Recent advances in managing septal defects: atrial septal defects

Management

The treatment of ASD patients is mostly dependent on the age at presentation, existence of symptoms of congestive heart failure, and the degree of the shunt. In an occasional infant with congestive heart failure, anti-congestive measures (diuretics and digoxin) should be provided. Subsequently, surgical or trans-catheter closure of the defects should be performed. While it is feasible to percutaneously close the ASD, even in infants, because spontaneous closure of even large ASDs can occur, the ASD should not be closed in the small asymptomatic child. Such children may be followed by periodic echocardiography, giving an opportunity for spontaneous closure. SBE prophylaxis is not necessary and activity restriction is not recommended for these patients.

Surgery. Subsequent to the description of cardiopulmonary bypass techniques for the surgical closure of ASDs by Gibbon, Lillehei, and Kirklin in the 1950s, surgery has become a customary treatment for ASDs. Under general anesthesia, a median sternotomy or a right submammary incision is performed and the aorta and vena cavae are cannulated to place the patient on cardiopulmonary bypass. Right atriatomy exposes the defect. Closure of the defect is done by either approximating the defect margins with suture material or using a pericardial or Dacron patch, based on the size of the defect and the surgeon’s preference. Primary closure is generally reserved for small defects, while patch closure is used for larger defects. Primary closure allows for the possibility of suture rupture and reopening of the defect, while patch closures may be associated with residual shunt. More recently, minimally invasive and robotic-assisted surgery has been used with good results^14,15.

Surgical closure of ostium secundum ASDs is considered safe and effective with negligible (<1%) mortality. However, the morbidity related to sternotomy/thoracotomy and cardiopulmonary bypass and the potential for postoperative complications are unavoidable. Additional disadvantages of surgery are the associated expense and residual scar and psychological trauma to the patient and/or their parents. Presumably because of these reasons, trans-catheter methods have been developed, as reviewed elsewhere^16–20. Currently, surgery is mainly reserved for ASDs with poor septal rims deemed difficult to close with trans-catheter techniques or unsuccessful percutaneous attempt to close the defect. In addition, if the repair of other associated defects is anticipated, surgical closure of the ASD during that surgery may be accomplished concurrently.

Percutaneous closure. King and Mills initially described the transcatheter occlusion of ASDs²¹. Shortly thereafter, Rashkind and Cuaso presented another type of device to close ASDs²². A large number of other devices have subsequently been developed over the last four decades, as reviewed elsewhere^{16–20,23,24}, and include: modified Rashkind’s device with six stainless steel arms with every other arm impregnated with a miniature “fish” hook, modified Rashkind device with double-disc, clamshell occluder, original buttoned device, atrial septal defect occluding system (ASDOS), second- and third-generation buttoned devices, Monodisk device, Das-Angel-Wing device, modified Rashkind PDA umbrella device, centering buttoned device, inverted buttoned device, Amplatzer^® Septal Occluder (ASO), CardioSEAL^® device, STARFlex device, fourth-generation buttoned device, Sideris’ wireless device, Sideris’ transcatheter patch, Gore HELEX^® Septal Occluder, centering-on-demand buttoned device, fenestrated Amplatzer^® device, hybrid buttoned device, cribriform device to occlude multiple defect, BioSTAR^®, nanoplatinum-coated Amplatzer^® device, Solysafe septal occluder device, Bio-STAR device, BioTREK device, Occlutech septal occluder, ATRIASEPT I-ASD device, ATRIASEPT II-ASD and ULTRASEPT, the pfm ASD-R device, biodegradable polycaprolactone occlusion device, Nit-Occlud ASD-R^® (NOASD-R) device, Lifetech Cera, and perhaps others. The majority of the devices had initial device closure attempts in animal models followed by clinical trials in human subjects with local IRB approval, CR Mark approval in Europe, or under FDA-approved clinical trials in the USA. Feasibility, safety, and effectiveness of occluding the ASD have been demonstrated for most of the devices. However, as of this time, the ASO, Amplatzer^® Cribriform device, and Gore HELEX^® are the only devices that have received approval for clinical use by the FDA in the USA. The Occulutech Septal Occluder, which has design similarities to the ASO, is widely used outside of the USA.

