Real world MRI experience with nonconditional and conditional cardiac rhythm devices after MagnaSafe

MRI in Adult Patients with Active and Inactive Implanted MR-conditional, MR-nonconditional, and Other Devices

Active implanted medical devices (AIMDs) enable therapy and patient monitoring by way of electrical activity and typically have a battery and electrical leads. The most common types of AIMDs include cardiac implantable electronic devices (CIEDs), spinal cord stimulators, deep brain stimulators, bone growth or fusion stimulators, other neurostimulators, and drug infusion pumps. As more patients with AIMDs undergo MRI, it is important to consider the safety of patients who have these implanted devices during MRI. The authors review the physics concepts related to MRI safety, such as peak spatial gradient magnetic field, specific absorption rate, root mean square value of the effective magnetic component of the transmitted RF pulse, and gradient slew rate, as well as the parameters necessary to remain within safety limits. The roles of MRI safety personnel, as set forth by the International Society of Magnetic Resonance in Medicine, are emphasized. In addition, the relevant information provided in vendor manuals is reviewed, with a focus on how to obtain relevant up-to-date information. The radiologist should be able to modify protocols to meet safety requirements, address possible alternatives to MRI, and weigh the potential benefits of MRI against the potential risks. A few more advanced topics, such as fractured or abandoned device leads and patients with multiple implanted medical devices, also are addressed. Recommended workflows for MRI in patients with implanted medical devices are outlined. It is important to implement an algorithmic MRI safety process, including a review of the MRI safety information; patient screening; optimal imaging; and monitoring patients before, during, and after the examination. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Shetty et al in this issue.

Role of advanced imaging with cardiac computed tomography and MRI in atrial and ventricular ablation

PURPOSE OF REVIEW

Increasing evidence supports the use of advanced imaging with cardiac computed tomography (CCT) and cardiac magnetic resonance (CMR) in the work-up of patients with arrythmias being considered for ablation.

RECENT FINDINGS

Advances in imaging technology and postprocessing are facilitating the use of advanced imaging before, during and after ablation in patients with both atrial and ventricular arrhythmias.In atrial arrythmias, quantitative assessment of left atrial wall thickness on CCT and quantification of late gadolinium enhancement (LGE) on CMR identify patients more likely to develop recurrent atrial arrythmias following ablation. In addition, in patients with recurrent arrythmia post ablation, LGE CMR can potentially identify targets for repeat ablation.In ventricular arrythmias, qualitative assessment of LGE can aide in determining the optimal ablation approach and predicts likelihood of ventricular arrythmias inducibility. Quantitative assessment of LGE can identify conduction channels that can be targeted for ablation. On CCT, quantitative assessment of left ventricular wall thickness can demonstrate myocardial ridges associated with re-entrant circuits for ablation.

SUMMARY

This review focuses on the utility of CCT and CMR in identifying key anatomical components and arrhythmogenic substrate contributing to both atrial and ventricular arrhythmias in patients being considered for ablation. Advanced imaging has the potential to improve procedural outcomes, decrease complications and shorten procedural time.

Signal voids of active cardiac implants at 3.0 T CMR

Recent technical advancements allow cardiac MRI (CMR) examinations in the presence of so-called MRI conditional active cardiac implants at 3.0 T. However, the artifact burden caused by susceptibility effects remain an obstacle. All measurements were obtained at a clinical 3.0 T scanner using an in-house designed cubic phantom and optimized sequences for artifact evaluation (3D gradient echo sequence, multi-slice 2D turbo spin echo sequence). Reference sequences according to the American Society for Testing and Materials (ASTM) were additionally applied. Four representative active cardiac devices and a generic setup were analyzed regarding volume and shape of the signal void. For analysis, a threshold operation was applied to the grey value profile of each data set. The presented approach allows the evaluation of the signal void and shape even for larger implants such as ICDs. The void shape is influenced by the orientation of the B0-field and by the chosen sequence type. The distribution of ferromagnetic material within the implants also matters. The void volume depends both on the device itself, and on the sequence type. Disturbances in the B0 and B1 fields exceed the visual signal void. This work presents a reproducible and highly defined approach to characterize both signal void artifacts at 3.0 T and their influencing factors.

