Remote monitoring of implantable cardiac monitors in patients with unexplained syncope: Predictors of false-positive alert episodes

BACKGROUND

Remote monitoring is recommended for patients with implantable cardiac monitors (ICMs), but compared to other cardiac implantable devices, ICMs are less accurate and transmit a higher number of alerts.

OBJECTIVE

The aim of this study was to investigate the predictors of false-positive (FP) arrhythmic alerts in patients with unexplained syncope who were implanted with ICM and followed by an automatic remote monitoring system.

METHODS

We retrospectively evaluated all consecutive patients who received a long-sensing vector ICM for unexplained syncope between January 2019 to September 2021 at our Syncope Unit. The primary endpoint was the incidence of the first FP episode. The secondary endpoints included assessing the incidence of FP episodes for all types of algorhythms and indentifying the reasons for the misdetection of these episodes.

RESULTS

Among 105 patients (44.8% males, median age 51 years), 51 (48.6%) transmitted at least one FP alert during a median follow-up of 301 days. The presence of pre-ventricular complexes (PVCs) on the resting electrocardiogram was the only clinical characteristic associated with an increased risk of FP alerts (adjusted Hazard ratio [HR] 5.76 [2.66-12.4], p = 0.010). The other significant device-related variables were a low-frequency filter at 0.05 Hz versus the default 0.5 Hz (adjusted HR 3.82 [1.38-10.5], p = 0.010) and the R-wave amplitude (adjusted HR 0.35 [0.13-0.99], p = 0.049).

CONCLUSION

Patients who have PVCs are at higher risk of inappropriate ICM activations. To reduce the occurrence of FP alerts, it may be beneficial to target a large R-wave amplitude during device insertion and avoid programming a low-frequency filter at 0.05 Hz.

Remote monitoring of implantable loop recorders reduces time to diagnosis in patients with unexplained syncope: a multicenter propensity score-matched study

Background

There are little data on remote monitoring (RM) of implantable loop recorders (ILRs) in patients with unexplained syncope and whether it confers enhanced diagnostic power.

Objective

To evaluate the effect of RM in ILR recipients for unexplained syncope for early detection of clinically relevant arrhythmias by comparison with a historical cohort with no RM.

Methods

SyncRM is a propensity score (PS)-matched study prospectively including 133 consecutive patients with unexplained syncope and ILR followed up by RM (RM-ON group). A historical cohort of 108 consecutive ILR patients with biannual in-hospital follow-up visits was used as control group (RM-OFF group). The primary endpoint was the time to the clinician's evaluation of clinically relevant arrhythmias (types 1, 2, and 4 of the ISSUE classification).

Results

The primary endpoint of arrhythmia evaluation was reached in 38 patients (28.6%) of the RM-ON group after a median time of 46 days (interquartile range, 13-106) and in 22 patients (20.4%) of the RM-OFF group after 92 days (25-368). The PS-matched adjusted ratio of rates of arrhythmia evaluation was 2.53 (95% confidence interval, 1.32-4.86) in the RM-ON vs. RM-OFF group (p = 0.005).

Conclusion

In our PS-matched comparison with a historical cohort, RM of ILR patients with unexplained syncope was associated with a 2.5-fold higher chance of evaluations of clinically relevant arrhythmias as compared with biannual in-office follow-up visits.

Effectiveness and safety of implantable loop recorder and clinical utility of remote monitoring in patients with unexplained, recurrent, traumatic syncope

BACKGROUND

Implantable loop recorder (ILR) is still underutilized in clinical practice, especially in the setting of elderly patients with recurrent, traumatic, unexplained syncope. Data on the actual risk of traumatic syncopal recurrence during ILR monitoring in this specific patient setting are lacking.

RESEARCH DESIGN AND METHODS

Prospective, multicentre registry enrolling consecutive patients undergoing ILR insertion for unexplained, recurrent, traumatic syncope. In a proportion of enrolled patients, remote monitoring (RM) was used for device follow-up. The risk of traumatic and non-traumatic syncopal recurrences during ILR observation were prospectively assessed.

