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

Ventricular Tachycardia Ablation in Nonischemic Cardiomyopathy

Catheter ablation is being increasingly performed as adjunctive treatment to prevent recurrent implantable cardioverter-defibrillator therapies in patients with nonischemic cardiomyopathy and ventricular tachycardia (VT). In the context of VT ablation, nonischemic cardiomyopathy usually refers to dilated cardiomyopathy (DCM) as one morphological phenotype. Over the past decades, progress has been made to better characterize distinct subtypes and to differentiate between causes of DCM, which has important practical and prognostic implications. The goal of this review is to summarize available data on VT ablation in patients with DCM and, more specifically, review procedural and outcome data in specific etiologies and substrate location. It will focus on our current understanding of nonischemic scars, as well as the value of multimodal imaging, image integration, and electroanatomic mapping for substrate identification, procedural planning, and ablation. In addition, recent findings from whole human heart histology of patients with DCM and VT and their potential implications for imaging and mapping will be discussed.

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.

Artefacts in 1.5 Tesla and 3 Tesla cardiovascular magnetic resonance imaging in patients with leadless cardiac pacemakers

BACKGROUND

There are limited data on patients with leadless cardiac pacemakers (LCP) undergoing magnetic resonance imaging. The aim of this prospective, single-center, observational study was to evaluate artefacts on cardiovascular magnetic resonance (CMR) images in patients with LCP.

METHODS

Fifteen patients with Micra™ LCP, implanted at least 6 weeks prior to CMR scan, were enrolled and underwent either 1.5 Tesla or 3 Tesla CMR imaging. Artefacts were categorized into grade 1 (excellent image quality), grade 2 (good), grade 3 (poor) and grade 4 (non-diagnostic) for each myocardial segment. One patient was excluded because of an incomplete CMR investigation due to claustrophobia.

RESULTS

LCP caused an arc-shaped artefact (0.99 ± 0.16 cm2) at the right ventricular (RV) apex. Of 224 analyzed myocardial segments of the left ventricle (LV) 158 (70.5%) were affected by grade 1, 27 (12.1%) by grade 2, 17 (7.6%) by grade 3 and 22 (9.8%) by grade 4 artefacts. The artefact burden of grade 3 and 4 artefacts was significantly higher in the 3 Tesla group (3 Tesla vs 1.5 Tesla: 3.7 ± 1.6 vs 1.9 ± 1.4 myocardial segments per patient, p = 0.03). A high artefact burden was particularly observed in the mid anteroseptal, inferoseptal and apical septal myocardial segments of the LV and in the mid and apical segments of the RV. Quantification of LV function and assessment of valves were feasible in all patients. We did not observe any clinical or device-related adverse events.

CONCLUSION

CMR imaging in patients with LCP is feasible with excellent to good image quality in the majority of LV segments. The artefact burden is comparable small allowing an accurate evaluation of LV function, cardiac structures and valves. However, artefacts in the mid anteroseptal, inferoseptal and apical septal myocardial segments of the LV due to the LCP may impair or even exclude diagnostic evaluation of these segments. Artefacts on CMR images may be reduced by the use of 1.5 Tesla CMR scanners.

Severe tricuspid regurgitation due to interactions with right ventricular permanent pacemaker or defibrillator leads

Although thought to be a rare event, permanent pacemakers and implantable cardioverter-defibrillators with right ventricular intracardiac leads have the potential to induce tricuspid valve dysfunction. Adverse lead-valve interactions can take place through a variety of mechanisms including damage at the time of implantation, leaflet pinning, or long-term fibrosis encapsulating the leaflet tissue. Clinical manifestations can display a wide range of severity, as well as a highly variable time span between implantation and hemodynamic deterioration. This review aims to describe the potential pathophysiologic effects of intracardiac device leads on the tricuspid valve, with a focus on ideal diagnostic strategies and treatment options once lead-induced valvular dysfunction is suspected.

Wideband LGE MRI permits unobstructed viewing of myocardial scarring in a patient with an MR-conditional subcutaneous implantable cardioverter-defibrillator

