In the last decade, transcatheter closure of various cardiac defects has become a safe and effective alternative to surgery.1 The advantages include less procedure time, shorter hospital stay, less emotional stress, and no scar on the chest. The defects that can be closed non-surgically include intracardiac defects such as the atrial septal defect (ASD), patent foramen ovale (PFO), ventricular septal defect (VSD), etc., and extracardiac defects such as patent ductus arteriosus (PDA) and various abnormal vessels, etc. Different defects require different specially designed devices which are discussed below.
ASD
The secundum type ASD, located at the central portion of the atrial septum, is amenable to non-surgical closure.2 Many devices have been used, including the clamshell, Cardioseal, Starflex, button, Das Angel wings device and ASD occluder system etc., that are accompanied by a certain incidence of residual shunt.2,3 The Amplatzer Septal Occluder is the first and only device to ever receive full approval for clinical use in children and adults with secundum ASD from the US Food and Drug Administration (FDA). It is a self-expanding, double-disk device made from nitinol wires with Dacron polyester patches sewn into each disc and the connecting waist, to increase the thrombogenicity of the device. The mechanism of closure involves stenting of the ASD by the waist of the device and subsequent thrombus formation within the device with eventual complete neoendothelialization. The initial human use was reported in 1997 with correct placement in all 30 patients studied with a 100% complete closure rate in 25 patients completing the three-month follow-up.2 So far, the closure rate is greater than 98% and the implantation rate is exceptional at 95.6%.3 Because it is safe, user-friendly and effective, the ASO is poised to be the procedure of choice for secundum ASD closure by both patients and cardiologists.3
PFO
PFO has been recognized increasingly as a source of paradoxical embolism causing transient ischemic attack, stroke or migraine.3,4 It can be closed by various ASD devices with good results. The Amplatzer PFO occluder is similar in construction to the ASO. The right atrial disc is larger than the left atrial disc and measures 18, 25 or 35mm.4 There is a short 3mm waist segment. The initial results have been very encouraging with 100% successful placement and 100% complete occlusion.3
Morandi et al. reported a significant improvement in migraine with aura in patients who underwent PFO closure.5 The migraine score improved from 6.75 pre-procedure to 2.5 after PFO closure in eight patients with migraine and aura. Transcranial Doppler has been used as a very sensitive diagnostic tool to evaluate a residual right-to-left shunt. The issue of closure of PFO to prevent recurrent stroke will be answered by randomized trials comparing device closure with continued medical therapy in patients who sustained their first stroke. The Randomized Evaluation of Recurrent Stroke Comparing PFO Closure with Established Current Standard of Care Treatment (RESPECT) and Closure 1 trials using the Amplatzer PFO device and the Cardioseal device respectively are two such trials being conducted in the US.
Congenital Muscular VSD
There are two devices available in the US for catheter closure of muscular VSD.6 The Cardioseal device is an FDA-approved device for patients deemed to be surgically high-risk. This device was originally intended for ASD closure and is not designed specially for the muscular VSD. Amplatzer muscular VSD occluder designed specially for the muscular septum is a self-expanding, double-disk device made from nitinol wire with polyester mesh inside to enhance clotting. The waist is 7mm long and the left and right ventricle disks are 8mm larger than the connecting waist. The preliminary results included 83 procedures in 75 patients with a median age of 1.4 years who underwent percutaneous or perventricular closure of hemodynamically significant muscular VSDs.1,7The device was implanted successfully in 72 of 83 (86.7%) procedures. Major procedure- or device-related complications occurred in 10.7% of patients. Closure rates were excellent and increased from 47.2% 24 hours post-procedure to 92.3% at 12 monthsÔÇÖ follow-up. These results compare favorably with the surgical results.
Post-infarction VSD
The incidence of post-myocardial infarction VSD remains as high as 0.2%. It is extremely difficult to manage and carries a grave prognosis.1,8Without definite treatment, the mortality exceeds 90%. Even with surgical closure, the early mortality has been reported to be as high as 19% to 46%.8 Because these patients are usually high-risk candidates for surgical intervention, non-surgical closure seems to be the logical approach.
The Amplatzer post-infarction muscular VSD occluder is similar in design to the congenital device with the exception of the length of the waist (10mm for the post-infarct device) and the left/right ventricle disks are 10mm larger than the waist.8 The initial results demonstrated that the device was successfully deployed in 16 of 18 patients with a 30-day mortality of 28%.8 Further trials are required to assess long-term efficacy and compare the results with those of surgical closure.
Perimembranous/Membranous VSD
Perimembranous/membranous VSD accounts for 70% of all VSDs and is the most common type of congenital heart disease.6The button and Rashkind devices have been used with acceptable results. However, they are not designed for the membranous septum, are cumbersome to use, and are associated with a high incidence of residual shunt. The Amplatzer membranous VSD occluder is a specifically designed device for membranous septum. It is a self-expandable double-disk device with a 1.5mm-long waist. The aortic end of the left ventricle disk is 0.5mm larger than the waist and the other end is 5.5mm larger than the waist. The right ventricle disk is 2mm larger at both sides. Its initial use in six patients showed complete closure in all.9 At the most recent Pediatric Interventional Cardiac Symposium (PICS-VII) in Orlando, Florida, Holzer et al. reported a successful procedure rate of 97% (59/61) with 0% mortality. Only one patient had a major complication of complete heart block.
PDA
The Gianturco coil is currently the most commonly used device to close PDA in the world.3,10 It is a coiled spring made of stainless wire with the attachment of thrombogenic Dacron strands. It is packaged straight and is then pushed through a small diameter catheter to the PDA. When extruded from the catheter it assumes a coiled shape and induces thrombosis. It is safe and effective to close small PDAs. However, it is associated with significant complications and residual shunt in moderate to large PDAs. Fu et al. reported that the compete closure rate at one-year follow-up is higher for ductal size <3mm than that >3mm (98.5% versus 73.9%, p<0.001).10 They suggested ductal size >3mm may require other treatment strategies or other devices to achieve better results.
The Amplatzer duct occluder is a self-expandable mushroom-shaped device made from a Nitinol wire mesh.11 The initial results have proven to have excellent success with a complete closure rate of 100% at one-year follow-up. The ADO is safe and effective for PDA up to a diameter of 10.6mm.11
Abnormal Vascular Connections
Abnormal vessels requiring management include coronary artery fistulas and aortopulmonary collateral arteries, etc. Coils are most commonly used and are effective to close small vessels. The Amplatzer vascular plug is a self-expandable cylindrical device made from a Nitinol wire mesh. It is designed for arterial and venous embolizations in the peripheral vasculature. The device received FDA approval earlier this year.
Summary
Non-surgical closure is safe and effective for many intracardiac or extracardiac defects. It has changed the therapeutic strategy for both patients and cardiologists. In fact, it has replaced surgery as the treatment of choice for a few heart defects, including secundum type ASD, PDA, abnormal vessels, etc. With the improvement in devices and delivery systems, we believe non-surgical closure will further increase the scope of treatable defects in the future.