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

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.

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.

Pro-Con Debate: Are Patients With a Cardiovascular Implantable Electronic Device Suitable to Receive Care in a Free-Standing Ambulatory Surgery Center?

Migration of surgical and other procedures that require anesthesia care from a hospital to a free-standing ambulatory surgery center (ASC) continues to grow. Patients with cardiac implantable electronic devices (CIED) might benefit from receiving their care in a free-standing ASC setting. However, these patients have cardiovascular comorbidities that can elevate the risk of major adverse cardiovascular events. CIEDs are also complex devices and perioperative management varies between devices marketed by various manufacturers and require consultation and ancillary services, which may not be available in a free-standing ASC. Thus, perioperative care of these patients can be challenging. Therefore, the suitability of this patient population in a free-standing ASC remains highly controversial. Although applicable advisories exist, considerable discussion continues with surgeons and other proceduralists about the concerns of anesthesiologists. In this Pro-Con commentary article, we discuss the arguments for and against scheduling a patient with a CIED in a free-standing ASC.

Radiofrequency-induced heating of broken and abandoned implant leads during magnetic resonance examinations

Purpose

The risks of RF‐induced heating of active implantable medical device (AIMD) leads during MR examinations must be well understood and realistically assessed. In this study, we evaluate the potential additional risks of broken and abandoned (cut) leads.

Methods

First, we defined a generic AIMD with a metallic implantable pulse generator (IPG) and a 100‐cm long lead containing 1 or 2 wires. Next, we numerically estimated the deposited in vitro lead‐tip power for an intact lead, as well as with wire breaks placed at 10 cm intervals. We studied the effect of the break size (wire gap width), as well as the presence of an intact wire parallel to the broken wire, and experimentally validated the numeric results for the configurations with maximum deposited in vitro lead‐tip power. Finally, we performed a Tier 3 assessment of the deposited in vivo lead‐tip power for the intact and broken lead in 4 high resolution virtual population anatomic models for over 54,000 MR examination scenarios.

Results

The enhancement of the deposited lead‐tip power for the broken leads, compared to the intact lead, reached 30‐fold in isoelectric exposure, and 16‐fold in realistic clinical exposures. The presence of a nearby intact wire, or even a nearby broken wire, reduced this enhancement factor to <7‐fold over the intact lead.

Conclusion

Broken and abandoned leads can pose increased risk of RF‐induced lead‐tip heating to patients undergoing MR examinations. The potential enhancement of deposited in vivo lead‐tip power depends on location and type of the wire break, lead design, and clinical routing of the lead, and should be carefully considered when performing risk assessment for MR examinations and MR conditional labeling.

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.

Where do we go from here? Beyond the MagnaSafe trial: A focus beyond a 'safety-first' notion. An MRI study in 500 consecutive patients

BACKGROUND

In patients with conventional pacemakers or ICD's, MRI is infrequently performed due to safety concerns. Recent reports have allayed many of these concerns. However, the additive clinical value of scanning patients with cardiac implants has not been established.

OBJECTIVE

Assessing the additive value of thoracic and non-thoracic MRI in patients with implantable cardiac devices.

METHODS AND RESULTS

Prospective data were analyzed in 500 patients with implanted cardiac devices that underwent MRI over a 12 year period at a single institution (Allegheny General Hospital, Pittsburgh, PA). A set of three questions were answered following scan interpretation by both the MRI technologist and interpreting MRI physician(s): 1) Did the primary diagnosis change? 2) Did MRI provide additional information to the existing diagnosis? 3) Did patient management change? If 'Yes' was answered to any of the above questions, it was considered that the MRI scan was of value to patient diagnosis and/or guiding therapy. Scans encountered were neurological/neurosurgical 354 (70.8%), cardiac 98 (19.6%) and orthopedic 48 (9.6%) in nature. In 431 (86%) MRI added additional information to the primary diagnosis and in 277 (55.4%) MRI changed the primary diagnosis. In 304 (60.8%) cases management changed, 265 (53%) due to a change in diagnosis and in 39 (7.8%) due to providing additional information. No safety issues were encountered and no adverse effects of MRI scan were noted.

