Fitness-Tracker Assisted Frailty-Assessment Before Transcatheter Aortic Valve Implantation: Proof-of-Concept Study oleh Mach, Markus, Watzal, Victoria, Hasan, Waseem, Andreas, Martin, Winkler, Bernhard, Weiss, Gabriel, Strouhal, Andreas, Adlbrecht, Christopher, Delle Karth, Georg, Grabenwöger, Martin