Safety considerations for magnetic resonance imaging of pacemaker and ICD patients

Abstract

Magnetic resonance imaging (MRI) has evolved as an important diagnostic tool in medicine. However, due to safety concerns the presence of an implanted cardiac pacemaker is considered to be a contraindication to MRI in most medical centers. Previous in vitro and in vivo studies showed that strong electromagnetic fields in the MRI environment may cause asynchronous pacing, inhibition of a demand pacemaker, induced currents in the pacemaker system and pacing of the heart, or potential risk of thermal myocardial injury around the pacing lead tip. ICDs in addition are not able to charge and apply a therapy in the strong magnetic field. There are reported lethal consequences of MRI in patients with pacemakers. However, there are also recent reports of small series of pacemaker patients who have safely undergone MRI. At present time, non-MRI modalities should be considered, whenever possible, to make a diagnosis in pacemaker recipients. If other imaging modalities are not adequate, MRI at low field strengths (0.5 Tesla or less) with careful monitoring and preparation for adverse events may be considered only in experienced centers. The device should be programmed to an asynchronous, or if possible to a non-pacing mode, during MRI. Pacemaker mode changes, inappropriate pacing behavior due to induced voltages, and localized heating at the lead tip are the primary issues that remain to be fully investigated in future studies.