Can Patients With Implanted Pacemakers/ICD Undergo Magnetic Resonance Imaging?

Can Patients With Implanted Pacemakers/ICD Undergo Magnetic Resonance Imaging?

S. S

, M. M

, M. M

, G. P

Introduction

Magnetic resonance imaging (MRI) is a rapidly expanding diagnostic tool used in a wide range of clinical applications, such as oncology, musculoskele- tal disorders, and pathologies of the central nervous and cardiovascular sys- tems. About 35 million MRI studies are performed yearly worldwide [1]. In addition, the use of innovative cardiac-device-based therapies, including pacemakers and ICDs, with new indications for primary prevention of sud- den cardiac death and heart failure, is also rapidly increasing, resulting in an estimated 50–75% probability of a patient being indicated for an MRI over the lifetime of their device. In the USA, about 200 000 device recipients could have benefited from MRI in 2004 [2]. However, current pacemakers and ICDs and their connected leads have not been designed to be MRI safe.

Moreover, there is a great difference among MRI scanners and devices, some of which may be state-of-the-art but connected to old leads when newer pacemakers or ICDs are replaced. Although the problem persists, MRI manu- facturers’ are working with the Food and Drug Administration (FDA) in the USA to modify the situation [3–7]. Nonetheless, current labelling for pace- makers and defibrillators systems includes a warning against MRI proce- dures for patients with such devices.

Background

The use of MRI in clinical practice has been gaining in popularity since the early 1980s. At that time, there was concern that any implanted metal object

Department of Cardiovascular Diseases, Operative Unit of Cardiology, Infermi Hospital,

AUSL Rimini, Rimini, Italy

might be pulled out of the body or damaged by the very strong magnetic field generated by MRI. However, both pacemakers and ICDs utilise nonfer- rous metals, and there are no reports of devices being ripped out the body [8]. In contrast, animal studies, in vitro and in vivo, and anecdotal reports on humans have revealed several potential problems affecting the implanted system when exposed to the magnetic fields generated by MRI.

Potential Risks

Several studies have addressed the potential risks of using MRI in patients with pacemakers and ICDs. First, the magnetic field was shown to potentially induce a current in the lead, causing rapid cardiac stimulation [7]; however, since the applied currents are mostly subthreshold they are without clinical consequences [9]. Second, the reed switch in a pacemaker or ICD does not necessarily remain closed in response to strong magnetic fields (0.5, 1.5, 3.0 Tesla), and the state of the reed switch may not be predictable with certainty under clinical conditions [8, 10]. Third, magnetic fields inhibit or trigger pacemakers, resulting in patients having their ICD disabled during MRI or in false detection of tachyarrhythmias, leading to inappropriate ICD interven- tion [11]. Arrhythmogenic risks depend on scan parameters, patient, device position [12–14], and the design of the device, i.e. modern devices are less prone to the effects of MRI because of better built-in electromagnetic inter- ference (EMI) protection circuitry [6, 15, 16]. Finally, MRI may produce con- siderable heading at the tip of the lead and changes of pacing parameters in long-term experiments [17–19].

Comments

When there is a strongly appropriate clinical justification for an MRI study in a patient with a pacemaker or an ICD, general medical opinion is that many possible risks can be avoided or managed by an expert clinical team, appropriate device programming, and close monitoring of the patient both during the scan and after the study.

While the FDA recognises that MRI is a very powerful diagnostic tool that may be safe for application in pacemaker and ICD recipients, it will not remove the warnings and contraindications for this population until there is better knowledge of the mechanisms associated with the potential risks of complications.

MRI safety for device patients is important and will become increasingly

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relevant with time. The majority of manufacturers are actively involved in designing devices that do not interfere with a multiplicity of EMI generators, including MRI [4–6]. The goal is the development of a truly MRI-compatible device. In the meantime, one possible solution is to replace the pacemaker’s wire cable with a fibre-optic lead and to use an implantable low-power semi- conductor laser for sensing and regulating heartbeat [20].

References

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2. Kalin R, Stanton MS (2005) Current clinical issues for MRI scanning of pacemaker and defibrillator patients. PACE 28:326–328

3. Fisher JD (2005) MRI: safety in patients with pacemakers or defibrillators: is it prime time yet? PACE 28:263

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6. Levine PA (2005) Industry viewpoint: St. Jude Medical: pacemakers, ICDs and MRI.

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7. Hayes DL, Holmes DR, Gra JE (1987) Effect of 1.5 Tesla nuclear magnetic resonance imaging scanner on implanted permanent pacemakers. J Am Coll Cardiol 10:782–786

8. Garcia-Bolao I, Albaladejo V, Benito A et al (1998) Magnetic resonance imaging in patient with a dual chamber pacemaker. Acta Cardiol 53:33–35

9. Lauck G, Von Smekal A, Wolke S et al (1995) Effects of nuclear magnetic resonance imaging on cardiac pacemakers. PACE 18:1549–1555

10. Luechinger R, Zeijlemaker VA, Scheidegger MB et al (2002) Pacemaker reed switch behavior in 0.5, 1.5, and 3.0 Tesla magnetic resonance imaging units: are reed swit- ches always closed in strong magnetic fields? PACE 25:1419–1423

11. Gimbel JR, Kanal E, Schwartz KM et al (2005) Outcome of magnetic resonance imaging (MRI) in selected patients with implantable cardioverter defibrillators (ICDs). PACE 28:270–273

12. Rozner MA, Burton AW, Kumar A (2005) Pacemaker complications during magne- tic resonance imaging. J Am Coll Cardiol 45:161–162

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14. Faris OP, Shein MJ (2005) Government viewpoint: U.S. Food & Drug Administration: pacemakers, ICDs, and MRI. PACE 28:268–269

15. Loewy J, Loewy A, Kendall EJ (2004) Reconsideration of pacemakers and MR ima- ging. Radiographics 24:1257–1267

16. Del Ojo JL, Moya F, Villalba J et al (2005) Is magnetic resonance imaging safe in cardiac pacemaker recipients? Pacing Clin Electrophysiol 28(4):274–278

17. Sommer T, Vahlhaus C, Lauck G et al (2000) MR imaging anf cardiac pacemakers:

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Can Patients With Implanted Pacemakers/ICD Undergo Magnetic Resonance Imaging?

18. Martin ET, Coman JA, Shellock FG et al (2004) Magnetic resonance imaging and cardiac pacemaker safety at 1.5 Tesla. J Am Coll Cardiol 43:1315–1324

19. Luechinger R, Zeijlemaker VA, Pedersen EM et al (2005) In vivo heating of pace- maker leads during magnetic resonance imaging. Eur Heart J 26:376–383

20. High Tech Rochester. Inventor of MRI to work with pacemaker inventor on MRI- compatible pacemaker. Available at http://www.htr.org

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