Amplatzer^® Septal Occluder

The ASO consist of two discs created from 0.004” to 0.007” Nitinol (nickel–titanium compound) wire with shape memory and with Dacron polyester patches sewn into each disc; the discs are connected by a 4 mm long waist which sits within the defect. The disc on the left atrial side is slightly larger than the one on the right. Transesophageal echocardiography (TEE) or intracardiac echocardiography (ICE) is used to monitor device deployment. Most cardiologists use static balloon sizing of the ASD using NuMed PTS or AGA Amplatzer sizing balloons. However, the senior author does not recommend or perform balloon sizing routinely but relies on the TEE (or ICE) sizing utilizing the thick margins of the ASD, excluding the flail margins, a method suggested by Carcagnì and Presbitero²⁵. An ASO that is 1 to 2 mm larger than the diameter of the ASD is chosen for implantation. The device is deployed into the left atrium, and, after ensuring that the device does not impinge on any structures, the larger left atrial disc is pulled against the atrial septum, the waist of the device is delivered into the defect, and the right atrial disc is then deployed on the right side of the septum. Once the device is positioned, careful echocardiographic views are required to ensure the discs of the device are not impinging on any structures and in particular the left atrial disc is not impinging on the anterior leaflet of the mitral valve. The device is self-centering within the defect and is retractable into the delivery sheath to allow for repositioning as needed. A “mushroom” appearance of the device indicates that the device is too large for the defect and, in such cases, the device is removed and replaced with a smaller device. Too large a device within the defect increases the risk of erosion of the atrial wall or the aorta, as will be reviewed in the Complications section. Once the device position is considered satisfactory, the device cable is moved back and forth (so-called Minnesota Wiggle) and repeat TEE or ICE is performed. If this maneuver results in prolapse of the device into the atria, the device needs to be removed and replaced with a larger device and TEE/ICE repeated prior to release of the device and termination of the procedure.

Complex defects, namely large defects, small septal rims, multiple defects, and septal aneurysms are problematic, and suitable modifications in the technique should be embarked upon to guarantee success of the device implantation, as detailed elsewhere^26,27.

Immediate and follow-up results of ASO implantations appear encouraging, with immediate complete closure rates varying from 62 to 96%, which improved to 83 to 99% at 6- to 12-month follow-up²⁸. Other studies in children^29–33 and adults^34–36 show similar results. We undertook the closure of 150 ostium secundum defects with ASO; small residual shunts were seen in two patients at the end of the procedure, but the shunts disappeared at 1- and 6-month follow-up visits, respectively. One patient developed complete heart block, requiring transvenous pacemaker insertion. No residual shunts were observed during a mean follow-up of 24 months^37,38. In the USA, the ASO is becoming the device of choice based on the ease with which the device can be deployed, retrieved, and repositioned and the comfort that the device is approved by the FDA.

Amplatzer^® Cribriform Device

The cribriform device is fabricated in a way that is similar to that of the ASO; it consists of two equal-sized discs connected with a thin waist^39–41. The cribriform device is used for the closure of fenestrated ASDs. The device implantation is similar to that of the ASO, the delivery sheath should be positioned in the middle fenestration of the ASD, and the discs should cover the most peripheral fenestration to yield effective closure. The limited published information suggests satisfactory outcomes^39–41.

Gore HELEX^® Septal Occluder Device

The Gore HELEX^® device consists of a single Nitinol wire covered by ultrathin expanded polytetrafluoroethylene (ePTFE) which forms two inter-connected discs when deployed. Unlike the ASO device, it is not self-centering and is only useful in small to moderate defects (up to 18 mm in diameter). The device is manufactured in 15 to 35 mm diameter sizes in 5 mm increments.

The procedure of implantation is similar to that alluded to in the ASO section and is described in detail elsewhere⁴². In brief, the delivery catheter (green) is placed in the left atrium over a guide wire. The push-pinch-pull method is used to develop the left atrial disc and the disc is then withdrawn gently to engage the left side of the atrial septum while fluoroscopic monitoring and TEE or ICE is performed. Then the green catheter is withdrawn over the gray catheter until the mandrel (tan) engages the hub. The green catheter is then held steady while the gray catheter is advanced to place the right atrial disc on the right atrial side of the atrial septum, again using the push-pinch-pull method. Once the device’s position is confirmed by TEE or ICE, it is locked and then released.

A multicenter trial⁴³ demonstrated successful implantation in 87% of patients, with a 2.6% incidence of residual leaks at follow-up 1 year after device implantation. Other reports indicate similar results. Wire frame fractures were observed in 8% of patients. A more recent analysis of 435 patients in the USA revealed composite clinical success in 93% of patients at 12-month follow-up⁴⁴. The Gore HELEX^® device is generally thought to be a suitable device for the closure of small to medium-sized defects.

