We report the case of a severe prosthetic aortic stenosis in a 61-year-old male patient with an aortic Mitroflow LF bioprosthesis (Sorin Group) at early (6 months) postoperative echocardiographic follow-up. At reintervention, we found significant stent deformation, asymmetric orientation of the posts, and subsequent central kinking and prolapse of one leaflet. Maldistribution of pledgeted mattress sutures over the flexible stent was found to be the origin of its permanent deformation. Simple technical preventive strategies of this previously unreported complication are suggested.