Comparing the outcomes and costs of cardiac monitoring with implantable loop recorders and mobile cardiac outpatient telemetry following stroke using real-world evidence

Aim: Patients with ischemic stroke (IS) commonly undergo monitoring to identify atrial fibrillation with mobile cardiac outpatient telemetry (MCOT) or implantable loop recorders (ILRs). The authors compared readmission, healthcare cost and survival in patients monitored post-stroke with either MCOT or ILR. Materials & methods: The authors used claims data from Optum's de-identified Clinformatics® Data Mart Database to identify patients with IS hospitalized from January 2017 to December 2020 who were prescribed ambulatory cardiac monitoring via MCOT or ILR. They compared the costs associated with the initial inpatient visit as well as the rate and causes of readmission, survival and healthcare costs over the following 18 months. Datasets were balanced using patient baseline and hospitalization characteristics. Multivariable generalized linear gamma regression was used for cost comparisons. Cox proportional hazard regression was used for survival and readmission analysis. Sub-cohorts were analyzed based on the severity of the index IS. Results: In 2244 patients, readmissions were significantly lower in the MCOT monitored group (30.2%) compared with the ILR group (35.4%) (hazard ratio [HR] 1.23; 95% CI: 1.04-1.46). Average cost over 18 months starting with the index IS was $27,429 (USD) lower in the MCOT group (95% CI: $22,353-$32,633). Survival difference bordered on statistical significance and trended to lower mortality in MCOT (8.9%) versus ILR (11.3%) (HR 1.30; 95% CI: 1:00-1.69), led by significance in patients with complications or comorbidities with the index event (MCOT 7.5%, ILR 11.5%; HR 1.62; 95% CI: 1.11-2.36). Conclusion: The use of MCOT versus ILR as the primary monitor following IS was associated with significant decreases in readmission, lower costs for the initial IS and total care over the next 18 months, significantly lower mortality for patients with complications and comorbidities at the index stroke, and a trend toward improved survival across all patients.

False-positive alarms in patients with implantable loop recorder followed by remote monitoring: A systematic review

Remote Monitoring (RM) has been shown to provide useful information about arrhythmic events in patients with implantable loop recorders (ILRs), however there is few and conflicting data about the false positive (FP) alarms burden and characteristics among ILR recipients. The aim of the present systematic review was to evaluate incidence and characteristics of FP alarms among ILR patients followed by RM. We developed a systematic research in Embase, MEDLINE and PubMed databases and selected all papers focused on false positive ILR transmissions published from June 1, 2013 to June 1, 2023. Case reports, meeting summaries, posters and simple reviews were excluded. Twelve reports were finally selected, including five prospective and seven retrospective studies. Information about population characteristics, device type and setting, overall transmissions and FP alarms and any adopted strategies to reduce them were extracted from an overall population of 3.305 patients. FP alarms were 59.7% of the overall remote transmissions and were found in 1/5 of the analyzed population. FP alarms for atrial fibrillation were the most common cause of false transmissions and were mainly due to premature atrial and ventricular complexes. No clinical predictors of FP alarms were identified, except for nonparasternal ILR implantation site. Since the overload work due to FP alarms might reduce the benefit of remote monitoring of ILR patients, the device optimization is an important step until an help from machine-learning algorithms is available.

Utilization of remote reprogramming to manage insertable cardiac monitor arrhythmia alert burden

INTRODUCTION

The increasing use of insertable cardiac monitors (ICMs) for long-term continuous arrhythmia monitoring creates a high volume of transmissions and a significant workload for clinics. The ability to remotely reprogram device alert settings without in-office patient visits was recently introduced, but its impact on clinic workflow compared to the previous ICM iteration is unknown.

METHODS

The aim of this real-world study was to evaluate the impact of device reprogramming capabilities on ICM alert burden and on clinic workflow. Deidentified data was obtained from US patients and a total of 19 525 receiving a LINQ II were propensity score-matched with 19 525 implanted with LINQ TruRhythm (TR) ICM based on age and reason for monitoring.

RESULTS

After reprogramming, ICM alerts reduced by 20.5% (p < .001). Compared with patients monitored with LINQ TR, patients with LINQ II had their device reprogrammed sooner after implant and more frequently during follow-up. Adoption of remote programming was projected to lead to an annual total clinic time savings of 211 h per 100 ICM patients managed.

CONCLUSION

These data suggest that utilization of ICM alert reprogramming has increased with remote capabilities, which may reduce clinic and patient burden for ICM follow-up and free clinician time for other valuable patient care activities.

Predictors of pacemaker requirement in patients with implantable loop recorder and unexplained syncope: A systematic review and meta-analysis

Identifying the underlying cause of unexplained syncope is crucial for appropriate management of recurrent syncopal episodes. Implantable loop recorders (ILRs) have emerged as valuable diagnostic tools for monitoring patients with unexplained syncope. However, the predictors of pacemaker requirement in patients with ILR and unexplained syncope remain unclear. In this study, we shed light on these prognostic factors. PubMed/MEDLINE, EMBASE, Web of Science, and Cochrane CENTRAL were systematically searched until May 04, 2023. Studies that evaluated the predictors of pacemaker requirement in patients with implantable loop recorder and unexplained syncope were included. The "Quality In Prognosis Studies" appraisal tool was used for quality assessment. The pooled odds ratio (OR) with 95% confidence intervals (CIs) was calculated. The publication bias was evaluated using Egger's and Begg's tests. Ten studies (n = 4200) were included. Right bundle branch block (OR: 3.264; 95% CI: 1.907-5.588, p < .0001) and bifascicular block (OR: 2.969; 95% CI: 1.859-4.742, p < .0001) were the strongest predictors for pacemaker implantation. Pacemaker requirement was more than two times in patients with atrial fibrillation, sinus bradycardia and first degree AV block. Valvular heart disease, diabetes mellitus, and hypertension were also significantly more in patients with pacemaker implantation. Age (standardized mean difference [SMD]: 0.560; 95% CI: 0.410/0.710, p < .0001) and PR interval (SMD: 0.351; 95% CI: 0.150/0.553, p = .001) were significantly higher in patients with pacemaker requirement. Heart conduction disorders, atrial arrhythmias and underlying medical conditions are main predictors of pacemaker device implantation following loop recorder installation in unexplained syncopal patients.

The Beneficial Role of Telemedicine for Arrhythmic Risk Stratification in Asymptomatic Brugada Syndrome: An Exemplary Case Report

Telemedicine and remote monitoring devices, including implantable loop recorders (ILR), are increasingly adopted in the cardiologic setting. These are valuable tools in the arrhythmic stratification of patients at risk of sudden cardiac death, providing a tailored therapeutic management to prevent lethal arrhythmias. We report a case of an asymptomatic 18-year-old boy with a family history of syncope and cardiac arrest, who had a diagnosis of Brugada syndrome with an inducible type 1 pattern and carrier of a missense mutation of the SCN5A gene. In light of the risk factors, although not recommended by current guidelines, we decided to proceed with the implantation of an ILR with remote monitoring service. A few months later, an episode of asymptomatic sustained polymorphic ventricular tachycardia was promptly observed by the remote monitoring, leading to a timely implantation of a subcutaneous cardiac implantable defibrillator.

Correlation between the electrocardiogram amplitude detected by an implantable cardiac monitor and the implantation depth

INTRODUCTION

Implantable cardiac monitors (ICMs) primarily use R-R intervals in subcutaneous electrocardiograms (ECGs) to detect arrhythmias. Therefore, reliable detection of R-wave amplitude by an ICM is vital. Since ICMs detect subcutaneous ECGs, the impact of the implantation depth should be assessed.

METHODS AND RESULTS

This study investigated the influence of ICM depth on R-wave (ICM-R) amplitude on an ECG generated by an ICM (JOT Dx; Abbott). Overall, 58 patients who underwent ICM implantation at Kamagaya General Hospital from May 2022 to April 2023 were retrospectively reviewed. The depth-position was measured using ultrasound imaging after implantation. The depth of the ICM did not show any correlation with ICM-R amplitude (r = -.0141, p = .294). However, the distance between the ICM and the heart surface showed a significant correlation with ICM-R amplitude (r = -.581, p < .001). Body weight (r = -.0283, p = .033) and body mass index (r = -.0342, p = .009) were associated with ICM-R amplitude. S wave in the V1 -lead was also associated with ICM-R amplitude (r = .481, p < .001). After multivariate analysis, the distance between the ICM and heart surface and the S wave in V1 were independent determinants for the ICM-R amplitude.

CONCLUSION

The ICM-R amplitude may be higher with the ICM implanted deeper.

