The purpose of this study is to obtain data regarding the left ventricular mass (LVM) regression 6 months after the implant of an SJM Epic™ and SJM Epic™ Supra valve by comparing LVM regression measured with magnetic resonance imaging (MRI) to LVM regression measured with echocardiography (2-dimensional [2D] mandatory; 3-dimensional [3D] in sites where the technology is available).

Inclusion Criteria:

• Patient requires, for the first time, isolated aortic valve replacement due to aortic stenosis or mixed aortic stenosis disease etiology when aortic stenosis is predominant and aortic regurgitation is mild.
• Patient is of legal age in the host country.
• Patient (or legal guardian) has signed a study specific informed consent form

Exclusion Criteria:

• Patient was previously operated on with any heart surgery including heart valve replacement or coronary artery bypass graft (CABG); or underwent any form of myocardial revascularization in the past (including stents), etc.
• Patient requires any concomitant heart surgery other than the isolated native aortic heart valve replacement and concomitant ascending aortic replacement (e.g not allowed are: multiple valve replacements or concomitant CABG, pacemaker insertions, or severe septal hypertrophy needing surgical excision, etc.)
• Patient has unstable angina
• Patient is in New York Heart Association functional class IV
• Patient has significant abnormality in wall motion
• Patient is affected by active endocarditis.
• Patient has a cardiac pacemaker or automatic implanted cardiac defibrillator
• Patient is affected by acute aortic dissection.
• Patient is in chronic and persistent atrial fibrillation
• Patient receives hemodialysis therapy
• Patient has a medical condition which contraindicates implantation of the SJM Epic and Epic™ Supra Porcine Bioprosthetic Heart Valve (e.g. renal failure or abnormal calcium metabolism).
• Patient has aneurysmal clips or carotid artery vascular stents
• Patient has a neurostimulator
• Patient has an implanted or external drug infusion device (e.g. insulin pump)
• Patient has a bone growth/fusion stimulator
• Patient has a cochlear, otologic, or ear implant
• Patients with severe claustrophobia in which medical sedation is contraindicated or unable to resolve anxiety sufficiently
• Patients with ocular foreign body (e.g. metal shavings)
• Patient is pregnant or nursing