Safety of magnetic resonance imaging in patients with cardiac implantable electronic devices with generator and lead(s) brand mismatch

Magnetic resonance imaging (MRI) is a valuable imaging modality for the assessment of both cardiac and non‐cardiac structures. With a growing population of patients with cardiovascular implantable electronic devices (CIEDs), 50%–75% of these patients will need an MRI. MRI‐conditional CIEDs have demonstrated safety of MRI scanning with such devices, yet non‐conditional devices such as hybrid CIEDs which have generator and lead brand mismatch may pose a safety risk. In this retrospective study, we examined the outcomes of patients with hybrid CIEDs undergoing MRI compared to those patients with non‐hybrid CIEDs. A total of 349 patients were included, of which 24 patients (7%) had hybrid CIEDs. The primary endpoint was the safety of MRI for patients with hybrid CIEDs as compared to those with non‐hybrid devices, measured by the rate of adverse events, including death, lead or generator failure needing immediate replacement, loss of capture, new onset arrhythmia, or power‐on reset. Secondary endpoints consisted of pre‐ and post‐MRI changes of decreased P‐wave or R‐wave sensing by ≥50%, changes in pacing lead impedance by ≥50 ohms, increase in pacing thresholds by ≥ 0.5 V at 0.4 ms, and decreasing battery voltage of ≥ 0.04 V. The primary endpoint of any adverse reaction was present in 1 (4.2%) patient with a hybrid device, and consistent of atrial tachyarrhythmia, and in 10 (3.1%) patients with a non‐hybrid device, and consisted of self‐limited atrial and non‐sustained ventricular arrhythmias; this was not statistically significant. No significant differences were found in the secondary endpoints. This study demonstrates that MRI in patients with hybrid CIEDs does not result in increased patient risk or significant device changes when compared to those patients who underwent MRI with non‐hybrid CIEDs.

Cardiac magnetic resonance in patients with cardiac resynchronization therapy: is it time to scan with resynchronization on?

Cardiac resynchronization therapy (CRT) is recommended in international guidelines for patients with heart failure due to important left ventricular systolic dysfunction (or heart failure with reduced ejection fraction) and ventricular conduction tissue disease. Cardiac magnetic resonance (CMR) represents the most powerful imaging tool for dynamic assessment of the volumes and function of cardiac chambers but is rarely utilized in patients with CRT due to limitations on the device, programming and scanning. In this review, we explore the known utility of CMR in this cohort with discussion of the risks and potential benefits of scanning whilst CRT is active, including a practical strategy for conducting high quality scans safely. Our contention is that imaging in patients with CRT could be improved further by keeping resynchronization therapy active with resultant benefits on research and also patient outcomes.

Clinical experience of magnetic resonance imaging in patients with cardiac pacing devices: unrestricted patient population

Background

Magnetic resonance imaging (MRI) in patients with cardiac pacing devices has become available despite previously being considered absolutely contraindicated. However, most institutional safety protocols have included several limitations on patient selection, leaving MRI unavailable for many patients.

Purpose

To evaluate the first 1000 MRI examinations conducted on patients with cardiac pacing devices at Helsinki University Hospital for any potential safety hazards and also to evaluate the long-term functionality of the safety protocol in “real-life” clinical practice.

Material and Methods

A total of 1000 clinically indicated MRI scans were performed with a 1.5-T MRI scanner according to the safety protocol. The following information was collected from the electronic medical record (EMR): patients’ date of birth; sex; pacing device generator model; date of MRI scan; date of the latest pacing device generator implantation; and the body region scanned. The EMR of these patients was checked and especially searched for any pacing device related safety hazards or adverse outcomes during or after the MRI scan.

Results

Only one potentially dangerous adverse event was noted in our study group. In addition, patients with abandoned leads, temporary pacing devices, and newly implanted pacing device generators were scanned successfully and safely.

