Safe scanning, but frequent artifacts mimicking bradycardia and tachycardia during magnetic resonance imaging (MRI) in patients with an implantable loop recorder (ILR)

Multimodality imaging in patients with implantable loop recorders: Tips and tricks

An implantable loop recorder (ILR) is a leadless rectangular device used for prolonged electrocardiographic monitoring for up to 3 years. This miniaturized device, inserted subcutaneously, allows clinicians to investigate possible cardiac rhythm disturbances in patients suffering from recurrent unexplained syncope. As the age of the population increases rapidly and the number of ILR patients amplifies, the clinical significance of ILRs is undeniable. Although radioopaque and easily seen on plain chest radiographs and other imaging modalities, ILRs may represent a challenge for clinicians and radiologists to recognize their classic appearance and differentiate them from numerous other cardiac devices. This article aims to summarize current literature on ILRs, their basic function, types, and indications for implantation, but most of all, it aims to familiarize clinicians and radiologists with common imaging features of these devices, safety issues, and artifact-reducing methods. Specifically, this review discusses the typical appearance of ILRs on major diagnostic imaging modalities, including chest X-ray, mammography, ultrasonography, computed tomography, and magnetic resonance imaging (MRI). Furthermore, optimization strategies to mitigate image artifacts and safety issues regarding MRI are discussed.

Breast MRI in patients with implantable loop recorder: initial experience

OBJECTIVES

To investigate the feasibility of breast MRI exams and guided biopsies in patients with an implantable loop recorder (ILR) as well as the impact ILRs may have on image interpretation.

MATERIALS AND METHODS

This retrospective study examined breast MRIs of patients with ILR, from April 2008 to September 2022. Radiological reports and electronic medical records were reviewed for demographic characteristics, safety concerns, and imaging findings. MR images were analyzed and compared statistically for artifact quantification on the various pulse sequences.

RESULTS

Overall, 40/82,778 (0.049%) MRIs during the study period included ILR. All MRIs were completed without early termination. No patient-related or device-related adverse events occurred. ILRs were most commonly located in the left lower-inner quadrant (64.6%). The main artifact was a signal intensity (SI) void in a dipole formation in the ILR bed with or without areas of peripheral high SI. Artifacts appeared greatest in the cranio-caudal axis (p < 0.001), followed by the anterior-posterior axis (p < 0.001), and then the right-left axis. High peripheral rim-like SI artifacts appeared on the post-contrast and subtracted T1-weighted images, mimicking suspicious enhancement. Artifacts were most prominent on diffusion-weighted (p < 0.001), followed by T2-weighted and T1-weighted images. In eight patients, suspicious findings were found on MRI, resulting in four additional malignant lesions. Of six patients with left breast cancer, the tumor was completely visible in five cases and partially obscured in one.

CONCLUSION

Breast MRI is feasible and safe among patients with ILR and may provide a significant diagnostic value, albeit with localized, characteristic artifacts.

CLINICAL RELEVANCE STATEMENT

Indicated breast MRI exams and guided biopsies can be safely performed in patients with implantable loop recorder. Nevertheless, radiologists should be aware of associated limitations including limited assessment of the inner left breast and pseudo-enhancement artifacts.

KEY POINTS

• Breast MRI in patients with an implantable loop recorder is an infrequent, feasible, and safe procedure. • Despite limited breast visualization of the implantable loop recorder bed and characteristic artifacts, MRI depicted additional lesions in 8/40 (20%) of cases, half of which were malignant. • Breast MRI in patients with an implantable loop recorder should be performed when indicated, taking into consideration typical associated artifacts.

Magnetic resonance in patients with cardiovascular devices. SEC-GT CRMTC/SEC-Heart Rhythm Association/SERAM/SEICAT consensus document

Magnetic resonance has become a first-line imaging modality in various clinical scenarios. The number of patients with different cardiovascular devices, including cardiac implantable electronic devices, has increased exponentially. Although there have been reports of risks associated with exposure to magnetic resonance in these patients, the clinical evidence now supports the safety of performing these studies under specific conditions and following recommendations to minimize possible risks. This document was written by the Working Group on Cardiac Magnetic Resonance Imaging and Cardiac Computed Tomography of the Spanish Society of Cardiology (SEC-GT CRMTC), the Heart Rhythm Association of the Spanish Society of Cardiology (SEC-Heart Rhythm Association), the Spanish Society of Medical Radiology (SERAM), and the Spanish Society of Cardiothoracic Imaging (SEICAT). The document reviews the clinical evidence available in this field and establishes a series of recommendations so that patients with cardiovascular devices can safely access this diagnostic tool.

