitation, pericardial effusion, thrombus formation, transient or permanent atrial arrhythmias, infective endocarditis, neurological sequelae, or migraine. The occurrence of residual leakage between the ≥7 mm and <7 mm groups during the follow-up was not statistically different (0% vs 3%, respectively; P>.99).

Preoperative and postoperative heart function of patients who received a single occluder based on distance between defects. Heart function before and after surgery in patients who received a single occluder based on a distance between defects ≥7 mm and <7 mm is shown in Table 4. The mean pulmonary artery systolic pressure after surgery was significantly lower after surgery in both groups (distance ≥7 mm: 31.64 mm Hg after surgery vs 40 mm Hg before surgery [P=.02]; distance <7 mm: 32 mm Hg after surgery vs 41.6 mm Hg before surgery; P<.001). In patients with a distance <7 mm, the mean right ventricular end-diastolic diameter after surgery was significantly lower after surgery (23.84 mm after surgery vs 27.68 mm before surgery; P=.01). 

Discussion

Based on the results of this study, a single occluder is suitable for smaller ASDs and when the distance between ASDs is ≤7 mm. If the ASD diameter is large, or the distance between ASDs is >7 mm, then dual occluders should be considered. However, the placement of dual occluders is more difficult, and the risk of a residual shunt increases. The appropriate occluder is based on ASD size, the number of defects, the distance between the ASD, other cardiac structures, and physician experience. Given that the risk of residual shunting is increased with dual occluders, a single occluder may still be considered when the distance between the defects is >7 mm depending on these factors. It also must be considered that placement of dual occluders is more difficult than placement of a single occluder, while the clinical outcomes are not significantly different.  

The transcatheter closure of single ASDs and PFO has been shown to be safe and effective;²³ however, the use of occluders for the repair of multiple ASDs is only beginning to be explored and the results are encouraging.^2,6,12-19 Ewert et al²⁴ reported the treatment of 33 patients with multiple defects; 20 patients received one occluder and had a complete closure rate of 74%, while 13 patients received dual occluders and had a complete closure rate of 100%. Awad et al¹⁸ treated 33 patients with multiple ASDs with multiple Amplatzer occluders with an immediate complete closure rate of 45% and a complete closure rate of 100% at 6 months. Bramlet and Hoyer⁶ reported a closure rate at final follow-up of 100% in 15 patients with multiple ASDs in whom multiple devices were implanted. 

When there is a smaller ASD adjacent to a larger ASD, it is common to use an Amplatzer septal occluder placed in the larger defect such that the smaller defect is covered by the discs, and in many cases flattening of the defect helps reduce the size of the smaller defect.^4,19,25,26 Song et al²⁷ described this method, and reported that a single occluder is sufficient when the distance between the defects is ≤7 mm, while dual occluders are necessary when the distance is >7 mm. This result is similar to the findings of our study. The reason for the 7 mm cut-off is that the disc of Amplatzer devices >11 mm in diameter overhangs the central waist by 7 mm, ie, the disc diameter is 14 mm larger than the central waist diameter.

Implantation of dual occluders may be necessary when the distance between defects is large or the size of a single defect is too large to be managed with one occluder. Various techniques have been described for the sizing and deployment of more than one occluder. Some authors have suggested simultaneous sizing and implantation of both devices, with the larger occluder ‘‘sandwiching’’ the smaller.^4,28 Other authors have recommended sequential deployment, suggesting that this reduces procedural risk by allowing the first device time to stabilize, reduces the risk of displacement of the first device, and improves sizing of the second device as a result of partial compression of the second defect by the first device.^15,29,30 Roman et al³¹ have suggested that interweaving the discs of simultaneously placed devices allows a flatter profile, with less pressure on surrounding structures.

