Introduction
In babies under 3 months of age, coarctation of the aorta is usually treated surgically in the first instance. However, there are scenarios in which alternative treatment is indicated either due to unfavourable results after initial surgery, or due to patient characteristics.
Stenting of coarctation of the aorta (CoA) is well established in adults and children weighing more than 25 kg, but even in smaller children this technique is gaining acceptance [
1,
2]. In smaller children aged 3 months or more, ballooning is a treatment option for native and recurrent CoA [
3], but there are recent reports of even smaller patients undergoing stent therapy as either a bridge to operation or as primary treatment [
4‐
9]. Stenting of coarctations in small children has been carried out for several reasons in a limited number of patients [
4‐
8,
10].
In patients undergoing a hybrid procedure for hypoplastic left heart syndrome or borderline left ventricles, stenting of the descending arch may become necessary to facilitate adequate reverse flow into the aortic arch, should the ductal stent cover the distal aortic arch [
9].
We describe four cases of CoA stenting carried out in children under 3 months of age, in each one for a different reason. We think that these cases illustrate typical indications, which are: (1) severely impaired left ventricular function, where surgery as primary treatment carries a high risk; (2) postoperative thrombus formation within the operated area of the aorta; (3) prematurity in babies in whom surgery is postponed until a higher weight is reached; and finally (4) potential obstruction of the connection of the descending aortic arch to the ductal arch in patients after hybrid therapy for hypoplastic left heart syndrome and variants.
Discussion
Coarctation stenting can be carried out safely in small children to facilitate surgery at a later stage, or for acute postoperative problems. Of course, technical considerations include the choice of sheaths, catheters and stents. The smallest sheath possible should be chosen to avoid access problems, which have been described previously [
3]. Through the sheath, angiography even with dilute contrast can visualise the whole aorta, avoiding manipulation with a catheter. In children with a ductal stent in situ after hybrid palliation for hypoplastic left heart syndrome or a borderline left ventricle, a catheter placed closer to the stenosed aortic segment may be beneficial to delineate the anatomy in detail, and to avoid interference of the ductal arch filling with contrast.
Coronary guidewires like the Ironman we used in our case series are typically atraumatic and allow guidance of the balloon-crimped stent through the coarctation, giving enough support to the balloon-stent ensemble.
Stents can be coronary stents or small redilatable ones which can be deployed through small sheaths. We used Onyx stents in three of our patients. These are drug-eluting stents, which are frequently used in adult coronary interventions. At the time of our interventions, non-drug-eluting stents were not stocked (and hence not available). An ideal stent in this age group would be a bioabsorbable one which keeps its mechanical properties long enough to maintain vessel patency until, after absorption, no further scaffold is necessary. Unfortunately, no such stent exists yet. In our three patients treated with coronary stents, these were removed completely during further surgery. The Cook Formula stent can be redilated repeatedly, as necessary, according to patient size [
10]. Redilation is not possible in self-expanding stents, which therefore are not recommended in this clinical setting. Procedural details of all procedures are summarised in Table
1.
Table 1
Demographic data and interventional information
1 | 10 | CoA | n/a | 5.3 | 6 | Cook Formula 6 × 12 mm | 6.9 | 109.8 |
2 | 2 | CoA | n/a | 3.3 | 4 | Resolute Onyx 4.5 × 8 mm | 4.0 | 32.6 |
3 | 5 | CoA | Prematurity 33/40 weeks | 2.2 | 4 | Resolute Onyx 4 × 8 mm | 3.0 | 11.1 |
4 | 10 | CoA, borderline LV, s/p hybrid palliation | n/a | 4.0 | 5 | Resolute Onyx 5 × 9 mm | 9.3 | 94.3 |
Indications for stent placement in a coarctation in this age group vary, but this is mainly carried out to stabilise patients. Of course, one has to take into account that further interventions or operations are unavoidable, because of patient growth.
Our first case demonstrates how left ventricular function can be impaired by a severe (re‑)coarctation, and how this improved once the stent was placed. Depending on the duration of the impairment, recovery may take some time before the stent can be surgically removed [
11]. In a previously described case, multi-organ failure recovered completely after coarctation stenting in a newborn, which could be operated successfully 4 weeks later [
6]. We used a short stent, because during a coarctectomy typically a short aortic segment has to be removed anyway, and we did not want to extend the operation, i.e. by patch augmentation of the aorta.
Thrombus formation at the operation site of a coarctation is rare, and can be problematic. Compressing the thrombus into the vessel wall can be achieved, but the stent needs to be long enough to cover the whole thrombus. In our case, a stent of 8 mm length was sufficient. Anticoagulation may be necessary to avoid recurrent thrombus formation at the stent site. We opted for subcutaneous heparin, as oral anticoagulation in this age group can be challenging. Our knowledge to date indicates that this is the first patient in the literature to successfully undergo treatment for an acute thrombus after coarctation surgery with a stent. Comparable techniques have been used to treat thrombotic pulmonary artery occlusion, but in chronic settings [
12].
Patient size may also be an indication; in these cases stent placement facilitates growth of the patient until a coarctectomy can be carried out safely. This has been done in children with a weight as low as 680 g [
5]. Again, a short stent is preferable to make the operation as simple as possible; during coarctectomy the stented segment can simply be excised and end-to-end anastomosis performed. Operations can be delayed up to 2.5 years, and weight gain can be normalised until then [
5].
In children with hypoplastic left heart syndrome who have undergone a hybrid procedure either as a bridge to a Norwood procedure or as the first step of staged palliation, ‘reverse’ coarctation with obstruction of the descending arch can cause problems both for the upper half of the body and coronary perfusion, in the case of retrograde perfusion [
9]. In these cases, stenting can be performed through the side struts of a previously placed self-expandable Sinusflex-DS stent. Ballooning alone will not be sufficient, as the struts have a high tendency to recoil [
13]. In our case, there was forward flow through the aortic arch, but the technical considerations are the same.