RESULTS

A total of 483 consecutive patients (68±14 years, 59% male) were enrolled. During a median follow-up of 18 months, a final diagnosis was reached in 270 patients (55.9%). The risk of syncopal and traumatic syncopal recurrence was of 26.5 and 9.3%, respectively. RM significantly reduced the time to diagnosis (19.7±10.3 vs. 22.1±10.8 months; p=0.015) and was associated with a significant reduction in the risk of syncope recurrence of 48% (p<0.001), and of traumatic syncope recurrence of 49% (p=0.018).

CONCLUSIONS

ILR monitoring is effective and safe in patients with unexplained, recurrent, traumatic syncope. RM reduces the time to diagnosis and significantly reduces the risk of traumatic and non-traumatic syncopal relapses.

Clinical applications of heart rhythm monitoring tools in symptomatic patients and for screening in high-risk groups

Recent technological advances have facilitated and diversified the options available for the diagnosis of cardiac arrhythmias. Ranging from simple resting or exercise electrocardiograms to more sophisticated and expensive smartphones and implantable cardiac monitors. These tests and devices may be used for varying periods of time depending on symptom frequency. The choice of the most appropriate heart rhythm test should be guided by clinical evaluation and optimized following accurate characterization of underlying symptoms, 'red flags', risk factors, and consideration of cost-effectiveness of the different tests. This review provides evidence-based guidance for assessing suspected arrhythmia in patients who present with symptoms or in the context of screening, such as atrial fibrillation or advanced conduction disturbances following transcatheter aortic valve implantation in high-risk groups. This is intended to help clinicians choose the most appropriate diagnostic tool to facilitate the management of patients with suspected arrhythmias.

mCardia: A Context-Aware ECG Collection System for Ambulatory Arrhythmia Screening

This article presents the design, technical implementation, and feasibility evaluation of mCardia —a context-aware, mobile electrocardiogram (ECG) collection system for longitudinal arrhythmia screening under free-living conditions. Along with ECG, mCardia also records active and passive contextual data, including patient-reported symptoms and physical activity. This contextual data can provide a more accurate understanding of what happens before, during, and after an arrhythmia event, thereby providing additional information in the diagnosis of arrhythmia. By using a plugin-based architecture for ECG and contextual sensing, mCardia is device-agnostic and can integrate with various wireless ECG devices and supports cross-platform deployment. We deployed the mCardia system in a feasibility study involving 24 patients who used the system over a two-week period. During the study, we observed high patient acceptance and compliance with a satisfactory yield of collected ECG and contextual data. The results demonstrate the high usability and feasibility of mCardia for longitudinal ambulatory monitoring under free-living conditions. The article also reports from two clinical cases, which demonstrate how a cardiologist can utilize the collected contextual data to improve the accuracy of arrhythmia analysis. Finally, the article discusses the lessons learned and the challenges found in the mCardia design and the feasibility study.

Recurrence of atrial fibrillation post-ablation: which is the most effective approach for detection?

Over the last 20 years, catheter ablation of atrial fibrillation (AF) has evolved from a research tool into a fundamental therapeutic measure, with the potential to improve symptoms, quality of life, and even risk of major adverse cardiac events (among patients with heart failure and a reduced ejection fraction). Notwithstanding the tremendous evolution in techniques and tools, risk of AF recurrences post-ablation is not negligible, and a comprehensive structured follow-up is highly needed to deliver optimal patient care. In this follow-up process, monitoring of heart rhythm is quintessential to detect recurrences, and may be accomplished by means of symptoms-triggered, intermittent, or continuous monitors. In recent years, the development and widespread adoption of implantable cardiac monitors, by allowing continuous long-term rhythm assessment, has surged to become the gold-standard strategy, both in research settings and in clinical practice. In this review, we both summarize the present state-of-the art on the detection of post-ablation AF recurrences, and provide future perspectives on this emerging yet often neglected topic, aiming to give practical hints for evidence-based, personalized patient care.

Insertable cardiac monitors: current indications and devices

INTRODUCTION

Recurrent unexplained syncope is a well-established indication for an insertable cardiac monitor (ICM). Recently, the indications for an ICM have been expanded.

