Elevation of B‐Type Natriuretic Peptide at Discharge is Associated With 2‐Year Mortality After Transcatheter Aortic Valve Replacement in Patients With Severe Aortic Stenosis: Insights From a Multicenter Prospective OCEAN‐TAVI (Optimized Transcatheter Valvular Intervention–Transcatheter Aortic Valve Implantation) Registry | Synapse