Improved diagnostic performance of insertable cardiac monitors by an artificial intelligence-based algorithm

AIMS

The increasing use of insertable cardiac monitors (ICM) produces a high rate of false positive (FP) diagnoses. Their verification results in a high workload for caregivers. We evaluated the performance of an artificial intelligence (AI)-based ILR-ECG Analyzer™ (ILR-ECG-A). This machine-learning algorithm reclassifies ICM-transmitted events to minimize the rate of FP diagnoses, while preserving device sensitivity.

METHODS AND RESULTS

We selected 546 recipients of ICM followed by the Implicity™ monitoring platform. To avoid clusterization, a single episode per ICM abnormal diagnosis (e.g. asystole, bradycardia, atrial tachycardia (AT)/atrial fibrillation (AF), ventricular tachycardia, artefact) was selected per patient, and analyzed by the ILR-ECG-A, applying the same diagnoses as the ICM. All episodes were reviewed by an adjudication committee (AC) and the results were compared. Among 879 episodes classified as abnormal by the ICM, 80 (9.1%) were adjudicated as 'Artefacts', 283 (32.2%) as FP, and 516 (58.7%) as 'abnormal' by the AC. The algorithm reclassified 215 of the 283 FP as normal (76.0%), and confirmed 509 of the 516 episodes as abnormal (98.6%). Seven undiagnosed false negatives were adjudicated as AT or non-specific abnormality. The overall diagnostic specificity was 76.0% and the sensitivity was 98.6%.

CONCLUSION

The new AI-based ILR-ECG-A lowered the rate of FP ICM diagnoses significantly while retaining a > 98% sensitivity. This will likely alleviate considerably the clinical burden represented by the review of ICM events.

The Rate of Asystolic Reflex Syncope Is Not Influenced by Age

BACKGROUND

The head-up tilt test (HUT) and other evidence suggest that the vagal effect on the heart decreases with age.

OBJECTIVES

The main aim of the study was to assess whether this age effect also affects the rate of asystole in spontaneous reflex syncope (RS).

METHOD

We performed an analysis of pooled individual data from 4 studies that recruited patients ≥40 years of age affected by certain or suspected RS who received an implantable loop recorder (ILR) and reported follow-up data on syncope recurrence. We assessed the presence of asystolic syncope of >3 seconds or nonsyncopal asystole of >6 seconds recorded by ILR and compared the findings to tilt test results on the same patients.

RESULTS

A total of 1,046 patients received ILR because of unexplained syncope. Of these, 201 (19.2%) had a documentation of an asystolic event of 10-second (Q1-Q3: 6- to 15-second) duration. They were subdivided in 3 age tertiles: ≤60 years (n = 64), 61 to 72 years (n = 72), and ≥73 years (n = 65). The rate of asystolic events was similar in the 3 subgroups (50.1%, 50.1%, and 49.2%, respectively; P = 0.99). Conversely, the rate of asystolic syncope induced during HUT (performed in 169 of 201) was greatly age dependent (31.0%, 12.1%, and 11.1% in increasing age tertiles, respectively; P = 0.009).

CONCLUSIONS

The rate of the spontaneous asystolic form of RS documented by ILR is constant at any age >40 years. Conversely, the rate of asystolic syncope induced by HUT is higher in younger patients and decreases with age. The contrasting results between spontaneous and tilt-induced events cast doubt on the concept that asystole in RS is less common in older patients.

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.

Clinical utilisation of implantable loop recorders in adults with Fabry disease-a multi-centre snapshot study

Fabry disease (FD) is an X-linked deficiency of alpha-galactosidase-A, leading to lysosomal storage of sphingolipids in multiple organs. Myocardial accumulation contributes to arrhythmia and sudden death, the most common cause of FD mortality. Therefore, there is a need for risk stratification and prediction to target device therapy. Implantable loop recorders (ILRs) allow for continual rhythm monitoring for up to 3 years. Here, we performed a retrospective study to evaluate current ILR utilisation in FD and quantify the burden of arrhythmia that was detected, which resulted in a modification of therapy. This was a snapshot assessment of 915 patients with FD across three specialist centres in England during the period between 1 January 2000 and 1 September 2022. In total, 22 (2.4%) patients underwent clinically indicated ILR implantation. The mean implantation age was 50 years and 13 (59%) patients were female. Following implantation, nine (41%) patients underwent arrhythmia detection, requiring intervention (six on ILR and three post-ILR battery depletion). Three patients experienced sustained atrial high-rate episodes and were started on anticoagulation. Three had non-sustained tachyarrhythmia and were started on beta blockers. Post-ILR battery depletion, one suffered complete heart block and two had sustained ventricular tachycardia, all requiring device therapy. Those with arrhythmia had a shorter PR interval on electrocardiography. This study demonstrates that ILR implantation in FD uncovers a high burden of arrhythmia. ILRs are likely to be underutilised in this pro-arrhythmic cohort, perhaps restricted to those with advanced FD cardiomyopathy. Following battery depletion in three patients as mentioned above, greater vigilance and arrhythmia surveillance are advised for those experiencing major arrhythmic events post-ILR monitoring. Further work is required to establish who would benefit most from implantation.

Long-term outcomes of patients with ventricular arrhythmias and negative programmed ventricular stimulation followed with implantable loop recorders: Impact of delayed-enhancement cardiac magnetic resonance imaging

BACKGROUND

Programed ventricular stimulation (PVS) is a risk stratification tool in patients at risk for adverse arrhythmia outcomes. Patients with negative PVS may yet be at risk for adverse arrhythmia-related events, particularly in the presence of symptomatic ventricular arrhythmias (VA).

OBJECTIVE

To investigate the long-term outcomes of real-world patients with symptomatic VA without indication for device therapy and negative PVS, and to examine the role of cardiac scaring on arrhythmia recurrence.

METHODS

Patients with symptomatic VA, and late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR), and negative PVS testing were included. All patients underwent placement of implantable cardiac monitors (ICM). Survival analysis was performed to investigate the impact of LGE-CMR findings on survival free from adverse arrhythmic events.

RESULTS

Seventy-eight patients were included (age 60 ± 14 years, women n = 36 (46%), ejection fraction 57 ± 9%, cardiomyopathy n = 26 (33%), mitral valve prolapse [MVP] n = 9 (12%), positive LGE-CMR scar n = 49 (62%), history of syncope n = 23 (29%)) including patients with primarily premature ventricular contractions (n = 21) or nonsustained VA (n = 57). Patients were followed for 1.6 ± 1.5 years during which 14 patients (18%) experienced VA requiring treatment (n = 14) or syncope due to bradycardia (n = 2). Four/9 patients (44%) with MVP experienced VA (n = 3) or syncope (n = 1). Baseline characteristics between those with and without adverse events were similar (p > 0.05); however, the presence of cardiac scar on LGE-CMR was independently associated with an increased risk of adverse events (hazard ratio: 5.6 95% confidence interval: [1.2-27], p = 0.03, log-rank p = 0.03).

CONCLUSIONS

In a real-world cohort with long-term follow-up, adverse arrhythmic outcomes occurred in 18% of patients with symptomatic VA despite negative PVS, and this risk was significantly greater in patients with positive DE-CMR scar. Long term-monitoring, including the use of ICM, may be appropriate in these patients.

Eustachian Valve-Enhanced Paradoxical Cerebral Embolism: A Case Report

Cryptogenic stroke includes many suspicious embolic causes that do not fulfill the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification criteria. Atrial fibrillation (AF) is one of the major hidden causes of cryptogenic stroke, and an implantable loop recorder (ILR) is widely used for detecting AF. Herein, we report a case of paradoxical cerebral embolism due to a large Eustachian valve with large PFO under no molecular complete remission (CR) of acute monocytic leukemia (AMoL). A 75-year-old man arrived at our emergency room because of aphasia and right hemiparesis. He had a history of two cryptogenic strokes and implanted ILR. Magnetic resonance imaging showed left middle cerebral artery occlusion with slight acute ischemic lesion. The red clot was retrieved by mechanical thrombectomy, and complete recanalization was achieved. We checked ILR, but there was no AF. Transesophageal echocardiography revealed a large patent foramen ovale (PFO) and the large Eustachian valve in the right atrium. Although obvious deep vein thrombosis (DVT) was not detected in venous ultrasonography of the lower extremities, Wilms' tumor 1 messenger ribonucleic acid (WT1mRNA) expression level was high, and AMoL was considered to be not in molecular CR, suggesting a high risk of thrombosis to the large Eustachian valve. From large PFO and no molecular CR of AMoL, we diagnosed him with paradoxical cerebral embolism. Ruling out of AF by ILR and other etiologies, such as aortic or carotid atherosclerosis and pulmonary shunt, also supported the diagnosis of paradoxical cerebral embolism. Even in the absence of obvious DVT, paradoxical cerebral embolism should be considered in cases of a large Eustachian valve and PFO with a hypercoagulable state.

