Cardiac pacemaker: in vitro assessment at 1.5 T.

BACKGROUND In vitro testing is used to determine safe parameters before performing magnetic resonance imaging (MRI) on a patient with an implant. Therefore, the objective of this study was to evaluate a cardiac pacemaker using a 1.5-T magnetic resonance (MR) system. METHODS A modern cardiac pacemaker (INSIGNIA I PLUS, Model 1298, and FINELINE II, Model 4471, pacing leads; Guidant Corporation, St Paul, MN) was evaluated for magnetic field interactions at 1.5 T. Magnetic resonance imaging-related heating was assessed using 3 different 1.5-T scanners operating at various levels of radio-frequency power and imaging conditions. Functional aspects of the pacemaker were evaluated immediately before and after MRI (9 different pulse sequences). Artifacts were also characterized. RESULTS Magnetic field interactions for the pacemaker were minor. Temperature changes measured in vitro were at levels that are not expected to pose a risk for specific MR conditions (< 4.0 degrees C). The function of the pacemaker was unaffected by MRI. Artifacts were minor for the leads and relatively large for the implantable pulse generator. CONCLUSION The findings indicated that this pacemaker exhibited acceptable safety features relative to the use of a 1.5-T MR system. If induced currents do not occur for this device, it may be safe for a patient to undergo MRI by following specific conditions. The results are specific to the pacemaker tested, the MR systems, and conditions used in this evaluation.