Traditional repair of atrial septal defects (ASDs), ventricular septal defects (VSDs) and patent foramen ovales (PFOs) has necessitated open surgery either via sternotomy and cardiopulmonary bypass
Transcatheter Closure of Atrial and Ventricular Septal Defects
Bo Purtic, PhD
Associate Managing Editor
Traditional repair of atrial septal defects (ASDs), ventricular septal defects (VSDs) and patent foramen ovales (PFOs) has necessitated open surgery either via sternotomy and cardiopulmonary bypass or minimally invasive (so-called minithoracotomy) techniques. Such procedures however, are typically associated with significant complications rates, particularly if performed in patients with serious comorbidities, and they often require long hospital stays or protracted recuperation periods.
In response to such concerns, efforts to develop a safer and less invasive alternative to surgical closure began in the mid 1970’s. Since then, advances in device technology and percutaneous technique have enabled transcatheter repair to emerge as a safe and effective option.
To date, closure of secundum ASDs has been the indication for which transcatheter repair has been the most rigorously studied. The largest investigation, a multicenter controlled trial involving 442 children and adults, compared transcatheter closure to surgical closure for secundum ASDs. At 1 year, outcomes were similar between the two groups, however complication rates and hospital stays were significantly lower in the transcatheter closure group.
A smaller comparative series of 171 patients from Italy reached similar conclusions. A few articles have even suggested such secondary benefits to transcatheter correction as improved neuropsychological outcomes and reduced overall costs, but further studies are needed to substantiate these findings. Transcatheter closure has also been performed on ASDs or PFOs associated with paradoxical emboli or cryptogenic stroke, and for congenital and acquired (i.e., traumatic or post-infarction) VSDs.
The literature supporting these latter indications has so far been limited to case reports and smaller case series, but further trials are underway and initial results promising.
A variety of transcatheter device systems are available in the U.S. Currently the most widely used are the Amplatzer series, including: the Amplatzer Septal Occluder (ASO), the Amplatzer PFO Occluder (APO) and the Amplatzer Muscular VSD, Membranous VSD, and Post-Infarction VSD Occluders (AGA Medical Corp., Golden Valley, MN); and the CardioSEAL/STARflex occluders (NMT Inc., Boston, MA).
To date, only the Amplatzer ASO has been fully approved by the FDA (for closure of secundum ASDs and post-Fontan fenestration defects). The CardioSEAL device is available in the U.S. under a humanitarian device exemption (HDE), but the other devices are still considered investigational. Although each system is designed for a specific indication (e.g., for post-infarct VSD repair).
In clinical practice individual devices have occasionally been used outside their designated indications - either due to lack of local availability, regulatory reasons, or certain desirable device-specific characteristic – and there are numerous published reports of occluders being used successfully for such off-label indications. In addition to the aforementioned products, a number of other devices have also been reported in the literature and may be available abroad.
Most transcatheter septal closure systems work in a similar fashion. They typically consist of the same basic components: a defect sizer, the implant itself, and its delivery/deployment system. The implant consists of two expandable disks or umbrellas of varying sizes, made of polyester and wire mesh and separated by a narrow waist or isthmus which varies in width based on the indication (e.g., widest for post-infarction devices and narrowest for membranous VSD or ASD repair devices).
The delivery system is made up of a percutaneous sheath, a guidewire, and a polyurethane catheter of varying length, size, and angle for procedural optimization. Transcatheter septal closure can be performed in the catheterization laboratory under sedation or general anesthesia. Fluoroscopy, transesophageal echocardiography, intracardiac echocardiography, or any combination of the three, are used to guide device placement.
After sizing the defect with a balloon sizer or other method, the appropriate device is selected. A sheath is then inserted into the femoral vein using Seldinger technique; the delivery catheter with device are threaded over the guidewire and advanced into the correct location in the heart; and the device is deployed. Some systems employ a self-centering mechanism and others have a method for retrieving devices that have been deployed incorrectly.
When positioned correctly, one side of the implant remains in the left chamber while the other resides in the right chamber, sandwiching the defect. Over time, endocardial and scar tissue grows over the implant, securing it in place permanently, and often eliminating any remaining defect.
While safe and effective, transcatheter repair is technically quite complex, requiring considerable skill and expertise. The FDA and even certain device manufacturers recommend formal training for physicians planning to use the system. Studies have so far noted fewer complications with transcatheter repair than with surgery, but complications do occur, particularly among less-experienced clinicians.
Device embolization, dysrhythmias, and thrombus formation are the most common concerns. Unsuccessful closure of the defect has also been reported, often necessitating deployment of another device or subsequent surgery. Furthermore, certain defects may not be amenable to transcatheter repair - large, multiple, or trabeculated defects; those with insufficient septal rims; defects in patients with anomalous pulmonary drainage; and those too close to valvular or venous structures may all require surgical repair.
Despite its limitations, transcatheter device closure appears to be a viable and less invasive alternative to surgery for many patients with cardiac septal defects. Ongoing studies are likely to confirm its safety and efficacy for an even wider range of indications.