Determining the Risks of MRI at 1.5-Tesla for Patients with Pacemakers and Implantable
Cardioverter Defibrillators (The MagnaSafe Registry)
Author Block: Jennifer Cohen, Heather Costa, Robert Russo, Scripps Clinic, La Jolla, CA
Abstract:
Background: The MagnaSafe Registry is a multi-center study designed to evaluate the risk of
MRI at 1.5-Tesla for 1500 patients with pacemakers and implantable cardioverter-defibrillators
(ICD) who undergo clinically-indicated non-thoracic imaging.
Methods: Device interrogation was performed pre- and post-MRI using a standardized protocol.
For pacemaker-dependent patients the device was programmed to an asynchronous pacing
mode, and pacing functions were deactivated for non-dependent patients. For non-pacemaker
dependent ICD patients, all tachyarrhythmia therapies were disabled, while pacemaker
dependent ICD patients were excluded. Noninvasive monitoring was performed throughout the
MRI, and a physician proficient in device programming was present. Primary endpoints were
death, device failure, generator/lead replacement, induced arrhythmia, loss of capture, or
electrical reset. Secondary endpoints were clinically relevant device parameter changes:
Results: Between April 2009 and March 2010, 105 clinically-indicated MRI studies were
performed at 3 sites. Mean patient age was 73 ± 14 yrs. Seventy-four pacemakers and 31 ICDs
with 206 leads were scanned. Pacemaker dependence was noted in 21% (22/105). MRI duration
was 38 ± 19 min and was performed an average of 3.0 ± 1.7 yrs after device implant. Pacer
dependence was noted in 21% (22/105). There were no deaths, device failures, generator/lead
replacements, induced arrhythmias, losses of capture, or electrical reset. One episode of selfterminating atrial fibrillation was noted. A decrease in battery voltage of ≥0.04 V occurred in 2%of
devices, a pacing lead impedance change of ≥50 Ω in 3%, and a high voltage impedance change
of ≥3 Ω in 10%. A decrease in pacing threshold P and R wave amplitude occurred in 0% and 2%,
respectively. A pacing threshold increase of ≥ 0.5V at 0.4ms occurred in 1% (2/185) of leads.
Twelve percent of MRI studies resulted in at least one parameter change.
Conclusions: Preliminary results of the MagnaSafe Registry demonstrate no deaths, device
failures, generator/lead replacements, induced arrhythmias, losses of capture, or electrical reset
episode, and a low rate of clinically relevant device parameter changes after clinically-indicated
non-thoracic MRI at 1.5 Tesla.