Conclusion

MRI scans can be performed safely in patients with cardiac pacing devices if the dedicated safety protocol is followed.

Patient Orientation Affects Lead-Tip Heating of Cardiac Active Implantable Medical Devices during MRI

Purpose

To evaluate changes in patient orientation to mitigate radiofrequency-induced lead-tip heating (LTH) during MRI.

Materials and Methods

LTH was evaluated for device type, lead path, and distance to the isocenter of a 1.5-T MRI system. LTH for 378 conditions in both head-first (HF) and feet-first (FF) orientations was measured for nine MRI-unsafe cardiac active implantable medical devices (AIMDs) placed along three (two anatomic, one planar) left-sided lead paths at nine landmark locations. The devices were exposed to 5 minutes of continuous radiofrequency energy at 4 W/kg whole-body specific absorption rate.

Results

LTH was greater in HF than in FF orientation for the planar and one anatomic lead path (P < .05). LTH was significantly affected by lead path, distance to isocenter, and patient orientation (all P < .05), but not by cardiac AIMD device type. Maximum LTH was observed in an HF orientation for the planar lead path when the lead tip was at isocenter (right ventricular [RV] lead: 32.0 °C ± 16.3 [standard deviation], right atrial [RA] lead: 16.1°C ± 9.3). In the FF orientation, LTH was significantly reduced (RV lead: 1.6°C ± 1.4; mean RA lead: 0.5°C ± 1.0; P = .008).

Conclusion

LTH for supine FF patient orientations among patients with anterior left-sided cardiac AIMDs can be significantly lower than LTH for supine HF orientations. There was no scenario in which LTH was significantly worse in the FF position. Changing patient orientation is a simple method to reduce radiofrequency-induced LTH.© RSNA, 2019See also the commentary by Litt in this issue.

Cardiovascular magnetic resonance imaging in patients with cardiac implantable electronic devices: best practice and real-world experience

Aims

Cardiovascular magnetic resonance (CMR) imaging has long been a contraindication for patients with a cardiac implantable electronic device (CIED). Recent studies support the feasibility and safety for non-thoracic magnetic resonance imaging, but data for CMR are sparse. The aim of the current study was to determine the safety in patients with magnetic resonance (MR)-conditional or non-MR-conditional CIED and to develop a best practice approach.

Methods and results

All patients with a CIED undergoing CMR imaging (1.5 T) between April 2014 and April 2017 were included in the study. Devices were programmed according to the standardized protocol directly before and after the CMR examination. Follow-up interrogation was performed 6 months after CMR examination. Results were compared with a large, reference cohort of CIED patients not undergoing any MR examination. A total of 200 consecutive patients with a CIED (non-MR-conditional, n = 103) were included in the study. Directly after CMR imaging, one device failure (0.5%, battery status = end of service) was noted necessitating premature generator replacement. In three patients (2%) of pacemaker/implantable cardioverter-defibrillator (ICD) carriers a sustained ventricular tachycardia (VT) occurred during CMR imaging. Ten ICD showed a decrease in battery capacity immediately after CMR. Overall, the reference cohort showed comparable changes of CIED function during follow-up.

Conclusion

With adherence to a standardized protocol and established exclusion criteria CMR imaging could safely be performed in patients with a CIED. The potential risks of device malfunction necessitate the presence of a device trained individual during the entire CMR examination. If there is a history of VT storm the attendance of an experienced cardiologist, should be mandatory.

[Magnetic resonance imaging and active cardiac implants]

The combination of magnetic resonance imaging (MRI) and active cardiac implants, such as pacemakers and implantable cardioverter defibrillators (ICD) has been a challenge for electrophysiologists and imaging for many years. Diagnostic and therapeutic possibilities on the one hand and technical hazards on the other hand highlight the need for improvements and algorithms that enable a safe approach to these challenges. The advent of so-called MRI conditional implants provides safe procedures for at least some of the patients with an implant and the need for MRI. Recently published data encourage clinicians not to completely excluded an imaging modality as promising as MRI in clinically urgent cases in the presence of conventional implants. The interdisciplinary consensus paper of the German Society of Cardiology and the German Society of Radiology provides recommendations for these situations. This review article discusses these recommendations and provides an overview of the most recent publications with a focus on the long-term course of device parameters.

