European Heart Journal Advance Access originally published online on May 4, 2005
European Heart Journal 2005 26(12):1243-1244; doi:10.1093/eurheartj/ehi299
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Heating of pacemaker leads during magnetic resonance imaging: reply
Institute for Biomedical Engineering University and ETH Zurich
Gloriastrasse 35
CH 8092 Zurich
Switzerland
Tel: +41 44 255 30 64
Fax: +41 44 255 45 06
E-mail address: luechinger{at}biomed.ee.ethz.ch
Bakken Research Center
Medtronic, Inc.
Maastricht, The Netherlands
Division of Cardiology
University Hospital of Zurich
Zurich, Switzerland
Institute for Biomedical Engineering University and ETH Zurich
Zurich, Switzerland
We appreciate Dr Vahlhaus' interest in our paper.1 We agree that heating at the lead tip–myocardium interface may not significantly decrease due to the cooling effect. However, this is only valid for the chronically implanted leads. In the acute setting, scar formation is not prominent and the cooling effects may be more pronounced. In addition, in our study, we did not intend to make a direct comparison between the in vitro and in vivo settings, as lead configurations and positions were not identical.
We absolutely agree with Dr Vahlhaus' comments concerning the anatomical differences between pigs and humans, as mentioned in our study limitations. However, the pig model is much more representative of the human anatomy, when compared with canines with a smaller torso, as used in the recently published paper by Roguin et al.2 In our study, the pacemaker leads were implemented with loops comparable with those seen in the humans. Therefore, we do not expect any systematic underestimation of the heating problem. Nevertheless, we agree that special lead configurations may result in higher heating effects. In addition, other positions in the bore may result in higher temperatures as shown in Figure 2 in our paper.
Our paper does not serve the purpose of an overall recommendation for safe MRI procedures in pacemaker recipients, but to show the realistic temperature excursion in vivo to allow interpretation by physiologic accepted temperature limits used by safety requirements. We fully agree with Dr Vahlhaus that this study and the editorial should not be interpreted as a recommendation for clinicians to perform MRI in pacemaker patients. The diagnostic need for an MRI has to be evaluated individually for each patient, and if there is an urgent necessity and in the absence of an alternative imaging modality, MRI may be considered with the precautions and follow-up measures as recommended by Dr Vahlhaus, in accordance with our paper.
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] - Roguin A, Zviman MM, Meininger GR, Rodrigues ER, Dickfeld TM, Bluemke DA, Lardo A, Berger RD, Calkins H, Halperin HR. Modern pacemaker and implantable cardioverter/defibrillator systems can be magnetic resonance imaging safe: in vitro and in vivo assessment of safety and function at 1.5 T. Circulation 2004;110:475–482.
[Abstract/Free Full Text]
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