"Power-on resets" in cardiac implantable electronic devices during magnetic resonance imaging

Heart Rhythm. 2015 Mar;12(3):540-544. doi: 10.1016/j.hrthm.2014.10.039. Epub 2014 Nov 11.


Background: Magnetic resonance imaging (MRI) has been safely performed in some patients with cardiac implantable electronic devices (CIEDs) under careful monitoring and prespecified conditions. Pacemaker-dependent patients are often excluded, partly because of the potential for "power-on reset" (PoR), which can lead to a change from asynchronous to inhibited pacing with consequent inhibition of pacing due to electromagnetic interference during MRI.

Objective: The purpose of this study was to review risk factors for PoR during MRI.

Methods: A prospective study was performed between January 2008 and May 2013 in patients with CIEDs undergoing clinically indicated MRI. Eligible patients were not pacemaker dependent. Devices were interrogated before and after MRI, programmed to an asynchronous mode or an inhibition mode with tachyarrhythmia therapies turned off, and reprogrammed to their original settings after MRI.

Results: MRI scans (n = 256) were performed in 198 patients with non-MRI-conditional CIEDs between 2008 and 2013 (median age 66 years; interquartile range 57-77 years; 59% men). PoR occurred during 9 MRI scans (3.5%) in 8 patients. PoR was more frequent with Medtronic devices than with other generator brands (n = 9/139 vs 0/117 [6% vs 0%]; P = .005). Devices with PoR were all released before 2002 and were implanted from 1999 to 2004. Effects of PoR included a decrease in heart rate during MRI (n = 4) and transient anomalous battery life indication (n = 1). All devices functioned normally after MRI.

Conclusion: PoR occurs infrequently but can cause deleterious changes in pacing mode and heart rate. MRI should not be performed in pacemaker-dependent patients with older at-risk generators. Continuous monitoring during MRI is essential because unrecognized PoR may inhibit pacing or accelerate battery depletion due to high pacing output.

Keywords: Cardiac implantable electronic device; Magnetic resonance imaging; Pacemaker safety.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Cardiac Resynchronization Therapy Devices*
  • Electrodes, Implanted / adverse effects*
  • Equipment Failure / statistics & numerical data
  • Equipment Safety / instrumentation*
  • Equipment Safety / methods*
  • Female
  • Heart Rate
  • Humans
  • Magnetic Resonance Imaging / instrumentation*
  • Magnetic Resonance Imaging / methods
  • Male
  • Middle Aged
  • Patient Safety / statistics & numerical data*
  • Prospective Studies
  • Risk Factors