Reconsideration of pacemakers and MR imaging.

The presence of an implanted pacemaker is widely regarded as an absolute contraindication to magnetic resonance (MR) imaging; however, this viewpoint is based largely on safety concerns in the 1982-1996 period. Since 1996, changes in pacemaker electronics including decreased ferromagnetic content, increased sophistication of the circuitry, and onboard computer capabilities suggest that the absolute contraindication of MR imaging for pacemaker patients should be reconsidered. In addition, there are now data from prospective trials of 232 patients with demand pacemakers who underwent MR imaging at 0.5-1.5 T. Although a variety of pacemaker parameters were evaluated before, during, immediately after, and 3 months after MR imaging, no significant pacemaker changes were identified. No patients reported abnormal sensations such as pacemaker movement or irregular heartbeats even at direct questioning. These results suggest that peripheral locations such as the brain and knee may be considered for MR imaging. Thus, pacemaker patients should be assessed individually for their suitability for MR imaging, which may be performed safely under defined conditions.