DOI: 10.1148/rg.245045137
RadioGraphics 2004;24:1267-1268
Invited Commentary • Author's Response
Robert M. Steiner, MD
Department of Radiology, University of Pennsylvania Health Sciences Center, Philadelphia, Pennsylvania
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Introduction
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The preceding article is an important position paper about a problem that has plagued the imaging community since the earliest days of clinical nuclear MR: the apparent incompatibility of implanted pacemakers and MR imaging (1–4). Investigators recognized early on that the radiofrequency signal generated by MR might produce rapid and asynchronous pacing and inhibit the internal switching mechanism of the implanted pacemaker, raising serious concern about patient safety and medical liability (4).
Since that time, the presence of a pacemaker has been regarded as an absolute contraindication to both thoracic and peripheral MR imaging. This incompatibility issue is far from trivial, as there are approximately 2.4 million patients with implanted cardiac pacemakers in the United States and similar numbers in Europe who are denied access to the benefits of MR. In their well-researched review of the available literature, Loewy et al categorize the various proved and theoretical effects of MR-generated electromagnetic interference (EMI) and challenge the concerns about patient safety and pacemaker malfunction described in the medical literature.
According to the authors, changes in pacemaker technology during the past decade including a significant decrease in ferromagnetic content of the pacemaker housing and other components, as well as improved circuitry sophistication and communication between the pacemaker and extracorporeal monitoring devices, have ameliorated many of the concerns about MR incompatibility (5,6).
As part of their review, the authors compiled the data of several hundred individuals from several clinical series who had demand pacemakers in place and who were studied with MR imaging under controlled conditions in which few adverse effects were discovered. It was also interesting that in a recent survey of both radiologists and cardiologists, 97% of the radiologists but only 66% of the cardiologists responded that MR imaging should not be performed in patients with pacemakers under any circumstance (7).
The authors speculate, quite correctly, that the cardiologists have less fear about the ability of the pacemakers and the patients to "handle" minor changes in function related to EMI and the radiologists have a better understanding of the secondary effects of MR. The recent mechanical innovations in pacemaker technology and mode of operation and the details of serial patient trials emanating from the Oklahoma Heart Institute and a study performed in Bonn, Germany, are described in some detail (8,9).
Other effects of EMI including heat deposition, artifacts, battery life, programming options, and the complications of rhythm disturbances attributed to MR are also discussed in a point-counterpoint fashion. The authors summarize their message effectively in three tables. These tables present theoretical concerns related to the pacemaker in the MR environment, a compendium of previously published studies and case reports from 1989 to 2003, and, most useful, a proposed protocol for the study of demand pacemakers with MR imaging. Their final and probably overly conservative recommendation is that it is feasible at this time to perform MR imaging in patients with peripheral indications but to continue to avoid MR imaging for thoracic indications.
The authors are to be congratulated for tackling a concept that has been mythologized for the last several decades and set new and broader parameters, which should permit many if not most patients currently denied access to MR imaging to undergo at least extrathoracic MR imaging.
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Financial Interest:
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The author has no financial relationships to disclose.
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References
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- Pavlicek W, Geisinger M, Castle L. The effect of nuclear magnetic resonance on patients with cardiac pacemakers. Radiology 1983; 147:149-153.[Abstract/Free Full Text]
- Steiner RM, Tegtmeyer CJ, Morse D, et al. The radiology of cardiac pacemakers. RadioGraphics 1986; 6:373-399.[Abstract]
- Erlebacher JA, Cahill PT, Pannizzo F, Knowles RJ. Effect of magnetic resonance imaging on DDD pacemakers. Am J Cardiol 1986; 57:437-440.[CrossRef][Medline]
- Hayes DL, Holmes DR, Gray JE. Effect of 1.5 tesla nuclear magnetic resonance scanner on implanted cardiac pacemakers. J Am Coll Cardiol 1987; 10:782-786.[Abstract]
- Shan PM, Ellenbogen KA. Life after pacemaker implantation: management of common problems and environmental interactions. Cardiol Rev 2001; 9:193-201.[CrossRef][Medline]
- Duru F, Lueching R, Sceidegger MB, et al. Pacing in the magnetic resonance imaging environment: clinical and technical considerations on compatibility. Eur Heart J 2001; 22:113-124.[Free Full Text]
- Gimbel JR, Lorig RJ, Wilkoff BL. Survey of magnetic resonance imaging in pacemaker patients. Heartweb [periodical online]. Available at: http://www.heartweb.org. Accessed May 1 2001.
- Martin ET, Coman JA, Shellock FG, Pulling CC, Fair R, Jenkins K. Magnetic resonance imaging and cardiac pacemaker safety at 1.5-Tesla. J Am Coll Cardiol 2004; 43:1315-1324.[Abstract/Free Full Text]
- Vahlhaus C, Sommer T, Lewalter T, et al. Interference with cardiac pacemakers by magnetic resonance imaging: are there reversible changes at 0.5 Tesla? Pacing Clin Electrophysiol 2001; 24:489-495.[CrossRef][Medline]
Author’s Response
John Loewy, MD
Department of Medical Imaging, Humber River Regional Hospital, Toronto, Ontario, Canada
Dr Steiner has rightly pointed out that we have offered a very conservative conclusion. We have done this to stay within the bounds of the majority of the cases currently available in documented clinical trials. The case numbers for MR imaging within the chest and abdomen are still small but point in the same direction.
It is our hypothesis that the largest source of data on pacemaker patients and MR imaging lies in the number of patients with pacemakers who have been inadvertently imaged. These tend to be isolated incidents and thus tend not to be reported. There may also be sites that have studied pacemaker patients along similar lines to those suggested in our protocol, but the numbers are low. We invite colleagues in these situations to contribute to a communal Web site. The site www.pacemaker.ca has been developed as a public service to the profession to ease data collection. In addition, anyone who submits a case gains access to all the data files and thus can continue to evolve their own approach. The data are shared property and participants are free to publish and interpret the data as they see fit, in the language of their choice (1).
We hope that a continued conversation on this topic will allow a more rational approach and individually tailored MR imaging studies in any region of the body for the millions of pacemaker patients in the world.
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References
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- Loewy J, Loewy A. MUMNETR: a possible new research model, and an invitation to join a demonstration project. Proceedings of the 23rd International Congress of Radiology. Bethesda, Md: International Society of Radiology, 2004; 104.
Related Article
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Reconsideration of Pacemakers and MR Imaging
- John Loewy, Amanda Loewy, and Edward J. Kendall
RadioGraphics 2004 24: 1257-1267.
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