The results of numerous investigations have demonstrated that metal-containing valves do undergo magnetically induced torques, but the magnitude of this effect is much less than the force exerted by the beating heart itself. Thus at present, we consider all implanted heart valves and annuloplasty rings safe for MR imaging, and do not require any waiting period after surgery before they can be scanned.
Advanced Discussion (show/hide)»
Pre-6000 series Starr-Edwards valves were once considered contraindicated for MR imaging, but this prohibition has now been removed. In any case, because most of these valves were implanted over 40 years ago, few, if any, patients are still alive who received them.
At one time worries existed that an electromagnetic phenomenon known as the "Lenz effect" could inhibit the opening and closing of valves (such as the Björk-Shiley) made of metal disks or leaflets. This theoretical concern was not born out experimentally, so all-metal valves remain safe to scan at fields at least up to 3T.
Edwards M-B, Draper ERC, Hand JW, et al. Mechanical testing of human cardiac tissue: some implications for MRI safety. J Cardiovasc Magn Reson 2005;7:835-840.
Shellock F. MRISafety.com. (The essential resource providing MR safety information and links for over 5000 implanted devices
Can some patients with cardiac pacemakers undergo MRI?