Dilation Optimisation for Uniform Bioprosthetic Leaflet Expansion

The goal of this clinical trial is to discover if routine \'double tap\' balloon post-dilation improves valve expansion and clinical outcomes in adults undergoing Transcatheter Aortic Valve Implantation (TAVI) with the SAPIEN balloon-expandable TAVI prosthesis. The primary hypothesis is that routine \'double tap\' balloon post-dilation improves TAVI valve expansion. The secondary hypothesis is that routine \'double tap\' balloon post-dilation improves TAVI valve haemodynamic performance. Participants will be randomised to balloon-expandable TAVI either with or without routine \'double tap\' balloon post-dilation.