Magnetic resonance in patients with cardiovascular devices. SEC-GT CRMTC/SEC-Heart Rhythm Association/SERAM/SEICAT consensus document

Magnetic resonance has become a first-line imaging modality in various clinical scenarios. The number of patients with different cardiovascular devices, including cardiac implantable electronic devices, has increased exponentially. Although there have been reports of risks associated with exposure to magnetic resonance in these patients, the clinical evidence now supports the safety of performing these studies under specific conditions and following recommendations to minimize possible risks. This document was written by the Working Group on Cardiac Magnetic Resonance Imaging and Cardiac Computed Tomography of the Spanish Society of Cardiology (SEC-GT CRMTC), the Heart Rhythm Association of the Spanish Society of Cardiology (SEC-Heart Rhythm Association), the Spanish Society of Medical Radiology (SERAM), and the Spanish Society of Cardiothoracic Imaging (SEICAT). The document reviews the clinical evidence available in this field and establishes a series of recommendations so that patients with cardiovascular devices can safely access this diagnostic tool.

Magnetic Resonance Imaging Safety in Patients with Cardiac Implantable Electronic Devices

High strength magnetic and electric fields used in magnetic resonance imaging (MRI) render images with unmatched soft tissue contrast. These imaging attributes have made MRI an increasingly preferred diagnostic tool in many medical conditions. Initially there was substantial concern regarding the safety of performing these imaging studies in patients with cardiac implantable electronic devices (CIEDs), which have the potential to be affected by the intense electric and magnetic fields of the MRI. More recently, there has been increasing evidence that MRI can be performed safely in patients with devices that have not been specifically labelled by regulatory agencies for use in an MRI environment (MRI nonconditional devices), which has allowed the Centers for Medicare and Medicaid Services (CMS) to start providing reimbursement for MRIs of patients with MRI nonconditional devices. For CMS to reimburse scans, a rigorous protocol must be followed, which recognizes that there are still potential adverse effects that can be mitigated by appropriate procedures. In this review we will survey the initial experiences and efforts to understand the magnitude of risk for device malfunction and harm, as well as current efforts to minimize the potential risks of MRI effects on devices and leads (heating, device movement, lead dislodgement, and device malfunction, the latter including inhibition of pacing and generation of arrhythmias).

2021 Update on Safety of Magnetic Resonance Imaging: Joint Statement From Canadian Cardiovascular Society/Canadian Society for Cardiovascular Magnetic Resonance/Canadian Heart Rhythm Society

Magnetic resonance imaging (MRI) is often considered the gold-standard test for characterizing cardiac as well as noncardiac structure and function. However, many patients with cardiac implantable electronic devices (CIEDs) and/or severe renal dysfunction are unable to undergo this test because of safety concerns. In the past 10 years, newer-generation CIEDs and gadolinium-based contrast agents (GBCAs) as well as coordinated care between imaging and heart rhythm device teams have mitigated risk to patients and improved access to MRI at many hospitals. The purpose of this statement is to review published data on safety of MRI in patients with conditional and nonconditional CIEDs in addition to patient risks from older and newer GBCAs. This statement was developed through multidisciplinary collaboration of pan-Canadian experts after a relevant and independent literature search by the Canadian Agency for Drugs and Technologies in Health. All recommendations align with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. Key recommendations include: (1) the development of standardized protocols for patients with a CIED undergoing MRI; (2) patients with MRI nonconditional pacemakers and pacemaker dependency should be programmed to asynchronous mode and those with MRI nonconditional transvenous defibrillators should have tachycardia therapies turned off during the scan; and (3) macrocyclic or newer linear GBCAs should be used in preference to older GBCAs because of their better safety profile in patients at higher risk of nephrogenic systemic fibrosis.

Feasibility of MRI in patients with non-Pacemaker/Defibrillator metallic devices and abandoned leads

Objective

To evaluate feasibility of MRI in patients with non-pacemaker (PM)/ Implantable cardioverter defibrillator (ICD) metallic devices and abandoned leads.

