# 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  
Ductal stenting may be performed as a palliative procedure to ensure ductal patency in newborns with single ventricle physiology, with either duct-dependant systemic circulation (HLHS) or duct-dependant pulmonary circulation (pulmonary atresia). Table 1 provides a clear picture of the wide variety of devices that have been used over the years and are still currently adopted, following the stent classification proposed in paragraph 2. By examining the existing literature, it emerges how the vast majority of devices for ductal stenting are used on an off-label basis. Many endovascular stents developed for adult patients for different anatomical locations are exploited, among which are coronary, iliac, biliary, renal, carotid, and peripheral stents. To understand this scenario, one should consider that medical devices for CHD are classified as orphan devices, intended for the treatment of rare pathologies interesting less than 1 in 2000 people [88]. In the market of CHD devices, the high cost associated with the development of a new device and regulation is unbalanced with respect to profitability to the industry given the restricted number of cases [89]. Moreover, the variety of congenital problems and anatomical configurations requires high flexibility and unique treatment strategies, with very few devices approved for specific indications [90]. In spite of the fact that the objective of using stenting in HLHS and pulmonary atresia is similar, the distinct ductal morphology calls for different devices and intervention approaches. In HLHS, the ductus is typically straight, without narrowing, with a large diameter of around 3 mm to 6 mm at the pulmonary end and 5 mm to 8 mm at the aortic end. An accurate preliminary delineation of the ductal morphology by angiography is mandatory to select the proper device. The stenting procedure is quite straightforward and stents of a diameter between 6 mm and 10 mm are generally needed [69]. Since, from a histological point of view, the ductus has a significant muscular component that applies an active closing action at birth [91], a device with sufficient radial strength is needed to avoid collapse. Moreover, since especially the distal part of the ductus is strongly prone to constrict if a \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Off-Label Use** & **Ad Hoc for CHD** \\ \hline \multicolumn{2}{c}{**Balloon-Expandable**} & **Self-Expandable** \\ \hline \multirow{10}{*}{HLHS} & Palmaz-Schatz (C) [43; 49; 63] & \multirow{10}{*}{Thisus-Repo-DS (C) [68]} \\  & Palmaz-Genesis (C) [68] & \\  & Herculink (O) [68; 69] & \\  & Nir Royal (C) [69] & \\  & Mega-Link (O) [69] & Precise (O) [74] & \\  & Liberte (O) [70] & Protège (O) [70; 74; 75] \\  & Jo stent (C) [68; 71; 72] & \\  & Omnilink (O) [68; 72] & \\  & Saxx stent (C) [68; 71; 72] & \\  & Cook Formula 414 (O) [73] & \\ \hline \multirow{10}{*}{Pulmonary atresia} & Palmaz–Schatz (C) [7; 49; 79] & \multirow{10}{*}{NA} \\  & Multi-Link Vision (O) [80; 81; 82; 83] & \\  & Promus Premier \({}^{*}\) (O) [80] & \\  & Driver (O) [83; 84; 85; 86] & \\  & Tsunami (O) [84] & \\  & Liberte (O) [84; 85] & \\  & Ephesos (O) [85] & \\  & Jostent (C) [87] & \\  & Express (O) [87] & \\  & Cordis Bx Velocity \({}^{*}\) (O) [87] & \\  & AVE 670 (O) [87] & \\  & VeriFLEX (O) [82; 83] & \\  & Integrity (O) [82; 83] & \\  & Omega (O) [82] & \\  & Skylor (C) [82] & \\  & Amazonia \({}^{*}\) (O) [82] & \\ \hline \hline \end{tabular}  
* Drug-eluting stent (DES); others, where no specification is provided, are bare metal stents (BMS).  
\end{table} 
Table 1: State of the art of stents adopted in the treatment of HLHS and pulmonary atresia. A distinction is made between those stents developed for other applications, thus used off-label in CHD, and those specifically developed for cardiac congenital malformations. Devices are classified among balloon-expandable and self-expandable stents, having a closed-cell (C) or open-cell (O) geometry.