M R I fo r P a t i e n t s w i t h Ca rd i a c I m p l a n t a b l e El e c t r i c a l D e v i c e s Grant V. Chow, MDa, Saman Nazarian, MD, PhDa,b,* KEYWORDS  MRI  Pacemaker  Defibrillator  Cardiac implantable electrical device

KEY POINTS

INTRODUCTION

KNOWN RISKS ASSOCIATED WITH MRI

The use of MRI for the diagnosis of soft tissue and bony abnormalities is increasing as scanners have become more available throughout the United States. MR scans yield higher spatial resolution than CT images, without the need for ionizing radiation or iodinated contrast injection.1 At present, approximately 2 million Americans have CIEDs,2 and an estimated 50% to 75% of these individuals will have an indication for MRI during the lifetime of their device.3,4 The body of evidence reporting successful use of MRI in patients with CIEDs is growing.5–8 This article reviews the risks and recent literature on the use of MRI in patients with CIEDs and reports the Johns Hopkins safety protocol.

Current guidelines from the American Heart Association discourage MRI scanning in non– pacemaker-dependent patients, except in cases of a strong clinical indication (highly compelling) where benefits clearly outweigh the risks and an alternative diagnostic modality is unavailable.4 There are 3 major sources of risk associated with MRI with regard to implantable devices. First, CIED components are subject to potential magnetic field–induced force and torque that might result in system dislodgement or internal reed switch activation (in older devices), the latter of which could permanently disable tachycardia therapies or result in asynchronous pacing.9,10 Second, electrical current may be induced by the

Disclosures and Financial Support: Dr S. Nazarian is a scientific advisor to and principal investigator for research support to Johns Hopkins from Biosense Webster Inc. Dr S. Nazarian is also funded by NIH grants K23HL089333 and R01HL116280. a Section for Cardiac Electrophysiology, Department of Medicine, Johns Hopkins University School of Medicine, Carnegie 592A, 600 North Wolfe Street, Baltimore, MD 21287, USA; b Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA * Corresponding author. Carnegie 592A, 600 North Wolfe Street, Baltimore, MD 21287. E-mail address: [email protected] Cardiol Clin 32 (2014) 299–304 http://dx.doi.org/10.1016/j.ccl.2013.12.002 0733-8651/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.

cardiology.theclinics.com

 The clinical utility of MRI scans may outweigh the risk of performing the study in patients with a cardiac implantable electrical device (CIED).  MRI evaluations can be performed safely in patients with certain pacemaker and implantable cardioverter-defibrillator (ICD) systems, using a protocol based on device selection, appropriate device reprogramming, and close monitoring during the scan.  MRI should only be performed in cases where the potential benefit clearly outweighs the risks and with adequate subspecialty supervision and monitoring equipment.  A Food and Drug Administration (FDA)-approved, magnetic resonance (MR)-conditional pacemaker system is now available for use in the United States, with all major device companies in the process of refining their technology.  MR-conditional systems is needed to ensure that complication rates remain reasonable in comparison with the benefit attained.

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Chow & Nazarian magnetic field and result in myocardial capture and, rarely, ventricular or atrial arrhythmia induction. Third, device leads can act as an antenna and amplify local energy deposition, resulting in lead heating, tissue damage, and resultant sensing or capture threshold changes.11,12 Radiofrequency noise may also result in inappropriate inhibition of demand pacing, tachycardia therapies, or programming changes. Early use of MRI in patients with CIEDs resulted in suboptimal outcomes or even death in a small number of patients13; therefore, several institutions initiated MRI protocols to evaluate the safety of this imaging modality for strong clinical indications.

THE HOPKINS PROTOCOL The authors’ institution initiated a protocol for both noncardiac and cardiac MRI more than 10 years ago in patients with either permanent pacemakers or ICDs.10 Since its inception, the authors’ program has successfully performed more than 1500 MRI examinations under an institutional review board–approved research protocol (Fig. 1).2 Imaging at the authors’ institution was performed using 1.5-T scanners. Patients with newly implanted (

MRI for patients with cardiac implantable electrical devices.

MRI has become an invaluable tool in the evaluation of soft tissue and bony abnormalities. The presence of a cardiac implantable electrical device (CI...
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