CONCLUSIONS

MRI in patients with implanted cardiac devices was of additive value to diagnosis and management thereby informing risk-benefit considerations.

CONDENSED ABSTRACT

500 patients with implanted cardiac devices who underwent a MRI examination over a 12 year period were followed prospectively. Imaging primarily focus on three anatomical regions (neurological/neurosurgical, cardiac and orthopedic) providing added information to the primary diagnosis in 431 (86%) cases and changing the primary diagnosis in 277 (55.4%) cases. In 304 (60.8%) cases management changed with 265 (53%) being due to a change of diagnosis and in 39 (7.8%) due to providing additional information. No safety issues were encountered using a defined protocol.

CONCLUSIONS

MR imaging retains its diagnostic yield in patients with implanted devices.

Access to MRI for patients with cardiac pacemakers and implantable cardioverter defibrillators

OBJECTIVE

To determine provision of MRI for patients with cardiac implantable electronic devices (CIEDs; pacemakers and defibrillators) in England, to understand regional variation and assess the impact of guideline changes.

METHODS

Retrospective data related to MRI scans performed in patients with CIED over the preceding 12 months was collected using a structured survey tool distributed to every National Health Service Trust MRI unit in England. Data were compared with similar data from 2014/2015 and with demand (estimated from local CIED implantation rates and regional population data by sustainability and transformation partnerships (STPs)).

RESULTS

Responses were received from 212 of 223 (95%) hospitals in England. 112 (53%) MRI units' scan patients with MR-conditional CIEDs (10% also scan non-MR conditional devices), compared with 46% of sites in 2014/2015. Total annual scan volume increased over fourfold between 2014 and 2019 (1090 to 4896 scans). There was widespread geographical variation, with five STPs (total population >3·5 million representing approximately 25 000 patients with CIED) with no local provision. There was no correlation between local demand (CIED implantation rates) and MRI provision (scan volume). Complication rates were extremely low with three events nationally in 12 months (0·06% CIED-MRI scans).

CONCLUSIONS

Provision of MRI for patients with CIEDs in England increased over fourfold in 4 years, but an estimated 10-fold care gap remains. Almost half of hospitals and 1 in 10 STPs have no service, with no relationship between local supply and demand. Availability of MRI for patients with non-MR conditional devices, although demonstrably safe, remains limited.

2020 MR Safety for Cardiac Devices: An Update for Radiologists

Magnetic resonance imaging (MRI) is a unique and powerful diagnostic tool that provides images without ionizing radiation and, at times, can be the only modality to properly assess and diagnose some pathologies. Although many patients will need an MRI in their lifetime, many of them are still being unjustly denied access to it due to what were once considered absolute contraindications, including MR nonconditional pacemakers and implantable cardioverter-defibrillators. However, there are a number of large studies that have recently demonstrated that MRI can safely be performed in these patients under certain conditions. In addition, there are an increasing number of novel cardiac devices implanted in patients who may require an MRI. Radiologists need to familiarize themselves with these devices, identify which patients with these devices can safely undergo MRI, and under which conditions. In this article, we will review the current literature on MR safety and cardiac devices, elaborate on how to safely image patients with cardiac devices, and share the expertise of our tertiary cardiac institute.

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.

MANAGEMENT OF PATIENTS WITH CARDIAC IMPLANTABLE ELECTRONIC DEVICES UNDERGOING MAGNETIC RESONANCE IMAGING - PROPOSAL FOR UNIFIED HOSPITAL PROTOCOL: CROATIAN WORKING GROUP ON ARRHYTHMIAS AND CARDIAC PACING

For many years, magnetic resonance imaging (MRI) was contraindicated in patients with cardiac implantable electronic devices (CIED). Today, there is a growing amount of evidence that MRI can be performed safely in the majority of patients with CIEDs. Firstly, there are devices considered MRI conditional by manufacturers that are available on the market and secondly, there is clear evidence that even patients with MRI non-conditional devices can also undergo MRI safely. Protocols have been developed and recommendations from different cardiac and radiologic societies have been published in recent years. However, the majority of physicians are still reluctant to refer these patients to MRI. Therefore, this document is published as a joint statement of the Croatian Working Group on Arrhythmias and Cardiac Pacing and Department of Radiology, Sestre milosrdnice University Hospital Centre to guide and ease the management of patients with CIED undergoing MRI. Also, we propose a unified protocol and checklist that could be used in Croatian hospitals.