Background

Relative safety of MRI performed using specified protocol has been established in MR non-conditional PM/ICDs. With limited safety data, many non-PM/ICD metallic devices and abandoned leads continue to be a contraindication for MRI.

Methods

We retrospectively analyzed consecutive patients with extra-cardiac devices, non-programmable cardiac devices, and abandoned leads, who underwent MRI (GE 1.5 Tesla, WI) at a single tertiary care center over a span of 13 years. Scan protocol was designed to maintain specific absorption rate (SAR) < 4.0 W/kg and scan time < 60 minutes.

Results

The cohort comprised 127 MRI exams representing 94 patients, with 13 patients having two or more scans. The devices consisted of: 23 vagal nerve stimulators (VNS), 22 implantable loop recorders, 16 spinal stimulators, 5 peripheral nerve stimulators, 3 bladder stimulators, 2 deep brain stimulators, 1 gastric stimulator, 1 bone stimulator, 1 WATCHMAN device, 22 abandoned PM/lCD leads and 1 VNS lead. There was no immediate (peri-MRI exam) morbidity or mortality. Patients did not report any discomfort, palpitations, heating, or sensation of device migration during the exam. Local follow-up data was available in 65% (100% for thoracic imaging) with a mean of 190±475 days (median 13 days). No device malfunction reported during follow-up.

Conclusions

With appropriate precautions, MRI is feasible in patients with extracardiac devices, nonprogrammable cardiac devices, and abandoned leads.

Cardiovascular implantable electronic devices: a review of the dangers and difficulties in MR scanning and attempts to improve safety

Abstract

An increasing number of patients are being treated with cardiovascular implantable electronic devices (CIEDs), many of which are MR conditional. There is a lack of literature on the safe scanning of MR conditional CIEDs. This review article discusses MR imaging safety in patients with implanted CIEDs. Guidelines on safe use and indications of imaging patients with MR conditional CIEDs are described, followed by a pictorial essay of the radiographic features of these devices. We also discuss the challenges of monitoring the patient in the MR environment, advances in MRI conditional imaging of devices, availability, limitations and workflow including vendor-specific and other collaborative efforts to simplify the scanning process. Radiologists must be able to facilitate the safe utilization of MR imaging in patients who have CIEDs. A thorough knowledge of the hazards of imaging non-MR compatible devices is required as well as knowing how to correctly identify and manage the imaging of patients with MR conditional CIEDs. Finally, we propose steps required to facilitate the safe scanning of patients with MR conditional CIEDs adopted in our institution and a contingency plan in the event that an inadvertent MR scan of a patient with a MRI unsafe CIED should occur.

Main Messages

• Risks of MR imaging in patients who have CIEDs have been worked around.

• There are many technical limitations in enabling safe MR scanning of CIEDs.

• Radiological identification of MRI-conditional status of CIEDs is useful.

• Standardizing conditions for safe MRI scanning is important.

• We offer example algorithms for facilitating safe MRI scanning of CIEDs.

Cardiovascular Magnetic Resonance Imaging in Patients with an Implantable Loop Recorder

BACKGROUND

Implantable loop recorders (ILRs) allow continuous cardiac monitoring for 3-6 years and are a valuable tool for the investigation of syncopal episodes, palpitations, and atrial fibrillations as well as risk stratification after myocardial infarction. Although magnetic resonance imaging (MRI) in patients with ILRs has been shown to be safe, the impact of ILRs on cardiac MRI image quality has not been investigated yet. Thus, we tested the diagnostic value of cardiac MRI in patients with various types of ILRs.

METHODS

Two patients with an ILR and a clinical indication to assess myocardial burden of scarring and fibrosis or stress-induced myocardial ischemia underwent cardiac MRI. Device interrogation was performed prior to, immediately after, and 3 months after cardiac MRI.

RESULTS

The post-MRI follow-ups revealed no change in programmed ILR parameters, sensing fidelity, and battery parameters. However, ILRs caused significant, uninterpretable hyperintensity artifacts in cardiac MRI.

CONCLUSIONS

Further clinical studies are warranted to investigate whether modified MRI techniques are helpful to eliminate imaging artifacts.

