No cardiac events in patients with pacemakers or ICDs who underwent MRI: The MagnaSafe registry

1. This prospective cohort study of patients with cardiac pacemakers or implantable cardioverter-defibrillators (ICDs) undergoing magnetic resonance imaging (MRI) demonstrated no deaths, episodes of lead failure requiring immediate replacement, or loss of capture.

2. No adverse events were reported with repeated MRI scans.

Evidence Rating Level: 2 (Good)       

Study Rundown: There are safety concerns when it comes to acquiring MRI images for patients who have implanted cardiac devices such as a cardiac pacemakers and ICDs. Therefore, such patients are excluded from undergoing MRI scanning. The MagnaSafe Registry attempted to determine the risks associated with MRI at a magnetic strength of 1.5T for patients with either a pacemaker or an ICD that was not designed to reduce the risks associated with MRI, otherwise referred to as “non-MRI-conditional” devices. The participants had to have an indication for a nonthoracic MRI for a field strength of 1.5T. The devices were interrogated before and after MRI.

The 1500 patients included in the study experienced no deaths, episodes of lead failures requiring immediate replacement, or loss of capture during MRI examination. However, a small number of cases revealed changes in pacing threshold, lead impedance, battery voltage, and R-wave and P-wave amplitude that exceeded the prespecified thresholds. While the findings suggest that MRI is safe for patients with “non-MRI-conditional devices, the prospective cohort design of the study and the fact that it included generators and leads from various manufacturers limits the strength of its conclusions and the generalizability of these results to the broader population.

Click to read the study, published today in NEJM

Relevant Reading: Effects of external electrical and magnetic fields on pacemakers and defibrillators: from engineering principles to clinical practice.

In-Depth [prospective cohort]: This prospective, multicenter study included 1000 patients with pacemakers and 500 patients with ICDs. The primary end points were death, induced arrhythmia, loss of capture, generator or lead failure, or electrical reset during the scanning. The secondary end points were changes in device settings.

Brain and spine MRI examinations were performed on 75% of the included patients, with patients spending a mean time of 44 minutes in the magnetic field. There were no deaths, lead failure requiring immediate replacement, or observed ventricular arrhythmias during MRI examination. There were a total of 6 observed atrial arrhythmias, with 5 such events seen in the pacemaker category (0.5%, 95%CI 0.2-1.2%) and 1 in the ICD category (0.2%, 95%CI 0.04-1.1%). A reduction of 50% or more in P-wave amplitude was identified in 0.9% of pacemaker leads and in 0.3% of ICD leads. A reduction of 25% or more in R-wave amplitude was found in 3.9% of pacemaker leads and in 1.6% of ICD leads, while a reduction of 50% or more in R-wave amplitude was found in no pacemaker leads and in 0.2% of ICD leads. There was no increase in adverse events with repeat MRI in this patient sample.

Image: PD

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