A Prospective Evaluation of a Protocol for Magnetic Resonance Imaging of Patients With Implanted Cardiac Devices
Can magnetic resonance imaging (MRI) be performed safely in patients with a pacemaker or implantable cardioverter-defibrillator (ICD)?
In this prospective study, 438 patients with a pacemaker (54%) or ICD (46%) underwent 555 MRI studies at 1.5 Tesla. Pacemaker-dependent patients with an ICD were excluded. The devices were interrogated shortly before and after the MRI. The devices were programmed to asynchronous mode in patients without a stable intrinsic rhythm. All device therapies were disabled. Electrocardiographic monitoring was performed. The devices were reprogrammed to original settings post-MRI. Device interrogation was repeated at 6 months.
The MRI studies were most commonly of the brain (40%), spine (22%), and heart (16%). Unintended reprogramming to an inhibited pacing mode during MRI occurred in 3/438 patients (0.7%). The MRI examination was discontinued in only one of these patients. There were small reductions in lead impedance and right ventricular (RV) sensing immediately post-MRI. At 6 months, there also were small reductions in lead impedance and RV sensing and a small increase in RV pacing threshold. No patient required device revision.
The authors concluded that selected patients with a pacemaker or ICD can safely undergo MRI examinations if appropriate precautions are taken.
ICDs and almost all pacemakers are considered a contraindication to MRI, and this study shows that this need not be the case. However, the results do not apply to all types of devices. In the inhibited mode, devices are subject to electromagnetic inhibition. Therefore, because ICDs typically cannot be programmed to asynchronous pacing, patients with an ICD who do not have a stable intrinsic rhythm should not undergo MRI.
Keywords: Electric Impedance, Pacemaker, Artificial, Electrocardiography, Heart Ventricles, Magnetic Resonance Imaging, Defibrillators, Implantable, Brain
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