Assessing the risks associated with MRI patients with a pacemaker or defibrillator


Clinical Question: What are the risks of nonthoracic MRI in patients with pacemakers or implantable cardioverter-defibrillators (ICD) who are not preapproved by the Food and Drug Administration for MRI scanning?

Background: Implantable cardiovascular devices could suffer heating in MRI magnetic fields leading to cardiac thermal injury and changes in pacing properties. The FDA approves “MRI-conditional devices” deemed safe for MRI, but up to six million patients worldwide (and two million in the United States) have non–MRI conditional devices.

Study Design: A prospective, multicenter registry of patients with non–MRI conditional pacemakers or ICDs.

Setting: U.S. Centers participating in the MagnaSafe registry.

Synopsis: Adults with non–MRI conditional pacemakers (1000 cases) or ICDs (500 cases) implanted in the thorax after 2001 were scanned with nonthoracic MRI at 1.5 Tesla. Patients with abandoned or inactive leads, other implantable devices, and low batteries and pacing-dependent patients with ICDs were excluded.

Devices were interrogated before each MRI and set to either no pacing or asynchronous pacing with all tachycardia and bradycardia therapies deactivated. Primary endpoints included immediate death, generator or lead failure, loss of capture in paced patients, new arrhythmia, and generator reset.

No patients suffered death or device or lead failure. Six patients developed self-terminating atrial arrhythmias, while an additional six had partial pacemaker electrical reset. Several devices had detectable changes in battery voltage, lead impedance, pacing threshold, and P- or R-wave amplitude without evident clinical significance. Multiple MRIs caused no increase in adverse outcomes. This study suggests that patients with non–MRI conditional devices may be at low risk from nonthoracic imaging if appropriately screened with temporary pacemaker function modification before MRI.

Bottom Line: Appropriately screened and prepared patients with non–MRI conditional thoracic pacemakers or ICDs may be at low risk for complications from nonthoracic MRI at 1.5 Tesla.

Reference: Russo RJ, Costa HS, Silva PD, et al. Assessing the risks associated with MRI in patients with a pacemaker or defibrillator. N Engl J Med. 2017;376:755-64.

Dr. Frederick is assistant clinical professor in the division of hospital Medicine, department of medicine, University of California, San Diego.

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