Elsevier

Heart Rhythm

Volume 8, Issue 1, January 2011, Pages 65-73
Heart Rhythm

Clinical
Imaging/mapping
Magnetic resonance imaging in patients with a pacemaker system designed for the magnetic resonance environment

https://doi.org/10.1016/j.hrthm.2010.10.002Get rights and content

Background

Magnetic resonance imaging (MRI) of pacemaker patients is contraindicated due to documented potential risks to the patient from hazardous interactions between the MRI and pacemaker system.

Objective

The purpose of this prospective, randomized, controlled, worldwide clinical trial was to evaluate the safety and effectiveness of a pacemaker system designed for safe use in MRI for any bradycardia indicated patient.

Methods

Patients (n = 464) were randomized to undergo an MRI scan between 9 and 12 weeks postimplant (MRI group, n = 258) or not to undergo MRI (control group, n = 206) after successful implantation of the specially designed dual-chamber pacemaker and leads. Patients were monitored for arrhythmias, symptoms, and pacemaker system function during 14 nonclinically indicated relevant brain and lumbar MRI sequences. Sequences were performed at 1.5 T and included scans with high radiofrequency power deposition and/or high gradient dB/dt exposure. Clinical evaluation of the pacemaker system function occurred immediately before and after MRI, 1 week and 1 month post-MRI, and at corresponding times for the control group. Primary endpoints for safety analyzed the MRI procedure complication-free rate and for effectiveness compared capture and sensing performance between MRI and control groups.

Results

No MRI-related complications occurred during or after MRI, including sustained ventricular arrhythmias, pacemaker inhibition or output failures, electrical resets, or other pacemaker malfunctions. Pacing capture threshold and sensed electrogram amplitude changes were minimal and similar between study groups.

Conclusion

This trial documented the ability of this pacemaker system to be exposed in a controlled fashion to MRI in a 1.5 T scanner without adverse impact on patient outcomes or pacemaker system function.

Introduction

Use of magnetic resonance imaging (MRI) as the imaging modality of choice in many fields (e.g., brain, spinal cord, and musculoskeletal system) is rapidly increasing. However, manufacturers of cardiac devices and MRI systems contraindicate MRI for patients with implanted pacemaker systems due to multiple associated risks. Approximately five million patients worldwide currently are implanted with a pacemaker or implantable cardioverter-defibrillator, and at least 50% of these patients are expected to be indicated to undergo clinical MRI over the lifetime of their device.1

Literature documents that several interactions between the MRI-associated static magnetic field, gradient fields, and radiofrequency (RF) field and the implanted pacemaker system may be hazardous to the patient and/or may damage the device.2, 3, 4 Despite the potential for adverse outcomes, a few centers perform MRI scanning of carefully selected pacemaker patients using precautions when the benefit outweighs the risk. Even in these centers and under extensive expert supervision, clinically significant irregular pacemaker system behavior cannot always be prevented or good patient outcomes assured.5

A pacemaker system (EnRhythm MRI SureScan implantable pulse generator and CapSureFix MRI leads [model 5086 MRI leads] used in support of the Revo MRI SureScan pacing system, Medtronic, Inc., Minneapolis, MN, USA) designed specifically to mitigate these hazards provides access to pacemaker patients for this important diagnostic modality. The aim of this study was to evaluate the safety and efficacy of this novel pacemaker system during MRI in a prospective, randomized, multicenter trial.

Section snippets

Pacemaker system

The following design modifications were made to the pacemaker system to improve MRI compatibility. (1) The leads were modified to reduce RF lead tip heating. (2) Internal circuits were changed to reduce the potential for cardiac stimulation. (3) The amount of ferromagnetic materials was limited. (4) Internal circuit protection was improved to prevent disruption of the internal power supply. (5) The reed switch was replaced by a Hall sensor, whose behavior in a static magnetic field is

Trial population

A total of 464 patients were randomized after successful pacemaker system implantation between February 2007 and August 2008 (258 to the MRI group and 206 to the control group). A summary of the distribution of patient enrollments, follow-up by randomized group, and inclusion and exclusion of data are given in Figure 1. Mean follow-up was 11.2 ± 5.2 months (range 0.1–21.5 months). Patient characteristics were typical of pacemaker patients (Table 2).

Safety

A total of 211 patients underwent MRI

Discussion

This prospective, randomized, controlled, multicenter trial evaluated the safety and efficacy of a pacemaker system specifically designed to be used during MRI. No MRI-related complications, no disturbances of pacemaker function, and no ventricular arrhythmia induction were observed. PCT and sensing amplitude changes from immediately before the MRI/control visit to the 1-month post visit were clinically equivalent between MRI and control groups. All pacemaker system-related complications were

Conclusion

MRI scanning of patients with this specific pacemaker system evaluated in the trial was performed safely with no adverse impact on either the patient or the pacemaker system. It is important to note that this safety is conditional upon the use of only this complete pacemaker system. Safety is also conditional upon the pacing system being evaluated to ensure normal function and appropriate programming as well as upon following specific limitations on the MR scan, including use in a 1.5-T MRI

Acknowledgments

We thank all of the physicians and their staff for participating in this trial. We also thank Michael Hull and Craig Balog for conducting the statistics, Inge Jenniskens and Amy Kalmes for review of the manuscript, as well as the other clinical team members.

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    Each author participated sufficiently in this work as follows: (1) provided substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data; and (2) drafted manuscript or revised for intellectual content. Medtronic, Inc., provided funding for this trial and is the manufacturer of the dual-chamber pacemaker system used in the trial. B.L. Wilkoff, D. Bello, E. Kanal, W.B. Johnson, B. Ramza, R. Luechinger, H. Puererfellner, F. Duru, R. Sutton, and T. Sommer are consultants to Medtronic.

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