Ventricular Septal Defect (VSD) is the most challenging heart defect occlusion. Muscular VSDs can be occluded by most disk devices; however they are rare. Membranous VSDs are common; however they are very close to critical structures like the aortic valve and the tricuspid valve. Careful measurements of the VSD-right aortic cusp distance need to be made before a disk device is deployed. There is also procedural difficulty since the majority of the defects are crossed from the left side, an arterio-venous connection needs to be made and they are corrected from the venous side. The femoral vein is used for the outflow defects (membranous) and the right jugular vein for the mid-muscular defects.

The buttoned device and its different modifications has been used for the occlusion of congenital muscular VSDs, post-infarction VSDs and several membranous VSDs after the first year of life. The results have been good.

9-11 F introduction is required

The transcatheter patch has the potential to revolutionize VSD occlusion, since most membranous VSDs can be repaired. The patch requires a minimal rim and therefore can occlude a defect without interference with the aortic valve.

The VSD patch requires 9-10F introduction.

TRANSCATHETER CORRECTION OF VENTRICULAR SEPTAL DEFECTS BY THE “SIDERIS” DEVICES

E.B. Sideris M.D.

Athenian Institute of Pediatric Cardiology and Custom Medical Devices

Introduction

Transcatheter ventricular septal defect occlusion is by far the most challenging heart defect occlusion. The reasons are both anatomic and technical.

Most ventricular septal defects are peri-membranous, in close proximity to critical structures like the aortic valve and the tricuspid valve( 1); most of these defects have deficient rim for disk device placement . Muscular VSDs are the ones traditionally considered as good candidates for transcatheter occlusion (2 ); they usually have enough supportive tissue(rim) for disk device placement ; they are also considered high risk for surgery, since they cannot always be approached from the tricuspid valve and require ventriculotomy ( 3 ).

The technical limitations are significant and include:

a. Difficulty crossing the defect: The easiest approach to cross a VSD is the transarterial approach. The size and the location of the defect are the most important factors; smaller than 3 mm defects and supracristal defects are the most difficult. Large mid-muscular defects can be frequently crossed directly transvenously, from the right jugular vein.

Need to establish an arterio-venous wire connection: after crossing the defect a

soft wire needs to be advanced into the pulmonary artery and snared to the most

appropriate vein (femoral for outflow defects, right jugular for mid-muscular

ones).

Selecting the proper device: disk devices (4,5 ) are appropriate for most muscular

VSDs; they certainly have an advantage with multiple defects, because of

significant overlapping; in contrast disk devices are applicable in only a small

percentage of membranous VSDs ( 5 ), because of the close proximity to critical

structures; careful measurements are required to select the appropriate disk

device size. The development of wireless devices (transcatheter patch and

detachable balloon) which require minimal rim and cannot interfere with critical

structures (6,7) has the potential to revolutionize the transcatheter treatment of

peri-membranous VSDs.

Difficulty delivering the device: delivery of most devices is performed through

long delivery sheaths. A straight rather an angulated route, is preferable to avoid

kinking of the sheath. Apical muscular VSDs are rather notorious in this aspect.

Over the wire placement of the device and kink-resistant sheaths can be helpful in

difficult VSD locations.

The Devices

Since 1994, the following devices have been used by us for the occlusion of VSDs:

the buttoned device
the self-adjustable device
wireless devices (detachable balloons and transcatheter patches).

Buttoned Device: This is the same device used for the occlusion of atrial septal defects ( 8 ). The current device is a 4^th generation device without centering since VSDs are relatively small in size. The device has been described extensively. In summary it consists off an occluder with the button loop, a counter-occluder and a loading or release wire. It can be placed directly through a long sheath or over a wire. The over the wire placement possibility makes the device quite attractive since chances to loose the arterio-venous connection in case of device mis-placement or retrieval are minimized. The occluder is placed from the left ventricular side, the button-loop adjusts for the septal thickness and the counter-occluder is buttoned with the occluder from the right ventricle.

The Self-Adjustable Device: The device consists off two disks (proximal and distal) connected by a latex thread (9). It can therefore self-adjust according to the septal thickness (Fig 1). The disks are made by polyurethane foam and stainless steel skeleton wire. There are two wire and one wire disks in different combinations as follows (Fig 2):

a. regular self-adjustable device, with a two wire distal disk and a one wire

proximal disk.

b. inverted self-adjustable device, with a single wire distal disk and a two wire

proximal disk . This is the device most commonly used for transarterial VSD

occlusion.

c. two disk device, both the proximal and the distal disks are made with two wires.

d. One wire device, both the proximal and the distal disks are made with a single wire.

Wireless Devices : Two types of wireless occluders have been used in the occlusion of VSDs. Detachable balloons and Transcatheter patches (6,7 ). These devices have been described extensively in a different chapter.

