Test balloon occlusion is required before patch placement; a balloon/patch 2 mm larger than the occluding diameter is selected.

There are two patch sizes at the present time:

a. Large Patch for defects 20-35mm , 12-13 F introduction,( LargeASD patch)

b. Small patch for defects up to 15mm, 9-10F introduction, for VSDs, PDAs and small ASDs. 

WIRELESS DEVICES FOR THE OCCLUSION OF ATRIAL SEPTAL DEFECTS.

E. B. Sideris  M.D.

Athenian Institute of Pediatric Cardiology and Custom Medical Devices

Introduction:

Surgery has been the traditional method for atrial septal defect repair. It is effective for all defects but it is associated with low mortality and significant morbidity(1 ). Patch

material is frequently used; suture patch placement though, requires thoracotomy and

cardiotomy with occasional problems (2 ).  A non surgical patch placement should offer

obvious advantages.

Disk device atrial septal defect occlusion has emerged as an alternative to surgery(3,4,5 );

it is only effective in some atrial septal defects (small to moderate secundum ASDs ).  

Imperfect centering and need for significant rim are the obvious limitations of  all disk

devices. Device related problems are mostly related to their skeleton wires. They are

including wire fractures and parts embolization, atrial perforation and valve leaflet

perforation (6,7,8  ). The long term problems of such wires or alloys are unknown;

however potential  hazards related to the Nickel content of these alloys  include

carcinogenicity, coronary spasm, tissue necrosis and allergy (9  ).

Wire related problems are obviously avoided by the use of wireless devices.

Furthermore since defect occlusion with these devices is balloon dependent, they have

excellent centering and minimal rim requirements . It is reasonable to assume that the

wireless devices could potentially have wider application than the disk devices.

Two wireless devices will be described: the detachable balloon device and the

transcatheter patch.

The Devices

Detachable Balloon Device (DBD)

The DBD (Fig 1) has the following components: The detachable balloon occluder, the

floppy disk, the loading wire, the needle catheter and the counter-occluder.

Detachable balloons are made from Latex in different sizes; they are attached to a needle

catheter. The 0.025” needle of the needle catheter is inserted in a protective 10mm long

5F catheter piece with several side holes. The needle and the tail of the balloon are tied

with a latex tie; the latex tie will seal the balloon after needle/catheter extraction. The

floppy disk is made by polyurethane and Nitinol hyper-elastic wire. It can be made in

different diameters. A regular counteroccluder (similar to the one used with the buttoned

device) can be delivered over the loading wire, to further support the stability of the

device. A double balloon DBD has been also used (totally wireless device).

The procedure includes the following steps :

1. The device is delivered to the left atrium, through a long sheath; the balloon

       occluder exits at the tip of the sheath first.

2. Inflation of the balloon with a predetermined volume of dilute contrast.

3. The whole complex including the inflated balloon is pulled to the septum occluding the defect; minor adjustments of the balloon volume can be made at this stage to optimize the result.

4. The tip of the long sheath is pulled to the right atrium liberating the floppy disk.

5. The balloon is detached by pulling and extracting the needle catheter through the long sheath.

6. A counteroccluder  is inserted over the loading wire and buttoned with the balloon occluder.

7. The device is released  in a similar manner to the buttoned device.     

The Transcatheter Patch

The transcatheter patch device (Fig 2) consists of the following components: The sleeve

patch , the double balloon support catheter and the double nylon thread.

The transcatheter patch is tailored from polyurethane foam; it is made in the form of a

sleeve covering the distal balloon of the support catheter. A nylon loop 2 mm in diameter

is sutured at the apical internal surface of patch; it is connected to a double nylon thread

for retrieval/retraction purposes. A radiopaque thread is sutured on the patch.

The supporting the patch double balloon is made by two latex balloons mounted on a

three lumen catheter. Each balloon can independently filled with dilute contrast through

its own lumen,  while the central lumen can be used for the over a wire insertion of the

device.

The procedure of introduction and release (Fig 3) is performed under fluoroscopy and

echocardiography and includes the following steps:

1. Introduction of the balloon/patch through a short sheath over a wire in the left atrium. Alternatively the balloon patch can be introduced directly in the left atrium through a long (Mullins type) sheath.

