Indications
1. Symptoms or complications of an atrial septal defect (ASD) 2. Paradoxical embolism and documented orthodeoxia-platypnea 3. Prophylaxis for professional divers or those undergoing pacemaker implantation 4. Pregnancy and delivery

Contraindications

1. Small ASD (diameter <5 mm) and no evidence of right ventricular volume overload

2. Irreversible pulmonary hypertension

3. Other contraindications include the following:

• Poor state of the patient with other serious conditions or comorbidities

• Patients with associated cardiac anomalies requiring cardiac surgery

• Patients with current systemic or local infection or sepsis within 1 month of device placement

• Patients with bleeding disorder or with other contraindications to aspirin therapy, unless another antiplatelet drug can be administered for 6 months

• Presence of intracardiac thrombus

• Unsuitable defect anatomy including deficient rims, superior/inferior or posterior. Deficient anterior rim is not a contraindication for the use of percutaneous closure devices.

• Patients allergic to nickel may suffer an allergic reaction. This is a relative contraindication. Most nickel allergies are contact reactions. It is unclear if intracardiac devices will mount a similar reaction. A consultation with an allergist may be needed.

Outcomes of ASD Closure

In patients undergoing successful ASD closure before they are 24 years of age, the long-term survival matches that seen in the general population. Significantly shorter survival in patients with pulmonary hypertension (PAP = 40 mmHg) after age 24 has been reported. Closure in patients over 40 years of age, while reducing mortality, improving symptoms, limiting functional deterioration, and limiting the incidence of heart failure compared with a conservatively managed control group, did not reduce arrhythmias or stroke on long-term follow-up. Independent predictors of mortality include functional NYHA Class III-IV, PAP > 40 mmHg and Qp/Qs > 3.5:1.

ASD Closure Devices

Currently the only two devices approved for the percutaneous closure of secundum ASD are the Amplatzer septal occluder and HELEX septal occluder device.

Amplatzer Septal Occluder (ASO)

The Amplatzer septal occluder (ASO) is a self-expandable double disc device made of nitinol (55% nickel, 45% titanium) wire mesh. The ASO is tightly woven into two flat discs (Fig. 20-1). There is a 3- to 4-mm connecting waist between the two discs, corresponding to the thickness of the atrial septum. Nitinol has super elastic properties, with shape memory. This allows the device to be stretched into an almost linear configuration and placed inside a small sheath for delivery and then return to its original configuration within the heart when not constrained by the sheath. The device size is determined by the diameter of its waist and is constructed in various sizes ranging from 4 to 40 mm (1-mm increments up to 20 mm; 2-mm increments up to the largest device currently available, 40 mm; the 40-mm size is not available in the United States). The two flat discs extend radially beyond the central waist to provide secure anchorage.

Figure 20-1 Amplatzer. Atrial septal defect occluder and patent foramen ovale occluder. LA, left atrial; RA, right atrial.

The LA disc is larger than the RA disc. For devices 4 to 10 mm in size, the LA disc is 12 mm and the RA disc is 8 mm larger than the waist. However, for devices larger than 11 mm and up to 32 mm in size, the LA disc is 14 mm and the RA disc is 10 mm larger than the connecting waist. For devices >32 mm, the LA disc is 16 mm larger than the waist and the RA disc is 10 mm larger than the waist. Both discs are angled slightly toward each other to ensure firm contact of the discs to the atrial septum.

A total of three Dacron polyester patches are sewn securely with polyester thread into each disc and the connecting waist to increase the thrombogenicity and endothelialization of the device. A stainless steel sleeve with a female thread is laser-welded to the RA disc. This sleeve is used to screw the delivery cable to the device. Each device costs US $5500.

Amplatzer Delivery System

For device deployment, we recommend using appropriately sized sheaths for the device as summarized in Table 20-3. The delivery system is supplied sterilized and separate from the device. It contains all the equipment needed to facilitate device deployment. It consists of the following:

1. Delivery sheath of specified French size and length, and appropriate dilator

2. Loading device, used to collapse the device and introduce it into the delivery sheath

3. Delivery cable (internal diameter [ID] 0.081 inch): the device is screwed onto its distal end allowing for loading for loading, placement, and retrieval of the device

4. Plastic Pin-vice: this facilitates unscrewing of the delivery cable from the device during device deployment

5. Tuohy Borst valve adapter with a side arm for the sheath, to act as a one-way stop-bleed valve

^{Table 20-3} Sheath Delivery System Sizing for Atrial Septal Defect Devices

6F delivery system for devices <10 mm in diameter

7F delivery system for devices 10–15 mm

8F sheath for devices 16–19 mm

9F sheath for devices 20–26 mm

10F sheath for devices 28–34 mm

12 F sheath for the 36-mm and 38-mm device

14 F sheath for the 40-mm device

All delivery sheaths have a 45-degree angled tip. The 6F sheath has a length of 60 cm, the 7F sheath is available in lengths of 60 and 80 cm and the 8F, 9F, 10F, and 12F sheaths are all 80 cm long. The delivery system costs US $580.

Amplatzer Exchange (Rescue) System

This is made up of the same components as the Amplatzer delivery system except that the inner lumen and tip of the dilator can accommodate the delivery cable. It is available in two sizes: 9F (dilator ID 0.087 inch) and 12F (dilator ID 0.113 inch), with a 45-degree curve and 80 cm in length. The distal tip of the delivery cable can screw into the back of another delivery cable. This allows it to become an exchange length cable. The damaged sheath then can be removed and the rescue sheath with its dilator can be inserted over the cable to recapture the device. The exchange system costs $580.