In Summary the detachable balloon device consists off a detachable balloon occluder, connected with a floppy disk. The detachable balloon occludes the defect from the left ventricle and the floppy disk(s) supports the balloon from the right ventricle.

The transcatheter patch is made by polyurethane foam in the form of a sleeve over a balloon. It is retrievable, retractable and radiopaque. It is delivered and supported by a double balloon for 48 hours. It is totally wireless.

Both detachable balloons and transcatheter patches require minimal rim and are always centered; however the detachable balloon method is an outpatient procedure where the transcatheter patch application requires 48 hours hospitalization.

Patient Selection

Indication for VSD occlusion is the persistence of a significant shunt with or without evidence of pulmonary hypertension. Exceptions for occlusion include irreversible pulmonary hypertension with right to left shunt (PVR> 10 units) and anatomy preventing the application of the device (lack of sufficient rim).

Calculation of adequate rim and examples are given in the included diagram (Fig3). The same rim requirements exist for both disk devices used. The wireless devices require a minimal rim. Balloon test occlusion should be performed prior to a wireless device application (transcatheter patch). Providing that it results in full occlusion without impairment of critical structures, patch deployment should follow.

Ventricular septal defects of all types can be occluded provided there is adequate rim for the deployment of the device. Baseline history, physical exam, EKG , echocardiogram and chest x-ray need to be obtained for screening purposes.

Exclusion Criteria:

1. Defects with severe pulmonary hypertension associated with significant R-L shunts. (PVR>10 units)

2. Defects without adequate rim for device deployment

3. Patients too small for a possible retrieval of the device into a 11 F sheath (10 Kg) for disk devices or

9-10 F for the transcatheter patch. Surgical retrieval

should be performed in patients where the appropriate sheath for the retrieval

cannot be introduced

Device Selection

The disk devices selected should have at least twice the size of the diameter of the VSD (similarly to the ASD selection). Caution should be applied in the selection of the proper device to avoid encroachment to the aortic valve leaflet. A long axial angiographic view should be obtained and the distance between the center of the defect and the right aortic cusp should be measured (DA) as well as the diameter of the defect (Fig 4,5 ). The diameter of the required device should be less than double that of the DA distance and be at least 2mm away from the right aortic cusp. The minimal sub-aortic rim (DA) for the smaller available device (15mm) is calculated therefore at 9.5mm.

The transcatheter balloon/patch diameter should be selected as 2mm larger than the test occluding diameter (Fig 6,7).

The Method

The procedure is performed in the cardiac catheterization laboratory. The patient is pre-medicated with the Toronto cocktail . Sedation is supplemented by Ketamine infusion. General anesthesia is reserved for the cases requiring transesophageal echocardiography or simple sedation is not considered adequate. The procedure should be performed using sterile technique. After obtaining routine pressure and oxygen saturation data to confirm the diagnosis of VSD, angiography is performed , including long axial left ventricular angiogram . The location of the defect is noted and the size is digitally measured (Fig 2).

In addition to the size, the distance from the center of the defect to the right aortic cusp is measured and the appropriate disk device is selected. If the distance is too small for a disk device the use of a wireless device is entertained. Heparinization is started (100 units/Kg).

The next step includes crossing the VSD by a catheter. Crossing from the right side is preferable, but not always possible; therefore in the majority of cases the defect is crossed from the left ventricle, utilizing a right Judkins or a modified Amplanz catheter.

Transvenous approach :

A regular 025” 260 cm wire is utilized and it is advanced in the pulmonary artery from where it is snared to the femoral vein (membranous defects) or the jugular vein (muscular defects). Attention is paid to avoid bleeding from the arterial and the venous sites.

A long sheath in a size appropriate to the device used is advanced over the wire and is positioned in the ascending aorta.

Buttoned Device Placement:

The occluder is introduced over the wire into the sheath and it is advanced to the aortic valve level, where releasing is started ; however the sheath is slowly pulled back until the entire occluder is released into the left ventricle . The occluder is manipulated away from the aortic valve and is aligned with the ventricular septum. Echocardiography confirms the good position and the occlusion of the defect. The counter-occluder is buttoned as usual and a repeat left ventricular angiogram is performed (Fig 5). The wire is withdrawn through the device with the tip of the sheath placed against the device. The device is subsequently released.

Transvenous approach using the transcatheter patch:

A long sheath in a size appropriate for the transcatheter patch used is advanced over the wire in the ascending aorta. The wire is taken out. Both the distal and the proximal balloons are entering the ascending aorta. The distal balloon/ patch is inflated and it is pulled until it obstructs the defect; fluoroscopy, echocardiography and pressure recording are guiding the procedure. After full occlusion is confirmed the proximal balloon in inflated. Subsequently, the balloon catheter and the long sheath are immobilized on the skin. A left ventricular angiogram and an aortogram confirm the result (Fig 7,8).