Detection of atrial fibrillation in real world setting in patients with cryptogenic stroke and an implantable loop recorder

INTRODUCTION

Implantable loop recorders (ILR) are used to screen for atrial fibrillation (AF) in patients with cryptogenic stroke (CS). However, there is limited real-world data regarding the long-term rate of AF detection using ILR and management consequences in patients with CS. The objective is to assess the rate of AF detection in patients with CS in a real-world study over 36 months of follow-up and its consequences on stroke prevention.

METHODS

This retrospective study included patients with an ILR placed for CS at Baylor College of Medicine and Baylor St. Luke's Medical Center between January 2014 and July 2021. The primary outcome was AF detection in patients with ILR. The secondary outcome was the rate of subsequent strokes after ILR placement in patients with or without diagnosed AF. The AF detection rate in our cohort was compared to the rate in CRYSTAL-AF Trial at 36-month follow-up. The impact of AF detection on clinical management was examined.

RESULTS

We identified 225 patients. 51.1% were women and 38.2% African American. Among 85 patients with ILR labeled AF, 43 patients had true AF, and 42 had incorrectly labeled AF (48.3% false positive). The estimated AF detection rate at 36 months follow-up was 28.6% (95% CI, 26.6%-30.6%). 58.1% of patients with AF were initiated on oral anticoagulation, 80.0% of whom were started on a direct oral anticoagulant. 13.8% of patients had recurrent strokes after ILR implantation; 4 of whom were diagnosed with AF.

CONCLUSION

Compared to CRYSTAL-AF, the AF detection rate in our cohort is similar, but this cohort includes a higher proportion of female and African American patients. Most patients with recurrent strokes after ILR implant did not have AF during 36 months of monitoring.

Subclinical postoperative atrial fibrillation: a randomized trial

Background

Postoperative atrial fibrillation (POAF) is the most common complication of cardiac surgery, requiring interventions and prolonging hospital stay. POAF is associated with increased mortality and a higher rate of systemic thrombo-embolism. The rates of recurrent AF, optimal follow-up and management remain unclear. We aimed to evaluate the incidence of recurrent atrial fibrillation (AF) events, during long term follow-up in patients with POAF following cardiac surgery.

Methods

Patients with POAF and a CHA₂DS₂-VASc score of ≥2 were randomized in a 2:1 ratio to either implantation of a loop recorder (ILR) or ECG monitoring using periodic Holters. Participants were followed prospectively for 2 years. The primary end point was the occurrence of AF longer than 5 min.

Results

The final cohort comprised of 22 patients, of whom 14 received an ILR. Over a median follow up of 25.7 (IQR of 24.7-44.4) months, 8 patients developed AF, representing a cumulative annualized risk of AF recurrence of 35.7%. There was no difference between ILR (6 participants, 40%) and ECG/Holter (2 participants, 25% p = 0.917). All 8 patients with AF recurrence were treated with oral anticoagulation. There were no cases of mortality, stroke or major bleeding. Two patients underwent ILR explantation due to pain at the implantation site.

Conclusions

The rate of recurrent AF in patients with POAF after cardiac surgery and a CHA₂DS₂-VASc score of ≥2 is approximately 1 in 3 when followed systematically. Further research is need to assess the role of ILRs in this population.

Vasospasm in the First Septal Perforator Branch and Late High-Grade Atrioventricular Block Following Successful Primary Percutaneous Coronary Intervention for the Proximal Left Anterior Descending Coronary Artery: A Case Report

We present a case of a high-degree advanced atrioventricular block (AVB), which occurred 24 hours after successful primary percutaneous coronary intervention (PCI) in the proximal left anterior descending coronary artery (LAD), the culprit of ST-segment elevation myocardial infarction (STEMI). The methylergometrine provocation test for coronary vasospasms, which was performed on the eighth hospital day, revealed transient total occlusion of the first septal perforator branch. After prescribing a calcium channel blocker to the patient, AVB did not recur for three years, as confirmed using an implantable loop recorder (ILR). In this patient, delayed high-grade AVB following primary PCI in the proximal LAD might be caused by the spasm of the first septal perforator branch. Documented cases of spasms in this branch are rare.

Tests for the identification of reflex syncope mechanism

INTRODUCTION

Treatment efficacy of reflex syncope is mainly related to the mechanism underlying syncope rather than its etiology or clinical presentation. The predominant mechanism underlying reflex syncope can be assigned to hypotensive or to bradycardic phenotypes.

AREAS COVERED

Methodology and diagnostic criteria of the most useful tests for the identification of hypotensive and bradycardic phenotypes are discussed. Diagnostic tests for the hypotensive phenotype include office blood pressure measurement with active standing test, home, and wearable blood pressure monitoring, 24-h ambulatory blood pressure monitoring and tilt table test. Diagnostic tests for the bradycardic phenotype include carotid sinus massage, tilt table test and prolonged ECG monitoring.

EXPERT OPINION

In reflex syncope, the documentation of bradycardia/asystole during a syncopal episode does not rule out the possibility that a preceding or parallel hypotensive reflex plays an important role. Similarly, even when a hypotensive mechanism is established, the possibility of an associated cardioinhibitory reflex should be investigated. Investigating the mechanism of reflex syncope is mandatory in patients with severe recurrent episodes, with the final aim to develop a personalized treatment strategy. Recent trials have demonstrated the benefits of personalized mechanism-based therapy, thus highlighting the importance of a comprehensive assessment of the mechanisms underlying syncope.

Usefulness of insertable cardiac monitors for risk stratification: current indications and clinical evidence

INTRODUCTION

The 2018 ESC Syncope guidelines expanded the indications for an insertable cardiac monitor (ICM) to patients with unexplained syncope and primary cardiomyopathy or inheritable arrhythmogenic disorders.

AREAS COVERED

This review article discusses the clinical evidence for using an ICM for risk stratification in different patient populations including Brugada syndrome, long QT syndrome, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, cardiac sarcoidosis, and congenital heart disease.

EXPERT OPINION

Clinical data on the usefulness of ICMs in different patient populations is limited but most studies demonstrate early detection of clinically relevant arrhythmias, such as nonsustained ventricular tachycardia or atrial fibrillation. It is important to emphasize that the study populations usually comprise selected populations where conventional diagnostic methods fail to clarify the mechanism of symptoms. The effect of an ICM on prognosis by earlier detection of arrhythmias is difficult to demonstrate in populations with rare disease. Risk stratification in patients with cardiomyopathy or inheritable arrhythmogenic disorders remains a niche indication for ICMs. The most important indication for an ICM remains unexplained syncope in patients at low risk of SCD. Given the device costs and uncertain clinical value of device-detected arrhythmias, it is unclear whether it is also useful in non-syncopal patients.

An implantable loop recorder or smartphone based single-lead electrocardiogram to detect arrhythmia in adults with congenital heart disease?

Background

The European Society of Cardiology (ESC) guidelines for the management of adult congenital heart disease (ACHD) recommend screening in patients at risk for arrhythmic events. However, the optimal mode of detection is unknown.

Methods

Baseline and follow-up data of symptomatic ACHD patients who received an implantable loop recorder (ILR) or who participated in a smartphone based single-lead electrocardiogram study were collected. The primary endpoint was time to first detected arrhythmia.

Results

In total 116 ACHD patients (mean age 42 years, 44% male) were studied. The ILR group (n = 23) differed from the smartphone based single-lead electrocardiogram group (n = 93) in having a greater part of males and had more severe CHD and (near) syncope as qualifying diagnosis. In the smartphone based single-lead electrocardiogram group history of arrhythmia and palpitations were more frequent (all p < 0.05). Monitoring was performed for 40 and 79 patient-years for the ILR- and smartphone based single-lead electrocardiogram group, respectively. Arrhythmias occurred in 33 patients with an equal median time for both groups to first arrhythmia of 3 months (HR of 0.7, p = 0.81). Furthermore, atrial fibrillation occurred most often (n = 16) and common therapy changes included medication changes (n = 7) and implantation of pacemaker or Implantable Cardioverter Defibrillator (ICD) (N = 4). Symptoms or mode of detection were not a determinant of the first event.

Conclusion

Non-invasive smartphone based single-lead electrocardiogram monitoring could be an acceptable alternative for ILR implantation in detecting arrhythmia in symptomatic ACHD patients in respect to diagnostic yield, safety and management decisions, especially in those without syncope.

