Treating vessel stenosis in adult patients with congenital heart defects by stent implantation requires the stents to have specific properties. Since most lesions occur in the great vessels, stents have to be dilated to large diameters and still have to provide stability and radial force. Of course, in children it is advantageous to use such a stent, dilated to smaller diameters,2,4,14,25
providing the possibility of adapting the stent diameter by redilatation after somatic growth of the patient. Owing to the smaller anatomical size of children, however, the stent has to be available in a variety of shorter lengths, carrying the same potential of dilatability to larger diameters without extreme foreshortening. The CP stent offers these features, which will probably be important in 18 of the patients in this study who have body weights less than 40 kg and have not yet reached their final body height. The availability of the stent in individual lengths enabled us to provide even small children with 8 zig stents of short length (fig 4). A variety of lengths is advantageous in adults, as we used stents from 22–80 mm.
Stents were redilated in eight patients, in each case as a planned second dilatation to yield the definitive diameter six months after implantation. These stents were redilated without any complications and with good results as was expected from the behaviour of other stents used in congenital heart disease.27–31
Thus, we hope to obtain similar results after redilatation at a later stage when this becomes necessary in the paediatric patients because of their somatic growth.
The availability of the stent in a covered version, in our opinion, seems to be especially useful in very narrow stenotic vessels. The cover may provide the extremely stressed vessel area with an additional seal to avoid vessel dissection and bleeding.26
Furthermore, it may offer a solution for the combination of stenosis and vessel aneurysm by stenting the stenosis and covering the aneurysm (fig 3). Of course, the coverage of side branches has to be taken into consideration. In extreme coarctations the coverage may seal the orifices of collaterals that meet the descending aorta directly beneath the coarctation. We did not consider this disadvantageous as far as the stenosis is eliminated by the stent.
A disadvantage of the stent is the necessity of sheaths 2 French larger than the implantation balloon and even 3 French larger if the stent carries a PTFE cover. It is difficult to crimp the stent to smaller diameters than 8 to 9 French. Although this may be of minor concern in a venous access site, it may be important in the case of the femoral arteries. In adults and children over 30 kg body weight, however, the use of a suture device before the introduction of the large implantation sheath has practically eliminated any problematic bleeding after the procedure. For small children no suitable suture device is available. Our benchmark in this study was 25 kg body weight. There was only one patient with a body weight below 30 kg (namely 28 kg), in whom we used the Perclose stitch. Whether 25 kg is a justified limit to the use of this device is beyond the scope of this study. To avoid damage at the arterial access site we were anxious to shorten the time the large sheath remained in the vessel as much as possible and to take special care after removal of the sheath. Well advised, minimal but effective manual compression was applied for several minutes and then the patient was observed closely with no compression for about one hour. A pressure dressing was then applied given that a good pulse was palpable at the feet. The duplex sonography at discharge and at follow up showed unrestricted flow (fig 7) in each of these patients.
Figure 7 Sonography of the femoral artery (*) of a 2.5 year old boy with a body weight of 15 kg three days after implantation of a CP stent through a 9 French sheath. (A) The access site can be seen (blue (more ...)
Three stents were fractured at the welds in cases of very high mechanical stress. Two of them affected singular struts without any dislodgment or mechanical instability of the stent. These patients were followed up by fluoroscopy at regular time intervals. The third, covered stent broke completely within six months after implantation. A second covered stent with reinforced gold brazed welds was implanted in the first one and resolved the stenosis. The latest follow up after 16 months showed stable conditions.26
We did not find any further fractures after the stents were manufactured with gold brazed welds beginning in December 2002, despite use of the stent in similar cases of high mechanical strain (fig 1). Whether the new design will solve this problem, which has also been described for other stents,32,33
will need to be elucidated in the future.
After a rather short follow up period of 12 months (range 1–30 months), we have seen no signs of restenosis by intima proliferation in any of our patients. So far, no dissections and no aneurysms at the implantation site of any stent have occurred, even in patients with subatretic vessels. We hope that the as yet theoretical advantage of the atraumatic edges of the stent, the frequent use of a balloon in balloon system to avoid excessive flaring during implantation, the PTFE cover in very severe stenosis, and the two step procedure in these lesions will help to maintain these good results over time.
Of course, one may argue that in the majority of cases an alternative stent already available on the market could have been used equally well. However, we feel that the CP stent contributes a degree of predictability, safety, confidence, and comfort to the procedures if one stent family can be used in a large range of indications.
Owing to its maximum expandable diameter of 25 mm combined with its variability in length from 11–50 mm and more, the CP stent is suitable for the treatment of vessel stenosis in congenital heart diseases from childhood to adulthood. The option of a PTFE cover can be advantageous for the treatment of very severe stenosis. Whether stent fractures can be prevented by the new design with gold brazed welds, and whether the good results achieved with the CP stent in this study will be stable in the long term, need to be investigated in future follow up.