Magnetic Resonance Imaging in patients with ICDs and Pacemakers

Prashant Nair, Ariel Roguin,                                                      199

“Magnetic Resonance Imaging in patients with ICDs and Pacemakers”

Table 1: Potential effects of MR imaging on pacemaker and ICD systems

1. Static Magnetic Field
Mechanical forces on ferromagnetic components
Unpredictable magnetic sensor activation, Reed-switch closure
Changes in electrocardiograms

2. Modulated Radio Frequency (RF) Field

Heating of cardiac tissue adjacent to lead electrodes

Possible induction of life-threatening arrhythmias

Pacemaker reprogramming or reset

RF interactions with the device (over- and under-sensing)

3. Gradient Magnetic Field
Possible induction of life-threatening arrhythmias
Induced voltages on leads cause over- and under-sensing

4. Combined Field Effects
Alteration of device function due to EMI
Mechanical forces (vibration)
Electronic reset of device

Supporting the current practice comes from several reported lethal consequences of MR
imaging in patients with implanted pacemakers¹³¹⁵. During the late 1980s incidentally 10 deaths
have been attributed to MR procedures in patients with pacemakers. However these fatalities
were poorly characterized and no electrocardiographic data were available. Most importantly no
deaths have been reported during physician supervised MR procedures in the last decade.

Despite the above-mentioned concerns, the effects of MR on cardiac pacemakers remain
controversial. Most of the previous studies that prohibit MR in pacemaker patients were based on
in vitro and animal model data in the 1980’s using older pacemaker and lead technology. During
the last decade, anecdotal reports describe a small series¹⁶-²¹ of pacemaker patients who have
safely undergone magnetic resonance scanning (Table 2). Advance in device technology drove
extensive and seminal in-vitro and animal studies of the pacemaker and ICD systems interaction
with the MR, and in recent years, several groups scanned safely larger number of patients.

Table 2: Published reports describing the non-lethal consequences of magnetic resonance
imaging n pacemaker patients (n=number of patients studied; n.a.=data not available;
PM=pacemaker;T=Tesla)

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

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