A subcutaneous implantable cardioverter-defibrillator (S-ICD) is an alternative device for prevention of sudden cardiac death, without any leads within the heart. Patients implanted with any type of ICD may need catheter ablation of ventricular tachycardia (VT) to reduce the overall arrhythmia burden (e.g., recurrent monomorphic VT) and lower the incidence of painful shocks induced by the device. Late gadolinium enhancement (LGE) MRI is a useful pre-test for guiding VT ablation, because it can be used to map myocardial scar and produce better outcomes. Growing evidence suggests that MRI can be performed with manageable risks on patients with a cardiac implantable electronic device (CIED). Nonetheless, the diagnostic yield of cardiac MRI is still low because of severe image artifacts, regardless of MR-conditional or non-MR conditional labeling. Image artifacts in the heart induced by an S-ICD is expected to be larger than the artifacts induced by a transvenous ICD, because the former is twice as large in size and implanted closer to the heart. This is the first reported case of successful wideband LGE MRI in a patient implanted with an MR-conditional S-ICD. A 37-year-old man with ischemic cardiomyopathy was referred for a cardiac MRI at 1.5 T ten months after S-ICD implantation, in order to rule out constrictive pericarditis. Clinical standard LGE MRI produced severe image artifacts, rendering it useless. In contrast, wideband LGE MRI provided unobstructed viewing of myocardial scarring. This case illustrates the usefulness of wideband LGE MRI for assessment of myocardial scarring in a patient with an MR-conditional S-ICD.

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.

Cardiovascular magnetic resonance imaging in heart failure

INTRODUCTION

Heart failure is a complex clinical syndrome resulting from heart structural remodeling and impaired function in ejecting blood; its incidence is increasing markedly worldwide. The observed variations in the structure and function of the heart are attributable to differences in etiology of heart failure. Cardiac magnetic resonance imaging (CMR) can characterize myocardial tissue, assess myocardial viability, and help diagnose specific cardiomyopathies. The emergence of T1 mapping techniques further improves our knowledge and the clinical assessment of myocardial diffuse fibrosis. Physicians, therefore, must identify the variations using CMR to improve patient's symptoms, survival, and quality of life. Area covered: Current reports regarding CMR and the evidence for heart failure diagnosis and therapy as a potential marker of therapeutic response, including low- and high-risk patients, were reviewed. Literature search was performed using PubMed and Google Scholar for literature relevant to CMR, late gadolinium enhancement, T1 mapping, assessment of fibrosis and remodeling, coronary artery, myocardial infarction, heart failure, and its outcomes. Expert commentary: The authors review current evidence and discuss the potential ability of CMR to guide, diagnose, plan risk strategies, and treat patients with heart failure.

The importance of integrated left atrial evaluation: From hypertension to heart failure with preserved ejection fraction

AIM

Functional analysis and measurement of left atrium are an integral part of cardiac evaluation, and they represent a key element during non-invasive analysis of diastolic function in patients with hypertension (HT) and/or heart failure with preserved ejection fraction (HFpEF). However, diastolic dysfunction remains quite elusive regarding classification, and atrial size and function are two key factors for left ventricular (LV) filling evaluation. Chronic left atrial (LA) remodelling is the final step of chronic intra-cavitary pressure overload, and it accompanies increased neurohormonal, proarrhythmic and prothrombotic activities. In this systematic review, we aim to purpose a multi-modality approach for LA geometry and function analysis, which integrates diastolic flow with LA characteristics and remodelling through application of both traditional and new diagnostic tools.

METHODS

The most important studies published in the literature on LA size, function and diastolic dysfunction in patients with HFpEF, HT and/or atrial fibrillation (AF) are considered and discussed.

RESULTS

In HFpEF and HT, pulsed and tissue Doppler assessments are useful tools to estimate LV filling pressure, atrio-ventricular coupling and LV relaxation but they need to be enriched with LA evaluation in terms of morphology and function. An integrated evaluation should be also applied to patients with a high arrhythmic risk, in whom eccentric LA remodelling and higher LA stiffness are associated with a greater AF risk.

CONCLUSION

Evaluation of LA size, volume, function and structure are mandatory in the management of patients with HT, HFpEF and AF. A multi-modality approach could provide additional information, identifying subjects with more severe LA remodelling. Left atrium assessment deserves an accurate study inside the cardiac imaging approach and optimised measurement with established cut-offs need to be better recognised through multicenter studies.

Consequences of Retained Defibrillator and Pacemaker Leads After Heart Transplantation-An Underrecognized Problem

BACKGROUND

Cardiovascular implantable electronic devices (CIEDs) are common in patients undergoing heart transplantation (HT), and complete removal is not always possible at the time of transplantation.

METHODS

We retrospectively assessed the frequency of retained CIED leads and clinical consequences in consecutive HT patients from 2013 to 2016. Clinical outcomes included bacteremia, upper-extremity deep venous thrombosis (UEDVT), lead migration, and inability to perform magnetic resonance imaging (MRI).