Insertable cardiac monitor with a long sensing vector: Impact of obesity on sensing quality and safety

Background

Fat layers in obese patients can impair R-wave detection and diagnostic performance of a subcutaneous insertable cardiac monitor (ICM). We compared safety and ICM sensing quality between obese patients [body mass index (BMI) ≥ 30 kg/m²] and normal-weight controls (BMI <30 kg/m²) in terms of R-wave amplitude and time in noise mode (noise burden) detected by a long-sensing-vector ICM.

Materials and methods

Patients from two multicentre, non-randomized clinical registries are included in the present analysis on January 31, 2022 (data freeze), if the follow-up period was at least 90 days after ICM insertion, including daily remote monitoring. The R-wave amplitudes and daily noise burden averaged intraindividually for days 61-90 and days 1-90, respectively, were compared between obese patients (n = 104) and unmatched (n = 268) and a nearest-neighbour propensity score (PS) matched (n = 69) normal-weight controls.

Results

The average R-wave amplitude was significantly lower in obese (median 0.46 mV) than in normal-weight unmatched (0.70 mV, P < 0.0001) or PS-matched (0.60 mV, P = 0.003) patients. The median noise burden was 1.0% in obese patients, which was not significantly higher than in unmatched (0.7%; P = 0.056) or PS-matched (0.8%; P = 0.133) controls. The rate of adverse device effects during the first 90 days did not differ significantly between groups.

Conclusion

Although increased BMI was associated with reduced signal amplitude, also in obese patients the median R-wave amplitude was >0.3 mV, a value which is generally accepted as the minimum level for adequate R-wave detection. The noise burden and adverse event rates did not differ significantly between obese and normal-weight patients.Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04075084 and NCT04198220.

Implantable loop recorder as a strategy following cardiovascular implantable electronic device extraction without reimplantation

BACKGROUND

Limited data exists for outcomes in patients undergoing cardiovascular implantable electronic device (CIED) transvenous lead extraction (TLE) without clear indications for device reimplantation. The implantable loop recorder (ILR) may be an effective strategy for continuous monitoring in select individuals.

OBJECTIVE

This retrospective analysis aims to investigate patients who have undergone ILR implant following TLE without CIED reimplantation.

METHODS

Clinical data from consecutive patients who have undergone TLE with ILR implant and without CIED reimplantation from October 2016 to May 2020 at a single center were collected.

RESULTS

Among 380 patients undergoing TLE, 28 (7.7%) underwent ILR placement without CIED reimplantation. TLE indications were systemic infection (n = 13, 46.4%), pain at the site (n = 8, 28.6%), device/lead malfunction (n = 4, 14.2%), and other. Devices extracted included: dual-chamber and single-chamber pacemaker (n = 14, 50%; n = 4, 14.2%), dual-chamber implantable cardiac defibrillator (n = 10; 35.7%), and cardiac-resynchronization therapy with defibrillator (n = 1, 3.5%). Reasons for no reimplantation included no longer meeting CIED criteria (n = 14, 50%), patient preference (n = 9, 32.1%), and no clear or inappropriate indication for initial CIED implantation (n = 5, 18%). During an average of 12.3 ± 13.1 months of follow-up, there were no lethal arrhythmias, and 4 (13.3%) patients underwent permanent pacemaker reimplantation due to symptomatic sinus bradycardia and atrioventricular block with syncope as discovered on ILR. Three patients died due to unknown causes (n = 1), non-cardiac (n = 1), and acute coronary syndrome (n = 1).

CONCLUSIONS

In patients undergoing TLE without reimplantation, an ILR may be an effective monitoring strategy in patients at low risk for cardiac arrhythmia. This article is protected by copyright. All rights reserved.

Adenosine, adenosine- deaminase and implantable recorder outcome in syncopal patients

BACKGROUND

Adenosine test was proposed as a tool for identification of syncopal patients who benefit from pacemaker implantation. Aim of the study was to assess the relationship between adenosine levels, the outcome of adenosine test and results of implantable loop recorder (ILR) monitoring in patients with syncope.

METHODS

In 29 patients (mean age 59 ± 11 years, 15men, 14 women) with unexplained syncope ILR was implanted. In addition, adenosine test (intravenous injection of 20 mg adenosine bolus) and assays of plasmatic adenosine and adenosine-deaminase were performed.

RESULTS

Adenosine test was positive in 15 patients and negative in 14 patients. Patients with positive adenosine test had lower adenosine levels compared to patients with negative test (8,86 ± 2,07 ng/ml vs 15,18 ± 2,14 ng/ml, p = 0,04). No difference was observed in adenosine deaminase levels (16,35 ± 2,20 IU/l vs. 13,20 ± 2,48 IU/l, p = 0,40). There was a negative correlation between adenosine level and AVB duration during adenosine test (p = 0,04; R2 = 0,22). Patients with positive adenosine test had more frequent asystole during ILR monitoring than patients with negative test (9 pts vs 1pt, p = 0,005). Adenosine levels were lower in patients with asystolic syncope on ILR compared to vasodepressor syncope 8,20± 2,86 ng/ml vs 13,27± 7,26 ng/ml, p = 0,05).

CONCLUSIONS

Patients with positive adenosine test have decreased production of endogenous adenosine compared to patients with negative adenosine test. Positivity of adenosine test and low adenosine level in the peripheral blood were associated with more frequent asystolic episodes during ILR monitoring. This article is protected by copyright. All rights reserved.

Accuracy of atrial fibrillation detection by an insertable cardiac monitor in patients undergoing catheter ablation: Results of the BioVAD study

BACKGROUND

Insertable cardiac monitors (ICMs) are increasingly used to evaluate the atrial fibrillation (AF) burden after catheter ablation of AF. BioMonitor III (BM3) is an ICM with a long sensing vector, which enhances sensing capabilities. The AF detection algorithm of the BM3 is based on R-R interval variability.

OBJECTIVE

To evaluate the performance of the AF detection algorithm of BM3 in patients before and after catheter ablation of AF using simultaneous Holter recordings.

METHODS

In this prospective study, we enrolled patients scheduled for catheter ablation of paroxysmal or persistent AF. After BM3 implantation, patients had a 4 days Holter registration before and 3 months after ablation. All true AF episodes ≥2 min on the Holter were annotated and matched with BM3 detected AF detections.

RESULTS

Thirty-one patients were enrolled (mean age 60 ± 8, 74% male, 68% paroxysmal AF). Fifty-six Holter registrations were performed in 30 patients. Twelve patients demonstrated at least one true AF episode with a total AF duration of 570 h. The AF burden accuracy of BM3 before catheter ablation was 99.6%, with a duration sensitivity of 98.6% and a duration specificity of 99.9%. The AF burden accuracy of BM3 after catheter ablation was 99.8%, with a duration sensitivity of 90.2% and a duration specificity of 99.9%. Overall, the AF burden detected on the Holter and BM3 demonstrated a high Pearson correlation coefficient of 0.996.

CONCLUSION

BM3 accurately detects AF burden in patients before and after catheter ablation of AF.

Outcome of Patients with Early Repolarization Pattern and Syncope

BACKGROUND

Syncope in patients with an early repolarization (ER) pattern presents a challenge for clinicians as it has been identified as an indicator of a higher risk of life-threatening ventricular arrhythmias (VAs).

OBJECTIVE

This study aimed to analyze the outcome of patients with an ER pattern and syncope, and to evaluate the factors predictive of VAs.

METHODS

Over a period of 5 years, we enrolled 143 patients with an ER pattern and syncope in a multicenter prospective registry.

RESULTS

Following the initial examinations, 97 patients (67.8%) were implanted with a device allowing electrocardiogram monitoring, including 84 with an implantable loop recorder. During a mean follow-up of 68 ± 34 months, we documented 16 arrhythmias presumably responsible for syncope (5 VAs, 10 bradycardias, and 1 supraventricular tachycardia). Additionally, recurrent syncope not associated with electrocardiogram documentation occurred in 16 patients (11.2%). The cause of syncope was identified in 23 of 97 (23.8%) patients with a monitoring device. The 5-year incidence of VAs and arrhythmic events presumably responsible for syncope was 4.9% and 11.0%, respectively. Patients who developed VAs showed no prodromes or specific triggers at the time of syncope. Neither the presence of a family history of sudden cardiac death nor the previously reported high-risk electrocardiographic parameters differed between patients with and without VAs.

CONCLUSIONS

VAs occurred in 4.9% of patients with an ER pattern and syncope. Device implantation based on detailed history taking seems to be a reasonable strategy. Previously reported high-risk electrocardiographic patterns did not identify patients with VAs.

