“Power-on resets” in cardiac implantable electronic devices during magnetic resonance imaging

Fundamental Electrophysiology Principles Related to Perioperative Management of Cardiovascular Implantable Electronic Devices

An increasing number of patients undergoing elective or emergency surgery in the United States have a cardiovascular implantable electronic device. Practice advisories and consensus statements have been issued by the American Society of Anesthesiologists and the Heart Rhythm Society, advocating a multidisciplinary approach. Unfortunately, anesthesia providers often find themselves in a situation in which they are left to manage these devices independently. At the University of Washington Medical Center, an anesthesiology-based service to manage these devices has existed for more than a decade. Many problems with devices have been observed, including confusing rhythms, failure of magnets to provide the desired change in device function, and actual device malfunction. With these clinical case examples taken from the authors' collective experience, this article provides an in-depth understanding of some key electrophysiology principles relevant to cardiovascular implantable electronic device function and appropriate perioperative management.

Joint British Society consensus recommendations for magnetic resonance imaging for patients with cardiac implantable electronic devices

Magnetic Resonance Imaging (MRI) is increasingly a fundamental component of the diagnostic pathway across a range of conditions. Historically, the presence of a cardiac implantable electronic device (CIED) has been a contraindication for MRI, however, development of MR Conditional devices that can be scanned under strict protocols has facilitated the provision of MRI for patients. Additionally, there is growing safety data to support MR scanning in patients with CIEDs that do not have MR safety labelling or with MR Conditional CIEDs where certain conditions are not met, where the clinical justification is robust. This means that almost all patients with cardiac devices should now have the same access to MRI scanning in the National Health Service as the general population. Provision of MRI to patients with CIED, however, remains limited in the UK, with only half of units accepting scan requests even for patients with MR Conditional CIEDs. Service delivery requires specialist equipment and robust protocols to ensure patient safety and facilitate workflows, meanwhile demanding collaboration between healthcare professionals across many disciplines. This document provides consensus recommendations from across the relevant stakeholder professional bodies and patient groups to encourage provision of safe MRI for patients with CIEDs.

The power of three: Atrial rate limit power-on-reset - A non-electromagnetic cause of pacemaker-induced extracardiac stimulation

BACKGROUND

Power-on reset (PoR) is most commonly due to electromagnetic interference. Full PoR results in a switch to an inhibited mode (VVI) pacing and resets pacing outputs to maximal unipolar settings, leading to extracardiac stimulation.

METHODS

We present a case of PoR occurrence in the absence of electromagnetic interference, resulting in pectoral stimulation triggered by violation of the atrial rate limit.

CONCLUSIONS

It is useful for clinicians to recognizethe occurrence of PoR in the setting of atrial limit violation andthe appropriate management in such circumstances.

Reducing cardiac implantable electronic device-induced artefacts in cardiac magnetic resonance imaging

OBJECTIVES

Cardiac implantable electronic device (CIED)-induced metal artefacts possibly significantly diminish the diagnostic value of magnetic resonance imaging (MRI), particularly cardiac MR (CMR). Right-sided generator implantation, wideband late-gadolinium enhancement (LGE) technique and raising the ipsilateral arm to the generator during CMR scanning may reduce the CIED-induced image artefacts. We assessed the impact of generator location and the arm-raised imaging position on the CIED-induced artefacts in CMR.

METHODS

We included all clinically indicated CMRs performed on patients with normal cardiac anatomy and a permanent CIED with endocardial pacing leads between November 2011 and October 2019 in our institution (n = 171). We analysed cine and LGE sequences using the American Heart Association 17-segment model for the presence of artefacts.

RESULTS

Right-sided generator implantation and arm-raised imaging associated with a significantly increased number of artefact-free segments. In patients with a right-sided pacemaker, the median percentage of artefact-free segments in short-axis balanced steady-state free precession LGE was 93.8% (IQR 9.4%, n = 53) compared with 78.1% (IQR 20.3%, n = 58) for left-sided pacemaker (p < 0.001). In patients with a left-sided implantable cardioverter-defibrillator, the median percentage of artefact-free segments reached 87.5% (IQR 6.3%, n = 9) using arm-raised imaging, which fell to 62.5% (IQR 34.4%, n = 9) using arm-down imaging in spoiled gradient echo short-axis cine (p = 0.02).