Automatic consultation system for patients with cardiac implantable electronic devices undergoing magnetic resonance imaging

Background

Safety evaluation for patients with cardiac implantable electronic devices (CIEDs) undergoing magnetic resonance imaging (MRI) scanning is often overlooked. We developed an automatic consultation system (ACS) to improve the screening rate in these patients.

Methods

ACS was developed by the Hospital Information System Development Department of Seoul National University Bundang Hospital. It was designed to automatically request pre-MRI cardiac evaluation in patients with CIED when MRI orders are issued. The proportion of the patients without pre-MRI cardiologic evaluation was evaluated before and after the ACS application.

Results

From January 2016 to June 2018, a total of 157 patients with CIEDs [pacemaker 136 (86.6%), ICD or CRT-D 21 (13.4%), MR-conditional 117 (74.5%)] visited the MRI facility. Before the ACS application, 23 out of 84 patients (27.4%) did not have adequate pre-MRI cardiologic evaluation. Despite urgent request for pre-MRI cardiac evaluation, MRI examination was postponed or cancelled in 14 (60.8%) cases. After the ACS application, all 73 patients underwent proper cardiologic evaluation before their MRI examinations (P < 0.001). The proportion of immediate request for pre-MRI evaluation at the moment of MRI order also improved with the ACS application (before ACS 57.1%, after ACS 100%, P < 0.001).

Conclusions

The newly developed ACS helped the patients with CIED receive MRI scan safely on the schedule, improving the quality of care in this population.

Feasibility, safety, and utility of brain MRI for patients with non-MRI-conditioned CIED

Feasibility, safety, and utility of brain MRI for patients with non-MRI-conditioned cardiac implantable electrical devices (CIEDs) remains controversial. While a growing number of studies have shown safe employment in select patients under strict protocols, there is an increasing clinical need for further off-label investigations. To assess the feasibility and utility of brain MRI in neurological and neurosurgical patients with non-MRI-conditioned CIEDs using off-label protocol. We retrospectively evaluated 126 patients with non-MRI-conditioned CIEDs referred to our hospital between 2014 to 2018 for MRI under an IRB-approved protocol. A total of 126 off-label brain MRI scans were performed. The mean age was 67.5 ± 13.0. Seventy percent of scans were performed on female patients. Indications for MRI are neurosurgical (45.2%), neurological (51.6%), and others (3.2%). MRI utilization for tumor cases was highest for tumor cases (68.3%), but employment was valuable for vascular (12.7%), deep brain stimulators (3.2%), and other cases (15.9%). In the tumor category, (37.2%) of the scans were performed for initial diagnosis and pre-surgical planning, (47.7%) for post-intervention evaluation/surveillance, (15.1%) for stereotactic radiosurgery treatment (CyberKnife). No clinical complications were encountered. No functional device complications of the CIED were identified during and after the MRI in 96.9% of the studies. A 49.6% of the off-label brain MRI scans performed led to a clinically significant decision and/or intervention for the patients. A 42.9% of obtained MRI studies did not change the plan of care. A 7.9% of post-scan decision-making data was not available. We demonstrate that off-label brain MRI scans performed on select patients under a strict protocol is feasible, safe, and relevant. Almost 50% of scans provided critical information resulting in clinical intervention of the patients.

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.

Experiences of magnetic resonance imaging scanning in patients with pacemakers or implantable cardioverter-defibrillators

BACKGROUND/AIMS

Despite the U.S. Food and Drug Adminstration approving a magnetic resonance imaging (MRI)-conditional pacemaker system in 2011, many physicians remain reluctant to perform MRI scanning in patients with cardiac implantable electronic devices. Herein, we aimed to evaluate the real-world safety of MRI in these patients.

