LAUSR

To the Editor: Ines Hribernik et al report on an important but well-known observation of duct obstruction following implantation of a Sinus-SuperflexDS in congenital heart diseases with ductdependent systemic blood flow. In this context, however, I remember one of my father's phrases: “What can the handle of the pump for it if the pump doesn't give water” or the materials are as good as their instructions for use and the handling in general. However, it should definitively no longer happen that general comments or recommendations are made due to limited institutional experience. As requested by the authors in their conclusions, the strengths and weaknesses of the CE-marked SSF-DS have already been published in many articles not cited by the authors and even in book chapters they are familiar with. At least some of the possibly many remarks must then be made. First of all, it should be noted that the hybrid approach is successfully used as a first-line therapy in several institutions around the world and is not always limited to small and critically ill newborns with HLHS and HLHC. As previously already described, hybrid experiences limited only to critically ill or small newborns could be one of the main reasons for inadequate results with the hybrid approach in general, and duct stenting in particular. Similar to Norwood surgery, the Hybrid approach also requires experience. It's about much more than just inserting a stent into the duct after surgically bilateral PAB's. I want specifically mention, that I never had any disclosures regarding the German company Optimed, but I urged the company to develop the open-cell SSF-DS to also have the ability to stent a wide-open, unobstructed neonatal duct by minimizing the risk of stent embolization, as would be the case utilizing a balloon-expandable stent. The SSF-DS is the first stent and currently only stent to be CE-marked for stenting the neonatal duct. The SSF-DS can be advanced through a 4Fr sheath according to a small vein or artery. The SSF-DS was intended for the Giessen-Hybrid procedure, which is characterized by the surgical placement of a bilateral PAB followed by duct stenting as a separate transcatheter, transfemoral access. The SSF-DS is now also the basis for a complete transcatheter-based stage-I (DIDI) procedure in newborns with HLHS. For the transpulmonary placement of a stent in the duct, the stent properties (self-expandable or balloon expandable) or the short sheath sizes for the simple type of placement are irrelevant for the first time. Like a creed, I have always emphasized in several publications and almost hundreds of scientific lectures, that no duct, especially not the duct-aortic junction, looks the same. Therefore, percutaneous duct stenting must follow a sophisticated strategy. In spite of continuous prostaglandin infusion, the strategy and also the material properties provided should consider an even slightly obstructed or a curved and elongated duct. The pulmonary side of the duct and especially the junction of the duct to descending aorta needs to be checked before and after stent placement. This preferentially requires two-plane radiographic observations and best an arterial and venous access. It not only requires a lateral 90 view, as shown on the authors' figures, but also and especially a 30 RAO plane. Therefore, the technical properties of the open-cell SSF-DS available in length from 12 to 24 mm must be taken into account in connection with the duct morphology and the follow-up treatment and monitoring. In contrast to balloon-expandable stents, the SSF-DS not only enables stenting of a completely unrestricted duct, but also that the blood-flow is not obstructed during the stent expansion. It is an enormous advantage if, in contrast to the patients described by the authors, there is no antegrade aortic blood flow. In addition, the prostaglandin infusion does not have to be stopped, but rather continued for further 24–48 h after the duct is stented. In this way, an immediate duct reaction to the foreign body of the stent can be avoided, which also promises long-term benefits. Along with continued PGE1 (5–10 ng/kg/min) in combination with heparin infusion in a dosage of 300 U/kg/day, oral clopidogrel treatment is used at a dosage of 0.2 mg/kg once a day during the total interstage. Clopidogrel is preferred in place of the cyclooxygenase-inhibitor aspirin, especially at an anti-inflammatory dosage of 3–5 mg/kg with possible contracting effects on the duct. In respect to the five cases described in detail, only case 3, in which an elongated duct required two stents to completely cover the duct tissue, indicated the use of SSF-DS. In addition, the lack of experience in handling the SSF-DS is clearly demonstrated in your Figure 2(B). The first stent was mistakenly placed distally within the descending aorta and the subsequent placement of a second stent to cover the pulmonary-side of the duct without regard of the properties of the open-cell device. In addition, regardless of how accurately the duct width and length can actually be measured through a mono-plane (lateral 90 ) view, it appears that 5 of the 7 hybrid patients described on Table 2 who were treated with SSF-DS had an imaginary duct size between 3 and 5 mm and thus per se the indicates the use of a balloon-expandable stent in patients with duct-dependent systemic blood-flow. In summary, I agree with the authors' decision to only use balloon-expandable stent in their facility. In the case of transpulmonary stent placement, especially in patients with antegrade blood flow to the ascending aorta or even an interrupted aortic arch, only a stent has to be placed in the duct. There is no need to differentiate whether or not a sufficient retrograde aortic arch perfusion is required. In addition, there is no need to consider a small introducer Received: 17 September 2021 Accepted: 3 October 2021