CONCLUSIONS

Arm-raised imaging represents a straightforward method to reduce CMR artefacts in patients with left-sided generators and can be used alongside other image quality improvement methods. Right-sided generator implantation could be considered in CIED patients requiring subsequent CMR imaging to ensure sufficient image quality.

KEY POINTS

• Cardiac implantable electronic device (CIED)-induced metal artefacts may significantly diminish the diagnostic value of an MRI, particularly in cardiac MRIs. • Raising the ipsilateral arm relative to the CIED generator is a cost-free, straightforward method to significantly reduce CIED-induced artefacts on cardiac MRIs in patients with a left-sided generator. • Right-sided generator implantation reduces artefacts compared with left-sided implantation and could be considered in CIED patients requiring subsequent cardiac MRIs to ensure adequate image quality in the future.

Is diversity harmful?-Mixed-brand cardiac implantable electronic devices undergoing magnetic resonance imaging

Background

Many patients with cardiac implantable electronic devices (CIED) undergo magnetic resonance imaging (MRI); however, a relevant proportion have a CIED system that has not been classified as MRI-conditional because of generators and leads from different brands (mixed-brand group). The available data concerning the outcome of these mixed patients undergoing MRI is limited.

Methods

A retrospective single center study, including all patients with CIEDs undergoing MRI between January 2013 until May 2020, was performed. Primary endpoints were defined as death or any adverse event necessitating hospitalization or CIED revision. Secondary endpoints were the occurrence of any sign for beginning device or lead failure or patient discomfort during MRI.

Results

A total of 227 MRI examinations, including 10 thoracic MRIs, were carried out in 158 patients, with 1–9 MRIs per patient. Of the patients 38 underwent 54 procedures in the mixed-brand group and 89 patients underwent 134 MRIs in the MRI-conditional group. Of the patients 31 were excluded since the MRI conditionality could not be determined. No primary endpoints occurred within the mixed-brand group but in 2.2% of the MRI-conditional group (p = 1.000), with 2 patients developing new atrial fibrillation during MRI, of whom one additionally had a transient CIED dysfunction. No secondary endpoints were met in the mixed-brand group compared to 3.4% in the MRI-conditional group (p = 0.554). No complications occurred in the excluded patients.

Conclusion

The complication rate of CIED patients undergoing MRI was low. Patients with a mixed CIED system showed no signs of increased risk of adverse events compared to patients with MRI-conditional CIED systems.

Supplementary Information

The online version of this article (10.1007/s00508-021-01924-w) contains supplementary material, which is available to authorized users.

MR Safety: Active Implanted Electronic Devices

New implanted medical devices continue to be made available for treatment of medical conditions. Many recipients can benefit from the diagnostic power of MR imaging. Provisions must be made to determine if these patients can be safely scanned. Metal-containing devices can be considered either MR unsafe or conditional. It is essential that all components of an implanted system are completely and accurately identified, with the most restrictive MR safety condition dictating the scanning approach. MR safety considerations for major classes of implanted devices are discussed, recognizing that there have been reports of serious device-related MR safety incidents.

Joint Position Paper of the Working Group of Pacing and Electrophysiology of the French Society of Cardiology (SFC) and the Société française d'imagerie cardiaque et vasculaire diagnostique et interventionnelle (SFICV) on magnetic resonance imaging in patients with cardiac electronic implantable devices

Magnetic resonance imaging (MRI) has become the reference imaging for the management of a large number of diseases. The number of MR examinations increases every year, simultaneously with the number of patients receiving a cardiac electronic implantable device (CEID). A CEID was considered an absolute contraindication for MRI for years. The progressive replacement of conventional pacemakers and defibrillators by MR-conditional CEIDs and recent data on the safety of MRI in patients with "MR-nonconditional" CEIDs have progressively increased the demand for MRI in patients with a CEID. However, some risks are associated with MRI in CEID carriers, even with "MR-conditional" devices because these devices are not "MR-safe". A specific programing of the device in "MR-mode" and monitoring patients during MRI remain mandatory for all patients with a CEID. A standardized patient workflow based on an institutional protocol should be established in each institution performing such examinations. This joint position paper of the Working Group of Pacing and Electrophysiology of the French Society of Cardiology and the Société française d'imagerie cardiaque et vasculaire diagnostique et interventionnelle (SFICV) describes the effect and risks associated with MRI in CEID carriers. We propose recommendations for patient workflow and monitoring and CEID programming in MR-conditional, "MR-conditional nonguaranteed" and MR-nonconditional devices.