Optional but Recommended Equipment

Amplatzer Sizing Balloon

The Amplatzer sizing balloon is a double-lumen balloon catheter with a 7F shaft size. The balloon is made from nylon and is very compliant, making it ideal for sizing the secundum ASD by flow occlusion (“stop-flow”) without overstretching of the defect. The balloon catheter is angled at 45 degrees and there are radiopaque markers for calibration at 2, 5, and 10 mm. The balloon catheters are available in three sizes: 18 mm (maximum volume is 20 mm and is used for defects up to 20 mm); 24 mm (maximum volume 30 mL and used to size defects up to 22 mm); and 34 mm (maximum volume 90 mL and used to size defects up to 40 mm).

Amplatzer Super Stiff Guidewire

The 0.035-inch Amplatzer super stiff exchange guidewire is used to advance the delivery sheath and dilator into the left upper pulmonary vein. Table 20-4 summarizes all the necessary materials for ASD closure.

^{Table 20-4} Materials/Equipment Required for Transcatheter ASD Closure Procedures

Item	Size	Cost each (US$)
Amplatzer Septal Occluder	4–40 mm	5500
Amplatzer PFO Occluder	18, 25, 35 mm	5000
Amplatzer Delivery System	7–12F	580
Amplatzer Super Stiff exchange	0.035-inch, 100 cm length guidewire	45
Multipurpose catheter	6–7F	10
Amplatzer Sizing Balloon	24, 34 mm	265
Amplatzer Rescue System	9 F, 12F	580

PFO, patent foremen ovale.

Step-by-Step Technique: Transcatheter Device Closure of Secundum ASD

6. Perform a right upper pulmonary vein angiogram (Fig. 20-3A) in the hepatoclavicular projection (35-degree left anterior oblique/35-degree cranial). This delineates the anatomy, shape, and length of the septum. This may come in handy when the device is deployed but not released—the operator can position the imaging tube in the same view of the angiogram and compare the position of the device with that obtained during the deployment (Fig. 20-3B, C).

Figure 20-2 Intracardiac echocardiographic images in a patient with a large secundum atrial septal defect (ASD). A, Home view demonstrating the right atrium (RA), tricuspid valve, right ventricle (RV), aortic root (Ao) and pulmonary artery (PA). B, Septal view, demonstrating the large ASD (arrow), the RA and the left atrium (LA), and the superior and inferior rims. C, Same view with color Doppler. D, Caval view demonstrating the entire superior rim and the defect (arrow). E, Short-axis view demonstrating the defect (arrow), the aortic root, the absent anterior rim and good posterior rim, and both atria. AV, aortic valve SVC, superior vena cava.

Figure 20-3 Cineangiographic images in a patient with secundum atrial septal defect (ASD). A, Angiogram in the right upper pulmonary vein in the hepatoclavicular projection (35 degrees left anterior oblique/35 degrees cranial) demonstrating left-to-right shunt. B, Angiogram in the right atrium in the hepatoclavicular projection prior to release of the device. Correct deployment manifest by opacification of the right atrial disc only and on levophase the left atrial disc only opacified. C, Cineangiographic image after the device has been released, demonstrating good device alignment with the septum.

7. Defect Sizing. Position the multipurpose catheter in the left upper pulmonary vein. Prepare the appropriate size of balloon according to the manufacturer’s guidelines. We prefer to use the 34-mm balloon because it is longer and during inflation it sits nicely across the defect. Pass an extra-stiff, floppy/J-tipped 0.035-inch exchange length guidewire (Fig. 20-4A). This gives the best support within the atrium for the balloon, especially in large defects. Remove the multipurpose catheter and the femoral sheath. We advance the sizing balloon catheter directly over the wire without a venous sheath. Most sizing balloons require an 8F or 9F sheath. The balloon catheter is advanced over the wire and placed across the defect under both fluoroscopic and echocardiographic guidance. The “stop-flow” balloon sizing is performed by inflating the balloon (previously prepared with 1:4 diluted contrast) until the left-to-right shunt ceases, as observed by color flow Doppler TEE/ICE. Once the shunt ceases, deflate the balloon slightly until shunt reappears. This “stop-flow” balloon sizing technique is used to select an ASO device size. The best echo view for measurement is to observe the balloon in its long axis (Fig. 20-4B). In this view the indentation made by the margins of the ASD can be visualized and precise measurement can be made.

Figure 20-4 Intracardiac echocardiographic images of the patient in Figure 20-2, showing defect sizing. A, The exchange wire (arrow) across the defect into the left upper pulmonary vein (LPV). B, Sizing balloon occluding the defect. This is the stretched diameter (arrows) of the defect.

8. Fluoroscopic Measurement. Angulate the x-ray tube so the beam is perpendicular to the balloon. Various calibration markers can be helpful. Ensure that the markers are separated and discrete. Measure the balloon diameter at the site of the indentation (or at the middle of the balloon) as per the diagnostic function of the laboratory (Fig. 20-5). We have found that when a discrepancy exists between the echocardiographic and the fluoroscopic measurements, the echocardiographic measurement is usually more accurate.

Figure 20-5 Cineangiographic image of the patient in Figure 20.3 during balloon sizing of the defect, demonstrating the stretched diameter (arrows) of the defect.

Once the size has been determined, deflate the balloon and pull it back into the junction of the right atrium and IVC, leaving the wire in the left upper pulmonary vein.

Recheck the ACT and give the first dose of antibiotics.

