Commentary

Catheter Closure of Atrial Septal Defects

P. Syamasundar Rao, MD
P. Syamasundar Rao, MD
Since the initial description in the mid 1970s by King and Mills et al.1–3 of an atrial septal defect occluding device, a number of other devices have been studied, including: Rashkind’s devices (hooked and double umbrella), Clamshell occluder, buttoned device, Pavcnik’s mono-disk device, modified Rashkind’s patent ductus arteriosus umbrella device, ASDOS (atrial septal defect occluding system), Das Angel Wing device, Amplatzer septal occluder, CardioSeal and StarFlex devices, Centering-on-demand buttoned device, Helex device, transcatheter patch and others, as reviewed elsewhere.4,5 Transcatheter closure of atrial septal defects using various devices6–18 is now an established practice in most cardiac centers. These techniques have proven to be safe, cost-effective and favorably compare with surgical closure.19,20 In this issue of the Journal, Staniloae and colleagues21 present the results of implantation of the Amplatzer Septal Occluder (ASO) in adults with ostium secundum atrial septal defects. Successful deployment of the ASO device was accomplished in 109 (91%) of 117 patients taken to the catheterization laboratory with intent to occlude. Patients in whom the device implantation was not feasible had larger defects with larger shunts than those in whom the device was successfully implanted. At the conclusion of the procedure, complete occlusion of the defect was demonstrated in 75% patients. Small ( 5 mm) residual shunts. At a mean follow-up of 19 months, remarkable improvement in symptomatology was observed. Residual shunts were present in 10% patients at 1-month follow-up, and in 1% of patients at 1-year follow-up. Only one patient, with fenestrated defect, required surgical intervention two years following initial device placement. The authors conclude that percutaneous closure of the atrial septal defects with ASO is safe, and mid-term results compare favorably with those reported following surgical closure. They recommend device closure as the first-line therapeutic option in adult patients with atrial septal defects. This is a well-written paper reporting a single-institution experience in closing atrial septal defects with ASO. They also mention the use of the 60º angulated delivery sheath (Hausdorf’s catheter, Cook Corporation) in patients in whom the device could not be positioned parallel to the interatrial septum. The candid reporting of air embolism brings the point home that we should continue to be diligent to prevent vacuum creation in the sheath and take all precautions to avoid air embolism. Whereas the authors used transesophageal echocardiography for monitoring device placement, intracardiac echocardiography22 appears to be gaining acceptance and may have advantages in that no general anesthesia is required. As reviewed in the introductory paragraph, many devices are available to the interventional cardiologist, but selection of a particular device becomes difficult because of lack of randomized clinical trials. A few studies23–26 attempted to compare the results of multiple devices, as and when they became available, but these studies are neither randomized nor blinded and are unlikely to shed any more light than the single device studies. With existing economical, ethical and medical considerations, it is not possible to conduct a prospective randomized clinical trial utilizing all the eligible devices. Because of this reason, selection of the device may have to be based on results of clinical trials conducted separately by the inventor or manufacturer of the device. A careful comparison27–30 of implantation feasibility (ratio of implantations VS patients taken to the catheterization laboratory with the intent to occlude), percent device dislodgements, misplacements, and embolizations, and percent of patients with effective occlusion and reintervention-free rates during follow-up, tabulated elsewhere,29,30 reveal that these are similar and comparable for most if not all devices. In addition to feasibility, safety and effectiveness data, the availability, cost, and size of the delivery sheath, as well as other factors, may have to be considered in the selection of the device. Of the devices listed above, some devices were discontinued because of the identified problems during the study of the respective devices. At the present time, ASO is the only device approved by the FDA for general clinical use for closure of the atrial septal defects. To my knowledge, CardioSeal/StarFlex, Centering-on-demand buttoned and Helex devices, and the transcatheter patch are undergoing FDA-approved clinical trials; they appear to be at varying stages in the clinical trials. These devices will be briefly reviewed: Amplatzer Septal Occluder. The