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CLINICAL RESEARCH: CARDIAC IMAGING

Magnetic Resonance Imaging at 1.5-T in Patients With Implantable Cardioverter-Defibrillators

Claas P. Naehle, MD^_*,_*, Katharina Strach, MD^_*, Daniel Thomas, MD^_*, Carsten Meyer, MD^_*, Markus Linhart, MD, Sascha Bitaraf, MD, Harold Litt, MD, PhD, Jörg Otto Schwab, MD, Hans Schild, MD^_* and Torsten Sommer, MD^||

^_* Department of Radiology, University of Bonn, Bonn, Germany
Department of Cardiology, University of Bonn, Bonn, Germany
Department of Internal Medicine–Cardiology, Katholisches Klinikum Koblenz–Marienhof, Koblenz, Germany
Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
^|| Department of Radiology, German Red Cross Hospital, Neuwied, Germany

Manuscript received January 22, 2009; revised manuscript received March 9, 2009, accepted April 15, 2009.

^_* Reprint requests and correspondence: Dr. Claas P. Naehle, Department of Radiology, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany (Email: cp{at}naehle.net).

Objectives: Our aim was to establish and evaluate a strategy for safe performance of magnetic resonance imaging (MRI) at 1.5-T in patients with implantable cardioverter-defibrillators (ICDs).

Background: Expanding indications for ICD placement and MRI becoming the imaging modality of choice for many indications has created a growing demand for MRI in ICD patients, which is still considered an absolute contraindication.

Methods: Non–pacemaker-dependent ICD patients with a clinical need for MRI were included in the study. To minimize radiofrequency-related lead heating, the specific absorption rate was limited to 2 W/kg. ICDs were reprogrammed pre-MRI to avoid competitive pacing and potential pro-arrhythmia: 1) the lower rate limit was programmed as low as reasonably achievable; and 2) arrhythmia detection was programmed on, but therapy delivery was programmed off. Patients were monitored using electrocardiography and pulse oximetry. All ICDs were interrogated before and after the MRI examination and after 3 months, including measurement of pacing capture threshold, lead impedance, battery voltage, and serum troponin I.

Results: Eighteen ICD patients underwent a total of 18 MRI examinations at 1.5-T; all examinations were completed safely. All ICDs could be interrogated and reprogrammed normally post-MRI. No significant changes of pacing capture threshold, lead impedance, and serum troponin I were observed. Battery voltage decreased significantly from pre- to post-MRI. In 2 MRI examinations, oversensing of radiofrequency noise as ventricular fibrillation occurred. However, no attempt at therapy delivery was made.

Conclusions: MRI of non–pacemaker-dependent ICD patients can be performed with an acceptable risk/benefit ratio under controlled conditions by taking both MRI- and pacemaker-related precautions. (Implantable Cardioverter Defibrillators and Magnetic Resonance Imaging of the Heart at 1.5-Tesla; NCT00356239)

Key Words: magnetic resonance imaging • implantable cardioverter-defibrillator • safety

Abbreviations and Acronyms   ATP = antitachycardia pacing   DC = direct current   ICD = implantable cardioverter-defibrillator   MRI = magnetic resonance imaging   PM = pacemaker   RF = radiofrequency   SAR = specific absorption rate

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