9. Device Selection. If the defect has adequate rims (>5 mm), select a device ≤2 mm larger than the “stop-flow” diameter of the balloon. However, if the superior/anterior rim is deficient (5–7 mm), we tend to select a device 4 mm larger than the balloon “stop-flow” diameter.

10. Device Delivery. Open the appropriate-sized delivery system. Flush the sheath and dilator. The delivery sheath is advanced over the guidewire to the left upper pulmonary vein (Fig. 20-6A). Both dilator and wire are removed, keeping the tip of the sheath inside the left upper pulmonary vein. Use extra care and do not allow air inside the delivery sheath. An alternative technique to minimize air embolism is passage of the sheath with the dilator over the wire until the IVC, at which point the dilator is removed and the sheath is advanced over the wire into the left atrium while continuously flushing the side arm of the sheath.

Figure 20-6 Intracardiac echocardiographic images of the patient in Figure 20-2, showing device delivery and deployment. A, Delivery sheath (arrow) across the defect into the left upper pulmonary vein. B, The left atrial disc (arrow) deployed in the left atrium. C, The right atrial disc (arrow) deployed in the right atrium. D, The device released, demonstrating good position. E, Color Doppler demonstrating no residual shunt and patent superior vena cava.

On the back table, the ASO device is then screwed to the tip of the delivery cable, immersed in normal saline to clear air bubbles, and drawn into the loader while under water injecting saline through the side arm of the loading sheath to expel air bubbles out of the system. A Y connector is applied to the proximal end of the loader to allow flushing with saline. The loader containing the device is attached to the proximal hub of the delivery sheath with a fluid-to-fluid connection. The cable with the ASO device is advanced to the distal tip of the sheath, taking care not to rotate the cable while advancing it in the long sheath to prevent premature unscrewing of the device. Both cable and delivery sheath are pulled back as one unit to the middle of the left atrium. Position of the sheath can be verified using fluoroscopy or TEE/ICE.

11. Device Deployment. The LA disc is deployed first under fluoroscopic and/or echocardiographic guidance by pulling back the sheath, while leaving the disc fixed in the LA away from the LA appendage (Fig. 20-6B). Part of the connecting waist should be deployed in the left atrium, very close (a few millimeters) to the atrial septum (the mechanism of ASD closure using the ASO is stenting of the defect). While applying constant tension on the entire assembly and withdrawing the delivery sheath off the cable, the connecting waist and the RA disc are deployed in the ASD itself and in the right atrium respectively (Fig. 20-6C).

12. Device Positioning. Proper device position can be verified using different techniques:

Fluoroscopy in the same projection as that of the angiogram. Good device position is evident by the presence of two discs that are parallel to each other and separated from each other by the atrial septum. In the same view the operator can perform the “Minnesota wiggle” (the cable is pushed gently forward and pulled backward). Stable device position manifests by the lack of movement of the device in either direction.

TEE/ICE. The echocardiographer should make sure that one disc is in each chamber. The long-axis view should be sufficient to evaluate the superior and inferior part of the septum and the short-axis view for the anterior and posterior part of the disc (Fig. 20-6D,E ).

Angiography. This is done with the camera in the same projection as for the first angiogram to profile the septum and device using either the side arm of the delivery sheath or a separate angiographic catheter, inserted in the sheath used for ICE or via a separate puncture site. Good device position manifests by opacification of the RA disc alone when the contrast is in the right atrium and opacification of the LA disc alone on pulmonary levophase.

If the position of the device is questionable, the device can be recaptured, entirely or partly, and repositioned following similar steps.

13. Device Release. Once the device position is verified, the device is released by counterclockwise rotation of the delivery cable using a pin vise. There is often a notable change in the angle of the device as it is released from the slight tension of the delivery cable and it self-centers within the ASD and aligns with the interatrial septum. To assess the results of closure, repeat TEE/ICE, color Doppler, and angiography (optional) in the four-chamber projection in the right atrium with pulmonary levophase are performed. Once the procedure is complete, recheck the ACT and, if appropriate, remove the sheath and achieve hemostasis. If ACT is above 250 seconds, reverse the effect of heparin by using protamine sulfate.

14. Postprocedure Care. Patients receive a dose of an appropriate antibiotic (commonly cefazolin 1 g) during the catheterization procedure and two further doses at 8-hour intervals. Patients are also asked to take endocarditis prophylaxis when necessary for 6 months after the procedure, as well as aspirin 81 to 325 mg orally once daily for 6 months. In addition, we have been adding 75 mg clopidogrel for 2 to 3 months. We have observed that the incidence of postclosure headaches is much less in those patients taking the clopidogrel. The patient is asked not to engage in contact sports for 1 month after the procedure. Full activity, including competitive sports, is usually allowed after 4 weeks of implantation. Magnetic resonance imaging (if required) can be performed any time after implantation.

15. Postprocedure Monitoring. Patients recover overnight in a telemetry ward. Some patients may experience an increase in atrial ectopic beats. Rarely, some patients may have sustained atrial tachycardias. The following day an ECG, a chest x-ray [optional] (posteroanterior and lateral), and a TTE with color Doppler should be performed to assess the position of the device and presence of residual shunt.

Recheck ECG, chest x-ray, and TTE/TEE at 6 months after the procedure to assess everything. If the device position is good with no residual shunt, antibiotic prophylaxis and aspirin can be discontinued. Clinical follow-up can be annually for the first 2 years, then every 3 to 5 years thereafter. Long-term follow-up of device performance should be assessed and any new information communicated to the patient.

