CORRESPONDENCE: LETTER TO THE EDITOR
Magnetic Resonance Imaging in Patients With Cardiac Pacemakers
Torsten Sommer, MD*,
Claas Philip Naehle, MD and
Hans Schild, MD
* Department of Radiology, University of Bonn, D-53127 Bonn, Germany (Email: t.sommer{at}uni-bonn.de).
We read with great interest the study "Magnetic Resonance Imaging and Cardiac Pacemaker Safety at 1.5-Tesla" by Martin et al. (1). We agree that with the opinion that pacemakers represent an absolute contraindication to magnetic resonance imaging (MRI) should be reevaluated and that MRI in patients with implanted pacemakers can be performed safely in carefully selected circumstances when appropriate imaging strategies are used.
However, the statement that "pacemakers automatically enter the asynchronous mode when in the presence of a powerful static magnetic field" is false and leads to an underestimation of the MRI-related risks in pacemaker patients. Our experimental and clinical data and recent studies have shown that the reed switch remains open in up to 50% of all orientations of the pacemaker device even in the strong static magnetic field of a 1.5-t magnetic resonance system (2,3). This may have important clinical implications, because if the reed switch is open potentially harmful false inhibition or false triggering of the pacemaker by the pulsed electromagnetic magnetic resonance fields may occur. Complete inhibition of pacemaker output in pacemaker-dependent patients and/or false triggering with tracking to the upper rate limit in patients with reduced left ventricular function may be detrimental.
Therefore, we cannot support the approach of Martin and co-workers—that is, to leave the pacemaker sensing function activated. In contrast, we recommend deactivating the sensing function in pacemaker-dependent patients by programming the pacemaker device to an asynchronous mode, to ensure continuous pacing, and to program the pacemaker device to a sensing-only mode (0X0) or subthreshold pacing in nonpacemaker-dependent patients to avoid MRI-related triggering.
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References
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1. Martin ET, Coman JA, Shellock FG, et al. Magnetic resonance imaging and cardiac pacemaker safety at 1.5-tesla J Am Coll Cardiol 2004;43:1315-1324.[Abstract/Free Full Text]
2. Luechinger R, Duru F, Zeijlemaker VA, et al. Pacemaker reed switch behavior in 0.5, 1.5, and 3.0 tesla magnetic resonance imaging unitsare reed switches always closed in strong magnetic fields?. Pacing Clin Electrophysiol 2002;25:1419-1423.[CrossRef][Medline]
3. Sommer T, Vahlhaus C, Lauck G, et al. Magnetic resonance imaging and cardiac pacemakersin vitro-evaluation and in vivo-studies in 51 patients at 0.5 T. Radiology 2000;215:869-879.[Abstract/Free Full Text]
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