Outcomes of Primary vs. Delayed Strategy of Implanting a Cardiac Monitor for Unexplained Syncope

Objective: Implantable cardiac monitors (ILR) have an important role in diagnosing unexplained syncope. However, outcomes of primary vs. delayed ILR implantation after initial syncope evaluation have not been explored. Methods: A total of 1705 patients with unexplained syncope were prospectively enrolled in the SYSTEMA (Syncope Study of Unselected Population in Malmö) cohort. Patients who underwent cardiovascular autonomic testing (CAT) and ILR were grouped into those referred to CAT after ILR implantation (primary ILR) and those in whom ILR was indicated after CAT (post-CAT ILR). Results: One-hundred-and-fifteen patients (6.7%) received ILRs. ILR recipients were older (58 vs. 52 years; p = 0.002), had more syncope recurrences (6 vs. 4; p < 0.001), more traumatic falls (72% vs. 53%; p < 0.001), and less prodrome (40% vs. 55%; p = 0.005) than patients without ILRs. During follow-up ≥16 months after ILR, 67 (58%) had normal sinus rhythm, 10 (8.7%) had sinus arrest, 10 (8.7%) AV-block, 13 (11.3%) atrial fibrillation, 9 (7.8%) supraventricular tachycardia, 4 (3.5%) sinus tachycardia and 2 (1.7%) ventricular tachycardia with clinical symptom reproduction. There were 52 patients (45%) in the primary-ILR group and 63 (55%) in the post-CAT ILR group. Proportions of negative ILR monitoring (17/52 vs. 25/63; p = 0.56) and pacemaker implantations (7/52 vs. 15/63; p = 0.23) did not differ between groups. Baseline ECG conduction disorders predicted pacemaker implantation (n = 11/17; odds ratio:10.6; 95%CI: 3.15−35.3; p < 0.001). CAT was more often positive (73% vs. 40%; p < 0.001) in primary-ILR group. Conclusions: Primary ILR implantation was associated with more positive CAT compared with delayed ILR implantation, but negative monitoring and pacemaker implantations were not different between groups. ECG conduction disorders predicted subsequent pacemaker implantation.

The BIOMONITOR III Injectable Cardiac Monitor: Clinical Experience with a Novel Injectable Cardiac Monitor

Background: Injectable cardiac monitors (ICMs) are leadless subcutaneous devices for long-term monitoring of arrhythmias. The BIOTRONIK BIOMONITOR III is a novel ICM with a miniaturized profile, long sensing vector, and simplified implantation technique. Methods: R-wave amplitude was recorded immediately after implantation, the day after implantation, and after 3 months. Follow-up was scheduled after 3 months or after an event. All data from the ICM were retrieved. The anatomical position of the ICM was determined post-implantation and after 3 months. A patient questionnaire was conducted after 3 months. Results: In 36 patients (mean age 67 ± 13 years; 40% male) an ICM was inserted. Six patients were not included in the final analysis. The median time from skin cut to wound closure was 6 [IQR 5–7] minutes. Mean R-wave amplitude increased over time (0.73 ± 32 mV vs. 0.78 ± 0.38 mV vs. 0.81 ± 0.39 mV; p = ns). Three months after implantation, the ICM was in an anatomically stable position. In 14 (47%) patients, true episodes were detected. False arrhythmia alerts were detected in 13 (43%) patients. The total number of false detections was low, and the patient satisfaction rate was high. Conclusion: Implantation of the novel BIOMONITOR III is fast and uncomplicated; its sensing characteristics are excellent and improve over time, and patient satisfaction is high.

Implantable Loop Recorder Monitoring and the Incidence of Previously Unrecognized Atrial Fibrillation in Patients on Hemodialysis

INTRODUCTION

Atrial fibrillation (AF) is common in patients with kidney failure on hemodialysis (KF-HD). We determined both AF incidence and burden in patients with KF-HD using implantable loop recorder (ILR) monitoring.

METHODS

Patients with KF-HD were enrolled and received an ILR. In 6 monitoring months, the incidence of AF events lasting ≥6 minutes was captured. Demographic, clinical, and dialysis characteristics were collected, and associations with incident AF were estimated using negative binomial regression models and expressed as incidence rate ratios and 95% CIs.

RESULTS

We enrolled 66 patients with KF-HD (mean age = 56 years, 70% male); 59 (90%) were without previously diagnosed AF. AF lasting ≥6 minutes was detected in 18 of 59 subjects (31%) without previously diagnosed AF and in 5 of 7 subjects (71%) with a previous AF diagnosis. Among the 23 with detected AF, episodes were present on 16% of patient days. Although 14 of 23 patients (61%) had AF on <5% of monitored days, the average duration of AF episodes was <1 hour in 13 of 23 patients (52%). Among patients with AF ≥6 minutes, 19 of 23 (83%) had a CHA2DS2-VASc score ≥2. When investigating individual HD parameters, higher dialysate calcium (>2.5 vs. 2.5 mEq/l: incidence rate ratio = 0.62; 95% CI, 0.48-0.80) was associated with lower AF risk whereas higher dialysate bicarbonate concentrations (>35 vs. 35 mEq/l: incidence rate ratio = 3.18; 95% CI, 1.13-8.94) were associated with higher AF risk.

CONCLUSION

New AF was detected in approximately one-third of patients with KF-HD. AF affects a substantial proportion of patient days and may be an underappreciated cause of stroke in KF-HD.

Meta-Analysis of Randomized Clinical Trials Comparing the Impact of Implantable Loop Recorder Versus Usual Care After Ischemic Stroke for Detection of Atrial Fibrillation and Stroke Risk

Implantable loop recorder (ILR) is recommended to detect subclinical atrial fibrillation (AF) after cryptogenic stroke; however, the clinical outcomes of this practice is unclear. We conducted a systematic review and meta-analysis of randomized controlled trials to evaluate 12-month AF detection, change in oral anticoagulation (OAC), and recurrent stroke in ILR versus usual care after ischemic stroke. We searched Medline, Embase, Web of Science, Cochrane Library for randomized controlled trials comparing ILR with usual care after any ischemic stroke. Primary outcomes were cumulative AF detection and recurrent stroke (ischemic or hemorrhagic) or transient ischemic attack over 12 months. Secondary outcome was OAC initiation. Meta-analysis was performed with Mantel-Haenszel pooled odds ratios (ORs) and random effects models. Of 200 identified articles, 3 trials were included (1,233 participants). Cryptogenic stroke and underlying AF included cryptogenic stroke only, stroke of known cause and underlying-AF included small or large vessel stroke only, and post embolic rhythm detection with implantable vs external monitoring included all ischemic strokes. The 12-month AF detection was 13% in the ILR group and 2.4% in controls. ILR was more likely to detect AF compared with usual care (OR 5.8, 95% confidence interval 3.2 to 10.2). Stroke or transient ischemic attack occurred in 7% with ILR and 9% with usual care (OR 0.8, 95% confidence interval 0.5 to 1.2). In patients with detected AF, 97% and 100% were started on OAC in cryptogenic stroke and underlying AF and post embolic rhythm detection with implantable vs external monitoring, respectively, compared with 68% in stroke of known cause and underlying-AF. In conclusion, ILR was superior to usual care in AF detection, but the relative low incidence of AF and the nondifferential risk of stroke between the ILR and usual care arms may suggest that most patients do not benefit from ILR implantation. Further studies are warranted to understand if patient selection can be improved to increase the diagnostic yield of ILR.

Cryptogenic Stroke and Embolic Stroke of Undetermined Source: Risk Factors and Approaches for Detection of Atrial Fibrillation

BACKGROUND

Stroke is a problem worldwide because of its high mortality and disability rates. Almost 90% of strokes are ischemic, and more than half of the deaths are caused by an ischemic stroke. Most risk factors for stroke are manageable so that it can be avoided with proper prevention. Despite the success in determining the causes of stroke in recent years, selectively, the "culprit" causing stroke remains unsolved. In such cases, a diagnosis of undetermined etiology (cryptogenic stroke) or embolic stroke of undetermined source (ESUS) is generated, resulting the prevention of a recurrent cerebrovascular occurrence impossible. Atrial fibrillation (AF) can be a cause of stroke by causing blood clots in the chambers of the heart.

PURPOSE

The aim was to determine the optimal method of heart rate monitoring in patients with ischemic stroke, as methods and approaches for detecting AF are very diverse, but there is still no single opinion, which would be universal.

PROCEDURES

In our review, we consider epidemiology, risk factors for the stroke of undetermined etiology, as well as analytical methods for detecting heart rhythm disturbances in this category of patients.

FINDINGS

Atrial fibrillation (AF) is detected by thorough monitoring of heart rate of patients with cryptogenic stroke and ESUS can be diagnosed in up to 46% of patients. .

CONCLUSION

After AF detection, consideration should be given to prescribing anticoagulants, instead of antiplatelet agents, for the secondary prevention of stroke.