AREAS COVERED

This review article discusses the current indications for ICMs and gives an overview of the latest generation of commercially available ICMs.

EXPERT COMMENTARY

The 2018 ESC Syncope guidelines have expanded the indications for an ICM to patients with inherited cardiomyopathy, inherited channelopathy, suspected unproven epilepsy, and unexplained falls. ICMs are also increasingly used for the detection of subclinical atrial fibrillation (AF) in patients with cryptogenic stroke. Whether treatment of subclinical AF (SCAF) with oral anticoagulation prevents recurrent stroke is yet unknown. The current generation of ICMs are smaller, easier to implant, have better diagnostics, and are capable of remote monitoring. The Reveal LINQ (Medtronic) is the smallest ICM and has the most extensive performance and clinical data. The BioMonitor 2 (Biotronik) is the largest ICM but has excellent R-wave amplitudes, longest longevity, and reliable remote monitoring. The Confirm Rx (Abbott) is capable to provide mobile data transmission enabled by a smartphone app. Future generation of ICMs will incorporate heart failures indices to facilitate remote monitoring of heart failure patients.

Trends in Subcutaneous Cardiac Monitoring Technology

Ambulatory cardiac monitoring is a rapidly expanding field and one that is likely to progress beyond electrocardiographic (ECG) and blood pressure recordings. To date, the primary cardiac monitoring focus has been ambulatory ECG (AECG) monitoring. In this setting, AECG monitoring has become a diagnostic tool used daily by physicians of many specialties. In this regard, both wearable and subcutaneous ECG monitoring technologies are now widely available, with the appropriate choice for a given patient being best determined by the frequency with which the patient’s symptom recurrences are expected. In other words, the less frequent the symptomatic events, then the longer the monitoring duration requirement should be. However, multiple factors other than the technology used impact success. For example, wearable AECG systems are only capable of monitoring patients for a period of a few days to several weeks due to limited battery longevity, patient intolerance to cutaneous ECG electrodes, the cumbersome nature of the device, or a combination of these factors. Current-generation insertable cardiac monitors (ICMs), on the other hand, offer three years of monitoring and infrequent skin irritation. Additionally, automatic remote download, a valuable feature in many cases, is only offered by certain wearable technologies, but is an option in all currently available ICMs. This report focuses on the current status of subcutaneous ICMs and their indications and limitations. The goal is to highlight the variety of utility of current ICM technologies and to provide insight into potential future subcutaneous ICM applications.

Multimodal Molecular Imaging: Current Status and Future Directions

Molecular imaging has emerged at the end of the last century as an interdisciplinary method involving in vivo imaging and molecular biology aiming at identifying living biological processes at a cellular and molecular level in a noninvasive manner. It has a profound role in determining disease changes and facilitating drug research and development, thus creating new medical modalities to monitor human health. At present, a variety of different molecular imaging techniques have their advantages, disadvantages, and limitations. In order to overcome these shortcomings, researchers combine two or more detection techniques to create a new imaging mode, such as multimodal molecular imaging, to obtain a better result and more information regarding monitoring, diagnosis, and treatment. In this review, we first describe the classic molecular imaging technology and its key advantages, and then, we offer some of the latest multimodal molecular imaging modes. Finally, we summarize the great challenges, the future development, and the great potential in this field.

Sensing performance, safety, and patient acceptability of long-dipole cardiac monitor: An innovative axillary insertion

BACKGROUND

The recommended location for implantable cardiac monitor (ICM) insertion is the left pectoral region. We tested whether an innovative left axillary implantation approach could be applicable for a new ICM, characterized by a long sensing dipole.

METHODS

We considered a series of 55 patients consecutively implanted with a long-dipole ICM (BioMonitor 2); the first 30 subjects underwent prepectoral location insertion, while the subsequent 25 received the ICM in the axillary region. Sensing performances collected at 1-month follow-up were compared between the two groups. During the visit, each patient was also asked to fill in a brief questionnaire to assess patient acceptability of the device.

