Viewpoint: Cardiac implantable electronic devices and magnetic resonance compatibility: was it really necessary?

Abstract

In 2005, Irnich et al. reported in Europace [1] the occurrence of six pacemaker patient deaths during magnetic resonance imaging (MRI). These deaths were identified from files in German institutional medicolegal offices in various cities; it was believed that the deaths were not previously published, and thereby should be considered additional to deaths already known to the medical community at that time [1]. Specifically, the authors found that the deaths had occurred under a variety of MRI circumstances, i.e., four different MRI manufacturers, 0.5–1.5 Tesla (T) with half the deaths occurring in low induction (0.5 T) machines. It was notable that all had sinus node dysfunction as an indication for pacing (pacemakers from four different manufacturers), but none was pacemaker-dependent [1]. ECG monitoring was not performed in any patient but ventricular fibrillation was given as the cause of death in three and suspected in two others. The remaining cause of death was not assigned. The authors provided little background information in the way of clinical data regarding the patients or their care. Although medical device manufacturers were aware of health risks before this time [2–4], the communication by Irnich et al. seems to have been the report that triggered manufacturers, led byMedtronic Inc. (Minneapolis, MN, USA), to initiate steps to modify hardware and software in their cardiac implantable electronic devices (CIEDs) and leads, and thereby make them as safe as possible during MRI. By 2011, after considerable research, development, and great expenditure, Medtronic completed a randomized controlled clinical trial of a new pacemaker and leads designed and built to minimize adverse MRI effects [5]. The trial included 464 patients with the new devices trademarked EnRhythm MRI SureScanTM and CapSureFix MR 5086TM leads. The patients were divided into a group of 258 who were scanned, using 1.5 T, and 206 who were not scanned. All underwent the same measurements chosen to assess potential MRI effects. No significant differences were found in terms of pacing parameters at implant, immediately before and after scanning (or no scanning) up to 4 months, and also there were no differences in complications over these four follow-up months. Other manufacturers were obliged to follow Medtronic’s lead. Approval by the US Food and Drug Administration (FDA) ensued for restricted use of MRI with these devices. Subsequently, Medtronic’s new pacemaker lead, model 5086, proved very stiff in clinical use and there were several reported cardiac perforations with some occurring several weeks after implant [6]. These adverse events prompted Medtronic to submit a previous lead design, model 5076 [7], without the re-engineering embodied in the 5086 MR conditional lead, and ultimately this “legacy” lead received MRconditional labeling. Approximately concurrently, Biotronik (Berlin, Germany) submitted their currently available and unmodified devices for FDA MR-conditional approval which was received, albeit with more restrictions than for Medtronic’s devices. The main difference was the area of the body which was permitted to be scanned. For Biotronik, the thorax had to be avoided. Gradually, all major manufacturers received FDA approval for MR-conditional labeling of implanted devices and leads with varying restrictions. Some, such as St. Jude Medical (now Abbott Labs, Chicago, IL) had gone to considerable engineering lengths to modify their devices and others had made no changes. However, MR imaging of device patients was not immediately accepted by radiologists. The latter was, especially the case in the United States (US) at least, partially due to the lack of * Richard Sutton [email protected]