Transarterial Approach Using the Self –Adjustable Device.

If the size and the location of the ventricular septal defect are considered appropriate for disk device occlusion , a 0.025” stiff exchange wire is placed at the apex of the right ventricle. An appropriate size sheath is placed over the wire in the right ventricle. An inverted self adjustable device is loaded and it is advanced until the distal (single wire disk) is released in the right ventricle; subsequently the loading wire of the device is pulled until the distal disk becomes perpendicular to the tip of the sheath. The whole complex is pulled back until it stops at the ventricular septal level. The sheath is pulled back in the left ventricle and the proximal disk is released, occluding the VSD. The proximal disk could be manipulated away from the aortic valve; the distance between proximal and distal disk is self-adjusted according to septal thickness (Fig1). The device is subsequently released in a similar fashion to the buttoned device.

Oximetry will be reserved to patients with residual shunts , but it should be done carefully to avoid disturbing the device. (Qp:Qs=1 no shunt, Qp:Qs 1-1.2=trivial shunt, 1.3-1.5=small residual shunt, Qp:Qs>1.5 large shunt.)

Antibiotic prophylaxis should be started (preferably Cephalosporins with the first dose given IV in the cath lab and the subsequent ones orally six and twelve hours later for the disk devices. Antibiotics are continued for 72 hours for the transcatheter patch. The patient should be discharged home within 24 hrs from the release of the device. Echocardiogram, chest x-rays and EKG will be obtained prior to discharge. The patient should be discharged home with daily medication of Aspirin (300mg) for six weeks and endocarditis prophylaxis for six months for full occlusions; in case of residual shunts endocarditis prophylaxis will continue indefinitely.

Results

Fifty five ventricular septal defects have been occluded by the “Sideris” devices since 1994. The majority of the defects (36) were occluded by the buttoned device, transvenously . The transarterial approach with the self-adjustable device was used in 14 cases. Wireless devices were used in 5 cases.

Most occluded defects were peri-membranous (45); five congenital muscular and five post-infarction VSDs were occluded as well. One of the congenital muscular VSDs was swiss-cheese type.

The size of the VSDs varied from 3-12mm (m=5) for the congenital and 12-25mm for the post-infarction. Patient age varied from 1 to 45 years (m=7) for the congenital VSDs and 65-75 years (m=70) for the post-infarction. The average procedure time was 2.5 hours for transvenous procedures and 30 minutes for transarterial procedures utilizing the self-adjustable device. However transarterial procedure could not be performed in 3 attempted cases which were performed transvenously instead. Wireless occlusions were performed in membranous VSDs inappropriate for disk device occlusion (three detachable balloons, two transcatheter patches).

There was immediate effective occlusion in all cases. Three early cases occluded transvenously with the buttoned device developed mild aortic insufficiency. In 2 the devices were extracted surgically in 48 hours. There was a transient 3^rd degree A-V block in one case and transient PVCs in most cases during implantation.

Despite early symptomatic improvement only 2/5 cases after myocardial infarction are long term survivors. No complications were seen with the self-adjustable device.

One detachable balloon leaked in 24 hours and had to be extracted surgically.

Complications

Serious complications requiring re-intervention were the two early buttoned device cases which developed aortic insufficiency and the case of the detachable balloon early leakage, which required extraction; however we are listing a series of potential complications ; this list should be useful in obtaining an informed consent from the patients.

Complications as seen in the ASD trials and the international VSD trials are defined as follows:

1: unbuttoning and embolization of the occluder on the left or on the right side of the heart (self explanatory)

2: cardiac perforation: perforation of a cardiac chamber by a catheter, a wire or a device component during the procedure

3: air embolism : introduction of air in the cardiac cavities from the introducing sheath, with findings of transient ST elevation, bradycardia and transient drop of the systemic pressure; this a self limited phenomenon within 5-10 minutes, seeing rarely during ASD occlusion. Such an episode is unlikely for VSD occlusion, since high pressure bleeding prevents air entrapment

4: excessive bleeding: small bleeding from the entry sites is not uncommon, especially if an arterio-venous connection is established ; the investigator should be ready for the appropriate measures (sealing with pressure, new valve sheaths etc) . Blood transfusions might be needed.

5: transient arrhythmia : PVCs are common during catheter, wire or device introduction in the ventricles; they are usually self-limited. Transient heart block has been seen as well.

6: mitral insufficiency : it has been seen in ASD occlusion; highly unlikely with VSD occlusion

7: tricuspid insufficiency: trivial tricuspid insufficiency has been seen without problems; in case of significant tricuspid insufficiency the device should be extracted.

8: aortic insufficiency : it is the commonest problem after membranous VSD occlusion, requiring extraction; it can be prevented by proper patient/device selection.

