Atrial septal defects (ASDs) are one of the most common congenital heart diseases and percutaneous closure has been shown to be safe and effective in closing defects in ”complex” conditions such as pulmonary arterial hypertension, association with coronary artery abnormalities and other heart malformations, lesions with multiple openings or rim deficiency and residual defects after previous surgical repair. In developing countries, FDA-approved devices are generally more expensive and sometimes unavailable, hence, the importance of reporting new devices is to include patients treated with other types of occlusors demonstrating adequate outcomes.

A 50-year-old male weighing 90 kg was referred to our clinic for evaluation for percutaneous closure of a large ostium secundum type atrial septal defect. Transthoracic echocardiogram showed an ostium secundum type atrial septal defect measuring 29 × 27 mm in diameter, right atrial and right ventricular dilatation, and mild pulmonary arterial hypertension. A cardiac catheterization under general anesthesia was performed and a 36-mm Nit Occlud ASD-R “XL” device was implanted uneventfully under transesophageal echocardiographic guidance. To the best of our knowledge, this is the first report of transcatheter closure of large, isolated, secundum ASDs using successfully the new Nit Occlud ASD-R “XL” device.

Atrial septal defects (ASDs) are one of the most common congenital heart diseases (CHD) with a reported incidence of 1.0/1000 live births with a 2:1 female-to-male ratio being the most common CHD in adults representing 25-40% of adult CHD cases. Key transcription factors are involved in atrial septation including GATA4, NKX2-5, and TBX5 (1). Initially, surgical suture of the defect had been the gold standard therapy, however, starting consistently in the late 1990s, transcatheter device closure has emerged as the treatment of choice even compared to surgical closure [2]. Moreover, percutaneous closure has also been shown safe and effective in closing defects in ”complex” conditions such as pulmonary arterial hypertension, association with coronary artery abnormalities and other heart malformations, lesions with multiple openings or rim deficiency and residual defects after previous surgical repair [3-5]

However, there are still large gaps in our understanding of the limitations of this therapeutic modality in cases of defects having a very large diameter. The definition to consider a defect too ‘large’ a defect for percutaneous closure varies widely among series [6] although, there is consensus in our group, that defects measuring 30 mm in diameter or more by means of echocardiography represent a technical challenge for the interventional cardiologist.

During the last 30 years, several devices have been introduced in our practice to occlude large defects and among them, the Nit Occlud ASD-R device which has “unique” design characteristics, has been widely utilized. It is available from 8 mm to 30 mm in waist sizes with 2 mm increments and recently, an “XL” size with waist diameter of 33mm, 36mm and 40mm have been introduced to the clinical practice [7].

In this case report, we described the first “XL” size Nit Occlud ASD-R device implanted in a human worldwide, describing its performance and short-term outcome of such a new device. 

The device:

The Nit Occlud ASD-R device has been described by us in detail elsewhere. [6] In brief, it is a double-umbrella, self-expandable, self-centering, and premounted device knitted from a single nitinol wire without any soldering or protruding clamps, pins or screws in either side of the occluder. It consists of two circular retaining discs linked together by a short connecting waist (Figure 1). The device comes pre-mounted on and connected to a flexible and low-profile delivery catheter. It should be noted that it has distinct design is based on several aspects: “reverse configuration” of the single-nitinol-layer that forms just the rim of the left atrial disc (hence the ASD-R terminology). Most of the circular area of the left disc is composed by a polyester membrane sutured to the nitinol rims. Both discs have the same diameter and an additional polyester membrane is sewn onto the right atrial disc to improve the device closure rate. “Snare-like” release mechanism which includes a central “locking wire” that crosses the device entirely and a “pusher” with a distal wire noose (“eyelet”). For release, a distal “security seal” is removed and the locking wire is retracted, disengaging the noose and freeing the implant. Moreover, it has no pin or screw in either side. The new “XL” version is available in 3 different sizes related to the connecting waist: 33 mm, 36 mm and 40 mm. The retention discs are 14 mm larger than the connecting waist. Fourteen Fr long sheaths are required for delivery (Table 1). Although the device is not FDA-approved, it is approved for clinical use by the ANMAT in Argentina which is the national regulatory agency for medical devices. The present case report was carried out in accordance with the current policy for observational studies under the Helsinki recommendations and informed consent was obtained from the patient for publication. 

Figure 1. Discs images of the Nit Occlud ASD-R “XL” device. Left disc (A), side profile (B) and right disc (C).

Table 1: New dimensions and required long sheath size of the Nit Occlud ASD-R “XL” devices.