Prospective evaluation of the utility of magnetic resonance imaging in patients with non-MRI-conditional pacemakers and defibrillators

BACKGROUND

Magnetic resonance imaging (MRI) in patients with legacy cardiovascular implantable electronic devices (CIEDs) in situ is likely underutilized. We hypothesized the clinical benefit of MRI would outweigh the risks in legacy CIED patients.

METHODS

This is a single-center retrospective study that evaluated and classified the utility of MRI using a prospectively maintained database. The outcomes were classified as aiding in diagnosis, treatment, or both for the patients attributable to the MRI. We then assessed the incidence of adverse effects (AE) when the MRI was performed.

RESULTS

In 668, MRIs performed on 479 patients, only 13 (1.9%) MRIs did not aid in the diagnosis or treatment of the patient. Power-on reset events without clinical sequelae in three scans (0.45%) were the only AE. The probability of an adverse event happening without any benefit from the MRI scan was 1.1 × 10^-4 . A maximum benefit in diagnosis using MRI was obtained in ruling out space-occupying lesions (121/185 scans, 65.4%). Scans performed in patients for elucidating answers to queries in treatment were most frequently done for disease staging at long term follow-up (167/470 scans, 35.5%). Conservative treatment (184/470 scans, 39%) followed by medication changes (153/470 scans, 28.7%) were the most common treatment decisions made.

CONCLUSIONS

The utility of MRI in patients with non-MRI-conditional CIEDs far outweighs the risk of adverse events when imaging is done in the context of a multidisciplinary program that oversees patient safety.

Cardiac Magnetic Resonance in Patients With Cardiac Implantable Electronic Devices: Challenges and Solutions

Until recently, cardiac implantable electronic devices (CIEDs) were an absolute contraindication to magnetic resonance imaging (MRI), due to concerns about their adverse interaction in the MRI environment. The increasing clinical need to perform MRI examinations in these patients was an impetus to the development of MR-Conditional CIEDs. Secure performance of MRI in these patients requires scanning under specified MR conditions as well as operating the device in MR-scanning mode. This requires robust institutional protocols and a well-trained multidisciplinary team of radiologists, cardiologists, device applications specialists, physicists, nurses, and MRI technologists. MRI can also be performed in patients with non-MRI Conditional or "legacy" CIEDs by following safety precautions and continuous monitoring. Cardiac magnetic resonance (CMR) is additionally challenging due to expected susceptibility artifacts generated by the CIEDs, which are either near or in the heart. As the most common indication for CMR in these patients is the evaluation of myocardial scar/fibrosis, acquiring a high-quality late gadolinium enhancement image is of the utmost importance. This sequence is hampered by artifactual high signal due to inadequate myocardial nulling. Several solutions are available to reduce these artifacts, including reducing inhomogeneity, technical adjustments, and use of sequences that are more resilient to artifacts. In this article, we review the precautions for CMR in patients with CIEDs, provide guidelines for secure performance of CMR in these patients, and discuss techniques for obtaining high quality CMR images with minimized artifacts.

Clinical and histopathological outcome of cervical and chest MRI involving non-MRI-conditional cardiac pacemakers: a study using sheep models

AIM

To examine the clinical and histopathological consequences of MRI in sheep implanted with non-MRI-conditional cardiac pacemakers.

