Real World MRI Experience With Nonconditional and Conditional Cardiac Rhythm Devices After Magnasafe

Steve Mason PA-C; Jeffrey S. Osborn MD; Ritesh Dhar MD; Allison Tonkin MD; Jon-David Ethington PA-C; Viet LeMPAS, PA-C; Jose Benuzillo PhD, MStat; Donald L. Lappe MD; Kirk U. Knowlton MD; T. Jared Bunch MD; Jeffrey L. Anderson MD

Disclosures

J Cardiovasc Electrophysiol. 2017;28(12):1468-1474. 

In This Article

Abstract and Introduction

Abstract

Introduction The recent MagnaSafe Registry demonstrated safety of nonthoracic magnetic resonance imaging (MRI) with nonconditional cardiac implantable electronic devices (CIEDs). However, independent validation and extension to thoracic MRIs are needed.

Methods and results We prospectively examined 178 consecutive patients with CIEDs who underwent 212 MRI scans (62 with implantable cardioverter/defibrillators) for clinical reasons between February 2014 and August 2016. Scans were done in standard modes with a limit of 2 W/kg. Pacing modes were ODO or OVO for intrinsic rates > 40 and DOO or VOO for rates ≤ 40. Patients were cleared prescan by both radiology and cardiology, and pre- and postscan CIED interrogations were performed. Primary outcome events were death and generator or lead failure. Secondary events included battery voltage loss > 0.04 V, decrease in P wave voltage > 50% or R wave voltage > 25%, threshold increase of > 0.5 V, and impedance change > 50 Ω. Scan sites were 87 (41%) C-spine/head/neck, 28 (13%) T-spine/cardiac/shoulder (thoracic), 69 (33%) L-spine/abdomen/pelvis, and 28 (13%) lower extremity. No primary or secondary outcome events occurred, and no periscan disruption of pacing was noted.

Conclusion In a real-world MRI experience in patients with CIEDs representing a broad range of models, types, and scan sites (including thoracic scans), no adverse safety signals were noted. This experience validates and extends that of the large but inclusion-restricted MagnaSafe Registry, profiles MRI scanning in CIED patients in general clinical practice, and argues against replacing nonconditional with conditional devices when MRI is performed in a carefully controlled environment.

Introduction

Given safety concerns, MRI imaging in patients with cardiac electronic devices (CIEDs; i.e., pacemaker or implantable cardioverter defibrillator [ICD]) initially was absolutely contraindicated,[1] and it continues to be not recommended for most CIED patients.[2,3] For over a decade, our institution has permitted consideration of MRI in patients with nonconditional CIEDs (i.e., devices not FDA-approved under MRI-specified conditions). However, these scans have been performed only under a strict institutional investigational protocol, when other noninvasive imaging tests (e.g., CT, ultrasound) are unable to provide diagnostic test results, and when the results of the proposed MRI study could provide information that would importantly alter diagnostic assessment, management approach, or clinical outcome.

The safety concerns with MRI imaging in the presence of CIEDs derive from the known potential for strong magnetic fields to induce heating of cardiac leads resulting in local myocardial injury, pulsed and radiofrequency energy fields that may lead to under- or oversensing with potentially adverse effects on pacing performance, generator battery depletion or component dysfunction, and arrhythmia provocation.[4] In addition, older pacemaker generators, i.e., models before 2001,[5] were particularly prone to dysfunction of electrical switches and of battery depletion, with potentially catastrophic consequences, when exposed to strong dynamic magnetic fields.[5–9] When inadvertently imaged in unmonitored settings, pacemaker dysfunction and even deaths were documented in early case reports. In contrast, the feasibility of safely performing MRI scans under carefully monitored conditions with 21st century CIED devices has been reported in several small to moderate-sized series from single institutions.[5,6,8,10]

Since 2011, a new generation of CIED devices specifically designed and tested to reduce the risks associated with MRI (MRI-conditional CIEDs) has been introduced.[10,11] However, these FDA-approved devices are more expensive and structurally less ideal than modern standard, nonconditional CIEDs. Although early evidence of MRI-conditional lead performance has been favorable, long-term outcomes are unknown, and it is unclear whether these devices will perform at rates expected with traditional leads and generators. Given that over half of patients with CIEDs are predicted to have a subsequent indication for an MRI during their lifetime,[12] the choice of CIED type at implantation has become an important issue. Moreover, whether an upgrade to, i.e., replacement of, a nonconditional with an MRI-conditional device is warranted prior to undergoing a clinically necessitated MRI, is a critical and unanswered clinical question. Indeed, in the REPLACE Registry, a 15% complication rate was noted when leads plus generator replacement was involved.[13]

In the recent landmark MagnaSafe Registry,[14] MRI at 1.5 tesla was performed in 1,500 cases with nonconditional CIEDs (1,000 pacemakers, 500 ICDs). Device or lead failure did not occur in any patient. However, MagnaSafe excluded thoracic scans, and no parallel comparison with scans with MRI-conditional devices was included. In this manuscript, we describe our recent single-center, real-world experience with MRI unrestricted by site (i.e., including thoracic scanning) and device type (i.e., both MRI conditional and nonconditional) to provide additional safety and demographic information necessary to support unrestricted MRI scanning with CIEDs in general clinical practice.

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