Troubleshooting

Air Embolism

Meticulous technique should be used to prevent air entry. The sheath should be positioned at the mouth of the left upper pulmonary vein. Doing so allows free flow of blood into the sheath. Forceful negative pressure should not be applied to aspirate the sheath. If a large amount of air is introduced on the left side, it will usually pool in the right coronary sinus and right coronary artery. This may manifest with bradycardia, asystole, or profound hypotension. If this occurs, immediately place a right coronary catheter in the right coronary sinus and forcefully inject saline or contrast to displace the air and hence reperfuse the right coronary system.

Cobra-Head Formation

This describes the situation when the left disc maintains a high profile when deployed, mimicking a cobra head. This can occur if the left disc is opened in the pulmonary vein or the LA appendage, or if the left atrium is too small to accommodate the device. It can also occur if the device is defective or has been loaded with unusual strain on it. If this occurs, check the site of deployment; if appropriate, recapture the device and remove and inspect it. If the “cobra head” forms outside the body, use a different device. If the disc forms normally, try deploying the device again. Do not release a device if the left disc has a “cobra-head” appearance.

Device Embolization

If a device embolizes, it must be retrieved, preferably by transcatheter snare and a long sheath, otherwise by surgery. The transcatheter technique is difficult and should not be performed if the operator is inexperienced in snaring techniques. Furthermore, the catheter laboratory should be equipped with large Mullins-type sheaths (12F–16F) and also should have various-sized snares. We use the Goose-neck Snare (ev3, Plymouth, MN) or the EN Snare (Merit Medical, Salt Lake City, UT). The device should not be pulled across valves, since it may damage the chordae and leaflets. Always use a long sheath to pull the device outside the body. To snare a device, we usually use a sheath that is two French sizes larger than the sheath that was used to deliver the device. On rare occasions, if the LA disc cannot be collapsed inside the sheath, another snare is introduced from the right internal jugular vein to snare the stud of the microscrew of the LA disc and stretch it toward the internal jugular vein while the assistant pulls the device with the snare toward the femoral vein. This allows the device to collapse further and come out of the sheath in the femoral vein.

Prolapse of the Left Disc Across the Defect During Deployment

On occasion, especially in patients with large defects with deficient anterior/superior rims, when the left disc is deployed it opens perpendicular to the plane of the atrial septum and prolapses through the anterior superior part of the defect. To overcome this problem, use a device that is at 4 mm larger than the measured “stop-flow” balloon diameter. If this is not possible or it does not work, change the angle of the deployment by placing the sheath either in the left or right upper pulmonary vein rather than mid left atrium. This may change the orientation of the disc. Another potential solution is to use the Hausdorf sheath (Cook Medical, Bloomington, IN), which has two posterior curves at the end. This sine curve can be quite useful in changing the deployment angle.

The use of the dilator technique or balloon-assisted technique is also helpful in preventing prolapse of the LA disc to the right. The dilator technique implies the use of a long dilator from the contralateral femoral vein to hold the LA disc in the left atrium while the assistant/operator deploys the remainder of the device. The balloon-assisted technique is similar to the dilator technique. A guidewire is positioned in the left upper pulmonary vein from the contralateral femoral vein. A balloon is inflated in the right atrium very close to the septum. The device is deployed in the usual fashion. The presence of the balloon will prevent prolapse of the left disc. Once the device has been deployed, the balloon is deflated slowly. After complete deflation, the guidewire is pulled out carefully from the left atrium.

Recapture of the Device

To achieve the smallest sheath size for device delivery, the sheath wall thickness is small, with a resultant decrease in strength. To recapture a device prior to its release, the operator should hold the sheath at the groin with the left hand and, with the right hand, pull the delivery cable forcefully inside the sheath. If the sheath is damaged or kinked (accordion effect), use the exchange (rescue) system to change the damaged sheath. First, extend the length of the cable by screwing the tip of the rescue cable to the proximal end of the cable attached to the device. Then remove the sheath or, if the sheath is 9 F or 12 F, introduce the dilator of the rescue system over the cable inside the sheath until it reaches a few centimeters from the tip of the sheath. This dilator will significantly strengthen the sheath, allowing the operator to pull back the cable with the dilator as one unit inside it. Then the operator can decide what to do next (change the entire sheath system or the device).

Release of the Device With a Prominent Eustachian Valve

To avoid the possibility of cable entrapment during release, advance the sheath to the hub of the right disc. Then release the cable and immediately draw back inside the sheath before the position of the sheath is changed.

Closure of Multiple Secundum ASD

If two defects are present and separated by more than 7 mm from each other, cross each defect separately. Size each one and then leave a delivery system in each defect. Initially deploy the smaller device, then the larger device, and release sequentially, starting with the smaller one.

If there are multiple fenestrations, use the Amplatzer multi-fenestrated septal occluder–“Cribriform” (these devices are similar in design to the Amplatzer PFO occluder except that the two discs are equal in size). The device should be deployed in the middle of the septum so that it can cover all fenestrations.

Complications

In the U.S. phase II trial comparing device closure to open surgical closure, the incidence of complications was 7.2% for device closure, far less than what was encountered when using an open surgical technique (24%). Most complications were related to rhythm disturbances, with very few patients requiring long-term medical therapy. Complications included the following:

1. Device embolization, the majority of which were encountered during the early learning curve of the investigators.

2. Heart block: rarely reported. Most likely related to the use of an oversized device.

3. Atrial arrhythmia: significant increase in atrial arrhythmias following device placement, generally resolving by 6 months.