Implantable loop recorder for monitoring patients with congenital heart disease

BACKGROUND

Patients with congenital heart defects (CHD) are prone to residua, sequels and complications from the underlying anomaly, where cardiac arrhythmias are one of the major causes for hospitalization, morbidity and mortality. The importance of the subcutaneous implantable loop recorder (ILR) for the detection and documentation of significant arrhythmias has increased over the last years. To date, however, there is little data on ILR use in the CHD population.

METHODS

In this single center, retrospective observational study, all CHD-patients with an ILR were identified who were under care of the German Heart Center Munich between February 2015 and January 2019. The primary endpoint of the study was the detection or exclusion of significant arrhythmias during follow-up in CHD-patients who had received an ILR. The secondary endpoint was to determine whether ILR findings influenced patient management, defined as initiation or adjustment of medication, cardioversion, electrophysiologic study, catheter ablation, or implantation of cardiac implantable electronic devices (CIEDs) such as pacemakers (PM) or implantable cardioverter-defibrillators.

RESULTS

An ILR was implanted in 33 CHD-patients (mean age, 43±20 years; 42.4% female) with CHD. During a mean observation period of 697±433 days, clinically relevant arrhythmias, correlating with the patients' complaints and symptoms, were detected in 19 patients (59.4%), encompassing supraventricular tachycardia (n=10), supraventricular or ventricular ectopic beats (n=10), non-sustained ventricular tachycardia (n=2), ventricular tachycardia (n=2), and bradycardia (n=2). In 9 patients (28.1%) the detected arrhythmia was considered an event requiring treatment. Treatment modalities included catheter ablation (n=5), modification of antiarrhythmic drug regime (n=2), adaptation of anticoagulation therapy (n=2), or implantation of a subcutaneous ICD (n=1). Regarding the occurrence of cardiac arrhythmias or a related need for therapeutic intervention, no significant differences were identified with respect to WHO functional class, the presence of pulmonary arterial hypertension or reduced resting peripheral oxygen saturation.

CONCLUSIONS

In symptomatic CHD-patients at risk for life-threatening cardiac events, ILR has a considerable complementary diagnostic value for the detection and differentiation of benign and malignant arrhythmias. Considering the overall low risk of complications, ILR implantation should be considered in patients with CHD of any complexity who need medium or long-term arrhythmia monitoring, especially if short-term Holter monitoring cannot provide sufficient diagnostic certainty.

Continuous Electrical Monitoring in Patients with Arrhythmic Myocarditis: Insights from a Referral Center

Background. The incidence and burden of arrhythmias in myocarditis are under-reported. Objective. We aimed to assess the diagnostic yield and clinical impact of continuous arrhythmia monitoring (CAM) in patients with arrhythmic myocarditis. Methods. We enrolled consecutive adult patients (n = 104; 71% males, age 47 ± 11 year, mean LVEF 50 ± 13%) with biopsy-proven active myocarditis and de novo ventricular arrhythmias (VAs). All patients underwent prospective monitoring by both sequential 24-h Holter ECGs and CAM, including either ICD (n = 62; 60%) or loop recorder (n = 42; 40%). Results. By 3.7 ± 1.6 year follow up, 45 patients (43%) had VT, 67 (64%) NSVT and 102 (98%) premature ventricular complexes (PVC). As compared to the Holter ECG (average 9.5 exams per patient), CAM identified more patients with VA (VT: 45 vs. 4; NSVT: 64 vs. 45; both p < 0.001), more VA episodes (VT: 100 vs. 4%; NSVT: 91 vs. 12%) and earlier NSVT timing (median 6 vs. 24 months, p < 0.001). The extensive ICD implantation strategy was proven beneficial in 80% of the population. Histological signs of chronically active myocarditis (n = 73, 70%) and anteroseptal late gadolinium enhancement (n = 26, 25%) were significantly associated with the occurrence of VTs during follow up, even in the primary prevention subgroup. Conclusion. In patients with arrhythmic myocarditis, CAM allowed accurate arrhythmia detection and showed a considerable clinical impact.

Analysis of the determining factors of detectable P-wave and amplitude of QRS complex sensed by implantable loop recorder

BACKGROUND

Determining factors for sufficient QRS amplitude and discernible P-wave sensing in implantable loop recorder (ILR) are unknown. We aimed to investigate determining factors and ILR implantation angle that may improve QRS complex and P-wave sensing in ILR.

METHODS

We retrospectively reviewed 220 patients who underwent ILR implantation or follow-up analysis. Patient demographic, clinical, echocardiography, electrocardiography, heart angle, and ILR angle data were collected as predictor variables. Associations between ILR QRS amplitude/P-wave detectability and each predictor variable were investigated.

RESULTS

Univariate linear regression showed that ILR QRS amplitude was significantly associated with age, height, ILR angle, and QRS amplitudes of 12-lead electrocardiogram (ECG) (lead I, II, aVR [inverted aVR], aVF, V1-V6) and Holter ECG (lead V3, V5). Among discrete variables, only left ventricular hypertrophy (LVH) affected ILR QRS amplitude (P = .016). A multivariate linear regression analysis revealed that ILR angle (β = -0.008, P < .001), lead aVR amplitude (β = 0.469, P = .003), Holter lead V5 amplitude (β = 0.116, P = .049), Age (β = -0.005, P = .014), and LVH (β = 0.213, P = .031) were independent determinants of ILR QRS amplitude. Logistic regression revealed that heart angle significantly affected ILR P-wave detectability (β = 0.12, P = .008). Multiple logistic regression revealed that heart angle (β = 0.121, P = .013) and lead V1 amplitude (β = 28.1, P = .034) were independent determinants of ILR P-wave detectability.

CONCLUSION

ILR insertion angle, lead aVR QRS amplitude, Holter lead V5 QRS amplitude, age, and LVH are determinants of ILR QRS amplitude. Heart angle and lead V1 P-wave amplitude of 12-lead ECG are determinants of ILR P-wave detectability.

Factors affecting signal quality in implantable cardiac monitors with long sensing vector

PURPOSE

Electrical artefacts are frequent in implantable cardiac monitors (ICMs). We analyzed the subcutaneous electrogram (sECG) provided by an ICM with a long sensing vector and factors potentially affecting its quality.

METHODS

Consecutive ICM recipients underwent a follow-up where demographics, body mass index (BMI), implant location, and surface ECG were collected. The sECG was then analyzed in terms of R-wave amplitude and P-wave visibility.

RESULTS

A total of 84 patients (43% female, median age 68 [58-76] years) were enrolled at 3 sites. ICMs were positioned with intermediate inclination (n = 44, 52%), parallel (n = 35, 43%), or perpendicular (n = 5, 6%) to the sternum. The median R-wave amplitude was 1.10 (0.72-1.48) mV with P waves readily visible in 69.2% (95% confidence interval, CI: 57.8%-79.2%), partially visible in 23.1% [95% CI: 14.3%-34.0%], and never visible in 7.7% [95% CI: 2.9%-16.0%] of patients. Men had higher R-wave amplitudes compared to women (1.40 [0.96-1.80] mV vs 1.00 [0.60-1.20] mV, P = .001), while obese people tended to have lower values (0.80 [0.62-1.28] mV vs 1.10 [0.90-1.50] mV, P = .074). The P-wave visibility reached 86.2% [95% CI: 68.3%-96.1%] in patients with high-voltage P waves (≥0.2 mV) at surface ECG. The sECG quality was not affected by implant site.

CONCLUSION

In ordinary clinical practice, ICMs with long sensing vector provided median R-wave amplitude above 1 mV and reliable P-wave visibility of nearly 70%, regardless of the position of the device. Women and obese patients showed lower but still very good signal quality.

Subcutaneous cardiac rhythm monitors: state of the art review

Introduction: Subcutaneous cardiac rhythm monitors (SCRMs) provide continuous ambulatory electrocardiographic monitoring for surveillance of known and identification of infrequent arrhythmias. SCRMs have proven to be helpful for the evaluation of unexplained symptoms and correlation with intermittent cardiac arrhythmias. Successful functioning of SCRM is dependent on accurate detection and successful transmission of the data to the device clinic. As the use of SCRM is steadily increasing, the amount of data that requires timely adjudication requires substantial resources. Newer algorithms for accurate detection and modified workflow systems have been proposed by physicians and the manufacturers to circumvent the issue of data deluge.Areas covered: This paper provides an overview of the various aspects of ambulatory rhythm monitoring with SCRMs including indications, implantation techniques, programming strategies, troubleshooting for issue of false positive and intermittent connectivity and strategies to circumvent data deluge.Expert opinion: SCRM is an invaluable technology for prolonged rhythm monitoring. The clinical benefits from SCRM hinge on accurate arrhythmia detection, reliable transmission of the data and timely adjudication for possible intervention. Further improvement in SCRM technology is needed to minimize false-positive detection, improve connectivity to the central web-based server, and devise strategies to minimize data deluge.