RESULTS

All patients had a successful insertion of ICM. Mean R-wave amplitude was 0.87 ± 0.44 mV in the prepectoral group and 1.00 ± 0.45 mV in the axillary one, without any significant difference. The percentage of patients with visible P wave was also comparable between the two approaches (65.5% vs 68.2%, P = 0.84). None of the patients reported device-related issues or discomfort, and ICM was generally well accepted and tolerated by all the involved patients.

CONCLUSION

Axillary insertion may represent a valid alternative to the standard one for long-dipole ICM technology providing not only patient acceptability but also high-quality sensing performances.

The Role of Implantable Cardiac Monitors in Atrial Fibrillation Management

Continuous heart rhythm monitoring using implantable cardiac monitors (ICMs) for atrial fibrillation (AF) management is steadily increasing in current clinical practice, even in the absence of an established indication provided by international guidelines. The increasing use of such devices is mainly associated with recent technological improvements including miniaturization, easier implant procedures, and remote monitoring, all of which make this strategy continuously more appealing and promising. For these and other reasons, ICMs have been proven to be a safe and highly effective tool for detecting AF episodes. However, ICMs are not the best option for every patient, as limitations exist. Therefore, it is imperative to weigh the possible benefits against the potential limitations of using these devices when deciding individualized patient care.

Performance of the New BioMonitor 2-AF Insertable Cardiac Monitoring System: Can Better be Worse?

BACKGROUND

Implantable loop recorders (ILR) are valuable tools for the investigation of patients with suspected arrhythmias. The BioMonitor 2-AF is a novel insertable ILR with enhanced atrial fibrillation (AF) detection algorithm and remote monitoring capability.

OBJECTIVE

The objective of this first-in-human study with the BioMonitor 2-AF was to analyze course of P-wave sensing performance and R-wave amplitude, prevalence of false and correctly sensed and classified episodes, and effectiveness of remote monitoring.

METHODS

All 19 patients who underwent ILR insertion were included in the BIOTRONIK Home Monitoring® system (BIOTRONIK GmbH, Berlin, Germany). Daily changes in P-wave and R-wave sensing were analyzed over 6 weeks. A breathing test (in- and expiration) was performed in two different body positions at baseline and during a 6-week in-house follow-up to investigate alterations of P-wave and R-wave sensing.

RESULTS

R-wave amplitude and the high P-wave visibility (94.4%) remained unchanged during the follow-up period. In most patients both an increase and decrease of R-wave amplitude, and in some cases a complete R-wave vector change (31.6%), was documented during the "breathing test." Change of body position did not alter R-wave sensing amplitude mostly. "Breathing test" and change of body position had no effect on P-wave sensing performance. In 15.8% of the patients, misclassification of episodes as AF or high ventricular rates due to P-wave oversensing occurred. No ILR-related complication occurred. Automatic transmission via BIOTRONIK Home Monitoring® was successful 100% of the time.

CONCLUSION

This study demonstrates that the BioMonitor 2-AF is a safe and effective tool for continuous cardiac monitoring.

The 12-lead electrocardiogram and risk of sudden death: current utility and future prospects

More than 100 years after it was first invented, the 12-lead electrocardiogram (ECG) continues to occupy an important place in the diagnostic armamentarium of the practicing clinician. With the recognition of relatively rare but important clinical entities such as Wolff-Parkinson-White and the long QT syndrome, this clinical tool was firmly established as a test for assessing risk of sudden cardiac death (SCD). However, over the past two decades the role of the ECG in risk prediction for common forms of SCD, for example in patients with coronary artery disease, has been the focus of considerable investigation. Especially in light of the limitations of current risk stratification approaches, there is a renewed focus on this broadly available and relatively inexpensive test. Various abnormalities of depolarization and repolarization on the ECG have been linked to SCD risk; however, more focused work is needed before they can be deployed in the clinical arena. The present review summarizes the current knowledge on various ECG risk markers for prediction of SCD and discusses some future directions in this field.

Results of remote follow-up and monitoring in young patients with cardiac implantable electronic devices

BACKGROUND

Remote monitoring is increasingly used in the follow-up of patients with cardiac implantable electronic devices. Data on paediatric populations are still lacking. The aim of our study was to follow-up young patients both in-hospital and remotely to enhance device surveillance.

