Magnetic Resonance Imaging and Cardiac Devices: How Safe Is Safe Enough?

Several million persons in the United States are currentlyliving with implanted cardiac rhythm management de-vices (CRMDs); a few hundred thousand new devices are implanted annually (1). The majority of these patients are older than 60 years. As the long-term survival of this pop-ulation improves and utilization of CRMDs continues to grow (2), the probability increases that many of these pa-tients will encounter medical situations for which magnetic resonance imaging (MRI) may be useful, or even critical, for optimal diagnosis and treatment. This likelihood is dif-ficult to assess because the value of MRI relative to alter-natives may vary, but estimates of greater than 50 % have been published (3). For many years, the presence of a CRMD has been widely considered an absolute contraindication to MRI. This is because of several hypothetical risks to the functio