European Heart Journal Advance Access originally published online on May 4, 2005
European Heart Journal 2005 26(12):1243; doi:10.1093/eurheartj/ehi298
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Heating of pacemaker leads during magnetic resonance imaging
Department of Cardiology
Hospital of the University of Münster
Germany
E-mail address: vahlhaus{at}uni-muenster.de
Is MRI contraindicated in PM-patients? In their carefully performed study, Luechinger et al.1 convincingly show the possible heating of pacemaker leads by measuring heating at the lead tip together with the pacing parameters. Heating, comparable with in vitro data, occurred in the presence of blood flow. Therefore, protection by the cooling effect of myocardial blood flow in any in vivo or clinical setting is small and must no longer be overestimated.
They speculate about the clinical significance and state that there is a lack of follow-up data with respect to significant threshold changes. Our follow-up data showed that battery current and impedance only tended to increase. The calculated rest of function time did not change nor was any significant threshold alteration with the need to modify programmed data observed.2
The heating problem may be even more pronounced in the clinical setting. The chest anatomy of swine, even if weighing 60–65 kg, does not resemble that in humans. The difference in radius of the semicircle lead configuration in the coronal plane may lead to heating effects of greater extent in humans. Heating is considered to be especially problematic when objects are configured in a loop or coil, as conducting loops are known to provide a high current density in low impedance, metallic, conductive materials.3
It is up to the reader to decide whether it is beside the point to present an editorial comment in an animal study paper that could be understood as a recommendation for clinicians planning to perform MRI scans in pacemaker patients. In a clinical setting, our recommendation is different. If the referring physician, the radiologist, and the cardiologist agree that MRI is an urgent diagnostic necessity without an acceptable imaging alternative in a patient with cardiac pacemaker, certain requirements have to be met. Written informed consent of the patient is needed. To reduce the risk of thermal injury during MRI, RF-exposure and sequence time have to be minimized. Like monitoring of systemic haemodynamics and cardiac rhythm with MRI compatible devices, cardiological standby for online analysis of cardiac rhythm and standby for immediate cardiopulmonary resuscitation belong to the minimal precautions. A complete pacemaker check including interrogation, evaluation of intrinsic rhythm, sensing thresholds, stimulation thresholds, lead impedance, and battery voltage is mandatory before and immediately after MRI. Additional assessments, i.e. 4 weeks following MRI, are recommended.
References
- Luechinger R, Zeijlemaker VA, Pedersen EM, Mortensen P, Falk E, Duru F, Candinas R, Boesiger P. In vivo heating of pacemaker leads during magnetic resonance imaging. Eur Heart J 2005;26:376–383.
[Abstract/Free Full Text] - Vahlhaus C, Sommer T, Lewalter T, Schimpf R, Schumacher B, Jung W, Luderitz B. Interference with cardiac pacemakers by magnetic resonance imaging: are there irreversible changes at 0.5 Tesla? Pacing Clin Electrophysiol 2001;24:489–495.[CrossRef][Medline]
- Lemieux L, Allen PJ, Franconi F, Symms MR, Fish DR. Recording of EEG during fMRI experiments: patient safety. Magn Reson Med 1997;38:943–952.[Web of Science][Medline]
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