1.

FROM  DISK DEVICES  TO  TRANSCATHETER PATCHES: THE EVOLUTION OF WIRE-LESS  HEART DEFECT OCCLUSION

E. B. Sideris MD,  S.E. Sideris RN,  S. Toumanides MD *,  S.D. Moulopoulos *

From : The Athenian Institute of  Pediatric Cardiology and Custom Medical Devices, Athens Greece

* The Department of Clinical Therapeutics University of Athens, Greece

Address for correspondence: E.B. Sideris MD: Director, The Athenian Institute of Pediatric Cardiology,  21 Rizariou st.,  Halandri, Athens, 15233, Greece.   Fax: 00301-6852270,

E mail: terry@hol.gr

                                                                                                               Sideris et al        2

Abstract

Double disk devices have been used by us since 1988 with several device generations and

improving results. Our current disk device “The ButtonSeal Centering on Demand

Device” is a multipurpose device made by stainless steel and polyurethane. It has shown

high occlusion rates and no significant complications in ASDs up to 30mm in diameter. It

can be used according to the ASD anatomy both in large single defects (centering) and

multiple fenestrations (non-centering). The ButtonSeal shares the same limitations of

the other disk devices; namely the possibility of wire related problems and the need for

significant septal rim. The development of  wireless balloon delivered devices and

patches addresses the related to disk devices problems and limitations. Both detachable

balloon devices and patches were used experimentally in animals and in feasibility

studies in humans. The results showed good occlusion rates and lack of wire related

complications. Both methods required a minimal rim, occluding more defects than the

disk devices. The transcatheter patch method was safer with the only disadvantage the

need for 48 hour balloon support.

                                                                                                                                             Sideris et al    3.

The “Button Seal” Centering On Demand Device

Atrial septal defects (ASDs), vary in anatomy and size; therefore conventional disk devices might not be

appropriate for all defects. 

It was apparent from our centering buttoned device experience (1  ), that placement of the centering device

is easier in large central defects; on the other hand  multiple ASDs required direct placement and the

regular buttoned device was more appropriate ( 2 ).

Many large ASDs have inadequate septal rims; in such cases neither the regular nor the centering buttoned

device could offer enough support .

The design of the centering on demand (COD) device was in response to the above weaknesses of the

previous devices.

The COD device is a multipurpose device (3); it can accommodate for the various clinical demands of

ASDs, by :

        1. Providing centering for large central defects

2.       Placed directly without centering (collapsed centering ring) for multiple fenestrations.

3.       In case of large ASDs with inadequate rim, the occluder is placed over the wire with centering   

        on the left side of the atrial septum and the counter-occluder is buttoned from the right atrial side;        

        therefore extra support is provided on the left side.

COD Construction:

       The COD device is a rounded 4^th generation device with centering ring(s) sutured at the center of the

occluder  (Fig 1). Two materials were used in the construction of the centering ring(s) and were tested in a

feasibility study : a. Stainless Steel (SS) floppy wire and  b: Nitinol (NI) wire.

The centering rings could be stretched for centering purposes ( large central defects), or  could be

buttoned with the occluder and collapse (direct placement- ring augmentation).

Thirty nine patients with secundum  ASD were repaired by the COD device; 21 had  had  SS 18  Ni

rings; the median diameter of the defects was 22mm and the median weight  16 kg. All had large L-R

shunts. Two cases with multiple defects were occluded with direct placement of the device. Eleven

                                                                                                                                        Sideris et al 4.

from the NI devices did not require counter-occluders. All the rest required counter-occluders. The

complication rate was higher in the NI group ( one atrial perforation, one mitral insufficiency).

All cases were effectively occluded (full occlusion + trivial shunts); however the full occlusion rate

was higher in the SS group (70% vs. 50%).

The conclusions of this feasibility study were:

1.     The COD device is a multipurpose device highly effective in a variety of heart defects.

       2.      The SS COD device was safer and had higher full occlusion rates than the NI COD device.

        3.      The NI COD device  was found to have a higher acute complication rate; furthermore Nitinol is       

         an alloy with high nickel content (55%) with known chronic toxicity (carcinogenicity, coronary

         spasm, allergy) . 

4.            The SS COD device is our choice for the majority of ASDs.

Disk Devices Limitations

All currently used devices for the occlusion of atrial septal defects ,  including the various types of the

buttoned device are disk devices. All of them share the same limitations in the occlusion of heart defects

which are related  to the defect anatomy and the device construction. All disk devices require sufficient

septal rim ( at least 4-5 mm on each direction) and have a diameter   1.5-2 times the defect diameter.

Many defects including large secundum ASDs with insufficient rim, sinus venosus and ostium primum

defects  cannot be corrected by  disk devices.

                                                                                                                                            Sideris et al.    5.

Detachable balloon Device

The detachable balloon device uses a detachable balloon as an occluder and either a disk or a balloon

( Fig 2 ) to support it from the right side .

It can have therefore partially (only the occluder) or totally wireless construction.

This device was first applied in the occlusion of experimental ASDs in piglets (4  ) and was subsequently

used in the occlusion of ASDs unsuitable for repair by traditional disk devices (5 ).

Twenty experimental ASDs were fully occluded with one case of embolization; the occluding balloons

were fully embedded in the atrial septal wall within a week after implantation and became flat within two

months maintaining the full occlusion.

Six human ASDs unsuitable for disk  device occlusion were repaired by a detachable balloon devices. Five

had full occlusions with one residual shunt. On follow-up there was one device embolization with the good

result maintained in all other cases on follow-up.