2. The occluding balloon/patch (distal balloon) is inflated at volumes predetermined by test balloon inflation. A balloon/patch diameter 2mm larger than the test occluding diameter is selected.

3. The balloon/patch is pulled to the septum and occludes the defect.

4. The right atrial (proximal) balloon is inflated.  Heparin is used during the procedure at 100 u/Kg. An additional dose of  Heparin 50u/Kg is given at the end of the procedure. Aspirin is started  in 24 hours for a month. Antibiotics (Cephalosporins) are started in the cath lab and continue for 72 hours.

5. The introducing sheath and the outside part of the balloon catheter along with the double nylon thread of the patch are immobilized by suture and adhesive tape on the groin.

6. The patient is taken to the intensive care or his room  under monitoring. Bed confinement without restrain is applied. Chest x-ray is obtained in bed in 12 hours and fluoroscopy along with trans-thoracic echocardiography in 24 hours.

7. The patch is released in 48 hours from the placement under fluoroscopy and echocardiography as follows:
1. The distal balloon is first deflated
2. The proximal balloon is deflated
3. Providing that there is a good result and the patch is well attached to the septum , the double nylon thread attached to the patch is removed as a single strand. The balloon catheter and/or the long sheath remain against the patch to counteract excessive pulling.
4. Extraction of the double balloon catheter through the sheath; extraction of the sheath.

        Experimental Studies

      DBDs were applied in the occlusion of experimental ASDs in 20 piglets ( 10 ); the

ASDs had been created by  balloon dilatation of the foramen ovale. The detachable

balloons were made from Latex. In 17 experiments the occluder balloon was supported

by a floppy disk and  a counter-occluder from the right side. In 3 experiments a double

detachable ballon was applied.

Full occlusion was noticed in all cases. 

One device was embolized in the descending aorta; in this case only a floppy disk

without a counter-occluder had been used. The balloon was ruptured using the sharp end 

of a wire and it was retrieved by transcatheter means.

All animals were followed by echocardiography and fluoroscopy up to two months. The

device was covered by tissue in 3-4 weeks. The detachable balloon lost its content and

became flat in approximately 2 months. All piglets recovered from the procedure in good

health and  were back in full activity in a few hours.

In conclusion  DBD ASD repair, is an outpatient procedure which  was found effective

and safe in the occlusion of experimental ASDs. It requires less rim than the disk devices

and it is retrievable. There is a small risk of device embolization.

The transcatheter patch was studied in the piglet model of  atrial septal defect (11 ).

Twenty experimental ASDs were created by balloon dilatation of the foramen ovale.

They were corrected by custom tailored polyurethane patches applied and supported

temporarily by specially made balloon catheters. Two types of patches were used; a flat

patch in 10 animals and a sleeve patch in 10. Patches. The patches were visualized by

echo as well as by fluoroscopy because of their radiopaque threads. They could be

retrieved and retracted in the introducing sheath (10F), if necessary.

The patches were supported by the specially made balloon catheters for periods varying

from one to six days. After this period the supporting catheter was withdrawn.

Fluoroscopy and echocardiography were used during implantation and follow-up. All

animals were sacrificed up to 14 hours after implantation. Pathology and histology was

performed.

There was immediate full occlusion of the experimental ASDs in all animals. Full

occlusion was maintained if the supportive catheter was withdrawn 48 hours or more

after implantation. In autopsy the patch was safely embedded in the atrial wall at 48 hours

or more after implantation; by histology fibrin and inflammatory cells were responsible

for the attachment. The sleeve patch was bulkier but better centered than the flat patch.

The conclusion of this experimental study was that the transcatheter patch was effective

and safe in the occlusion of experimental ASDs; it has minimal septal rim requirements

and excellent safety characteristics. The only disadvantage of the transcatheter patch is

the need for 48 hour balloon support.

                                                Patient Selection

Both the DBD and the transcatheter patch ASD occlusion are balloon occlusive methods,

in principle. A balloon is a three-dimensional structure with certain advantages to the two

dimensional disk devices.

It  is always centered when it is pulled to the atrial septal defect and requires a minimal

rim of 1-2 mm to sit on the defect, in comparison to over 5mm rim for the  disk devices.

We should expect therefore, a much wider application of  the balloon based occlusive

methods than the disk devices. Using the wireless methods described, the application

range of transcatheter ASD occlusion could extend to more secundum ASDs  with

insufficient rim and to some ostium primum ASDs without mitral insufficiency or sinus

venosus ASDs without anomalous pulmonary veins.