RESULTS

A total of 138 patients (55 ± 11 years of age, 76% male) were identified; 37 (27%) had retained lead fragments (RLFs) at discharge. Patients with RLFs were older, had longer lead implantation time before HT, and a higher prevalence of dual-coil CIED leads compared with those without RLFs (P < .05 for all). Lead implantation time was identified as an independent predictor for RLFs (P < .05). Patients with RLFs had a higher frequency of DVT compared with the non-RLF group during the 1-year study period (42% vs 21%; P < .04). There was no difference in bacteremia. Fourteen patients (38%) could not undergo clinically indicated MRI.

CONCLUSION

RLFs after HT occur commonly and are associated with a higher rate of UEDVT and limit the use of MRI. Although no significant difference was found in the rates of bacteremia between the groups, this finding might be explained by the overall low incidence. Patients with risk factors for RLFs should be identified before transplantation, and complete lead removal should be considered with a multidisciplinary approach.

An eight-year prospective controlled study about the safety and diagnostic value of cardiac and non-cardiac 1.5-T MRI in patients with a conventional pacemaker or a conventional implantable cardioverter defibrillator

OBJECTIVES

To investigate safety and diagnostic value of 1.5-T MRI in carriers of conventional pacemaker (cPM) or conventional implantable defibrillator (cICD).

METHODS

We prospectively compared cPM/cICD-carriers undergoing MRI (study group, SG), excluding those device-dependent or implanted <6 weeks before enrolment or prior to 01/01/2000, with cPM/cICD-carriers undergoing chest x-ray, CT or follow-up (reference group, RG).

RESULTS

142 MRI (55 cardiac) were performed in 120 patients with cPM (n=71) or cICD (n=71). In the RG 98 measurements were performed in 95 patients with cPM (n=40) or cICD (n=58). No adverse events were observed. No MRI prolonged/interrupted. All cPM/cICD were correctly reprogrammed after MRI without malfunctions. One temporary communication failure was observed in one cPM-carrier. Immediately after MRI, 12/14 device interrogation parameters did not change significantly (clinically negligible changes of battery voltage and cICD charging time), without significant variations for SG versus RG. Three-12 months after MRI, 9/11 device interrogation parameters did not change significantly (clinically negligible changes of battery impedance/voltage). Non-significant changes of three markers of myocardial necrosis. Non-cardiac MRI: 82/87 diagnostic without artefacts; 4/87 diagnostic with artefacts; 1/87 partially diagnostic. Cardiac MRI: in cPM-carriers, 14/15 diagnostic with artefacts, 1/15 partially diagnostic; in cICD-carriers, 9/40 diagnostic with artefacts, 22 partially diagnostic, nine non-diagnostic.

CONCLUSIONS

A favourable risk-benefit ratio of 1.5-T MRI in cPM/cICD carriers was reported.

KEY POINTS

• Cooperation between radiologists and cardiac electrophysiologists allowed safe 1.5-T MRI in cPM/cICD-carriers. • No adverse events for 142 MRI in 71 cPM-carriers and 71 cICD-carriers. • Ninety-nine per cent (86/87) of non-cardiac MRI in cPM/cICD-carriers were diagnostic. • All cPM-carrier cardiac MRIs had artefacts, 14 examinations diagnostic, 1 partially diagnostic. • Twenty-three per cent (9/40) of cardiac MRI in cICD-carriers were non-diagnostic.

Team Management of the Ventricular Tachycardia Patient

Ventricular tachycardia is a common arrhythmia in patients with structural heart disease and heart failure, and is now seen more frequently as these patients survive longer with modern therapies. In addition, these patients often have multiple comorbidities. While anti-arrhythmic drug therapy, implantable cardioverter-defibrillator implantation and ventricular tachycardia ablation are the mainstay of therapy, well managed by the cardiac electrophysiologist, there are many other facets in the care of these patients, such as heart failure management, treatment of comorbidities and anaesthetic interventions, where the expertise of other specialists is essential for optimal patient care. A coordinated team approach is therefore essential to achieve the best possible outcomes for these complex patients.

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 .).

Magnetic Resonance Imaging in People With Cardiac Implantable Electronic Devices: A Population Based Cohort Study

Magnetic resonance imaging (MRI) is a widely used diagnostic tool with great benefits but has been considered contraindicated in people with cardiac implantable electronic devices (CIED). We investigated the occurrence of MRI in people with CIEDs and associated adverse events in a national cohort. Of 17,848 people included, 56 (0.3%) had at least one MRI; 16 of 16,102 (0.1%) with MRI non-compatible CIEDs and 40 of 1746 (2%) with MRI compatible CIEDs. Following MRI exposure, hospitalisations for potential serious adverse events were rare.

Safety of magnetic resonance imaging in patients with legacy pacemakers and defibrillators and abandoned leads

BACKGROUND

During magnetic resonance imaging (MRI), abandoned leads may act as antennae that result in tissue heating and arrhythmia induction.