METHODS

This is an observational registry collecting data on consecutive patients followed-up with the CareLink system. Inclusion criteria were a Medtronic device implanted and patient's willingness to receive CareLink. Patients were stratified according to age and presence of congenital/structural heart defects (CHD).

RESULTS

A total of 221 patients with a device - 200 pacemakers, 19 implantable cardioverter defibrillators, and two loop recorders--were enrolled (median age of 17 years, range 1-40); 58% of patients were younger than 18 years of age and 73% had CHD. During a follow-up of 12 months (range 4-18), 1361 transmissions (8.9% unscheduled) were reviewed by technicians. Time for review was 6 ± 2 minutes (mean ± standard deviation). Missed transmissions were 10.1%. Events were documented in 45% of transmissions, with 2.7% yellow alerts and 0.6% red alerts sent by wireless devices. No significant differences were found in transmission results according to age or presence of CHD. Physicians reviewed 6.3% of transmissions, 29 patients were contacted by phone, and 12 patients underwent unscheduled in-hospital visits. The event recognition with remote monitoring occurred 76 days (range 16-150) earlier than the next scheduled in-office follow-up.

CONCLUSIONS

Remote follow-up/monitoring with the CareLink system is useful to enhance device surveillance in young patients. The majority of events were not clinically relevant, and the remaining led to timely management of problems.

Value of Ambulatory Electrocardiographic Monitoring in Syncope

Implantable loop recorders (ILRs) continuously monitor electrocardiographic signals and perform real-time analysis of heart rhythm for up to 36 months. ILRs are used to evaluate transitory loss of consciousness from possible arrhythmic origin, particularly unexplained syncope, and to evaluate difficult cases of epilepsy and unexplained falls, although current indications for their application in these areas are less clearly defined. This article analyzes the current indications for ILRs according the European Society of Cardiology guidelines on the management of syncope and the European Heart Rhythm Association guidelines on the use of implantable and external electrocardiogram loop recorders, and their limitations.

The Reveal LINQ insertable cardiac monitor

Insertable cardiac monitors (ICMs) are leadless subcutaneous devices that continuously monitor the heart rhythm and record events over a timeframe measured in years, allowing for the diagnosis of infrequent rhythm abnormalities that can be the cause of palpitations, syncope and stroke. To date, ICMs have primarily been used in the work-up and management of syncope; however, their use in other areas of rhythm evaluation, particularly atrial fibrillation monitoring, is increasing. The Reveal LINQ™ is the smallest and most versatile ICM available and represents a dramatic leap forward in ICM technology that has the potential to transform patient care in a number of circumstances. Device miniaturization, simplified implant procedure and enhanced automation vastly increase physician and patient acceptance. The next 5 years can be expected to bring a greatly increased use of ICMs for disease diagnosis and management in a variety of clinical settings.

Feasibility and efficacy of a remote real-time wireless ECG monitoring and stimulation system for management of ventricular arrhythmia in rabbits with myocardial infarction

The purpose of this study was to explore the feasibility of continuous remote monitoring, and the induction and termination of malignant ventricular arrhythmias (VAs) by a novel implantable electronic cardiovascular device (IECD) system in rabbits with myocardial infarction (MI). The IECD was implanted and MI was induced by ligation of the left anterior descending coronary artery in 20 adult rabbits. Internet-based remote electrocardiogram (ECG) monitoring and ventricular stimulation were conducted in remote locations with internet access. The voltage amplitudes of the stimulation signals were recorded synchronously by remote and surface ECG. Programmed stimulation with regular stimuli and regular stimuli with an added extra stimulus were performed prior to and following the MI surgery to induce and terminate VAs. IECD implantation and MI surgery, as well as qualified remote and bidirectional signal communications between the implanted IECD and extracorporeal system, were successfully achieved in 18 rabbits. The voltage of the stimulation signals recorded by the remote and surface ECGs showed a good correlation with the stimulation current (remote ECG, r=0.972 and surface ECG, r=0.988; P<0.001). Sustained ventricular tachycardia (VT) was induced in five rabbits (5/20, 25%) prior to MI induction and in 12 rabbits (12/16, 75%) following MI induction. Of the 17 induced VTs, 16 were successfully terminated by remote ventricular stimulation. The novel IECD system provides qualified remote wireless ECG monitoring and possesses the potential to induce and terminate VAs by remote ventricular pacing in this rabbit model of MI. Thus, this model of MI may be used to test the efficacy of novel drugs and devices for the management of VAs.