The limitations of the balloon based wireless methods for ASD occlusion are  related

either to the anatomy or to the particular device.

A single defect is more appropriate for a balloon based method than defects with multiple

fenestrations; however a larger balloon could conceivably cover more than one

fenestration.

A large balloon seems inappropriate for a small child with a small left atrium. The exact

balloon/ septal length ratio has not been established yet; however the balloon test

occlusion of the defect, prior to the application of the device seems of paramount

importance. If the balloon test occlusion achieves full occlusion without impairment of

the mitral flow or the pulmonary venous flow, the wireless balloon based  method will be

most likely successful.

DBD limitations include size of the introducing sheath (8-11 F depending on the balloon

size) and the slight risk of embolization or balloon leakage.

The operator should be able to respond to an unanticipated   embolization  by breaking

the balloon and extracting it percutaneously. No detachable balloon occluders larger than

the aortic valve annulus should be used with the current DBD since the balloon could

conceivably obstruct the aorta.

Large transcatheter patch devices are bulkier than DBD requiring currently a 12F

introduction; their use is currently restricted to patients over 15 Kg.

However transcatheter patch devices are much safer regarding embolization  since they

are doubly immobilized inside and outside the heart. In case of any unanticipated

problems they can be easily retracted and retrieved through the introducing sheath.

A single large balloon/patch device can occlude defects from 20-35mm, in comparison to

disk devices where multiple sizes are required for the same result.

As it was mentioned before, balloon test occlusion of the defect prior to the transcatheter

patch device application is the most important predictor of the success ( full occlusion of

the defect, no impairment of mitral flow or pulmonary venous return).

                                                   Results

Detachable Balloon Device :

A feasibility study was performed in four Centers (12  ). A total of 14 heart defects

inappropriate for disk device repair were occluded, including  secundum ASDs,

membranous VSDs and  large PDAs.

Six  secundum  ASDs (Fig4 ) inappropriate for disk device repair were selected. Reasons

for rejection for disk device repair included  insufficient rim or insufficient septal length

for a disk device.

The diameter of the defects varied between 18-27mm (med. 23) and the patient age from

6- 40 years (med 20).  The lowest patient weight was 14 kg.

The detachable balloons were inflated 1-2 mm more than the occluding diameter of the

defect. A floppy disk approximately twice as long  in size was supporting them from the

right septal side along with regular counteroccluder(s).

There was immediate full occlusion of all defects and one case with a small residual

shunt. The full occlusion was maintained in all cases with successful implantation on

long term, although the latex balloons became flat after two months approximately.

In the case with the residual shunt though, the shunt not only did not improve, but 

increased on long term.

There was one complication; a 26 mm DBD on a 19 year old  was embolized  40 hours

after implantation. It was embolized in the descending aorta causing numbness of the

lower extremeties; the balloon was ruptured by the sharp end of a wire and the device

was retrieved percutaneously uneventfully. All the symptoms disappeared.

Transcatheter Patch

A feasibility trial started in December 1999 (11  ). Less than 20 heart defects, most of

them inappropriate for disk device repair were taken to the cath lab for transcatheter

patch occlusion. They included cases of ASD secundum, sinus venosus ASD,

membranous VSD and large patent ductus arteriosus.

Fourteen  cases of atrial septal defect secundum were taken to the cath lab to be occluded

by transcatheter patch in 4 centers. Twelve of them were rejected for occlusion by  disk

devices (centering on demand buttoned device). The median diameter of the secundum

ASDs was 27mm (range 13-34 mm).  The youngest patient was 1.5 years old (range 1.5-

58 med.35). The lowest weight was 11 kg.

Eleven transcatheter patches were supported by double balloons and  three by a single

balloon with an incorporated floppy disk. Smaller balloon patches up to 15mm were

delivered through 10F sheaths. Larger patches required a 12F introduction.

All patches were successfully implanted; however only 12 implantations were successful

in 48 hours. One balloon/patch was  away from the septum and was not detected in 24

hours (no Echo); as expected it was not attached to the septum in 48 hours and was

retrieved through the introducing sheath.