Canadian Heart Rhythm Society and Canadian Association of Radiologists Consensus Statement on Magnetic Resonance Imaging with Cardiac Implantable Electronic Devices

Magnetic resonance imaging (MRI) has historically been considered contraindicated for individuals with cardiac implantable electronic devices (CIEDs) such as pacemakers and implantable defibrillators. Magnetic resonance scanners produce magnetic fields that can interact negatively with the metallic components of CIEDs. However, as CIED technology has advanced, newer MRI conditional devices have been developed that are now in clinical use and these systems have had demonstrated safety in the MRI environment. Despite the supportive data of such CIED systems, physicians remain reluctant to perform MRI scanning of conditional devices. This joint statement by the Canadian Heart Rhythm Society and the Canadian Association of Radiologists describes a collaborative process by which CIED specialists and clinics can work with radiology departments and specialists to safely perform MRI in patients with MRI conditional CIED systems. The steps required for patient and scanning preparation and the roles and responsibilities of the CIED and radiology departments are outlined. We also briefly outline the risks and a process by which patients with nonconditional CIEDs might also receive MRI in highly specialized centres. This document supports MRI in patients with MRI conditional CIEDs and offers recommendations on how this can be implemented safely and effectively.

MRI and cardiac implantable electronic devices; current status and required safety conditions

Magnetic resonance imaging (MRI) has evolved into an essential diagnostic modality for the evaluation of all patient categories. This gain in popularity coincided with an increase in the number of implanted cardiac implantable electronic devices (CIEDs). Therefore, questions arose with regard to the MRI compatibility of these devices. Various investigators have reported the harmless performance of MRI in patients with conventional (non-MRI conditional) devices. The recently published European Society of Cardiology (ESC) guidelines on cardiac pacing and cardiac resynchronisation therapy (CRT) indicate that MRI can be safely performed in patients with an implanted pacemaker or ICD (MRI conditional or not), as long as strict safety conditions are met. This is a major modification of the former general opinion that patients with a pacemaker or ICD were not eligible to undergo MRI. This review paper attempts to elucidate the current situation for practising cardiologists by providing a clear overview of the potential life-threatening interactions and discuss safety measures to be taken prior to and during scanning. An overview of all available MRI conditional devices and their individual restrictions is given. In addition, an up-to-date safety protocol is provided that can be used to ensure patient safety before, during and after the scan. Key points • Historically, MRI examination of patients with a CIED has been considered hazardous. • Ongoing advances in technology and increasing usage of MRI in clinical practice have led to the introduction of MRI conditional CIEDs and to more lenient regulations on the examination of patients with non-conditional CIEDs. • MRI investigations can be performed safely in selected patients when adhering to a standardised up-to-date safety protocol.

Inappropriate asystole detection in early postoperative phase after loop recorder implantation

The implantable loop recorder is a useful diagnostic tool for patients with unexplained syncope. The capability to automatically detect and store arrhythmic events, implemented in the last generations of these devices, can further improve the diagnostic yield, but this feature can be compromised by inappropriate detection of false arrhythmias. We herein report the case of a patient in which several inappropriate activations of long-lasting asystole occurred in the two days following the implant, probably because of an intermittently loose contact between the device and subcutaneous tissue for a small pocket haematoma.

A media player causes clinically significant telemetry interference with implantable loop recorders

BACKGROUND

The implantable loop recorder is a useful diagnostic tool for intermittent cardiovascular symptoms because it can automatically record arrhythmias as well as a patient-triggered ECG. Media players have been shown to cause telemetry interference with pacemakers. Telemetry interference may be important in patients with implantable loop recorders because capturing a patient-triggered ECG requires a telemetry link between a hand-held activator and the implanted device. The purpose of this study was to determine if a media player causes interference with implantable loop recorders.

METHODS

Fourteen patients with implantable loop recorders underwent evaluation for interference with a 15 GB third generation iPod (Apple, Inc.) media player. All patients had the Reveal Plus (Medtronic, Inc.) implantable loop recorder. We tested for telemetry interference on the programmer by first establishing a telemetry link with the loop recorder and then, the media player was placed next to it, first turned off and then, on. We evaluated for telemetry interference between the activator and the implanted device by placing the activator over the device (normal use) and the media player next to it, first turned off and then, on. We made 5 attempts to capture a patient-triggered ECG by depressing the activator switch 5 times while the media player was off or on.

