Magnetic Resonance Imaging in patients with ICDs and Pacemakers

Prashant Nair, Ariel Roguin,                                                      198

“Magnetic Resonance Imaging in patients with ICDs and Pacemakers”

The Growing Problem

Parallel to the growth and evolution of the MR field, is the burgeoning number of patients
benefiting from implantable cardiac systems including pacemakers and implantable cardioverter-
defibrillatos (ICDs) (Figure1). With new indications for heart failure, innovative device features
and expanded medical coverage; this trend is likely to continue its trajectory. The combination of
these two growing phenomena results in an estimated 50-75% probability of a patient being
indicated for an MR study over the lifetime of their device creating an estimated 200,000 device
patients who were denied the MR scan and more in the future^7,8.

Figure 1: Number of annual MR scans and of newly implanted ICDs in the USA.

Given the rapid expansion of technology in the fields of both MR imaging and device
arrhythmia management, there is increasing interest in the issue of implantable device safety in
the MR environment. Currently no implantable cardiac device has Food and Drug Agency (FDA)
approval for use in the MR environment and “Do not use magnetic resonance imaging on
patients who have an implanted device” appears on product labels⁸. The current state of affairs
significantly limits the performance of MR imaging on device patients. With a better
understanding of the hazards of performing MR scans on device patients as well as the
development of MR safe devices, we may soon enter an era where the ability of this imaging
modality may be more widely used to assist in the appropriate diagnosis of patients with devices.
Not only for heart imaging but mainly for brain, spine, and joints as knees and shoulder^1,7.

Hazards and Safety concerns

Permanent cardiac pacemakers have represented a contraindication to MR imaging.
Strong static, gradient and radiofrequency fields used for MR image creation are thought to be
detrimental to pacemaker function and cause harm to patients undergoing MR examinations. The
multiple potential adverse interactions between pacemakers and MR imaging^1,2,9-12 (Table 1)
include heating, rapid atrial pacing, pacing at multiples of the RF pulse and associated rapid
ventricular pacing, reed switch malfunction, asynchronous pacing, inhibition of pacing output,
alteration of programming with potential damage to the pacemaker circuitry or movement of the
device and the potential thermal injury at the lead tip.

Indian Pacing and Electrophysiology Journal (ISSN 0972-6292), 5(3): 197-209 (2005)

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