4. Headaches: reported in about 5% of patients following device placement, resolving within 6 months. The use of clopidogrel for 2 to 3 months after device closure has minimized this complication significantly.

Results

Closure rates have been similar to those achieved by open surgical results. However, patients who underwent device closure were somewhat older than those who underwent open surgical closure. Furthermore, the cost of device closure was much less than open surgical closure and the length of hospital stay was shorter (1 day) for the device group than the surgical group (3.4 days). In a study by Kim and Hijazi, the mean cost for transcatheter closure was $11,541 whereas for surgical closure it was $21,780.

HELEX Septal Occluder Device

The Gore HELEX septal occluder device (WL Gore & Associates, Flagstaff, AZ) is a non-self-centering double-disc device made of nitinol and expanded polytetrafluoroethylene (ePTFE) (Fig. 20-7). The device is designed such that, following introduction across the septum, one disc is constituted on the LA side and the other on the RA side of the septum. The construction of the device consists of a curtain of ePTFE (gore-tex, WL Gore & Associates Flagstaff, Arizona) bonded to a single-piece wire frame of nitinol (0.012 inch). The nitinol is manufactured into a helical pattern of opposing rotations which, on full configuration, assumes two parallel discs. The device is delivered through its own composite triaxial 10 F delivery catheter with a workable length of 75 cm. This obviates the need for a long transseptal sheath. For patent foramen ovale (PFO) closure, the delivery system can be “monorailed” through a hole close to its distal end using a wire placed through a diagnostic catheter positioned in one of the left pulmonary veins. The device is available in 15-, 20-, 25-, 30- and 35-mm diameters. The devices are delivered through a short 10 F femoral vein sheath; however, if using the monorail technique, a short 11F or 12F femoral sheath is required.

Figure 20-7 A, HELEX atrial septal defect (ASD) closure devices of various sizes. B, Closeup view of attached HELEX device to delivery cable.

The HELEX device is designed to be flexible and atraumatic, molding itself to the atrial septum and contiguous structures, rendering it particularly appealing for use in a growing heart. Similarly the proven low thrombogenicity of ePTFE imparts confidence in delivering devices on the systemic side of the circulation (left atrium). This is of particular relevance in closure of the PFO where there are implications of thrombotic events to the systemic circulation, producing transient ischemic attacks and strokes. ePTFE has been used in various formats as patches and vascular tubes in the growing heart for almost 30 years and thus has proven longevity and biocompatibility with rapid endothelialization characteristics. Studies particular to the HELEX device have confirmed this excellent biocompatibility.

Patient Selection

The HELEX occluder is designed to occlude only the central (secundum) type ASD. The morphology of secundum ASDs is variable, and multiple defects, fenestrated, and aneurysmal ASDs can be closed using this device. A deficient anterior superior rim, where there is a lack of effacement of the atrial septum at the aorta, can also be accommodated by relative oversizing of the device.

With a non–self-centering device, a device-to-defect diameter ratio of 1.8-2:1 is recommended for ASD closure. With the largest available HELEX device being 35 mm, the largest diameter defect that would be closable would be in the range of 18 to 19 mm. In addition, children with large ASDs tend to have a relatively small left atrium; our experience has shown that the 30- and 35-mm devices do not sit effectively on the LA side of the septum in children weighing less than 25 kg. Operators should also be aware that defects measuring more than 15 mm on a standard TTE will balloon to size 18 mm or more and be unsuitable for the HELEX device.

Technique of Closure

Anesthesia

In children, general anesthesia is required, usually with endotracheal intubation. In adults, conscious sedation can be used if ICE is used; if TEE is planned, general anesthesia is required. In our practice we use ICE exclusively because it has excellent image quality and because endotracheal intubation can be avoided.

Vascular Access

Venous access is established in a manner similar to that described for the ASO device. Heparin 100 U/kg is administered intravenously. A hemodynamic study is performed to assess the shunt and pulmonary artery pressure and resistance. Echocardiography demonstrates the morphology of the ASD with respect to size, margins, proximity to the aorta, and atrioventricular valves. At this stage, multiple defects, not apparent on transthoracic echo, may be imaged, as well as fenestrations and aneurysms of the septum.

The same steps for the ASO are used when placing the HELEX occluder device. However, for device size, we use a device size that is 1.8-2:1 the size of the “balloon diameter.”

Loading the Device

The HELEX device is supplied with its own delivery catheter (Fig. 20-8A) such that a long Mullins-type sheath is not necessary. The delivery system consists of three distal coaxial components transitioning to a parallel component arrangement at the proximal Y-arm hub: a 10 F green delivery catheter, a gray control catheter, and a tan mandrel (Fig. 20-8B). The proximal end of the control catheter exits the Y-arm hub and is terminated by a red retrieval cord cap. The proximal end of the mandrel exits the side port of the Y-arm hub and is terminated by a clear Luer-Lok. The control catheter is equipped with a retrieval cord if occluder repositioning or retrieval is deemed necessary (Fig. 20-8B). A 0.035-inch guidewire channel is incorporated into the distal end of the delivery catheter.

Figure 20-8 A, HELEX delivery device. B, Tuohy Borst Y connector for HELEX device.

Loading the Occluder Into the Green Delivery Catheter

Remove the device from the sterile tray. Discard the sterile tray and follow the following steps:

1. To reduce the chance of air entrapment in the delivery system, loading of the occluder should be conducted with the occluder and catheter tip submerged in a heparinized saline bath.