RESULTS

Telemetry interference on the programmer screen, consisting of either high frequency spikes or blanking of the ECG channel was seen in all patients. Telemetry interference with the activator resulted in failure to capture an event in 7 patients. In one of these patients, a green indicator light on the activator suggested that a patient-triggered event was captured, but loop recorder interrogation did not show a captured event. In the remaining 7 patients, an event was captured and appropriately recognized by the device at least 1 out of 5 times.

CONCLUSION

A media player playing in close proximity to an implanted loop recorder may interfere with capture of a patient-triggered event. Patients should be advised to keep media players away from their implanted loop recorder.

Safety of magnetic resonance imaging in patients with cardiovascular devices: an American Heart Association scientific statement from the Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology, and the Council on Cardiovascular Radiology and Intervention: endorsed by the American College of Cardiology Foundation, the North American Society for Cardiac Imaging, and the Society for Cardiovascular Magnetic Resonance

Advances in magnetic resonance (MR) imaging over the past 2 decades have led to MR becoming an increasingly attractive imaging modality. With the growing number of patients treated with permanent implanted or temporary cardiovascular devices, it is becoming ever more important to clarify safety issues in regard to the performance of MR examinations in patients with these devices. Extensive, although not complete, ex vivo, animal, and clinical data are available from which to generate recommendations regarding the safe performance of MR examination in patients with cardiovascular devices, as well as to ascertain caveats and contraindications regarding MR examination for such patients. Safe MR imaging involves a careful initial patient screening, accurate determination of the permanent implanted or temporary cardiovascular device and its properties, a thoughtful analysis of the risks and benefits of performing the examination at that time, and, when indicated, appropriate physician management and supervision. This scientific statement is intended to summarize and clarify issues regarding the safety of MR imaging in patients with cardiovascular devices.

MRI in patients with cardiac devices

Given the advances of MRI and cardiovascular technology, it is becoming increasingly likely that a patient with a cardiovascular device will be a candidate for an MRI procedure. However, many cardiac devices are currently considered to be contraindicated in the MR environment. This may prove to be a significant public health problem as many patients in need of MRI are denied the procedure because of the presence of a cardiovascular device. However, research studies have shown that with proper precautions and technique patients with cardiac devices can undergo successful MRI safely on the current platforms.

Generalized tonic-clonic seizures detected by implantable loop recorder devices: diagnosing more than cardiac arrhythmias

BACKGROUND

Both syncope and seizures are important causes of recurrent, unexplained episodes of loss of consciousness. Implantable loop recorders have identified serious arrhythmias in patients with repeated syncope; however, implantable loop recorder detection of seizures is less well established.

OBJECTIVES

The purpose of this study was to provide in-depth analysis of a characteristic myopotential pattern recorded by implantable loop recorders during generalized tonic-clonic seizures.

METHODS

Fourteen patients with refractory, video-EEG-documented epilepsy (complex partial, atonic, tonic, or generalized tonic-clonic seizures) underwent implantable loop recorder placement as part of a study protocol evaluating cardiac rhythm abnormalities in patients at high risk for sudden unexpected death in epilepsy.

RESULTS

Twelve generalized tonic-clonic seizure episodes were detected by the implantable loop recorder in six patients. Implantable loop recorder and EEG recordings of generalized tonic-clonic seizures were identical and revealed a tonic phase (sustained, rapid, high-frequency myopotentials) transitioning to a clonic phase (periodic bursts of high-frequency myopotentials with a decelerating burst frequency from 3-6 Hz to 1-2 Hz) prior to seizure termination. With the nonprogrammable bandpass filter of 0.85 to 32 Hz in the implantable loop recorder, all generalized tonic-clonic seizure episodes had escaped automatic detection and required activation by family members. None of the 76 nongeneralized tonic-clonic seizure episodes recorded on the implantable loop recorder in the 14 patients exhibited the stereotypical tonic-clonic pattern that defines generalized seizures.

CONCLUSION

Recognizing this specific myopotential pattern on an implantable loop recorder might help diagnose generalized tonic-clonic seizures as a cause of recurrent, unexplained episodes of loss of consciousness. Having a programmable bandpass filter in the implantable loop recorder might increase its diagnostic yield for such patients.