MATERIALS AND METHODS

Under general anesthesia, active fixation leads of two dual-chamber, non-MRI-conditional cardiac pacemakers (St. Jude Medical and Medtronic) were implanted either at the right ventricular apex or at the right atrium of two male sheep and connected to the V and A channels of the pacemakers, respectively. The generators were placed in cervical subcutaneous pockets. On day 5, both sheep underwent 1.5 T cervical and chest MRI with continuous electrocardiogram monitoring. Obtained sequences were T1-weighted (T1W), T2-weighted (T2W), T2-gradient echo and diffusion weighted (DW). The employed modes were OVO, VOO and VVI for one sheep and OAO, AOO and AAI for the other (unipolar and bipolar configuration of pacing and sensing for both). Battery impedance, pacing lead impedance, intrinsic amplitude and capture thresholds were checked at baseline and after each sequence, as well as 48 h after imaging. Histopathological examination of the cardiac tissue around the lead tip was performed 4 weeks post-imaging.

RESULTS

No significant changes in device position or configuration were observed during or after MRI. Clinical outcome was uneventful in both sheep. Minor inflammatory and necrotic changes were reported after histopathological examination of the cardiac tissue around the lead tip.

CONCLUSION

1.5 T MRI of two implanted non-MRI-conditional pacemakers was found safe in terms of device configuration and stability, clinical outcome and cardiac tissue histopathological findings.

Practice Advisory for the Perioperative Management of Patients with Cardiac Implantable Electronic Devices: Pacemakers and Implantable Cardioverter–Defibrillators 2020

This practice advisory updates the “Practice Advisory for the Perioperative Management of Patients with Cardiac Implantable Electronic Devices: Pacemakers and Implantable Cardioverter–Defibrillators: An Updated Report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Cardiac Implantable Electronic Devices,” adopted by the American Society of Anesthesiologists in 2010 and published in 2011. This updated advisory is intended for use by anesthesiologists and all other individuals who deliver or who are responsible for anesthesia care. The update may also serve as a resource for other physicians and healthcare professionals who manage patients with cardiac implantable electronic devices.

Supplemental Digital Content is available in the text.

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.

MRI safety and devices: An update and expert consensus

The use of magnetic resonance imaging (MRI) is increasing globally, and MRI safety issues regarding medical devices, which are constantly being developed or upgraded, represent an ongoing challenge for MRI personnel. To assist the MRI community, a panel of 10 radiologists with expertise in MRI safety from nine high-volume academic centers formed, with the objective of providing clarity on some of the MRI safety issues for the 10 most frequently questioned devices. Ten device categories were identified. The panel reviewed the literature, including key MRI safety issues regarding screening and adverse event reports, in addition to the manufacturer's Instructions For Use. Using a Delphi-inspired method, 36 practical recommendations were generated with 100% consensus that can aid the clinical MRI community. Level of Evidence: 5 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:657-674.

Magnetic resonance imaging in patients with cardiac implantable electronic devices

In recent years the prevalence of implantation of a cardiac implantable electronic device (CIED) has increased due to expanding implantation indications and prolonged life expectancy. Diagnostic strategies increasingly employ magnetic resonance imaging (MRI) to aid therapeutic strategies. In earlier guidelines, MRI was contra-indicated in patients with CIEDs, mainly due to previous reports of severe complications. With the development of MRI-conditional CIEDs and recent evidence concerning non-MRI-conditional CIEDs, MRIs in CIED patients can be safely performed in many hospitals.However, there are several questions that need to be addressed. Which patients can we scan? How can the scans be performed safely? And last but not least, can cardiac MRI provide diagnostic yield in patients with CIEDs?Current European guidelines are rather outdated and vague about patient selection and practical issues. There are national guidelines on this topic but several issues need extra attention and those are addressed in this point of view. It is important to create an environment with proper patient selection without unnecessary MRI scans in CIED patients, but also without unnecessary fear of complications, preventing access to MRI in patients who can benefit from this powerful diagnostic tool.

Magnetic resonance imaging in patients with cardiac implanted electronic devices: focus on contraindications to magnetic resonance imaging protocols

Aims

Magnetic resonance imaging (MRI) has been reported to be safe in patients with cardiac implantable electronic devices (CIED) provided a specific protocol is followed. The objective of this study was to assess whether this is also true for patients excluded from published protocols.