2. Fill a large volume (20–30 mL) syringe with heparinized saline.

3. Attach the syringe to the red retrieval cord cap.

4. Tighten the mandrel Luer-Lok.

5. Loosen the control catheter Luer-Lok.

6. Flush the control catheter into the bowl or sterile tray.

7. When the initial flushing is completed, draw back on the gray control catheter with the attached syringe until only about 3 cm of the occluder remains outside the delivery catheter and the tan mandrel appears slightly curved (Fig. 20-9A).

8. Loosen the mandrel Luer-Lok.

9. Complete loading by continuing to draw back on the gray control catheter hub until the entire occluder has been withdrawn into the green delivery catheter (Fig. 20-9B).

10. Flush the control catheter into the bowl or sterile tray.

11. Keep the flushing syringe attached to the red cap to prevent the entrance of air into the delivery system until the catheter tip is placed inside the introducer sheath.

Figure 20-9 A, Pulling the HELEX device into the delivery sheath. B, Captured HELEX device.

Device Delivery

Load the delivery catheter onto a guidewire through the guidewire port from the luminal surface out; ensure that the occluder is sufficiently withdrawn into the green delivery catheter to avoid interference with the guidewire (monorail system) (Fig. 20-10A). Load the delivery system into the appropriately sized introducer sheath. At this stage, remove the flushing syringe. Verify that the red retrieval cord cap affixing the retrieval cord is securely attached to the gray control catheter.

Deployment

LA Disc Deployment

1. Under direct fluoroscopic visualization, advance the catheter tip across the ASD until the radiopaque marker at the tip of the green delivery catheter is positioned within the middle left atrium. Verify that the tip of the green delivery catheter is across the defect and away from the LA appendage using TEE or ICE.

2. At this stage, the guidewire should be removed before attempting to deploy the occluder.

3. Use the following “push-pinch-pull” method to deploy the LA occluder disc:

(a) Push the gray control catheter, moving the occluder into the LA chamber off of the septum but do not push against the atrial wall, or if the chamber space is adequate, push until the tan mandrel Luer-Lok stops against the Y-arm hub (approximately 2 cm).

(b) While holding the green delivery catheter to maintain position, pinch the gray control catheter.

(c) Then pull the tan mandrel back approximately 2 cm or less to form exposed segment of occluder. Repeat the “push-pinch-pull” sequence until the center eyelet exits the green delivery catheter tip demarcated by the radiopaque marker (Fig. 20-10B, 20-11A).

4. Once the LA disc is deployed, hold the entire system as one unit and pull it back until the LA disc is in contact with the atrial septum under echocardiographic and fluoroscopic guidance.

RA Disc Deployment

1. To prepare for RA disc deployment, hold the gray control catheter in a fixed position and gently expose a portion of the RA side by withdrawing the green delivery catheter until the mandrel Luer-Lok stops on the Y-arm hub. Tighten the mandrel Luer-Lok.

2. Deploy the RA disc by holding the green delivery catheter in a fixed position with left hand and pushing the gray control catheter with the right hand until the control catheter Luer-Lok contacts the Y-arm hub. Then tighten the control catheter Luer-Lok.

3. Confirm that both left and right discs appear planar and apposed to the septum with septal tissue trapped between the discs (Figs. 20-10C, 20-11B).

4. Confirm proper position using TEE/ICE and angiography in the LAO-cranial (35-35) position (Figs. 20-10D, 20-11C). If the position is not correct, refer to the repositioning steps later in this chapter.

5. Completely remove the red retrieval cord cap and set it aside.

Figure 20-10 Intracardiac echocardiography in patient with atrial septal defect (ASD). A, Septal view, demonstrating the ASD (arrow), the right and left atria, and the superior and inferior rims. B, The left atrial disc (arrow) deployed in the left atrium. C, The right atrial disc (arrow) deployed in the right atrium. D, The device released, demonstrating good position.

Figure 20-11 Cineangiographic image in the patient whose ICE is shown in Fig. 20-10. A, The left atrial disc (arrow) deployed in the left atrium. B, The right atrial disc (arrow) deployed in the right atrium. C, The device released, demonstrating good position.

Occluder Lock and Release

1. It is important to note that the occluder can only be repositioned prior to lock release.

2. If position and occlusion are acceptable, loosen the mandrel Luer-Lok. Hold the green delivery catheter in a fixed position and release the lock by sharply pulling the tan mandrel at least 2 cm.

3. At the completion of the lock and release step, the occluder is still loosely attached to the gray control catheter by the retrieval cord. If the occluder position is not acceptable, refer to the section titled “Removing the Occluder With the Retrieval Cord,” later in this chapter. Once the delivery system is withdrawn (next step), the occluder cannot be removed using the delivery system.

4. If position is acceptable, remove the entire delivery system as a single unit, making sure the retrieval cord moves smoothly through the control catheter hub.

Repositioning the Occluder

1. Replace and tighten the red retrieval cord cap and tighten the mandrel Luer-Lok.

2. Repeat steps mentioned in the earlier section “Loading the Occluder Into the Green Delivery Catheter” in order to bring the occluder back into the catheter.

3. Reposition across the defect.

4. Repeat steps listed in the “Deployment” section (earlier in this chapter).

5. During repositioning, if increased force is required to move the catheter components due to abnormal conditions (such as a kinked mandrel, curved mandrel-lock loop or premature lock release), remove the occluder and delivery system entirely and utilize a new device.

Removing the Occluder With the Retrieval Cord

1. If the lock is released and if the retrieval cord is still attached to the gray control catheter, the occluder can be removed by taking up any slack in the retrieval cord and securely reattaching the red retrieval cord cap.

