# Stents in Congenital Heart Disease: State of the Art and Future Scenarios
## 4 Stents in the Treatment of Congenital Heart Disease
### Ductal Stenting: HLHS and Pulmonary Atresia
short tract is left unstented, a stent slightly longer than the ductus should be implanted to ensure complete coverage. In the literature, there are reported cases on such use of open-cell stents to alter the local hemodynamics less, either balloon or self-expandable [70; 77]. In many cases, multiple overlapping stents need to be adopted according to the available sizes [49; 92]. Nowadays, self-expandable stents with a cell design suitable to guarantee a high radial force are the preferred choice [67], chosen among carotid and peripheral stents. Balloon-expandable stents, selected among coronary, renal, and biliary devices, are only indicated in case of ductal stenosis to reduce stent migration risk [68]. The great advantage of self-expandable stents relies on their higher flexibility and conformability to duct shape with respect to balloon-expandable stents and the possibility of implantation through smaller sheaths [70; 73; 77; 93]. Among the most common complications, stent migration, need for re-stenting, aortic isthmus jialing, and stent obstruction are reported [70; 77; 92]. According to stent design, an open-cell configuration is a quite common choice thanks to the reduced foreshortening and the high conformability [67]. Moreover, since the ductus is typically short and straight, large cross-sections, thick struts, and small cell areas are indicated, allowing for good scaffolding with minimum tissue prolapse [94]. It is relevant to mention that there are on the market two stents specifically designed and certified for hybrid palliation of HLHS: the nitinol Sinus-SuperFlex-DS and the Sinus-Repo-DS (Optimed, Germany). The former is characterized by an open-cell design to provide an effective combination between conformability and radial force, with diameters ranging from 4 mm to 9 mm; the latter has a closed-cell design and is indicated for combined treatment of aortic coarctation, with size of 5 mm and 6 mm. However, controversial outcomes have been reported: while some studies reveal positive follow-up with sufficient radial strength, good hemodynamics, and reduced wall trauma [77; 78], others report early collapse due to insufficient radial force and severe restenosis [73; 76]. In pulmonary atresia, due to the reduced blood flow, the ductus arteriosus typically assumes a narrow and tortuous morphology [7; 49; 84]. Therefore, stenting might be changeling or even unsuitable [49; 85; 87], and it is associated with a high unplanned re-intervention rate [95]. Also, in this case, accurate delineation of the ductal morphology by angiography is needed. A stent slightly longer than the ductus should be implanted for complete coverage [94], relying in many cases on overlapping stents [49; 84] with sufficient radial force to counteract ductal active closure. Probably for this reason, there are no reported uses of self-expandable stents. The small size of the ductus arteriosus in this condition leads to the use of coronary balloon-expandable stents with diameters ranging from 3 mm to 5 mm in most cases. These devices provide sufficient radial strength to ensure ductal patency, allowing pulmonary arteries growth, good systemic oxygenation, and spontaneous improvement of pulmonary circulation [84; 86]. Moreover, they allow for the possibility of further dilation by balloon expansion to counteract duct constriction [7]. However, they poorly conform to the curvature of the ductus, and their implantation is associated with a transient blockage of cardiac output that unbalances hemodynamics [77]. According to stent geometry, open-cell designs are widely adopted also in this case, preferring larger cell areas to improve flexibility and conformability given the strong duct tortuosity. At the moment, no ad hoc devices specifically developed for pulmonary atresia have been found in the literature. Despite DESs being shown to reduce early coronary artery restenosis when compared to uncoated stents, limiting thrombosis and neointimal proliferation, their use is rarely reported for ductal stenting in HLHS or pulmonary atresia.