Methods and results

A total of 160 MRIs were obtained in 142 consecutive patients with CIEDs [106 patients had an implantable cardioverter defibrillator (ICD) and 36 had a pacemaker implanted] using an adapted, pre-specified protocol. A cardiac MRI was performed in 95 patients, and a spinal/brain MRI was performed in 47 patients. Forty-six patients (32%) had either abandoned leads (n = 10), and/or were pacemaker dependent with an implanted ICD (n = 19), had recently implanted CIEDs (n = 1), and/or had a CIED device with battery depletion (n = 2), and/or a component of the CIED was recalled or on advisory (n = 32). No major complications occurred. Some device parameters changed slightly, but significantly, right after or at 1-week post-MRI without requiring any reprogramming. In one patient with an ICD on advisory, the pacing rate changed inexplicably during one of his two MRIs from 90 to 50 b.p.m.

Conclusion

Using a pre-specified protocol, cardiac and non-cardiac MRIs were performed in CIED patients with pacemaker dependency, abandoned leads, or depleted batteries without occurrence of major adverse events. Patients with devices on advisory need to be monitored carefully during MRI, especially if they are pacemaker dependent.

Cause of the "power-on reset" phenomenon other than electric magnetic interference in a patient with a pacemaker

A 67-year old male with a dual-chamber pacemaker visited for a regular check-up. An unfamiliar message emerged on the display just after placing the programmer wand. We could recognize that the pacemaker had already been in the safe back-up mode of DDI, and the programmer prompted a re-initialization request. We are so surprised because there was no indication of device malfunction the day before in daily monitoring and a 12-lead electrocardiogram revealed normally working in the DDD mode just before checking the device. The pacemaker was immediately re-programmed to the former setting. This phenomenon has not recurred for 12 months.

Safety of Magnetic Resonance Imaging in Patients with Cardiac Devices

BACKGROUND

Patients who have pacemakers or defibrillators are often denied the opportunity to undergo magnetic resonance imaging (MRI) because of safety concerns, unless the devices meet certain criteria specified by the Food and Drug Administration (termed "MRI-conditional" devices).

METHODS

We performed a prospective, nonrandomized study to assess the safety of MRI at a magnetic field strength of 1.5 Tesla in 1509 patients who had a pacemaker (58%) or an implantable cardioverter-defibrillator (42%) that was not considered to be MRI-conditional (termed a "legacy" device). Overall, the patients underwent 2103 thoracic and nonthoracic MRI examinations that were deemed to be clinically necessary. The pacing mode was changed to asynchronous mode for pacing-dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled. Outcome assessments included adverse events and changes in the variables that indicate lead and generator function and interaction with surrounding tissue (device parameters).

RESULTS

No long-term clinically significant adverse events were reported. In nine MRI examinations (0.4%; 95% confidence interval, 0.2 to 0.7), the patient's device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed; the device was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patients. At long-term follow-up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P-wave amplitude (in 4% of the patients), increases in atrial capture threshold (4%), increases in right ventricular capture threshold (4%), and increases in left ventricular capture threshold (3%). The observed changes in lead parameters were not clinically significant and did not require device revision or reprogramming.

CONCLUSIONS

We evaluated the safety of MRI, performed with the use of a prespecified safety protocol, in 1509 patients who had a legacy pacemaker or a legacy implantable cardioverter-defibrillator system. No long-term clinically significant adverse events were reported. (Funded by Johns Hopkins University and the National Institutes of Health; ClinicalTrials.gov number, NCT01130896 .).

Pacemakers in MRI for the Neuroradiologist

Cardiac implantable electronic devices are frequently encountered in clinical practice in patients being screened for MR imaging examinations. Traditionally, the presence of these devices has been considered a contraindication to undergoing MR imaging. Growing evidence suggests that most of these patients can safely undergo an MR imaging examination if certain conditions are met. This document will review the relevant cardiac implantable electronic devices encountered in practice today, the background physics/technical factors related to scanning these devices, the multidisciplinary screening protocol used at our institution for scanning patients with implantable cardiac devices, and our experience in safely performing these examinations since 2010.