2. Position the green delivery catheter in the right atrium. Withdraw the gray control catheter while pulling the occluder into a linear form and drawing the occluder back into the green delivery catheter.

3. Do not use excessive force in an attempt to withdraw all of the occluder into the green delivery catheter. Doing so could cause the retrieval cord to break or result in occluder fracture.

• Note: Without the mandrel to support the wire frame of the occluder, the operator must ensure that the lock loop and eyelets do not catch on the delivery catheter tip or introducer sheath. If the lock loop or eyelet catch and the delivery system are forcibly retracted, the retrieval cord or wire frame is at risk of fracture.

4. Normal removal practices withdraw 50% to 100% of the occluder into the green delivery catheter. If a portion of the locked or unlocked occluder remains outside of the delivery catheter, the control catheter and delivery catheter should be withdrawn together. If necessary, remove the introducer sheath and occluder together.

If the occluder is removed, it should be disposed of and a new occluder should be used to complete the procedure.

Recapture

1. In the event that the occluder is malpositioned or embolized, it can be recaptured with the aid of a loop snare. A long sheath (≥10 F) positioned close to the device is recommended for recapture.

2. Place the loop snare around any portion of the occluder frame.

3. Pull the occluder into the sheath using the snare. If a portion of the occluder frame cannot be retracted into the long sheath, it may be necessary to remove the occluder, loop snare, and long sheath as one unit.

4. Bring the recaptured occluder into the sheath to avoid pulling the unlocked device across valve tissue.

Postprocedure Management

See recommendations for ASO procedure (earlier in this chapter).

Complications

Serious complications following HELEX closure of an ASD are rare. Embolization occurs, but almost always the device can be retrieved using a snare device and a long 10F sheath. Wire fractures have been seen in a small percentage of patients (about 5%–6%) and are usually of no clinical consequence as the wire is held secure by the fabric of the device and its comprehensive endothelialization.

Results

Early experience has demonstrated the ease of use of this device, its complete retrievability, and excellent closure of small to moderate ASDs in children.

Results of the U.S. Multicenter Pivotal Study of the HELEX Septal Occluder for Percutaneous Closure of Secundum ASDs showed that closure of ASD with the HELEX septal occluder is safe and effective when compared with surgical repair, with reduced anesthesia time and hospital stay. Clinical success was achieved in 91.7% (100 of 109) of device patients and in 83.7% (72 of 86) of surgical control patients. The most common major adverse event for the HELEX septal occluder group was device embolization requiring catheter retrieval (1.7%); in the surgery group, it was post-pericardiotomy syndrome (6.3%), including one death due to tamponade.

Patent Foramen Ovale

A PFO is part of normal fetal development. Following birth, an increase in pulmonary blood flow, and higher LA relative to RA pressure, the foramen ovale physiologically closes. The foramen is created by the overlap of the septum primum and septum secundum (Fig. 20-12) and fuses closed in latter life. This anatomy can behave like a flap valve, opening if the RA pressure exceeds the LA pressure. Pathologic studies have suggested that the foramen ovale may be probe-patent in 25% of the population.

Figure 20-12 Schematic sketch demonstrating the patent foramen ovale (PFO) as a flaplike structure created between septum primum (1°) and septum secundum (2°).

There are three anatomical types:

1. “Flap” type

2. Tunnel type

3. Aneurysmal septum primum with a PFO

Clinical Significance

A PFO is a potential source for right-to-left intracardiac shunt and can result in paradoxical emboli. Presentation is usually in the third or fourth decade of life and rarely in adolescence.

Cerebrovascular Accident

Paradoxical emboli crossing the PFO with associated neurologic deficits (or stroke), or other systemic events are the most easily recognized manifestations of PFO. Cryptogenic stroke (stroke with no identifiable cause) accounts for 40% of stroke in young adults. Contrast echocardiography has demonstrated a higher than normal prevalence of PFO in cryptogenic stroke patients younger than 55 years old. In addition, the presence of an aneurysmal septum primum with a PFO enhances the risk of stroke. The presence of a prominent eustachian valve of the IVC has also been postulated to enhance the risk for paradoxical emboli, although no clear evidence exists for this hypothesis.

The recently reported PFO in Cryptogenic Stroke Study provides data from a large cohort of patients in a prospective manner. A PFO was present in 39% of the patients with cryptogenic stroke compared to 29% in patients with an identifiable cause for the stroke. Large PFOs (≥2 mm separation between septum primum and secundum or ≥10 microbubbles appearing in the left atrium with a contrast TEE) were present in 20% of the cryptogenic group versus 9.7% of the patients with an identifiable cause for their stroke.

Risk of Recurrence After a Presumed Cryptogenic Transient Ischemic Attack or Stroke

A recurrence risk of 3% to 5% has been reported in most series with medical management of embolic stroke. However, the Warfarin-Aspirin Recurrent Stroke Study (WARSS) yielded a recurrent event or death over a 2-year period of 15% with warfarin and 17% with aspirin when the subset of patients with cryptogenic stroke only was analyzed. The Mayo Clinic reported a 4.1% recurrence rate of any neurologic event following surgical closure of PFO. It is likely that a percentage of these represent patients in whom the hypothesis that their problem resulted from a paradoxical embolus was incorrect.

Divers

An interesting group of PFO patients are those who are deep-sea or scuba divers. This population may report decompression sickness with unusual symptoms despite following an appropriate and rigid protocol during a dive ascent. An incidence of neurologic symptoms as high as 61% has been reported. Decompression problems have also led to more brain defects in individuals with PFO than without.