METHODS

This single-center retrospective study examined the interrogation data and outcomes of patients with pacemakers or implantable cardioverter defibrillators who underwent MRI. MRI interrogation data were collected pre- and post-MRI and after 1 month of follow-up; these included the lead impedance, measured P- and R-wave amplitudes, and capture threshold. We compared these results between the magnetic resonance (MR)-conditional and conventional groups.

RESULTS

From September 2013 to December 2015, 35 patients with cardiac implantable electronic devices underwent 43 MRI scans, with a mean follow-up of 5 months. Among these 35 patients, 14 (40%) had MR-conditional devices and 21 (60%) had conventional devices. Seven patients had high voltage devices, which were all the conventional type. There were no adverse events associated with MRI during the follow-up period, and there were no significant differences in the interrogation data changes between the conventional and MR-conditional groups.

CONCLUSION

This single-center retrospective study found that MRI can be performed safely in patients with pacemakers or implantable cardioverter defibrillators, regardless of the MRI support, as long as appropriate precautions are taken.

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.

Diagnostic Value of MRI in Patients With Implanted Pacemakers and Implantable Cardioverter-Defibrillators Across a Cross Population: Does the Benefit Justify the Risk? A Proof of Concept Study

OBJECTIVES

The objective of this study was to assess the diagnostic usefulness of thoracic and nonthoracic magnetic resonance imaging (MRI) imaging in patients with implantable cardiac devices (permanent pacemaker or implantable cardioverter-defibrillators [ICDs]) to determine if there was a substantial benefit to patients with regard to diagnosis and/or management.

BACKGROUND

MRI is infrequently performed on patients with conventional pacemakers or ICDs. Multiple studies have documented the safety of MRI scans in patients with implanted devices, yet the diagnostic value of this approach has not been established.

METHODS

Evaluation data were acquired in 136 patients with implanted cardiac devices who underwent MRIs during a 10-year period at a single institution. Specific criteria were followed for all patients to objectively define if the diagnosis by MRI enhanced patient care; 4 questions were answered after scan interpretation by both MRI technologists and MRI physicians who performed the scan. 1) Did the primary diagnosis change? 2) Did the MRI provide additional information to the existing diagnosis? 3) Was the pre-MRI (tentative) diagnosis confirmed? 4) Did patient management change? If "Yes" was answered to any of the preceding questions, the MRI scan was considered to be of value to patient diagnosis and/or therapy.

RESULTS

In 97% (n = 132) of patients, MR added value to patient diagnosis and management. In 49% (n = 67) of patients, MRI added additional valuable information to the primary diagnosis, and in 30% (n = 41) of patients, MRI changed the principle diagnosis and subsequent management of the patient. No safety issues were encountered, and no adverse effects of undergoing the MRI scan were noted in any patient.

CONCLUSIONS

MRI in patients with implanted pacemakers and defibrillators added value to patient diagnosis and management, which justified the risk of the procedure.

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.

Assessing the Risks Associated with MRI in Patients with a Pacemaker or Defibrillator

BACKGROUND

The presence of a cardiovascular implantable electronic device has long been a contraindication for the performance of magnetic resonance imaging (MRI). We established a prospective registry to determine the risks associated with MRI at a magnetic field strength of 1.5 tesla for patients who had a pacemaker or implantable cardioverter-defibrillator (ICD) that was "non-MRI-conditional" (i.e., not approved by the Food and Drug Administration for MRI scanning).

METHODS

Patients in the registry were referred for clinically indicated nonthoracic MRI at a field strength of 1.5 tesla. Devices were interrogated before and after MRI with the use of a standardized protocol and were appropriately reprogrammed before the scanning. The primary end points were death, generator or lead failure, induced arrhythmia, loss of capture, or electrical reset during the scanning. The secondary end points were changes in device settings.

RESULTS

MRI was performed in 1000 cases in which patients had a pacemaker and in 500 cases in which patients had an ICD. No deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI. One ICD generator could not be interrogated after MRI and required immediate replacement; the device had not been appropriately programmed per protocol before the MRI. We observed six cases of self-terminating atrial fibrillation or flutter and six cases of partial electrical reset. Changes in lead impedance, pacing threshold, battery voltage, and P-wave and R-wave amplitude exceeded prespecified thresholds in a small number of cases. Repeat MRI was not associated with an increase in adverse events.