In the current study, 8% of patients in the single-occluder group had residual shunting (4 cases), while 31% of patients in the dual-occluder group (5 cases) had residual shunting. Moreover, after almost a year, residual leakage was significantly more common in the dual-occluder group compared with the single-occluder group (19% vs 2%, respectively; P=.04). Interactions between multiple occluders may be one of the reasons for a greater incidence of residual shunting. First, with the cross-implantation of dual occluders (sandwich method), the disk of one occluder may affect the closure of the disk of the second occluder, increasing the risk of residual shunt. In addition, the defects may not be in the same plane, which can alter the occluder shapes, thus affecting closure and the contact between the discs and the atrial septum. 

It is well known that residual shunts may close with time. In some cases in which an adjacent defect is not completely covered, gradual restoration of the device to its original shape may increase the area of coverage to seal the defect. In addition, platelet aggregation in the occluder, thrombosis, and coverage of the occluder by endothelium can result in the elimination of residual shunting. Boutin et al³³ reported that medium-sized residual shunts, as well as small and trivial shunts, are likely to close with time. Masseli et al³³ also reported resolution of residual shunts in patients with multiple ASDs and single occluder placement. Szkutnik et al³¹ treated 41 patients with multiple ASDs (39 patients received a single Amplatzer occluder and 2 patients received dual occluders), and the complete closure rate increased from 61% at 24 hours post procedure to 95% at 2-year follow-up. More residual shunts occurred when the distance between the defects was >7 mm, but all shunts decreased or resolved over time. Harper et al²⁴ suggested that reduction in the size of a residual shunt or closure is likely related to endothelialization of the occluder and fibrosis around the device. This effect is typically seen 3-6 months post implantation, when occluder endothelialization is complete. Residual leakage after this time may be related to inadequate contact of the disc with the atrial septum or erosion of tissue around the occluder disc edges.

The most common complication of device closure is new-onset atrial fibrillation, which has been reported in approximately 10% of patients with closure of single defects.^33-35 In our study, there was 1 case (2%) of an atrial arrhythmia in the single-occluder group and 2 cases (12%) in the dual-occluder group. Moreover, after approximately 1 year of follow-up, only patients with dual occluders still had atrial arrhythmia (2 cases; 12%). It is possible that placement of >1 occluder alters the atrial anatomy, which increases the possibility of arrhythmias. It is also likely that heart abnormalities that are present prior to occluder placement, such as atrial enlargement, increase the possibility of arrhythmias in these patients.   

When multiple ASDs are present, placement of a single occluder may require oversizing because of a thin and floppy septum, or one occluder may not be large enough and two devices must be placed. However, it is not clear if oversizing or placement of more than one occluder increases the risk of complications, although some reports have suggested that oversizing or implantation of more than two devices may increase the risk of atrial wall erosion.^18,28,36 The results of our study indicated that the placement of two devices increased the chance of a residual shunt, but our study did not include long-term follow-up to evaluate the risk of atrial wall erosion. 

Study limitations. There are limitations to this study that should be considered. This was a retrospective study, patients were not randomized, and the total number of patients was relatively small; however, this is the first large-scale study comparing single vs dual occluders for the management of multiples ASDs. The use of a single or double occluder was primarily based on the distance between defects, which is standard practice at our hospital. However, other factors, including physician judgment and experience, were likely incorporated into decision-making in individual cases. Although characteristics between groups at baseline were similar, individual physician practice may have affected the results. As patients were not randomized, we cannot know if the residual leakage in individual patients would have been less if one device was used instead of two devices. Lastly, long-term results cannot be determined because the follow-up period was relatively short.  

Conclusion

A single occluder is safe and effective for the closure of smaller ASDs and when the distance between ASDs is ≤7 mm. Dual occluders should be considered if the ASD diameter is large or the distance between ASDs is >7 mm; however, the placement of two occluders is more difficult, and the risk of a residual shunt increases. Clinical outcomes are not significantly different whether single or dual occluders are placed.  

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From the Department of Cardiovascular Medicine, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi, China.

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 February 27, 2014, provisional acceptance given April 25, 2014, final version accepted July 23, 2014.

Address for correspondence: Yushun Zhang, MD, No. 277 West Yanta Road, Xi’an, Shaanxi 710061, China. Email: zhangyushun5964@yeah.net