**4. Device**

Transcatheter therapies for the treatment of aortic stenosis have seen a fast and progressive development in technology. Many platforms are nowadays available; it is possible to categorize the devices according to the deployment mechanism: balloonexpandable valves (BEV) and self-expandable valves (SEV). The third category of devices, mechanically expandable, is less widespread. They also differ in the leaflets' position and their relationship with the annular plane (**Figure 5**).