A 50-year-old male weighing 90 kg, construction worker, was referred to our clinic for evaluation for percutaneous closure of a large ostium secundum type ASD. He had history of systemic arterial hypertension and unilateral hip replacement, and during examination for a pre-surgical revision of his left hip prosthesis, he complained of worsening of functional class during the last five years with progressive shortness of breath and easy fatigue. Physical examination revealed the classical findings of a large ostium secundum type ASD and normal blood pressure receiving proper medication.  A 12-lead ECG showed sinus rhythm, right atrial enlargement, and complete right bundle branch block. A 24-hour Holter monitoring showed isolated ventricular ectopy with no atrial arrhythmias. His chest x-ray demonstrated moderate to severe cardiomegaly and increased pulmonary vascular markings. A 2D color Doppler transthoracic echocardiogram showed an ostium secundum type ASD measuring 29 × 27 mm in diameter, right atrial and right ventricular dilatation, and mild pulmonary arterial hypertension. A 2D and 3D color Doppler transesophageal echocardiogram was performed before the intervention and demonstrated a rounded ostium secundum type ASD measuring 32 mm × 30 mm in diameter with adequate rims around the defect. A cardiac catheterization under general anesthesia was performed and a 36-mm Nit Occlud ASD-R “XL” device was implanted uneventfully under transesophageal echocardiographic guidance (Figure 2). The ECG remained unchanged during the intervention. The device was released, and the patient had an uneventful recovery with hospital discharge the following day on aspirin 100 mg daily [7]. After two months from the intervention, his clinical course has been satisfactory with improved symptoms such as shortness of breath and palpitations. His last transthoracic echocardiogram showed the device well seated within the interatrial septum, lack of pericardial effusion, mildly elevated pulmonary artery pressure and absence of residual shunt.

Figure 2: Color Doppler echocardiographic images. Transesophageal views including 2D and 3D with real time reconstruction of the large atrial septal defect pre (A) and post (B–C) immediate closure.

Transcatheter closure of isolated secundum ASDs is the preferred treatment strategy in most cases. Large defects constitute a challenging subgroup usually leading to surgical closure. There has been a paucity of data on transcatheter closure of large ASDs with major concerns because of reports of severe complications which include device migration/malposition, infection, severe arrhythmias, thromboembolism, device-related valvular regurgitation, and cardiac erosion/perforation [7]. 

Nevertheless, recent accumulated evidence showed that closure of large, isolated, secundum ASDs using a large device is safe and effective, in both adults and pediatric patients [8]. In experienced hands, the procedure can be performed routinely under echocardiography guidance with a very low incidence of complications. Transthoracic, transesophageal or intracardiac echocardiography are widely used to guide device implantation with no difference in success among them. Posterior and inferior septal rim deficiencies are associated with higher incidence of procedural failure [5, 9].

Due to its “unique design characteristics” such as reverse left atrial disc reconfiguration, constitution of the left disc mostly by polyester fabric with highly reduced nitinol skeleton, lack of either left or right atrial pin or screw and a “snare like” release mechanism, the Nit Occlud ASD-R device is considered a “different or unique occlusor” compared to the other common existing devices in the market. Generally speaking, the other devices are similar or even sometimes identical to the former Amplatzer Septal Occluder with the only other exception being the Cardioform Septal Occluder presenting also a peculiar design: low nitinol mass frame, five independent petals configuration filled with e-PTFE. 

During a long period of time, based on concerns regarding percutaneous closure of very large atrial defects but more importantly related to its softness, flexibility, less nitinol constitution and lack of pin/screw in either discs, it was thought that the development of larger sizes Nit Occlud ASD-R devices would be risky in terms of septal stability and complete closure of such large defects. With extensive experience accumulation and specially after implanting very frequently the 30 mm in waist Nit Occlud ASD-R device (the largest occlusor available) in our daily practice with no complications and excellent device performance as shown in long term follow up data6, it was evident the need for larger size devices. As a result, the designers moved forward to manufacture larger size devices and after the required initial pre-market studies were completed, we report the initial human experience implanted such a larger device. It is our impression and we hypothesized, that due the design characteristics of the occlusor which were previously discussed, it might have less incidence of erosion/perforation as well as arrhythmia appearance, mainly in the pediatric population. Moreover, due to the lack of pin/screw and the absence of a complete nitinol skeleton on the left atrial disc (which is just manufactured with a nitinol frame), creating a fenestration for decompression or puncturing the device for left atrial access in the future, would be easier than in the regular Amplatzer Septal Occluder type of devices [9]. 

Regarding technical considerations of this new device, the loading, advancement, positioning, delivery, recapture and release are similar than the other device sizes. they are clearly visualized in both echocardiography and fluoroscopy images. The required long sheath size for implantation is 14F for all the three new devices. In case of embolization, the known principles such as securing the device in a stable position, upsizing the long sheath in one to two French sizes larger than the initial delivery sheath and attempting to rescue the device using a combination of snare and bioptome/forcep (most useful is the Maslanka bioptome) similarly to previously reported for our group in detail, is recommended [10].

Finally, in developing countries, FDA-approved devices are generally more expensive and sometimes unavailable, hence, the importance of reporting new devices is to include patients treated with other types of occlusors demonstrating adequate outcomes. To the best of our knowledge, this is the first human report describing the implantation and the immediate clinical performance of the new Nit Occlud ASD-R “XL” device for transcatheter closure of a large ostium secundum type ASD. 

Transcatheter closure of large, isolated, secundum ASDs using the new Nit Occlud ASD-R “XL” device appears feasible and safe in this initial experience. A larger number of cases and mid- and long-term follow-up data will be required to confirm this encouraging initial human worldwide experience. 

We gratefully acknowledge Dr. Franz Freudenthal for providing the information on the new device.

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