Clinical recognition of pacemaker battery depletion and automatic reprogramming

All contemporary pacemakers undergo automatic reprogramming upon reaching elective replacement indication due to battery depletion. The majority of such reprogramming will result in changes to both pacing mode and pacing rate. The exact software reprogramming varies considerably among pacemaker manufacturers and may even vary among models of the same manufacturer. Accordingly, it is essential for healthcare providers managing pacemaker patients to have a detailed understanding of the automatic reprogramming seen at elective replacement indication as well as their potential physiological and clinical consequences.

Cardiac Pacemakers: Function, Troubleshooting, and Management: Part 1 of a 2-Part Series

Advances in cardiac surgery toward the mid-20th century created a need for an artificial means of stimulating the heart muscle. Initially developed as large external devices, technological advances resulted in miniaturization of electronic circuitry and eventually the development of totally implantable devices. These advances continue to date, with the recent introduction of leadless pacemakers. In this first part of a 2-part review, we describe indications, implant-related complications, basic function/programming, common pacemaker-related issues, and remote monitoring, which are relevant to the practicing cardiologist. We provide an overview of magnetic resonance imaging and perioperative management among patients with cardiac pacemakers.

Safety and utility of magnetic resonance imaging in patients with cardiac implantable electronic devices

BACKGROUND

Off-label magnetic resonance imaging (MRI) for patients with cardiac implantable electrical devices has been limited owing to concerns about safety and unclear diagnostic and prognostic utility.

OBJECTIVE

The purpose of this study was to define major and minor adverse events with off-label MRI scans.

METHODS

We prospectively evaluated patients with non-MRI-conditional cardiac implantable electrical devices referred for MRI scans under a strict clinical protocol. The primary safety outcome was incidence of major adverse events (loss of pacing, inappropriate shock or antitachycardia pacing, need for system revision, or death) or minor adverse events (inappropriate pacing, arrhythmias, power-on-reset events, heating at the generator site, or changes in device parameters at baseline or at 6 months).

RESULTS

A total of 189 MRI scans were performed in 123 patients (63.1% [78] men; median age 70 ± 18.5 years; 56.9% [70] patients with implantable cardioverter-defibrillators; 33.3% [41] pacemaker-dependent patients) predominantly for brain or spinal conditions. A minority of scans (22.7% [43]) were performed for urgent or emergent indications. Major adverse events were rare: 1 patient with loss of pacing, no deaths, or system revisions (overall rate 0.5%; 95% confidence interval 0.01-2.91). Minor adverse events were similarly rare (overall rate 1.6%; 95% confidence interval 0.3-4.6). Nearly all studies (98.4% [186]) were interpretable, while 75.1% [142] were determined to change management according to the prespecified criteria. No clinically significant changes were observed in device parameters acutely after MRI or at 6 months as compared with baseline across all patient and device categories.

CONCLUSION

Off-label MRI scans performed under a strict protocol demonstrated excellent short- and medium-term safety while providing interpretable imaging that frequently influenced clinical care.

Magnetic Resonance Imaging in Nondependent Pacemaker Patients with Pacemakers and Defibrillators with a Nearly Depleted Battery

BACKGROUND

Magnetic resonance imaging (MRI) in patients with non-MRI-conditional cardiac implantable electronic devices (CIEDs) has been shown to be safe when performed under closely monitored protocols. However, the safety of MRI in patients with devices with a nearly depleted battery has not been reported.

METHODS

Prospective data were collected between January 2008 and May 2015 in patients with non-MRI-conditional CIEDs undergoing clinically indicated MRI under institutional protocol. Patients who were pacemaker dependent were excluded. Patients whose devices were at elective replacement indicator (ERI) at the time of MRI or close to ERI (ERI or replacement for battery depletion within 3 months of scan) were identified through database review and analyzed for clinical events.

RESULTS

MRI scans (n = 569) were performed in 442 patients. Of these, we identified 13 scans performed with a nearly depleted battery in nine patients. All scans with implantable cardioverter defibrillators (ICDs, n = 9) were uneventful. However, two scans with pacemakers close to ERI resulted in a power-on-reset (PoR) event. One scan with a pacemaker close to ERI that was programmed to DOO mode reached ERI during MRI and automatically changed to VVI mode. Additionally, one scan with a pacemaker at ERI did not allow programming. All pacemakers with events were implanted before 2005.