CONCLUSIONS

In this study, device or lead failure did not occur in any patient with a non-MRI-conditional pacemaker or ICD who underwent clinically indicated nonthoracic MRI at 1.5 tesla, was appropriately screened, and had the device reprogrammed in accordance with the prespecified protocol. (Funded by St. Jude Medical and others; MagnaSafe ClinicalTrials.gov number, NCT00907361 .).

Utilization and likelihood of radiologic diagnostic imaging in patients with implantable cardiac defibrillators

Purpose

To examine imaging utilization in a matched cohort of patients with and without implantable cardioverter defibrillators (ICD) and to project magnetic resonance imaging (MRI) utilization over a 10‐year period.

Materials and Methods

The Truven Health MarketScan Commercial claims and Medicare Supplemental health insurance claims data were used to identify patients with continuous health plan enrollment in 2009–2012. Patients with ICDs were identified using ICD‐9 and CPT codes, and matched to patients with the same demographic and comorbidity profile, but no record of device implantation. Diagnostic imaging utilization was compared across the matched cohorts, in total, by imaging categories, and in subpopulations of stroke, back pain, and joint pain. MRI use in the nonimplant group over the 4‐year period was extrapolated out to 10 years for ICD‐indicated patients.

Results

A cohort of 18,770 matched patients were identified; average age 65.5 ± 13.38 and 21.9% female. ICD patients had significantly less MRI imaging (0.23 0.70 SD vs. 0.00 0.08 SD, P < 0.0001) than nonimplant patients. Among patients with records of stroke/transient ischemic attack (TIA) (ICD 5%, nonimplant 4%) and accompanying diagnostic imaging, 44% of nonimplant patients underwent MRI vs. 1% of ICD patients (P < 0.0001). Forecast models estimated that 53% to 64% of ICD‐eligible patients may require an MRI within 10 years.

Conclusion

MRI utilization is lower in ICD patients compared to nonimplant patients, yet the burden of incident stroke/TIA, back, and joint pain suggests an unmet need for MR‐conditional devices. J. MAGN. RESON. IMAGING 2016;43:115–127.

Etiology and Risk Factors of Posterior Circulation Infarction Compared with Anterior Circulation Infarction

BACKGROUND

Many clinicians regard posterior circulation infarction (PCI) as different from anterior circulation infarction (ACI), leading them to apply different treatments. Few studies have validated this practice by directly comparing the etiology and risk factors of PCI and ACI.

METHODS

We compared the etiology and risk factors of 2245 consecutive patients with a diagnosis of PCI or ACI confirmed by magnetic resonance imaging in the Chengdu Stroke Registry. Stroke etiology in each patient was classified according to Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria.

RESULTS

Our sample included 482 patients (21.5%) with PCI and 1763 (78.5%) with ACI. The most frequent etiology for both infarction types was small-artery occlusion, occurring in 37.6% of patients with PCI and 37.1% of those with ACI. Cardioembolism caused infarction in a significantly smaller proportion of patients with PCI (5.4%) than in patients with ACI (13.3%; odds ratio [OR] = .373; 95% confidence interval [CI], .245-.566). Frequencies of other stroke etiologies were similar between the 2 patient groups. Analysis of risk factor frequencies in the 2 groups showed hypertension to be the most common, occurring in 47.9% of patients in either group. Multivariable analysis identified 2 factors as conferring greater risk of PCI than ACI: male gender (OR = 1.392; 95% CI, 1.085-1.786) and diabetes mellitus (OR = 1.667; 95% CI, 1.275-2.180). The same analysis identified 2 factors as conferring greater risk of ACI: atrial fibrillation (OR = .530; 95% CI, .295-.951) and heart valve disease (OR = .433; 95% CI, .203-.922). Frequencies of other possible risk factors were similar between the 2 groups.

CONCLUSIONS

These findings suggest that PCI and ACI are more similar than different in their etiology and risk factors and that the 2 types of infarction should be treated based more on etiology and risk factors than on their posterior or anterior localization.