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Editor,—Rigby's editorial on transcatheter closure of atrial septal defects is a generally well written review,1 but several misconceptions pertaining to buttoned device are apparent.
Device delivery sheath—Rigby states that the buttoned device is delivered through a 6–8 F catheter. In each of the publications on this device,2-7 it is clearly stated that the device is delivered via an 8–9 F sheath.
Device retrieval—Rigby stated that the retrieval is difficult. The device can easily be retrieved transvenously7 with the help of the loading wire. To prevent inadvertent disconnection of the loading wire with the occluder, we use an additional snare. Even after release from the loading wire, the device can be retrieved by use of a simple snare. However, the device is damaged during the retrieval and cannot be reused.
Embolisation rate—The embolisation rate quoted by Rigby for the buttoned device was 10%, which is very high and we believe is unsupported by the data. In the first 180 implantations in the international trial,7 there were 13 unbuttonings and one whole device embolisation giving a 7.8% device dislodgement rate for the entire cohort. That trial also showed that there was a decrease in the unbuttoning rate with successive generations of the device: 1st generation, 11.1%; 2nd generation, 9.4%; 3rd generation, 3.1%. In the 4th generation device with two spring buttons, the unbuttoning rate has further decreased (p < 0.001) to less than 1.0%.8 9
Occlusion of large defects—Rigby's statement that the buttoned device, along with other devices, has only been used for defects up to 20 mm, except for his preferred Amplatzer device, which has been used for sizes up to 34 mm, is incorrect. The buttoned device has been used in hundreds of large defects, often more than 30 mm in diameter; the results were as effective as in small defects, provided that the septal rims are adequate.10
Residual shunt rate—It was stated that the buttoned device has the highest residual shunt rate compared with all previous devices. A careful comparison of residual shunts for all devices11 12 revealed similar residual shunt rates. Furthermore, the effective occlusion rate with non-measurable residual shunt is excellent acutely, and has further improved with follow up.6 7 13 The Nitinol mesh of the Amplatz device has better acute full occlusion rates, but the buttoned device has achieved good long term results because of better endothelialisation of the polyurethane foam. Elimination of residual shunts is possible with better centring and the use of inverted counteroccluders, with the newer modifications of the buttoned device like the centring and centring on demand buttoned devices.10
The reason for these misconceptions is not clear, but is probably related to referring to an abstract14 from our group while ignoring many full papers in a variety of journals2-8 13 15-18 including the full paper13 of the referenced abstract.14 Or it may be related to relying on personal communications in preference to objective, peer reviewed, published data.7 9
Another issue worthy of discussion is wire problems and chronic wire toxicity. Rigby has only superficially touched on the wire problems of the different devices, both acutely and on follow up. Acute problems, including atrial perforation and interference with heart valves, have been shown with all devices. Wire fractures up to 80% have been shown with the Clamshell device19 and with its successor the CardioSeal device (10% for the first year only). Among all metals used with the different devices, Nitinol has the most acute and chronic complications, despite its very attractive functional characteristics. Unfortunately, chronic nickel toxicity is not simply theoretical, as Rigby mentioned, but rather a well established fact. Hundreds of people have died from lung cancer in the nickel mines, coronary spasm has been shown in experimental animals, and allergic reactions and tissue necrosis are well known. We believe that in 30–50 years time many wires in all devices will be fragmented and some others will have demonstrated some toxicity.
Although the 10 year follow up of the buttoned device showed less than 1% wire related problems, we believe that there is a need for wireless non-toxic devices for heart defect occlusion. We believe that all current disc devices have the same limitations and very similar application and we do not believe that the Amplatz, CardioSeal or the buttoned device can correct more defects than any other. Perhaps a significant factor for the proper device selection is the cost and availability. For countries more price conscious than USA and the UK the fact that the Amplatz device is four times more expensive than the buttoned device can be important. The availability of excellent long term results with one device,9 13 20 and the absence of long term follow up with the others is another factor. However, we agree with Rigby in his assessment that “none of the devices is perfect, each having its own strengths and weaknesses” and “the modifications of the existing devices and the introduction of new systems will result in current practice changing rapidly in the near future.”
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