9: peripheral vascular problems

. Discussion

The concurrent use of three device types, illustrates the inherent difficulties of VSD occlusion. The muscular VSDs were unquestionably the easiest to close by disk devices. Both the buttoned device and the self-adjustable device were used. The advantage of the significant overlapping of the disk devices could be best illustrated in the occlusion of a “swiss-cheese” type VSD by the buttoned device.

The size of the self-adjustable device is restricted to 25mm; therefore the use of the buttoned device was preferable for the large post-infarction muscular VSDs. Apical muscular VSDs are rather difficult for buttoned device delivery, with the long sheath kinking in two occasions. Over the wire placement and kink-resistant sheaths was the solution of this problem. Despite the successful post-infarction VSD occlusion in 5 cases and their symptomatic improvement only two of them are long term survivors. The necessity of a stressful and high risk procedure with questionable long-term outcome is raised.

The main procedural difficulty for transvenous VSD occlusion is crossing the VSD and establishing an arterio-venous connection. The possibility of over the wire placement with the buttoned device makes the procedure more secure.

On the other hand if the procedure can be done trans-arterially using the self-adjustable device, it is much faster; the average procedural time is only 30 minutes in comparison to 2.5 hours for the transvenous procedure.

The majority of ventricular septal defects are peri-membranous; this is the reason we focused our research effort in this category and the majority of our occlusions were related to peri-membranous defects ( 10 ). The first and the most commonly used device for peri-membranous VSD occlusion was the buttoned device. The use of oversized devices early in the clinical trial, was responsible for three instances of aortic insufficiency; two of them required surgical extraction of the device.

Careful measurements of the defect to right aortic cusp distance and selection of smaller devices positioned at least 2mm away from the aortic cusp was the solution of the problem; indeed no more cases of aortic insufficiency were noticed.

The presence of an aneurysm of the membranous septum was helpful in several cases since the occluder could be pulled away from the aortic valve in the aneurysm.

The use of disk devices in the peri-membranous VSD occlusion is limited; and the majority of such VSDs are sent to surgery. The evolution of the wire-less devices has the potential to change this practice. The 5 cases performed by us are in favor of this projection. All of them were inappropriate for disk device occlusion and all of them were surgical candidates.

Both wireless devices used, are working on a balloon occluding principle. A balloon is a 3-dimensional structure requiring a minimal rim for support; a sub-aortic rim as small as 1 mm in enough for the occlusion.

One detachable balloon device used leaked prematurely; it embolized in the pulmonary artery and had to be extracted surgically.

The transcatheter patch offers the efficacy of the detachable balloons but unparallel safety with double cardiac and extracardiac immobilization and retractability in the introducing sheath. Despite the need for 48 hour balloon support, this wireless method has the potential to become the procedure of choice for the majority of peri-membranous VSDs.

Current Status

The use of devices for the transcatheter occlusion of VSDs is investigational. All such devices are used under protocols and regulations acceptable in each center.

The FDA has approved clinical trials with the buttoned device in the occlusion of ventricular septal defects, in USA. Both peri-membranous and muscular defects are occluded under the approved protocols.

An Investigational Device Exception for the transcatheter patch use for the occlusion of heart defects has been submitted to the FDA.

Conclusions

Transcatheter VSD occlusion using the different “Sideris” devices has been applied successfully since 1994. Three types of devices have been used to optimize the results.

The buttoned device is the commonest one used, over an arterio-venous wire, for transvenous occlusion.

The self-adjustable device has the easiest application since it can be applied transarterially.

Wireless devices and specially the transcatheter patch are the most promising methods for transvenous peri-membranous VSD occlusion.

References

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2. Lock JE, Block PC, McCay RG et al. Transcatheter closure of ventricular septal defects. Circulation 1988:78:361-8

3.Bridges ND, Perry SB, Keane JF et al. Preoperative transcatheter closure of

congenital muscular ventricular septal defects. N Engl J Med 1991;324:1312-7

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279

Figure Legents

Figure 1: The Self-Adjustable Device

Figure 2: The different types of self-adjustable device: 1. Regular 2. Inverted 3. Two

Disk, 4. Single disk

Figure 3: Angiographic measurements: 1. VSD diameter, 2. VSD-Right Aortic Cusp

Dimension

Figure 4: Example of Angiographic Measurements and Device Selection for

Perimembranous VSD: D1= VSD diameter, 5.1 mm, D2= VSD- right aortic

cusp dimension 13mm; any device 25mm or smaller could be used.

Figure 5: Occlusion of a 5mm perimembranous defect (same case of Fig.4) by a 20 mm

buttoned device with full occlusion.

Figure 6: Large perimembranous VSD (12 mm) in a 4 year old child, very close to the

aortic valve (3mm)

Figure 7: Transcatheter Patch Occlusion supported by a double balloon 14mm in

diameter; same case as Figure 6.

Figure 8: Aortogram shows no interference to the aortic valve.