Another patient had a respiratory arrest 2 hours after a successful implantation, probably

related to anesthesia; the patient was treated in the ICU with continuous IV  Heparin. At

48 hours the  patch was not attached to the septum and it was retrieved through the

introducing sheath.

There was a case of partial occlusion of a very large  (30mm) defect with insufficient rim

on  a 7 year old; the balloon lost its content  in 24 hours. It was elected though, to remain

in place. It resulted in a significant residual defect 6-7mm in diameter.

The balloon/ patch position was away from the septum at the 24 hour follow-up in one

case by chest X-ray and Echo; the balloon was  re-adjusted and the patient had an

excellent result  at 48 hours.

All patients with successful implantations are alive and well.

 DISCUSSION

We have shown that wireless ASD occlusion is feasible both with detachable balloons

(wireless occluder only),  as well as with the transcatheter patch (total wireless

occlusion).

The two methods have differences in the need for hospitalization: 

The detachable balloon method can be done as an outpatient procedure; in contrast

transcatheter patch placement requires 48 hours hospitalization, at least.

The results of the detachable balloon device ASD occlusion, demonstrated the

effectiveness of the method in the occlusion of defects inappropriate for disk device

repair (12  ). Spherical well centered detachable balloons occluded the defects

immediately; they were released right after implantation and they  became flat  2 months

later with full occlusion maintained..

The minimal rim requirement is an attraction of the method; however the lack of

significant overlapping could result in residual shunts without improvement overtime, as

it was shown in one case.

There are concerns related to the safety of the detachable balloon device used; the

stability of the device was the main concern since embolization  in the descending aorta

occurred in one case.  The occluder obstructed totally the descending aorta with

temporary symptoms ; it was broken by the sharp end of  a wire and was retrieved

uneventfully.

 Total obstruction of the ascending aorta can be potentially lethal; therefore the current

device cannot be routinely used, before better stability is assured. The operator should be 

ready to rupture and remove the detachable balloon in case of embolization. No defects

larger than the aortic root diameter should be occluded.

The other concern is the emerging risk of Latex allergy (13 ); careful history as well as

Latex antibodies should be obtained and alternative to Latex materials should be used in

cases of Latex allergy.

The transcatheter patch is balloon delivered; therefore it maintains the advantages of the

detachable balloon occlusion, like the minimal rim requirement and excellent centering;

in addition to those the stability of the device is very good since it is doubly secured

inside and outside the heart. The attachment of the patch to the atrial wall is fast (48 hrs)

and its endothelialization probably faster than the disk devices (Fig 6 a). By histology the

attachment of the patch to the septum is due to fibrin and inflammatory cells

(Fig 6 b). We  should be very careful therefore with the duration of heparin treatment

since the patch attachment depends on fibrin. In our experimental study no additional

heparin was used

and all patches were securely attached on the septum after 48 hours; in our current

protocol an additional dose of  Heparin 50 u/kg is given at the end of implantation.

Aspirin is started in 24 hrs for one month. 

Continuous heparin use for 48 hours in one patient  resulted in a free patch which

required retrieval. 

The balloon/ patch needs to be immobile for fast embedding in the septum; the 24 hour

fluoroscopy and echo are very important to verify the position and the stability of the

patch; further adjustment is possible at this stage to assure a good result at 48 hours.

Small technical problems like those of premature deflation of the supporting balloons

need to be resolved before generalized used of the device is recommended.  Deflation of

the supporting balloon in less than 24 hours can result in a significant residual shunt;

therefore it is better, to be retrieved and replaced by a new one.

Retrieval and retraction of the balloon in the introducing sheath is possible the first 24

hours.  The patch not only is echogenic but radiopaque as well, since radiopaque thread is

sutured.

Double balloon supporting catheters were used in the majority of cases so far; they are

safer to single balloon/floppy disk combinations for large defects. They are currently

made with three lumens; the central lumen is used for the over the wire introduction of

the balloon/patch through a short sheath, thus eliminating the use of  the more dangerous

long sheath (Mullins type).     

The sleeve patch is designed to be used for single defects; an oversized balloon/patch has

been used successfully though, for a case with multiple fenestrations .

The transcatheter patch could be useful in the occlusion of other lesions than secundum

ASDs like sinus venosus and ostium primum defects because of the minimal rim

requirement. The single most useful predictor of a successful patch occlusion is the test

occlusion of the defect during sizing. A full occlusion without impairment of the mitral

valve or the pulmonary vein flow is a good predictor of success.

