SJM Masters HP 15mm Rotatable Mechanical Heart Valve as Aortic Valve Replacement Therapy

Inclusion Criteria: * Inclusion criteria for prospectively enrolled subjects * Subject's legal guardian must provide written informed consent prior to any clinical study related procedure. * Subject requires aortic valve replacement and is intended to be implanted with a 15mm SJM15 AHPJ-505 MHV as determined by the implanting physician in accordance with the Instructions for Use. * The legal guardian and site agree to follow the subject per the assessment schedule and complete all required assessments per this protocol for the duration of the clinical study. * Inclusion criteria for retrospectively enrolled subjects : In an effort to ensure data on all real-world use conditions are consistently collected and reported on, a subject is eligible to participate in this post-approval study if he/she meets all of the following inclusion criteria and meets no exclusion criterion. For those subjects with a previous implant attempt to be eligible for study participation, the following inclusion criteria must be met: * Echocardiography data at a time point greater than 90 days is available or may be acquired. * An implant was attempted with the 15mm MHV, where implant attempt is defined as the device physically contacting the subject's cardiac anatomy. * Either: * For living subjects who already received the 15mm MHV, the legal guardian signs the study informed consent for this protocol allowing access to all relevant historical medical information, and complete all required assessments according to this protocol from the time of consent going forward (if applicable). OR * For subjects who are deceased or explanted, an implantation with 15mm MHV was attempted and the subject's legal guardian provides written informed consent for retrospective data collection of patient and study valve related information through death or explant of the study device. Exclusion Criteria: * Exclusion criteria for prospectively enrolled subjects: Subject has a contraindication to anticoagulant/antiplatelet medication. * Exclusion criteria of retrospectively enrolled subjects: None