MRI Risks in Patients With a Pacemaker or Defibrillator

Study Questions:

What are the risks associated with magnetic resonance imaging (MRI) in patients with non–MRI-conditional pacemakers and defibrillators?

Methods:

This was a multicenter registry of patients who needed nonthoracic MRI at a field strength of 1.5 tesla and who had pacemakers or implantable cardioverter–defibrillators (ICDs) that had not been approved by the Food and Drug Administration (FDA) for MRI scanning. The primary endpoints were death, generator or lead failure, induced arrhythmia, loss of capture, or electrical reset during the scanning. The secondary endpoints were changes in device settings.

Results:

MRI was performed in 1,000 cases in which patients had a pacemaker and in 500 cases in which patients had an ICD. No deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI. One ICD generator could not be interrogated after MRI and required immediate replacement; the device had not been appropriately programmed per protocol before the MRI. There were six cases of self-terminating atrial fibrillation or flutter and six cases of partial electrical reset. Changes in lead impedance, pacing threshold, battery voltage, and P-wave and R-wave amplitude exceeded prespecified thresholds in a small number of cases. Repeat MRI was not associated with an increase in adverse events.

Conclusions:

Device or lead failure did not occur in any patient with a non–MRI-conditional pacemaker or ICD who underwent nonthoracic MRI at 1.5 tesla.

Perspective:

While MRI used to be an absolute contraindication in patients with pacemakers and ICDs, there has been a growing body of evidence reporting safe use of MRI even in patients whose devices are not approved by the FDA as MRI-conditional. This multicenter experience adds to our knowledge of the small complication risk among patients who are appropriately screened and had the device reprogrammed in accordance with the prespecified protocol. This risk should be weighed against the potential benefit of MRI. Of note is the fact that this particular study excluded patients undergoing thoracic imaging. All major manufacturers have introduced or are in the process of introducing pacemakers and ICDs, but a significant number of patients will continue to have devices predating the MRI conditionality approvals, highlighting the need for studies like this one.


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