OBJECTIVE

The purpose of this study was to assess the safety of MRI in patients with abandoned leads, with the addition of cardiac troponin T (cTnT) assessment to screen for myocardial damage.

METHODS

We reviewed our prospectively collected database of patients with cardiovascular implantable electronic devices (CIEDs) undergoing MRI between 2008 and 2017 at Mayo Clinic, Rochester, MN, and selected patients who had abandoned leads. We compared the adverse events in this population with an age, sex, and site of MRI-matched cohort of patients selected from this database. We evaluated paired (before/after) cTnT values using MRI in these patients.

RESULTS

Of 952 patients, 80 (8.4%) underwent 97 MRI scans with CIEDs in situ with 90 abandoned leads in place during the scans. The median age was 66 years (interquartile range 22.3 years) 66.1 years (interquartile range, Q1,Q3: 53.6, 75.9) with 66.3% (53 patients) men. There was no clinical or electrical evidence of CIED dysfunction, arrhythmias, or pain. Paired samples for the measurement of cTnT values were available in 40 patients undergoing 44 MRI examinations. The mean difference between the pre- and postimaging values was -0.002 ± 0.006 ng/mL (interquartile range 0). There was no difference after adjustment for total number of leads per patient and total number of implantable cardioverter-defibrillator coils.

CONCLUSION

There was no evidence of myocardial injury as measured by paired cTnT. The risk of MRI with abandoned leads appears low, suggesting a favorable risk-benefit profile in patients with CIEDs and abandoned leads who are considered for MRI.

Cardiac magnetic resonance imaging using wideband sequences in patients with nonconditional cardiac implanted electronic devices

BACKGROUND

Magnetic resonance imaging (MRI) has been performed safely in patients without MRI-conditional cardiac implantable electronic devices (CIEDs), but experience specifically with cardiac magnetic resonance imaging (CMR) is limited in this patient population.

OBJECTIVE

Evaluate the safety of CMR in non-MRI-conditional CIEDs and the interpretability of images using wideband sequences.

METHODS

We performed 114 consecutive CMR studies in 111 patients (mean age 59 ± 14 years, with 12 pacemakers, 73 implantable cardioverter defibrillators, 29 biventricular defibrillators) using a wideband pulse sequence for late gadolinium enhancement (LGE) imaging. A standardized protocol for device management and patient monitoring was followed. Patients were evaluated for major clinical adverse events and device parameter changes immediately after CMR and at clinical follow-up.

RESULTS

In total, 111 CMR studies were completed successfully. There were no patient deaths, new arrhythmias, immediate generator or lead failures, electrical resets, or pacing capture failures in dependent patients. Right atrial, right ventricular, and left ventricular lead impedances were significantly lower post CMR, with median differences -7 Ω (interquartile range [IQR] -20 to 0 Ω; P < .0001), 0 Ω (IQR -19 to 0 Ω; P = .0001), and -10 Ω (IQR -30 to 0 Ω; P = .023), respectively. These changes persisted through the follow-up period, with median differences -18.5 Ω (IQR -41 to -66 Ω; P = .007), -19 Ω (IQR -44 to -7 Ω; P = .006), and -30 Ω (IQR -130 to 0 Ω; P = .003), respectively. Ninety-seven studies (87%) had no artifact limiting interpretation.

CONCLUSIONS

CMR can be performed safely in non-MRI-conditional CIEDs using a standardized protocol. Use of a wideband pulse sequence for LGE imaging yields a high rate of studies unaffected by artifact.

MRI of patients with implanted cardiac devices

Cardiac implanted electronic devices (CIEDs) have historically been regarded as a contraindication for performing magnetic resonance imaging (MRI), limiting the availability of this exam for large numbers of patients who may have otherwise benefited from the unique diagnostic capabilities of MRI. Interactions between CIEDs and the magnetic field associated with MRI systems have been documented, and include potential effects on CIED function, lead heating, and force/torque on the generator. Several device manufacturers have developed "MR-Conditional" CIEDs with specific hardware and software design changes to optimize the device for the MR environment. However, a substantial body of evidence has been accumulating that suggests that MRI may be safely performed in patients with either conditional or nonconditional CIEDs. Institutional policies and procedures, including preexam screening and assessment by skilled electrophysiology personnel and intraexam monitoring, allow MRI to be safely performed in CIED patients, as evidenced by at least two, large multicenter prospective studies and multiple smaller, single-institution studies. Cross-departmental collaboration and a robust safety infrastructure at sites that perform MRI should allow for the safe imaging of CIED patients who have a clinical indication for the study, regardless of the conditionality status of the device.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018;47:595-603.

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.

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.