ASO consists of two self-expandable round discs connected to each other with a 4-mm waist, made up of 0.004–0.005´´ nitinol wire mesh filled with Dacron fabric. This is a relatively new, double-disc, self-centering device with rapid accumulation of implantation data, recently approved by the FDA. Short- and mid-term follow-up data have been published. Implantation of the device is relatively easy and requires a small delivery sheath. The device can be retrieved with ease into the sheath prior to release. It can also be repositioned. The prevalence of residual shunts is low. The disadvantages are a thick profile of the device and concern related to a large amount of nitinol (a nickel-titanium compound) in the device and consequent potential for nickel toxicity. CardioSeal/StarFlex devices. Following withdrawal of the clamshell device because of fracture of the arms of the device, the device was redesigned. An additional bend was introduced and the wire material was changed to non-ferromagnetic alloy. At the same time, the fabric covering the device was changed to Dacron. It received HDE (Humanitarian Device Exemption) from the FDA for use in some cardiac defects, but does not include ostium secundum atrial defects. The preliminary experience with implantation of the device is reasonably good, but requires a large delivery sheath and is difficult to retrieve. The CardioSeal is not a self-centering device, but the further modified version by StarFlex system made it more self-centering than CardioSeal. Arm fractures seen with the clamshell device have also been reported with this device, thus raising concerns about long-term safety. Centering-on-demand (COD) buttoned device. This is a modified fourth-generation buttoned device with two spring buttons and a centering mechanism sutured on the right atrial aspect of the left atrial occluder. Also, the device was made round. The technique of implantation of the COD device implantation is more complex than the fourth-generation buttoned device, but it can easily be learned. The device delivery catheter is small (10 French [Fr]) for most devices, although larger devices (>= 50 mm) require 11 or 12 Fr sheaths. The COD buttoned device has been approved by FDA for clinical trials in the U.S., and the clinical trials continue. However, the clinical experience thus far16,31 is encouraging. Helex device. This is the newest of the devices. It is a double-disc device built on single strand nitinol wire draped with ultrathin ePTEE. It may be delivered via a 9 Fr delivery catheter without a sheath. The implantation of the device is simple, and the device can be withdrawn into the catheter before detachment and redeployed as desired. However, the human experience with this device is limited. FDA-approved clinical trials with an IDE are currently in progress. Transcatheter Patch. The currently available devices are double-disc devices and have similar limitations in that they require septal rims to hold the device. Furthermore, wire-related problems such as atrial perforation, aortic perforation, mitral valve injury, wire fractures and embolization potentially exist in all devices. In response to resolving these problems, wireless devices have been conceived by Sideris and his associates;18,32 detachable balloon and transcatheter deliverable patches have been developed. Polyurethane patches, supported by modified balloon catheters, are implanted across atrial septal defects, left in situ for 48 hours, and balloon withdrawn, leaving the patch in place. Following the feasibility and safety studies in piglets,32 human trials began outside the US.33 FDA approval with IDE for human trials in the U.S. has been recently granted for a pilot study. Summary and conclusions. Following the pioneering works of King, Rashkind and their associates in mid 1970s, a number of devices have been designed and tested in animal models and human subjects. Some devices have been discontinued and others were modified followed by further clinical trials. At the time of this writing, only one device, ASO, was approved by the FDA for general clinical use to occlude atrial defects. There are a number of other devices which are in clinical trials, including the CardioSeal/StarFlex, COD buttoned, Helex and transcatheter patch devices. The preceding paper reports on the utility of ASO in occluding atrial defects in adult patients; the results appear good with extremely rare major complication and little need re-intervention during follow-up. It is envisioned that several other devices will be approved by the regulatory authorities in the foreseeable future so that an appropriate device for a given type of atrial septal defect may be selected by the practicing interventional cardiologist.
References
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