CONCLUSION

Patients with pacemakers and ICDs with a nearly depleted battery can safely undergo MRI when patients are not pacemaker dependent. Attention should be paid because old devices can result in PoR or ERI during MRI, which may lead to oversensing and inhibition of pacing.

The Safety of Cardiac and Thoracic Magnetic Resonance Imaging in Patients with Cardiac Implantable Electronic Devices

RATIONALE AND OBJECTIVES

Studies reporting the safety of magnetic resonance imaging (MRI) in patients with a cardiac implantable electronic device (CIED) have mostly excluded examinations with the device in the magnet isocenter. The purpose of this study was to describe the safety of cardiac and thoracic spine MRI in patients with a CIED.

MATERIALS AND METHODS

The medical records of patients with a CIED who underwent a cardiac or thoracic spine MRI between January 2011 and December 2014 were reviewed. Devices were interrogated before and after imaging with reprogramming to asynchronous pacing in pacemaker-dependent patients. The clinical interpretability of the MRI and peak and average specific absorption rates (SARs, W/kg) achieved were determined.

RESULTS

Fifty-eight patients underwent 51 cardiac and 11 thoracic spine MRI exams. Twenty-nine patients had a pacemaker and 29 had an implantable cardioverter defibrillator. Seventeen percent (n = 10) were pacemaker dependent. Fifty-one patients (89%) had non-MRI-conditional devices. There were no clinically significant changes in atrial and ventricular sensing, impedance, and threshold measurements. There were no episodes of device mode changes, arrhythmias, therapies delivered, electrical reset, or battery depletion. One study was prematurely discontinued due to a patient complaint of chest pain of which the etiology was not determined. Across all examinations, the average peak SAR was 2.0 ± 0.85 W/kg with an average SAR of 0.35 ± 0.37 W/kg. Artifact significantly limiting the clinical interpretation of the study was present in 33% of cardiac MRI studies.

CONCLUSIONS

When a comprehensive CIED magnetic resonance safety protocol is followed, the risk of performing 1.5-T magnetic resonance studies with the device in the magnet isocenter, including in patients who are pacemaker dependent, is low.

Sites of Successful Ventricular Fibrillation Ablation in Bileaflet Mitral Valve Prolapse Syndrome

BACKGROUND

Although the vast majority of mitral valve prolapse (MVP) is benign, a small subset of patients, predominantly women, with bileaflet prolapse, complex ventricular ectopy (VE), and abnormal T waves comprise the recently described bileaflet MVP syndrome. We compared findings on electrophysiological study in bileaflet MVP syndrome patients with and without cardiac arrest to identify factors that may predispose to malignant ventricular arrhythmia.

METHODS AND RESULTS

Fourteen consecutive bileaflet MVP syndrome patients (n=13 women; median [limits], age at index ablation, 33.8 [21.0-58.7] years; ejection fraction, 60% [45%-67%]; all ≤ moderate mitral regurgitation; n=6 with previous cardiac arrest and implantable cardioverter defibrillator shocks for ventricular fibrillation; and n=8 without implantable cardioverter defibrillator although with symptomatic complex VE) were included. The 2 groups had similar baseline echocardiographic and electrocardiographic characteristics. All patients had at least 1 left ventricular papillary or fascicular VE focus. Purkinje origin VE was identified as the ventricular fibrillation trigger in 6 of 6 cardiac arrest patients (4 from papillary muscle) and Purkinje origin of dominant VE was seen in 5 of 8 (3 from papillary muscle) nonarrest patients. Acute success was seen in 17 of 19 procedures, and a ventricular fibrillation storm occurred within 24 hours of ablation in a single patient. Repeat ablation for recurrent symptomatic arrhythmia was performed in 6 patients. At 478 (39-2099) days of follow-up, 2 cardiac arrest patients received appropriate shocks. Symptoms from VE were reduced in 12 of 14.

CONCLUSIONS

Bileaflet MVP syndrome is characterized by fascicular and papillary muscle VE that triggers ventricular fibrillation. Ablation of clinically dominant VE foci improves symptoms and reduces appropriate implantable cardioverter defibrillator shocks.