[Safety of magnetic resonance imaging in patients with pacemaker and implantable defibrillator]

The presence of a cardiac implantable device is ICD considered an absolute contraindication to magnetic resonance imaging (MRI). The purpose of this study was to evaluate the safety of performing MRI in patients with cardiac pacemakers and ICDs that had a compelling clinical need for MRI examination.

During a period of nine years we have included 65 patients with cardiac devices (60 pacemakers and five ICDs) who underwent a total of 73 MRI examinations at 1.5 T. All pacemakers were reprogrammed before MRI to asynchronous mode to avoid MRI-induced inhibition or to sense only mode to avoid MRI-induced competitive pacing and potential pro-arrhythmia. All devices were interrogated immediately before and after the MRI examination, which included measurement of sensitivity, pacing capture threshold (PCT) and lead impedance.

MRI examinations were completed safely in 63 patients. Inhibition of pacemaker output was observed in one patient and induction of ventricular fibrillation was observed in another with ICD. A significant increase in PCT was rare and only detected in 1% of all electrodes.

MRI can be performed safely in patients with pacemakers with an acceptable risk-benefit ratio, while MRI of patients with ICDs must still be considered an experimental procedure.