Migraine

Migraine has a higher prevalence in patients with PFO—57% in one study. PFOs are a potential cause of postoperative complications in surgical procedures prone to venous fat or air embolism. Migraine headaches are not yet an approved indication for PFO closure.

Conditions Increasing Right-to-Left Shunt

Conditions associated with elevated RA pressure will enhance the potential for a right-to-left shunt. For example, chronic restrictive pulmonary or recurrent pulmonary embolus, hypercoagulable states, prothrombin gene G20210A, factor V Leiden mutations, anticardiolipin antibodies, protein S and C deficiencies, and thrombocytosis may promote venous thrombosis and increase the chance of a paradoxical embolus occurring.

Transcatheter Closure of PFO

Two devices are currently designed to specifically close PFO: the Amplatzer PFO occluder and the PFO Star devices. The CardioSEAL (NMT Medical) and the HELEX (WL Gore & Associates) were designed for ASD closure; however, they have also been used for PFO closure.

The Amplatzer PFO occluder is a self-expanding, double-disc device made from a nitinol wire mesh (see Fig. 20-1). The nitinol mesh wire is 0.005 to 0.006 inches in diameter.

The two discs are linked together by a connecting waist 2 mm in diameter and 4 mm in length. This thin waist allows free motion of each disc so that the device can conform to the PFO shape and position the two discs in the plane of the atrial septum. The discs are filled with a polyester fabric sewn securely to each disc by a polyester thread. The polyester increases the closing ability of the device by trapping blood, thus forming the initial plug and promoting the endothelialization of the device.

The devices are available in three sizes, 18, 25, and 35 mm, corresponding to the diameter of the right disc. The diameter of the left disc is 18 mm for the 18- and 25-mm devices and 25 mm for the 35-mm device. The connecting waist is the same for both—2 mm in diameter and 4 mm in length. The devices are packaged individually and supplied sterilized ready for use. The device costs $5000.

Place a 7F sheath in the right femoral vein. An arterial monitoring line can be useful if the procedure is performed under TEE with general anesthesia. Administer a full heparin dose and administer antibiotics as for secundum ASD. Perform a right heart hemodynamic study. Perform a TEE/ICE to assess the anatomy of the PFO and to perform a contrast bubble study with and without Valsalva maneuver.

Some operators determine the septal length and the distance of the surrounding structures, especially the free wall of the atrium. The type of PFO—simple flap type, tunnel type, or PFO with an aneurysmal septum primum—may influence device selection.

Suggested Measurements With TEE/ICE Images

1. Total septal length and edge of the defect to the mitral valve in the four-chamber view

2. SVC to the edge of the defect (long-axis TEE view/caval view by ICE)

3. Edge of defect to the aorta in short-axis view. Do not implant a device if the distance either from the defect to the SVC or from defect to the aortic root is < 9 mm.

Device Selection

For defects without an aneurysmal septum primum use the 18- or 25-mm device, depending on the length of the septum. If there is a significant aneurysm or if the septum primum appears very thin and floppy, use the 35-mm device as long as the distance from the SVC to the edge of the defect and from the edge of the defect to the aortic root is >17.5 mm. If there is an aneurysm and the distance from the edge of the defect to either SVC or aortic root is between 12.5 and 17.5 mm, the 25-mm device should be used.

Procedure Steps

The procedure is identical to that described for secundum ASD except that balloon sizing is not performed. Prior to device release, careful reassessment of the edge of the device along the free atrial wall by TEE/ICE is needed. Do not release the device if it does not conform to its original configuration or if it appears unstable. In this case the operator should recapture and redeploy the device. Figures 20-13 and 20-14 demonstrate the steps of PFO closure.

Figure 20-13 Schematic demonstration of patent foramen ovale (PFO) closure using the Amplatzer PFO occluder. A, Sheath in mid left atrium. B, Deployment of left atrial disc. C, Deployment of connecting waist and right atrial disc. D, Device released.

Figure 20-14 Intracardiac echocardiographic images in a young patient who has a patent foramen ovale (PFO), demonstrating the steps of closure. A, Septal view demonstrating the PFO (arrow) and the thin septum primum. B, Contrast bubble study demonstrating significant right-to-left shunt. C, Guidewire (arrow) positioned through the defect into the left pulmonary vein. D, Deployment of atrial the left disc (arrow). E, Deployment of the right atrial disc (arrow); release of the device. F, Contrast bubble study repeated after the device has been released, demonstrating successful closure.

Postprocedure follow-up is similar to that for secundum ASD closure except that most investigators maintain 81 to 325 mg aspirin per day for 6 months in combination with an antiplatelet agent, usually clopidogrel 75 mg/day, for 1 to 6 months. Follow-up echocardiogram at 3 to 6 months should include assessment for right-to-left atrial level shunt with a venous contrast injection, with Valsalva maneuver. (Figs. 20-15, 20-16)

Figure 20-15 Intracardiac echocardiography in a patient with patent foramen ovale (PFO). A, Septal view, demonstrating the PFO (arrow) and the thin septum primum. B, The left atrial disc (arrow) deployed in the left atrium. C, The right atrial disc (arrow) deployed in the right atrium. D, The device released, demonstrating good position.

Figure 20-16 Cineangiographic image of the patient whose intracardiac echocardiogram is shown in Figure 20-15. A, The left atrial disc (white arrow) deployed in the left atrium. B, The right atrial disc deployed in the right atrium. C, The device released, demonstrating good position. Red arrow shows position of intracardiac echo transducer.