In addition to the wireless construction the balloon occluder has the following advantages:

1.        Requires minimal rim; it is therefore applicable in more defects than the disk devices.

2.       The balloon has perfect centering  since has the shape of a sphere and it is easily applicable.

The disadvantages of balloon detachable devices were the probability of Latex Allergy and the

questionable stability of very large balloons .  Both problems can be easily solved by the use of alternative

to Latex materials in patients with Latex allergy and better stability measures (additional counter-occluders,

double balloons etc).

Transcatheter Patch Occlusion

The concept of  transcatheter patch application is simple; if a patch can be precisely delivered at a desired

cardiac position or defect and can be maintained immobile for the required time, it can be embedded in the

heart and eventually endothelialized, without the use of surgical sutures or supporting wires.

Endothelialization rate is depending on different factors including the porosity of the patch material and its

proximity to the endothelium.

                                                                                                                                       Sideris et al   6.

Polyurethane  is a porous material with very fast endothelialization . Less porous materials  require longer

periods to be endotheliazed.

Modified balloon catheters  were made to deliver and support the patches until they were securely attached 

on the septum.

 Experimental validation of the transcatheter patch was studied in piglets (6). Experimentally created ASDs

were corrected by polyurethane patches supported by modified  balloon catheters (Fig 3), from 1-6 days.

 Twenty experiments were performed using two types of transcatheter patch:

a.       Flat Patch    

b.       Sleeve Patch.

The patches were made radiopaque  and they were retrievable, retractable into the delivery sheath, and

re-positionable.  All patches supported for forty-eight hours or more, were embedded in the atrial septum.   

Full occlusion without complications was achieved in all cases. The full occlusion was maintained even

after  the balloon support was withdrawn.

The flat patch showed more overlapping and in two cases was partially crossing into the right atrium. The

sleeve patch was more precisely positioned, requiring minimal rim, similar to the detachable balloon

occluder.

The flat patch was endothelialized faster than the sleeve patch.

Clinical trials  using transcatheter patches have started and they have shown impressive results. A single

sleeve patch mounted  on a large double balloon catheter can occlude atrial septal defects ranging from 20-

35mm with minimal septal requirements.

Seven secundum  atrial septal defects,  inappropriate for disk device occlusion  were corrected using sleeve

patches. Defect size varied from 13 to 32 mm; all had deficient rims; the only useful selection criterion was

the full “test”occlusion of the defect by a sizing balloon prior to the patch placement. Supportive balloon

/patch diameters   1-2 mm larger than the test occlusive diameter were used with immediate full occlusion. 

Full occlusion was achieved in 6 secundum ASD cases and a small residual  shunt in one, after balloon

withdrawal in 48 hrs.. One case needed balloon position adjustment at 24 hours.  The method was equally

effective for large and small ASDs (7).  All patients are doing well up to 9 months after transcatheter patch

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occlusion.

We showed  that wireless and device-less  ASD occlusion in feasible by both detachable balloons and

patches. Both methods appear effective and  relatively safe in animals. Feasibility studies has been

performed successfully, on both detachable balloon devices and transcatheter patches.

 Both appear to have a wider application spectrum than the disk devices; however the transcatheter  patch

appears safer.

REFERENCES

1.       Occlusion of large atrial septal defects with a centering buttoned device. E. B. Sideris, M. Leung, J.H.

       Yoon, C.R. Chen, R. Lochan, A-M Worms, B. Meier, C. Rey. American Heart Journal, 1996; 131:356-            

        59

2.       Transcatheter Closure of Atrial Septal Defects: Role of Buttoned Devices .  Sideris EB, Rao PS. The

         Journal of Invasive Cardiology, 1996; 289-296

3.       The centering on demand device: early results in atrial septal defect occlusion. Sideris E. Kaneva A,

        Haddad J., Chiang C.W., Wang JK, Toumanides S. Cardiology in the Young, 1999; 9: p91 

4.       Atrial septal defect occlusion by balloon detachable buttoned devices. An experimental study. A.

        Kaneva, E.B. Sideris, S. Sideris, S. Moulopoulos. Cardiology in the Young, 1998; 9:38

5.        Transcatheter correction of heart defects by detachable balloon buttoned devices; A feasibility study.

         E.B. Sideris, C.W. Chiang, J.C. Zhang, W.S. Wang. 1999;23:528A.

6.       Transcatheter occlusion of experimental atrial septal defects by wireless occluders and patches. Sideris E, Sideris S, Kaneva A, Moulopoulos S. Cardiology in the Young, 1999; 9: p92

7.        Transcatheter patch correction of atrial septal defects: Experimental validation and early clinical

         experience. Sideris E, Sideris S, Poursanov M, Toumanides S, Stamatelopoulos S, Moulopoulos S.

          Cardiology in the Young, 2000; 10:p13.

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                                                                                       LEGENDS

FIGURE 1,

ButtonSeal- Centering on Demand Device

1a: centering

1b: direct placement

FIGURE 2,

Diagram of Detachable Double Balloon  ASD Occlusion

FIGURE 3,

Diagram of Transcatheter Patch ASD Occlusion

3a  balloon support

3b  patch release 

Abbreviations:

Bl   balloon

Bt   button loop

Fl    floppy disk

La   left atrium

Lw  loading wire

M.sh Mullins sheath

Nc  Needle catheter

P    Patch

Ra   Right atrium