Ectopy in Patients with Permanent Pacemakers and Implantable Cardioverter-Defibrillators Undergoing an MRI Scan

Background: Recent series suggest that magnetic resonance imaging (MRI) scanning can be performed safely in select patients with pacemakers or implantable cardioverter-defibrillators (ICDs). Limited data have been reported on ectopy during MRI scans in patients with pacemakers or ICDs. This study evaluated increased ectopy observed in patients with permanent pacemakers or ICDs undergoing MRI scanning of any landmark without peak specific absorption rate (SAR) limit. Methods: Fifty-two patients with a total of 119 leads underwent a total of 59 MRI scans of any landmark using usual protocols with standard peak SAR settings for the scan. No patient was pacemaker dependent. All devices were programmed to single-chamber demand mode (VVI) or dual-chamber demand mode (DDI) with a lower rate of 40 bpm. Both telemetry and pulse oximetry plethysmographic waveform were observed continuously throughout the scans for ectopy. Results: Increased ectopy was observed during seven scans. The ectopy in four scans was ventricular and had fixed coupling intervals of 1,500 and 3,000, and was likely due to device noise rejection behavior. The etiology of ectopy observed during the other three scans could not be determined. Ectopy could not be predicted by peak SAR, scan time duration, or landmark. No significant changes in pacing thresholds were seen postscan. Conclusions: The current series suggests that a minority of patients with implanted pacemakers may have MRI-related ectopy. A significant proportion of this ectopy may arise from normal device behavior within the MRI environment. (PACE 2009; 32:772-778).