Preliminary Experiences Closing Secundum Atrial Septal Defect Using the Modified Cardia Intrasept‚Ñ¢ Device

The secundum type atrial septal defect is the fourth most common congenital heart defect, with an incidence of 3.78 per 10,000 live births,¹ corresponding to 5.9% of the diagnosed congenital heart disease in children.² Over the past decade, transcatheter closure of secundum atrial septal defects (Type II ASDs) has become a widely accepted alternative to surgical closure; few devices are available, and most of the experience reported has been collected concerning the CardioSEAL^®(NMT Medical, Boston Massachusetts) and Amplatzer closure devices, without significant differences between the two.^3–6 The newest ASD occlusion devices undergoing clinical trials in the United States are the Helex™ septal occluder (W.L. Gore & Associates, Newark, Delaware), and the Cardia Intrasept™ device (Cardia Inc., Burnsville, Minnesota).
To date, over 6,000 patients have been treated with a Cardia Intrasept PFO device for the percutaneous closure of patent foramen ovale (PFO). This is a report of the use of a modified Cardia Intrasept device to close Type II ASDs in 4 patients.

Case Reports

Among the patients routinely referred to our hospital for ASD closure due to progressive right ventricular volume overload, 4 were judged suitable for the modified Cardia Intrasept device implantation (Table 1). Transthoracic echocardiography confirmed the diagnosis, and all 4 patients underwent cardiac catheterization (Table 1).
Acetylsalicylic acid (5 mg/kg) was initiated 1 day prior to the procedures. On the date of implantation, 3 doses (1 g each) of ceftazidime (for prophylaxis of bacterial endocarditis) were administered, as well as 100 U/kg of unfractionated heparin. The patients were administered general anesthesia and intubated. Transesophageal echocardiography (TEE) confirmed the diagnosis of central Type II ASDs with adequate rim and sufficient distance to the atrioventricular valves and coronary sinus. Standard balloon sizing was performed. Diameters of the defects were 14 mm (Patient 1), 12 mm (Patient 2), 11 (Patient 3) and 13.5 mm (Patient 4), respectively, at the stretched diameter.
Delivery technique. After crossing the septum with a 5 Fr multipurpose catheter, the tip of the catheter was placed into the left superior pulmonary vein and the catheter was then exchanged for a 12 Fr transseptal sheath (preshaped manually) by means of an extra-stiff 0.035 inch exchange guidewire. The Intrasept device is available in 3 sizes: 25 x 12 mm, 30 x 16 mm and 35 x 20 mm. The first number indicates the diameter of the sail and the second number indicates the diameter of the self-centering system, which corresponds to the maximum defect diameter. Thus, the first size can be used for defects up to 12 mm in diameter, the second up to 16 mm and the third up to 20 mm. The 12 Fr long sheath allows for implantation of the 12 x 25 mm and the 16 x 30 mm devices; for the 20 x 35 mm device, a 13 Fr long sheath is recommended. The device can be removed at any point before releasing it without causing damage; this characteristic is very helpful because it allows the device to be reutilized and replaced.
The device was delivered though the transseptal sheath under fluoroscopic and TEE guidance as well. Once the left atrial disc was deployed, the device was pulled back along with the sheath until it came in contact with the septum. At this point the self-centering system was exposed, while keeping the device in position and paying careful attention that none of the arms of the distal sail came through the defect. The sheath was then fully retracted until the right atrial disk of the occluder opened. Once proper position was confirmed by TEE monitoring, the device was released, and the position of the device was checked by TEE and fluoroscopy with a right atrial contrast injection through the transseptal sheath. The device is well visualized by both fluoroscopy and TEE, with no differences in comparison to the other devices. All patients (or their parents) signed an informed consent; no Institutional Review Board Consent was necessary because this device was specifically modified for ASD closure.

Results

A 30/16 mm device (parts 1 and 4) was chosen for 2 of our patients; patients 2 and 3 had a 25/12 mm device implanted. Repositioning, replacement or removal of the device was not necessary in any patient, and in each case, there was arm prolapse during the deployment. There were no residual shunts on TEE color Doppler and no complications occurred in any of the 4 patients. The patients were discharged 24 hours after a chest X-ray and transthoracic echocardiography (TTE) were performed. The patients were prescribed clopidogrel (75 mg) for 3 months and acetylsalicylic acid (5 mg/kg) for 6 months. Standard bacterial endocarditis prophylaxis was recommended for 6 months. The patients were instructed to return to Policlinico San Donato for follow up after 1, 6 and 12 months. At the 6-month follow up visit, no residual shunt was detected on TTE.

Discussion

Transcatheter occlusion of ASDs has most often been performed with the Amplatzer,⁴ the Cardio-Seal/Starflex occluders,³ and the Helex device,⁶ with very good results. This paper, to the best of our knowledge, is the first to report the routine closure of ASD using the modified Intrasept device.
The Cardia Intrasept occluder is a relatively new member to the family of ASD closure devices and its indications and limitations have been defined mainly for patients with PFO.⁷ The first-generation device was constructed with 2 mm center posts, 2 mm thick foam Ivalon sails and titanium protective end caps. In the second-generation version, the frame was strengthened using “stranded” wires, and the left atrial disc was mounted on the outside of the frame. In addition, the Ivalon sail was thinned. The third-generation device was constructed with two additional arms per umbrella, resulting in hexagonal-shaped umbrellas. The fourth-generation device (Figure 1) is unique in that it has a dual articulating double-umbrella design. The articulating center post and end caps are made of titanium. The sails and umbrellas are made from polyvinyl alcohol (PVA), which is mounted onto arms made of 19 woven strands of NiTi (nitinol) for strength as well as flexibility. The device was modified for ASD occlusion with the addition of a PVA honeycomb “center ring.” The honeycomb is designed to allow self-centering of the device within the defect (Figure 2). A fourth-generation modified Intrasept occluder was used in all of our patients.
The 4 cases performed had no complications and showed that this device was safe and feasible. The maximum defect diameter that can be closed with this device is approximately 20 mm. TEE should be included as a routine part of monitoring during the procedure.^8,9
A specific feature of the device is its extreme flexibility. The self-centering mechanism is designed to optimize the positioning of the device, particularly after release. After this brief experience, however, we found the self-centering mechanism to be less effective than that of the Amplatzer device, and believe it needs improvement.
The flexibility of each arm allows variable distances between opposite arms and thus adjustment to individual anatomy and the variable thickness of the intra-atrial septum. The potential friction lesions due to the device are limited to the tips of each sail and umbrella. Although implantation is not difficult, it is more challenging than what is required with the Amplatzer. The devices can be removed and repositioned at any point; this is not possible with the CardioSeal/Starflex or the Helex devices. The low profile can be useful in children and young adults, but the major limitation is the 12-Fr-long sheath needed to introduce it.
Our 4 cases demonstrate that delivery of the Intrasept occluder device is feasible and safe. Its unique design allows for excellent conformity to the atrial septum with a minimum amount of material, making it a compelling choice for this indication.
Patient recruitment is ongoing at our center, and the authors look forward to acquiring further experience and additional data regarding this device in order to improve it.

References

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