Diagnostic value of implantable loop recorders in patients with unexplained syncope or palpitations

Background

The implantable loop recorder (ILR) is a small cardiac rhythm‐monitoring device. Our aim was to determine ILR diagnostic value in patients with unexplained syncope, presyncope, or palpitations suggesting cardiac arrhythmias.

Methods

This has been a retrospective, observational, single‐center study. We included 181 patients in whom ILR was implanted at the Clinical Center of Serbia between January 2006 and July 2019. An event was marked as diagnostic if it led to a diagnosis and ILR was considered diagnostic if it verified or excluded an arrhythmia as the cause of syncope or palpitations.

Results

The mean age was 51.8 ± 17.8 years and 94 (51.9%) were male. The mean follow‐up period was 20.2 ± 15.8 months. ILR was diagnostic in 98 patients (54.1%). There was no significant difference in diagnostic value of ILR in regard to the baseline patients’ characteristics. The mean time to occurrence of the diagnostic event was 11.1 ± 9.6 months. The time to occurrence of a diagnostic event did not differ significantly between patients who underwent basic as compared to extended diagnostics before ILR implantation.

Conclusions

ILR was able to achieve an etiological diagnosis in 54.1% of patients with unexplained syncope, presyncope, or palpitations suggesting cardiac arrhythmias. In a subgroup of patients with recurrent palpitations, ILR was significantly less diagnostic than in patients with syncope or presyncope. ILR should be implanted beforehand in syncope evaluation process.

Impact of P-wave indices in prediction of atrial fibrillation-Insight from loop recorder analysis

BACKGROUND

Several P-wave indices are associated with the development of atrial fibrillation (AF). However, previous studies have been limited in their ability to reliably diagnose episodes of AF. Implantable loop recorders allow long-term, continuous, and therefore more reliable detection of AF.

HYPOTHESIS

The aim of this study is to identify and evaluate ECG parameters for predicting AF by analyzing patients with loop recorders.

METHODS

This study included 366 patients (mean age 62 ± 16 years, mean LVEF 61 ± 6%, 175 women) without AF who underwent loop recorder implantation between 2010-2020. Patients were followed up on a 3 monthly outpatient interval.

RESULTS

During a follow-up of 627 ± 409 days, 75 patients (20%) reached the primary study end point (first detection of AF). Independent predictors of AF were as follows: age ≥68 years (hazard risk [HR], 2.66; 95% confidence interval [CI], 1.668-4.235; p < .001), P-wave amplitude in II <0.1 mV (HR, 2.11; 95% CI, 1.298-3.441; p = .003), P-wave terminal force in V₁  ≤ -4000 µV × ms (HR, 5.3; 95% CI, 3.249-8.636; p < .001, and advanced interatrial block (HR, 5.01; 95% CI, 2.638-9.528; p < .001). Our risk stratification model based on these independent predictors separated patients into 4 groups with high (70%), intermediate high (41%), intermediate low (18%), and low (4%) rates of AF.

CONCLUSIONS

Our study indicated that P-wave indices are suitable for predicting AF episodes. Furthermore, it is possible to stratify patients into risk groups for AF using simple ECG parameters, which is particularly important for patients with cryptogenic stroke.

Syncope associated with supraventricular tachycardia: Diagnostic role of implantable loop recorders

Syncope represents a relatively uncommon symptom of supraventricular tachycardia (SVT). It is likely that an impaired autonomic vasomotor response to the hemodynamic stress of tachycardia is the determinant of hemodynamic changes leading to cerebral hypoperfusion and syncope. In this regard, tilt‐table test may detect abnormalities in the autonomic nervous function and predict the occurrence of syncope during SVT. Electrophysiology studies may reproduce the SVT, distinguish it from other life‐threatening ventricular tachyarrhythmias, and exclude other causes of syncope. Not infrequently mixed syncope mechanisms are revealed during the above diagnostic workup raising doubts about the operating mechanism in the clinical setting. In such cases of uncertainty, an implantable loop recorder, providing long‐term cardiac monitoring, may play a pivotal role in the establishment of the diagnosis, confirming the association of an arrhythmic event with the symptom. Herein, we present four such cases with recurrent unexplained syncope finally attributed to paroxysmal SVT guiding them to a potentially radical treatment through radiofrequency catheter ablation.

Supervised Obesity Reduction Trial for AF Ablation Patients: Results from the SORT-AF trial

Aims

Weight management seems to be beneficial for obese atrial fibrillation (AF) patients; however, randomized data are sparse. Thus, this study aimed to investigate the influence of weight reduction on AF ablation outcomes.

Methods and results

SORT-AF is an investigator-sponsored, prospective, randomized, multicentre, and clinical trial. Patients with symptomatic AF (paroxysmal or persistent) and body mass index (BMI) 30–40 kg/m² underwent AF ablation and were randomized to either weight-reduction (group 1) or usual care (group 2), after sleep–apnoea–screening and loop recorder (ILR) implantation. The primary endpoint was defined as AF burden between 3 and 12 months after AF ablation. Overall, 133 patients (60 ± 10 years, 57% persistent AF) were randomized to group 1 (n = 67) and group 2 (n = 66), respectively. Complications after AF-ablation were rare (one stroke and no tamponade). The intervention led to a significant reduction of BMI (34.9 ± 2.6–33.4 ± 3.6) in group 1 compared to a stable BMI in group 2 (P < 0.001). Atrial fibrillation burden after ablation decreased significantly (P < 0.001), with no significant difference regarding the primary endpoint between the groups (P = 0.815, odds ratio: 1.143, confidence interval: 0.369–3.613). Further analyses showed a significant correlation between BMI and AF recurrence for patients with persistent AF compared with paroxysmal AF patients (P = 0.032).

Conclusion

The SORT-AF study shows that AF ablation is safe and successful in obese patients using continuous monitoring via ILR. Although the primary endpoint of AF burden after ablation did not differ between the two groups, the effects of weight loss and improvement of exercise activity were beneficial for obese patients with persistent AF demonstrating the relevance of life-style management as an important adjunct to AF ablation in this setting.

Trial registration number

NCT02064114.

Cryoballoon ablation for paroxysmal atrial fibrillation: mid-term outcome evaluated by ECG monitoring with an implantable loop recorder

BACKGROUND

The success rate after cryoballoon ablation (CB-A) performed for paroxysmal atrial fibrillation (PAF) might be overestimated by traditional noninvasive monitoring techniques. The purpose of this study was to evaluate the mid-term outcome of CB-A in patients with PAF implanted with an implantable loop recorder (ILR) after the procedure.

METHODS

Between January 2017 and March 2019, all patients who underwent CB-A for PAF and who were subsequently implanted with an ILR were retrospectively included. All devices were equipped with remote monitoring. All ILR-documented atrial tachycardia (AT) or AF episodes ≥ 6 min were considered as recurrence; both true and false episodes were collected. A 3-month post-procedural blanking period (BP) was applied.

RESULTS

A total of 102 patients (77 men, mean age 60.6 ± 9.6 years) who underwent pulmonary vein isolation (PVI) by CB-A were included; mean time from first diagnosis of AF to PVI was 51.5 ± 46.9 months. Mean follow-up was 29.3 ± 8.1 months; at 12-month follow-up, the success rate was 65.7%, while at 2-year follow-up, freedom from AT/AF recurrences was achieved in 59.3% of the patients. In the follow-up, a total of 4987 ECG strips were analyzed; true-positive episodes were confirmed in 2026 cases (40.6%), whereas 2961 episodes (59.4%) were considered false-positive.

CONCLUSION

In patients with PAF implanted with an ILR, CB-A results in freedom from any AT/AF recurrence in 65.7% of patients at 12-month follow-up and in 59.3% of patients when evaluated at 2-year. Careful adjudication of all ILR-documented AF episodes is required to avoid misdiagnosis.

AI Filter Improves Positive Predictive Value of Atrial Fibrillation Detection by an Implantable Loop Recorder

OBJECTIVES

The purpose of this study was to determine whether incorporation of a 2-part artificial intelligence (AI) filter can improve the positive predictive value (PPV) of implantable loop recorder (ILR)-detected atrial fibrillation (AF) episodes.

BACKGROUND

ILRs can detect AF. Devices transmit data daily. It is critical that the PPV of ILR-detected AF events be high.

