There are several reasons one is concerned about implanted devices in patients undergoing MRI imaging. Certain metallic devices may overheat during MRI, leading to burns or other thermal injuries. Certain ferromagnetic implants may migrate to undesirable locations when the magnetic field is applied. And yet other devices may simply malfunction when the magnetic field is applied.
For many years implanted pacemakers and implanted defibrillators were considered contraindications to MRI procedures, forcing patients with such devices to get alternative imaging studies that might have other risks or which might provide lesser diagnostic information. So newer “MRI-conditional” devices were developed and approved by the FDA if they met certain criteria.
But a new study (Nazarian 2017) looked at MRI safety of devices that were not considered to be MRI-conditional (termed “legacy” devices). Over 1500 patients with a pacemaker (58%) or an implantable cardioverter–defibrillator (42%) underwent over 2100 thoracic or non-thoracic clinically indicated MRI’s at a magnetic field strength of 1.5 Tesla. Certain protocols were followed prior to scanning. The pacing mode was changed to asynchronous mode for pacing-dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled.
Results from a safety standpoint were very reassuring. No long-term clinically significant adverse events were reported. In nine MRI examinations the patient’s device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed and was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patients.
And CMS (Centers for Medicare & Medicaid Services) just issued a Proposed Decision Memo for Magnetic Resonance Imaging (MRI) (CMS 2018). It proposes that the evidence is sufficient to conclude that magnetic resonance imaging (MRI) for Medicare beneficiaries with an implanted pacemaker (PM), implantable cardioverter defibrillator (ICD), cardiac resynchronization therapy pacemaker (CRT-P), or cardiac resynchronization therapy defibrillator (CRT-D) is reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member. Thus, CMS is proposing to modify its national coverage determination to eliminate the collection of additional information.
So it looks like patients having these older devices will now be eligible to have clinically indicated MRI studies that they previously would have been excluded from. Perhaps our one caveat would be to note that the safety study performed by Nazarian and colleagues was done using a relatively weak magnetic field. Many facilities are now using much higher magnetic field strength MRI’s and we’d be somewhat reluctant to extrapolate the current safety data to those units.
As above, a more common problem is that certain metallic devices may overheat during MRI, leading to burns or other thermal injuries. Now may be an appropriate time to raise again a warning about unexpected ingestion of metallic items in children. In our August 2012 What's New in the Patient Safety World column “Newest MRI Hazard: Ingested Magnets” we cited a case in which an MRI done on a 5-year old who had unexpectedly swallowed magnets resulted in a bowel perforation (Bailey 2012).
Ingestion of rare earth magnets subsequently was recognized as a serious ongoing hazard for pediatric patients and led to a 2012 Consumer Product Safety Commission (CPSC) policy action and efforts from consumer and physician advocacy groups. A recent study (Reeves 2017) showed that the frequency of magnet ingestions continued to rise from 2010 and then peak in 2012, followed by a decline in magnet ingestion ED visits during the post-federal action years.
But a new hazard has popped up: the popular “fidget spinner”! Ingestion of components (such as the fidget spinner cap or the button batteries) by small children have recently been reported (Khalaf 2018, Tipnis 2018). While we have not yet heard of any incidents involving MRI in children with such ingestions, it would not be surprising if such occur.
In the 2012 Bailey article relating to ingested magnets, the hospital changed their MRI screening protocol. While they still do a written and verbal questionnaire of the children and parents for presence of metallic objects, they now also have all children change into a hospital gown and undergo screening using a hand-held ferromagnetic detection scanner. Given the new hazard related to fidget spinners, that sort of protocol may not be a bad idea for small children prior to MRI.
Some of our prior columns on patient safety issues related to MRI:
Nazarian S, Hansford R, Rahsepar AA, et al. Safety of Magnetic Resonance Imaging in Patients with Cardiac Devices. N Engl J Med 2017; 377: 2555-2564
CMS (Centers for Medicare & Medicaid Services). Proposed Decision Memo for Magnetic Resonance Imaging (MRI) (CAG-00399R4). CMS 2018; January 11, 2018
Bailey JR, Eisner EA, Edmonds EW. Unwitnessed magnet ingestion in a 5 year-old boy leading to bowel perforation after magnetic resonance imaging: case report of a rare but potentially detrimental complication. Patient Safety in Surgery 2012; 6: 16 (19 July 2012)
Reeves PT, Nylund CM, Krishnamurthy J, et al. Trends of Magnet Ingestion in Children, an Ironic Attraction. Journal of Pediatric Gastroenterology and Nutrition 2017; Published Ahead of Print: November 7, 2017
Khalaf RT, Gurevich Y, Marwan AI, et al. Button Battery Powered Fidget Spinners: A Potentially Deadly New Ingestion Hazard for Children. Journal of Pediatric Gastroenterology and Nutrition 2018; Published Ahead of Print: January 24, 2018
Tipnis NA, Ciecierega T. Fidget Spinner Ingestion. Journal of Pediatric Gastroenterology and Nutrition 2018; Published Ahead of Print: January 24, 2018