The learning curve associated with transapical aortic valve implantation - Kempfert, Jörg; Rastan, Ardawan; Holzhey, David; Linke, Axel; Schuler, Gerhard; Mohr, Friedrich Wilhelm; Walther, Thomas (Annals of Cardiothoracic Surgery; Vol 1, No 2 (July 26, 2012): Transapical Aortic Valve Implantation, 2012)