METHODS

In total, 1,500 AF episodes were evaluated from patients with cryptogenic stroke or known AF who underwent ILR implantation (Reveal LINQ, Medtronic, Minneapolis, Minnesota). Each episode was annotated as either a true or false AF episode to determine the PPV. A 2-part AI-based filter (Cardiologs, Paris, France) was then employed using a deep neural network (DNN) for AF detection. The impact of this DNN filter on the PPV was then assessed.

RESULTS

The cohort included 425 patients (mean age 69 ± 10 years; 62% men) with an ILR. After excluding 17 (1.1%) uninterpretable electrocardiograms, 800 (53.9%) of the remaining 1,483 episodes were manually adjudicated to represent an actual atrial arrhythmia. The PPV of ILR-detected AF episodes was 53.9% (95% confidence interval (CI): 51.4% to 56.5%), which increased to 74.5% (95% CI: 71.8% to 77.0%; p < 0.001) following use of the DNN filter. The increase was greatest for AF episodes ≤30 min. The most common reason for a false-positive AF event was premature atrial contractions. There was a negligible failure to identify true AF episodes.

CONCLUSIONS

Despite currently available ILR programming options, designed to maximize PPV in a given population, false-positive AF episodes remain common. An AI-based solution may significantly reduce the time and effort needed to adjudicate these false-positive events.

Do implantable loop recorders impact the survival of patients with recurrent unexplained syncope?

Aim: This study compares the outcomes of patients who receive an implantable loop recorder (ILR) for unexplained syncope to a control group without the diagnostic device in German claims data. Methods  and materials: Patients with ILR were matched to a control group based on prior syncope events, age, gender and Charlson Comorbidity index (CCI). Survival, syncope hospitalizations, treatment and costs were compared. Results/conclusion: Four hundred and twelve ILR patients were matched with controls, mean age was 68, mean CCI was 2.7, 42% females. ILR patients lived on average 1.2 years longer than patients in the control group. Twenty-five percent of ILR patients received a therapeutic device compared with 5% in the control group. ILRs might help to diagnose and treat patients with positive impact on survival.

Remote Monitoring Alert Burden: An Analysis of Transmission in >26,000 Patients

OBJECTIVES

This study sought to determine the remote monitoring (RM) alert burden in a multicenter cohort of patients with a cardiac implantable electronic device (CIED).

BACKGROUND

RM of CIEDs allows timely recognition of patient and device events requiring intervention. Most RM involves burdensome manual workflow occurring exclusively on weekdays during office hours. Automated software may reduce such a burden, streamlining real-time alert responses.

METHODS

We retrospectively analyzed 26,713 consecutive patients with a CIED undergoing managed RM utilizing PaceMate software between November 2018 and November 2019. Alerts were analyzed according to type, acuity (red indicates urgent, and yellow indicates nonurgent) and CIED category.

RESULTS

In total, 12,473 (46.7%) patients had a permanent pacemaker (PPM), 9,208 (34.5%) had an implantable cardioverter-defibrillator (ICD), and 5,032 (18.8%) had an implantable loop recorder (ILR). Overall, 82,797 of the 205,804 RM transmissions were alerts, with the remainder being scheduled transmissions. A total of 14,638 (54.8%) patients transmitted at least 1 alert. Permanent pacemakers were responsible for 25,700 (31.0%) alerts, ICDs for 15,643 (18.9%) alerts, and ILRs for 41,454 (50.1%) alerts, with 3,935 (4.8%) red alerts and 78,862 (95.2%) yellow alerts. ICDs transmitted 2,073 (52.7%) red alerts; 5,024 (32.1%) ICD alerts were for ventricular tachyarrhythmias and antitachycardia pacing/shock delivery.

CONCLUSIONS

In an RM cohort of 26,713 patients with CIEDs, 54.8% of patients transmitted at least 1 alert during a 12-month period, totaling over 82,000 alerts. ILRs were overrepresented, and ICDs were underrepresented, in these alerts. The enormity of the number of transmissions and the growing ILR alert burden highlight the need for new management pathways for RM.

Implantable loop recorders can detect paroxysmal atrial fibrillation in Standardbred racehorses with intermittent poor performance

Background

Limited information is available on paroxysmal atrial fibrillation (PAF) in the horse. Indeed, undiagnosed PAF could result in poor performance. Due to the intermittent occurrence, PAF is difficult to diagnose. However, implanting a small ECG device (implantable loop recorder, ILR) subcutaneously, allows the continuous and automatic detection of PAF.

Objectives

The aim was to investigate the potential of ILRs as a tool for diagnosing PAF in horses with poor performance.

Study design

Prospective field study.

Methods

Twelve racing Standardbred trotters with intermittent reduced performance (mean age: six years) were enrolled prospectively. The ILR was implanted subcutaneously at the fifth or sixth left intercostal space and data from the ILR was collected during the study period in which the horses were followed for a median duration of 7.5 month (range 6‐28).

Results

The ILR was able to detect PAF in four out of twelve racehorses. The ILR also detected sustained atrial fibrillation (AF) in one horse during the study. The ILRs rely on RR detection and R waves were correctly identified in 96%. One hundred episodes were categorised as AF by the ILRs and subsequently visual ECG inspection categorised 12 as sinus rhythm (SR), 28 as sinus arrhythmia (SA), 14 as other arrhythmias and 46 as AF episodes. The Root Mean Square of the Successive Differences (RMSSD) values were significantly increased for AF compared to SR and SA.

Main limitations

Few horses included and duration of study period varied among the horses. Further it was not possible to assess the sensitivity of the device in the current study and the ILRs proved to have a high rate of false positive misclassifications.

Conclusions

This study indicates that ILRs can be used for detection of PAF episodes and could be a useful ECG tool for horses presenting with poor performance. This methodology provides a platform to facilitate the long‐term assessment of AF development and quantification of AF burden in horses. Further studies including both healthy and poor performing horses are needed in order to learn more about PAF prevalence in racehorses.

A Systematic Review of the Incidence of Arrhythmias in Hemodialysis Patients Undergoing Long-Term Monitoring With Implantable Loop Recorders

Introduction

Establishing the frequency and nature of arrhythmias in hemodialysis (HD) is an important step in improving outcomes of these patients. We undertook this systematic review and meta-analysis to characterize arrhythmia frequency in maintenance HD patients.

Methods

We identified studies on arrhythmias in adult patients on maintenance HD detected via implantable loop recorders (ILRs). Studies included were in English and reported ILR-detected arrhythmia incidence in HD patients. Data were extracted by one author using electronic spreadsheets and verified by a second author. Random effects models were used for pooled inferences. The I² statistic was used to quantify heterogeneity.

Results

Five studies qualified for inclusion (317 patients). The overall estimates for the annualized rate of death and sudden cardiac death (SCD) was 0.14 (95% confidence interval [CI]: 0.11–0.18) and 0.06 (95% CI: 0.03–0.10), respectively. Across all 5 studies, the combined annualized rate of patients experiencing at least 1 bradycardia/asystole event was 0.19 (95% CI: 0.11–0.33) but heterogeneity was high (I² = 79.8%). The average annualized rate of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) episodes (0.02, 95% CI: 0.01–0.05) was significantly lower (P < 0.001) than the rate of bradycardia/asystole reported in the same patients. Incidence of atrial fibrillation (AF) varied significantly across the studies (from 0.07 to 0.83 patients per year) reflecting variable definitions (new-onset vs. total number of episodes).

Conclusion

The incidence of arrhythmias among chronic HD patients is high, with bradycardia/asystole occurring more frequently than ventricular arrhythmias. Additional studies to refine estimates particularly of AF are needed.

[Implantable loop recorders for prolonged heart-rhythm monitoring in patients with cryptogenic stroke]

OBJECTIVE

The timely diagnosis of atrial fibrillation (AF) in patients with cardiac embolism with implantable loop recorders (ILR).

MATERIAL AND METHODS

Twenty-nine patients, hospitalized within 6 months after stroke (n=19) or transient ischemic attack (n=10), were included in the study. ILR were implanted in all cases. The mean time of follow-up was one year.

RESULTS

Five hundred and thirteen transmissions were detected during the whole follow-up period. Symptomatic episodes were recorded in 165 cases. Such episodes as bradycardia, asystole, AF, atrial tachycardia and ventricular tachycardia were recorded in 98 cases out of 348 planned transmissions. All transmissions were analyzed by an operator. However, 70 cases were false-positive because of ILR over-sensing. In total, arrhythmias were detected in 5 patients, including sick sinus syndrome (1), supraventricular tachycardia (1), ventricular tachycardia (1) and atrial fibrillation (3). Anticoagulant therapy was started immediately after the diagnosis of AF.

CONCLUSION

Loop recording monitoring is an effective strategy in patients with cardiac embolism for timely diagnosis and further treatment of arrhythmia.