Complications associated with device closure

Device-associated complications include device dislodgement and embolization, residual shunts, wire fractures, and heart block, although these are rare. Migration of the device along with erosion of the aorta during follow-up was detected in 18 out of 15,900 (0.12% or 1 in 1,000) ASO implantations in a US study^45,46. A similar prevalence (37 out of 35,000, 0.11%, or 1 in 1,000) in ASO implants worldwide was noted^44–47. The data were examined by the Review Board and AGA Medical (AGA 2006); these reviews indicated that the device erosion may be associated with over-sizing of the device and recommended that a device size more than 1.5 times the TEE/ICE diameter size of the ASD should not be used for closure of the defect. A more recent analysis revealed that patients with aortic erosion are more likely to have oversized devices, deficient aortic or superior vena caval rims, large balloon size, large ASO, larger device size-static ASD diameter difference, smaller patient age:device size ratio, and smaller weight:device size ratio than are control subjects⁴⁸.

Benefits and risks of transcatheter versus surgical intervention

A number of studies^49–56 compared surgical with device closure; these studies suggest equal effectiveness, and the transcatheter closure of ostium secundum ASDs has been proven to be a safe and effective alternative to surgical closure. The benefits of avoiding thoracotomy/sternotomy, cardio-pulmonary bypass, and cardiotomy, a decreased period of hospitalization (one day versus three to four days), and fewer complications (complication rates of transcatheter intervention have been reported at 7.2%, while the surgical group is reported at 24%) are measurable. In addition, percutaneous closure is less expensive than surgery. Percutaneous closure of secundum ASDs utilizing various devices is currently a conventional practice in the majority of institutions offering state-of-the-art care to subjects with cardiac disease^13,57.

Management

The indications for repair are similar to those listed for the closure of ostium secundum ASDs, and the usual recommended age for surgical repair is three to five years. However, in the presence of congestive heart failure secondary to mitral insufficiency, surgical repair may be performed at presentation following control of the heart failure by medical management.

Medical management. Though rare, congestive heart failure is seen with moderate to severe mitral insufficiency and should be treated with anti-congestive measures (afterload reducing agents, diuretics, and digoxin). Once the symptoms of congestive heart failure are controlled, surgical repair should be undertaken. SBE prophylaxis is recommended in the presence of significant mitral valve abnormalities.

Surgical management. As mentioned in the preceding section, the conventional treatment option for ostium secundum ASDs is percutaneous occlusion; however, surgical correction is required for ostium primum ASDs. Percutaneous occlusion is not feasible in patients with ostium primum ASDs because there is no inferior septal rim and there is the need to address mitral valve cleft and mitral insufficiency. A median sternotomy incision is made under general anesthesia, and the patient is placed on cardiopulmonary bypass by cannulating the aorta and vena cavae. Right atriatomy will allow the exposure of the ASD and mitral valve. Interrupted suture material is used to close the mitral valve cleft. Additional reparative procedures (such as annuloplasty) to deal with the detected mitral valve abnormalities are undertaken. The atrial defect is then closed using an autologous pericardial patch. Rarely, other prosthetic materials such as Dacron or Gore-Tex are used. If ostium secundum ASDs or a PFO is present, they should also be closed at the same time.

The results of surgery are usually good, with a mortality rate of less than 3%. Poor results are likely in patients with severe mitral insufficiency, failure to thrive, and congestive heart failure. Late reoperations for mitral regurgitation, mitral stenosis, or subaortic stenosis may be required in 10 to 15% of patients.

Management

The indications for intervention are, again, similar to those described in the ostium secundum ASDs. While device closure is a standard therapy in the management of ostium secundum ASDs, such an approach may not feasible in sinus venosus ASDs because of the lack of superior rim and the requirement for redirecting the anomalous pulmonary vein(s). However, some attempts to circumvent such problems by the implantation of a covered stent to direct the superior vena caval flow into the right atrium while occluding the atrial defect and redirecting the anomalous pulmonary vein into the left atrium have been made (Lin CH and Breinholt JB, personal communication, 2017). Further experimentation/research with such percutaneous approaches is warranted.

At the present time, surgical repair is the treatment of choice. Closure of the ASD along with diversion of the anomalous right pulmonary vein(s) into the left atrium are performed under cardiopulmonary bypass. Sometimes this may entail constructing a tunnel with an autologous pericardial patch along with enlargement of the superior or inferior vena cava, as the case may be. The results are generally good, with rare superior vena caval or pulmonary venous obstruction.

Management

Surgical repair with patch closure of the defect, leaving the coronary sinus opening in the left atrium, is the usual approach⁵⁹. These defects are typically not amenable to percutaneous closure. Nonetheless, small defects may be amenable to percutaneous closure⁶⁰.