Feasibility of Cardiac Magnetic Resonance Wideband Protocol in Patients With Implantable Cardioverter Defibrillators and Its Utility for Defining Scar

Implantable cardioverter defibrillators (ICDs) have been a relative contraindication to cardiovascular magnetic resonance imaging. Although cardiovascular magnetic resonance provides valuable information regarding scar in patients with ventricular arrhythmias or cardiomyopathy, ICDs in these patients frequently cause artifacts hindering accurate interpretation of both cine and late gadolinium enhancement (LGE) images. We sought to quantify the frequency and severity of artifact on LGE images and assess whether a modified wideband LGE protocol could improve the diagnostic yield of scar identification in agreement with invasive electroanatomic mapping (EAM). Forty-nine patients with ICDs and ventricular tachycardia (VT) or cardiomyopathy underwent CMR (Philips 1.5T), including standard and wideband LGE imaging. A safety algorithm was followed throughout the protocol. Standard and wideband LGE short-axis images were graded using an artifact score on a per-slice basis. LGE on wideband images was compared with EAM in 27 of 49 patients who underwent VT ablation. There were no adverse patient- or device-related events. With standard LGE imaging, 84% of patients demonstrated some degree of hyperenhancement artifact, which persisted in 22% on wideband LGE but with much less extent. Wideband LGE imaging resulted in an increase from 48% to 94% diagnostic-quality slices, with a significant reduction in artifact score, and correlated with EAM in 21 of 27 patients (78%). In conclusion, assessment of standard LGE is markedly limited by artifact in patients with ICD. The use of wideband LGE significantly improves image quality and can accurately localize myocardial scar before VT ablation.

State-of-the-art approach towards magnetic resonance imaging of the nervous system structures in patients with cardiac implantable electronic devices

INTRODUCTION

MRI generated forces are the source of potential complications in patients with cardiac implantable electronic devices (CIED). The technological progress, and growing clinical evidence concerning the operation of the contemporary MR non-conditional CIEDs during MRI, have started to significantly change our every-day clinical practice. Nevertheless, a lot of patients who could have an MRI performed safely, still have been refused the examination.

STATE-OF-THE-ART

In many clinical situations, an MRI examination in a patient with a CIED is reasonable, and is linked to a negligible risk of complications if performed under strict precautions. The MagnaSave Registry that evaluated the influence of nonthoracic MRI on the function of MR non-conditional CIEDs, and numerous studies involving thoracic and non-thoracic MRIs in patients with legacy CIEDs, have confirmed the feasibility and safety of such examinations. In this article, practical tips aimed towards improving the safety of MRI in MR conditional and non-conditional CIED patients are largely based on the very recently released (2017) HRS expert consensus statement.

CLINICAL IMPLICATIONS

Clinical data emphasize the necessity of making the MRI more accessible to CIED patients, also in the case of MR non-conditional systems or when the thorax MR imaging is clinically reasonable. This goal should be achieved by increasing the number of centers complying with respective recommendations and applying protocols that would guarantee the highest safety level.

FUTURE DIRECTIONS

Further studies are warranted to assess safety issues related to the main current contraindication to MRI, i.e., the presence of abandoned leads.

Cardiac implanted electronic devices and MRI safety in 2018-the state of play

Traditionally, the presence of cardiac implanted electronic devices (CIEDs) was a contra-indication to magnetic resonance (MR) imaging. Professional groups from around the world are releasing updated guidelines for the imaging of MR-conditional and legacy CIEDs, reflecting increasing evidence that this can be performed safely when strict protocols are followed.

KEY POINTS

• The presence of a pacemaker or automatic implanted cardioverter defibrillator is no longer an absolute contraindication to magnetic resonance imaging. • Strict protocols enable diagnostic quality images to be obtained with minimal risk. • Close collaboration among radiologists, cardiologists and device manufacturer representatives is required.