Remote monitoring as a key innovation in the management of cardiac patients including those with implantable electronic devices

This Introduction to the Supplement provides a brief history of remote monitoring, discusses its current status, and indicates the bright future that it possesses with a broad application in many branches of cardiology, at least including arrhythmias, heart failure, and ischaemic heart disease in addition to the management of implantable electronic devices.

Implantable diagnostic monitors in the early assessment of syncope and collapse

The implantable diagnostic monitor, or loop recorder (ILR) is a subcutaneous monitor capable of continuous ECG monitoring up to 3 years. It is an elegant investigative tool for the assessment of patients with recurrent, unexplained syncope in whom an arrhythmic cause needs to be excluded, and is now increasingly utilised very early in the diagnostic work-up of these patients, in line with current guidelines. This review examines the evidence underpinning these recommendations as well as the relevant clinical trials evaluating the use of the ILR in syncope. Continued research will be needed to validate its role as a first line investigation in a sub-select of syncopal patients, especially with the addition of remote monitoring capabilities.

Key challenges in the current management of syncope

Patients commonly present with syncope at emergency departments and other facilities for urgent care. Syncope is understood by physicians to be a transient, self-terminating period of cerebral hypoperfusion that usually results from systemic hypotension, and clinical guidelines for the care of patients with presumed syncope are available. However, the diagnosis and management of such patients continue to pose important diagnostic, therapeutic, and economic challenges, which are the focus of this Review. First, we discuss how to improve symptom characterization to distinguish syncope from other forms of transient loss of consciousness and syncope mimics. Second, we compare methods of risk stratification in patients with suspected syncope, and recommend the introduction of syncope clinics with enhanced interdisciplinary collaboration to optimize patient care at reduced expense. Third, we highlight the importance of the appropriate selection of diagnostic tools and treatment strategies in these syncope clinics. Finally, we address the difficulties associated with therapy for the most-common form of syncope--vasovagal or reflex syncope.

Current and emerging indications for implantable cardiac monitors

Implantable cardiac monitors (ICMs) continuously monitor the patient's electrocardiogram and perform real-time analysis of the heart rhythm, for up to 36 months. The current clinical use of ICMs involves the evaluation of transitory symptoms of possible arrhythmic origin, such as unexplained syncope and palpitations. Moreover, ICMs can also be used for the evaluation of difficult cases of epilepsy and unexplained falls, though current indications for their application in these sectors are less clearly defined. Finally, the ability of new-generation ICMs to automatically record arrhythmic episodes suggests that these devices could also be used to study asymptomatic arrhythmias, and thus could be proposed for the long-term evaluation of the total (symptomatic and asymptomatic) arrhythmic burden in patients at risk of arrhythmic events. In particular, ICMs may have an emerging role in the management of patients with atrial fibrillation and in those at risk of ventricular arrhythmias.

Syncope in adults: systematic review and proposal of a diagnostic and therapeutic algorithm

This review aims to provide a practical and up-to-date description on the relevance and classification of syncope in adults as well as a guidance on the optimal evaluation, management and treatment of this very common clinical and socioeconomic medical problem. We have summarized recent active research and emphasized the value for physicians to adhere current guidelines. A modern management of syncope should take into account 1) use of risk stratification algorithms and implementation of syncope management units to increase the diagnostic yield and reduce costs; 2) early implantable loop recorders rather than late in the evaluation of unexplained syncope; and 3) isometric physical counter-pressure maneuvers as first-line treatment for patients with neurally-mediated reflex syncope and prodromal symptoms.