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MRI deemed safe for patients with selected implanted cardiac devices
Nazarian S. Ann Intern Med. 2011;155:415-424.
Reynolds MR. Ann Intern Med. 2011;155:470-472.
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MRI can be performed safely in patients with selected pacemaker and implantable cardioverter defibrillators when using device selection and programming protocol, new data suggest.
Patients with clinical indication for MRI and an implantable device were enrolled in a study between February 2003 and April 2010. Researchers enrolled 438 patients (54% had a pacemaker; 46% had ICDs) who underwent 555 MRI examinations. Most MRIs were of the brain, 22% of the spine, 16% of the heart, 13% of the abdomen or pelvis and 9% of an extremity.
Immediately after MRI, right ventricular sensing (median change, 0 mV), and atrial (median change, –2 Ù) and right (median change, –4 Ù) and left (–11 Ù) ventricular lead impedances were reduced, according to researchers. At long-term follow-up, 61% of patients had decreased right ventricular sensing (median, 0 mV), right ventricular lead impedance (median, –3 Ù), battery voltage (median, –0.01 V) and increased right ventricular capture threshold (median, 0 V).
Three patients had their device reverted to a transient backup programming mode, with no long-term effects. According to the researchers, this was the “primary clinically significant event attributable to MRI.”
They concluded that “MRI was performed safely in all patients.” However, image distortion, signal voids or bright areas, and poor fat suppression were noted when the device was located in the MRI field of view. “Given the potential for changes in device variables and programming, monitoring by device experts is necessary,” they wrote.
The researchers said patients were selected and treated based on previous safety studies. Only patients with pacemakers manufactured after 1998 and defibrillators manufactured after 2000 were enrolled, and researchers followed programming and monitoring protocol.
“The risks and benefits of MRI in a patient with a cardiac rhythm management device should be assessed on an individualized basis, as with any important medical decision,” Matthew R. Reynolds, MD, MSc, and Peter Zimetbaum, MD, of the division of cardiology, Beth Israel Deaconess Medical Center, wrote in an accompanying editorial. “The authors have not demonstrated that MRI in these patients is risk-free, only that the risks are quantitatively small. Therefore, before permitting a patient to have MRI, the potential benefits of the MRI relative to alternative diagnostic strategies should be established.”
Disclosure: Dr. Nazarian received a grant from the NIH Career Development and received payment for lectures from Biotronic, Boston Scientific and St. Jude Medical. Dr. Reynolds consulted for Medtronic and St. Jude Medical.
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