The disadvantage of  the transcatheter patch occlusion, is the need for an additional day

in the hospital; however no bed restrain is necessary.

Current Status

The use of wireless devices is experimental and are only used under appropriate

protocols, approved  in each center.

The use of transcatheter patches should not require the strict regulations of implantable

Devices, since custom modification of existing materials (balloon catheters and patch) is

only required; however carefully contacted clinical trials are planned  to 

evaluate its effectiveness and safety.

An  investigational device exception application has been filed for the performance of 

FDA approved clinical trials with the transcatheter patch in United States .

Conclusions

Wireless ASD occlusion is feasible and effective both by detachable balloon devices and

transcatheter patches.

The transcatheter patch appears safer and should be the preferred  wireless method  for

defects inappropriate for disk device repair. Larger clinical trials are necessary.

References

1. Fyler DC. Atrial septal defect secundum. In: Fyler DC, ed. Nadas’ Pediatric

 Cardiology. Philadelphia:Hanley and Belfus;1992. p.513-34

2. Robins RC. Atrial septal defects:Surgical Procedure. In: Critical heart disease in

      infants and children. Nichols DG, Cameron DE, Greeley WJ, editors, Mosby-

       Year Book; 1995. p. 584-86     

3. King TD, Mills NL. Nonoperative closure of atrial septal defects. Surgery

       1974;75:383-38

4.  Rashkind WJ, Cuaso CC. Transcatheter treatment of congenital heart disease.

       Circulation 1983;67:711-16

5. Sideris EB, Sideris SE, Thanopoulos BD et al. Transvenous atrial septal defect

     occlusion by the “buttoned “ device. Am J Cardiol 1990; 123:191-200

6. Prieto LR, Foreman CK, Cheatham JP et al. Intermediate –term outcome of

      transcatheter secundum atrial septal defect closure using the Bard Clamshell

      septal occluder. Am J Cardiol 1996; 78:1310-12

7. Agarwal SK, Ghosh PK, Mittal PK. Failure of devices used for closure of atrial

       septal defects, mechanisms and management. J. Thorac Cardiovasc Surg 1996;  

        112:226-230

8. Rao PS, Sideris EB, Hausdorf G et.al. International experience with secundum

      atrial septal defect occlusion by the buttoned device. Am Heart J 1994;128:1022-

      35

9. Sunderman FW. A review of the metabolism and toxicology of Nickel. Ann Clin

        Lab Science 1977;81::377-98

10. Sideris E, Kaneva A, Sideris S, Moulopoulos S. Transcatheter atrial septal defect

            occlusion in piglets by balloon detachable devices. Catheter.    

           Cardiovasc.Interventions. 2000;  In Press

11. Sideris E, Toumanides S, Alekyan B, Varvarenko V, Sideris C, Sideris C,

      Moulopoulos S, Stamatelopoulos S. Transcatheter patch correction of atrial septal

      defects: Experimental validation and early clinical experience. Circulation 2000;   

      102: Suppl.II-588

12. Sideris EB, Chiang CW, Zhang JC, Wang WS. Transcatheter correction of heart

       defects by detachable balloon buttoned devices: A feasibility study. JACC

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        97, 1992   

FIGURE LEGENTS

Figure 1:

A drawing of  detachable balloon device  correction of  atrial septal  defect

Bl= balloon, Bt= button, COC= counter-occluder, FD= folding disk, LA=left atrium,

RA= right atrium

Figure 2:

Double Balloon Sleeve Patch : distal balloon supporting the patch, proximal balloon,

double nylon thread.

Figure 3:

Method of application of the double balloon sleeve patch: the distal balloon is

supporting the patch from the left atrium with the proximal balloon immobilizing it

from the right atrium; in 48 hours the balloons are deflated and the patch is released.

Figure 4:

1. 27 mm ASD secundum with deficient rim

2. Full occlusion five months after detachable balloon occlusion; the balloon is flat

Figure 5:

1. 32 mm ASD with deficient rim before and after tr.patch placement

2. Color flow mapping before and after same patient, trivial residual shunt

Figure 6:

1. Patch pathology 10 days after implantation; the patch is fully covered

b.Histology of  transcatheter patch 48 hours after implantation; the patch is covered