Home Monitoring and MRI Compatibility: A Case Report

Introduction

Magnetic resonance imaging (MRI) was once contraindicated for patients with cardiac implantable electronic devices (CIEDs) such as implantable cardioverter-defibrillators (ICDs),¹ but in recent years, CIEDs that allow for conditional use of MRI scans have entered clinical practice. The advent of MR-conditional CIEDs represents a major advancement, because it allows device patients to benefit from MRI technology, which offers excellent, possibly unprecedented, multiplanar images and high resolution of soft tissue without exposing the patient to X-ray radiation.² In fact, MRI technology has advanced to the point that MRI scans today have emerged as a preferred diagnostic modality for numerous conditions. About 30 million MRI scans are conducted worldwide each year, and the likelihood that an MRI will be necessary doubles after the age of 65.^3,4 So important is MR imaging that it has been estimated that as many as half of all ICD patients will need to undergo an MRI scan within ten years, and 75% of CIED patients will need to undergo an MRI during the lifetime of their device.^1,5 This is even more important for younger patients who get an ICD early in life and who may require an MRI over the course of a lifetime. 

CIEDs labeled as MR-conditional are those systems (leads and pulse generators) with hardware and software modifications designed to allow patients to undergo an MRI with reduced risks. These risks might include injury to the patient, damage to the device, and inappropriate device function (such as pacing inhibition or therapy delivery).⁶ As in all matters of device-based arrhythmia therapy, of paramount concern is the safety of the patient. MR-conditional systems are relatively new to clinical practice, and many CIED patients have older, non-compatible systems that do not allow for MRI. Furthermore, these new devices use a variety of different techniques to accomplish compatibility with MR scanning.

Case Report

A 41-year-old white male, active duty Marine, presented to the hospital with a shoulder injury for which an MRI was indicated. The patient has dilated cardiomyopathy, for which he previously had received a primary-prevention ICD (Inventra Dx®, BIOTRONIK). His ICD is MR-conditional, meaning that the device could be deactivated and programmed in such a way that the patient could safely undergo the necessary MRI for his shoulder. The MRI clinical team contacted the electrophysiologist, who then programmed the device into MRI mode (allowing for asynchronous pacing and deactivating tachycardia therapy deactivation). The patient underwent the scan, the MRI proceeded normally, and the device was then programmed to restore normal operation.

A few hours later, the electrophysiologist as well as a member of the clinical care team received an alert message from the patient’s Home Monitoring® system (BIOTRONIK). The patient’s device was set up to automatically transmit specific notifications to the clinical team when unusual conditions were observed. In this case, the Home Monitoring® alert notified the clinical team that the patient’s device had been inadvertently left with tachycardia therapies turned off. When in the MRI environment, this programming is appropriate; however, it should be reverted to the clinician’s preferred programming once the MRI has concluded. 

The patient was notified in a timely manner, and came back in to have the device checked. The physician was able to determine that the device’s tachycardia therapies — although properly deactivated for the MRI — inadvertently had not been appropriately restored following the MRI. It was then possible to reprogram the device with a programming step and normal function could be confirmed. The patient left the hospital reassured that his ICD was working properly.

Discussion

Cardiac devices, including ICDs, are made to be MRI compliant in the United States and in most countries by conforming to ISO 10974.⁷ ISO 10974 outlines multiple hazards within the MRI environment that can affect devices and their function in an MRI environment. MR-conditional devices and leads are designed to meet the specific standards to mitigate these hazards. Several of these hazards are further reduced by programming the device into an “MRI mode.” As the ICD patient is prepared for the MRI scan, the device is programmed to this MRI mode, which turns off tachycardia therapy and prevents inappropriate therapy delivery during the scan. If the patient needs pacing support, asynchronous pacing can be programmed; otherwise, pacing may be turned off completely.

Thus, all MR-conditional devices require special programming prior to the scan to prepare the device for the imaging procedure, and subsequent programming to restore normal operation.⁴ These can be accomplished in short programming steps. The MRI mode is designed to protect both the device from the MRI environment as well as the patient from inappropriate device functions that could occur during the MRI. Different devices accomplish this in different ways, but essentially, all devices are programmed to a special mode for the MRI scan and then returned to normal operation.  

At this time, BIOTRONIK and Medtronic are the only companies who manufacture MR-compatible ICDs. Since the programming of all MR-compatible devices on the market requires a specific programming step, they are all vulnerable to human error. The BIOTRONIK ICDs require a programming step to turn on MR-compatible mode prior to the MRI, and then another programming step to restore regular programmed parameters following the MRI (Medtronic devices have a slightly different architecture). 

A new device feature, available internationally but not yet approved in the United States, allows the device to self-detect whether or not it is in the MRI environment and to avoid restoring regularly programmed parameters during the scan. The MRI AutoDetect (BIOTRONIK) feature was first presented at CARDIOSTIM-EHRA EUROPACE 2016.^8,9 The MRI AutoDetect helps to automate the entire process by allowing the physician to set up both MRI-compatible settings and the regularly programmed parameters, as well as allowing the device to automatically switch to MRI-compatible settings during the MRI and restoring the previously programmed values when the patient is no longer in the MRI environment. 

This particular ICD was set up with Home Monitoring^® to allow for the device to continuously self-report unusual or remarkable conditions. The value of Home Monitoring^® was evident in this case, in that the unusual situation following this patient’s MRI was quickly reported by the device itself to the clinical team before the patient experienced any symptoms. Indeed, his ICD was only deactivated for a matter of hours.

The patient’s response to this sequence of events was extremely positive. He was pleased that he could undergo the MRI for his shoulder injury despite having an ICD, and that the Home Monitoring^® alert notified the clinical team to reprogram his device within hours after the scan. As a young primary-prevention patient, he has been extremely concerned about his cardiac condition and the new role of ICD therapy in his life. Seeing Home Monitoring^® in action reassured him of the value of continuous monitoring and alerts that could notify his physician about events before he experienced any symptoms or adverse effects. It was also an important benefit to him that he did not have to sacrifice the potential diagnostic benefits of an MRI because he had an ICD.

Conclusion

For young patients that are facing potentially lifelong device-based therapy, MR-compatibility is an important — and even crucial — device feature. In this particular case, the combination of an MR-conditional ICD plus Home Monitoring^® ensured that the patient could safely undergo a necessary MRI for his shoulder injury and still be assured of reliable device function. In the event that proper device function is not restored for any reason following an MRI scan, Home Monitoring^® can quickly alert the clinical team. Advances in MR-compatible devices hold great promise to make MRI available to more and more CIED patients in the future.

Disclosure: The author has no conflicts of interest to report regarding the content herein.   

References

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This article is published with support from BIOTRONIK, Inc.