Pre dicting D eterminants of A trial Fibrillation or Flutter for T herapy E lucidation in Patients at Risk for Thromboembolic Events (PREDATE AF) Study

Novel Technologies in the Detection of Atrial Fibrillation: Review of Literature and Comparison of Different Novel Technologies for Screening of Atrial Fibrillation

Atrial fibrillation (AF) is globally the most common arrhythmia associated with significant morbidity and mortality. It impairs the quality of the patient's life, imposing a remarkable burden on public health, and the healthcare budget. The detection of AF is important in the decision to initiate anticoagulation therapy to prevent thromboembolic events. Nonetheless, AF detection is still a major clinical challenge as AF is often paroxysmal and asymptomatic. AF screening recommendations include opportunistic or systematic screening in patients ≥65 years of age or in those individuals with other characteristics pointing to an increased risk of stroke. The popularities of well-being and taking personal responsibility for one's own health are reflected in the continuous development and growth of mobile health technologies. These novel mobile health technologies could provide a cost-effective solution for AF screening and an additional opportunity to detect AF, particularly its paroxysmal and asymptomatic forms.

The incidence of atrial fibrillation detected by implantable loop recorders: a comparison between patients with and without embolic stroke of undetermined source

Aims

Stroke is the most debilitating outcome of atrial fibrillation (AF). The use of implantable loop recorders increases the detection of AF episodes among patients with embolic stroke of undetermined source. The significance of device-detected AF, or subclinical AF, is unknown. This study aimed to compare the incidence of AF detected by implantable loop recorder in patients with and without embolic stroke of undetermined source.

Methods and results

We retrospectively studied all patients without known AF who were referred to our institution for implantable loop recorder implantation following embolic stroke of undetermined source, syncope, or palpitations from March 2009 to November 2019. The primary endpoint was any detection of AF or atrial flutter by implantable loop recorder. Seven hundred and fifty patients were included and followed up for a mean duration of 731 days (SD 443). An implantable loop recorder was implanted following embolic stroke of undetermined source in 323 and for assessment of syncope, palpitations, or another reason in 427 patients. The incidence of AF was significantly (P < 0.001) higher among patients with embolic stroke of undetermined source compared with the non-embolic stroke of undetermined source group; 48.6% vs. 13.8% (for any duration of AF) and 32.2% vs. 12.4% (for AF lasting ≥30 s) both P < 0.001. Kaplan-Meier analysis showed significantly higher incidence of AF for incremental durations of AF up to >5.5 h, but not >24 h. This was driven by longest AF durations of <6 min and between 5.5 h and 24 h, suggesting a bimodal distribution. In a multivariable Cox regression analysis, embolic stroke of undetermined source independently conferred an almost 5-fold increase in the hazard for any duration of AF.

Conclusion

The incidence of AF is significantly higher amongst embolic stroke of undetermined source vs. non-embolic stroke of undetermined source patients monitored constantly by an implantable loop recorder. A high number of embolic stroke of undetermined source survivors have short-duration AF episodes. Further work is needed to determine the optimal treatment strategy of these AF episodes in embolic stroke of undetermined source.

Direct oral anticoagulants for stroke prevention in patients with device-detected atrial fibrillation: assessing net clinical benefit

Subclinical, device-detected atrial fibrillation (AF) is frequently recorded by pacemakers and other implanted cardiac rhythm devices. Patients with device-detected AF have an elevated risk of stroke, but a lower risk of stroke than similar patients with clinical AF captured with surface electrocardiogram. Two randomized clinical trials (NOAH-AFNET 6 and ARTESiA) have tested a direct oral anticoagulant (DOAC) against aspirin or placebo. A study-level meta-analysis of the two trials found that treatment with a DOAC resulted in a 32% reduction in ischaemic stroke and a 62% increase in major bleeding; the results of the two trials were consistent. The annualized rate of stroke in the control arms was ∼1%. Several factors point towards overall net benefit from DOAC treatment for patients with device-detected AF. Strokes in ARTESiA were frequently fatal or disabling and bleeds were rarely lethal. The higher absolute rates of major bleeding compared with ischaemic stroke while on treatment with a DOAC in the two trials are consistent with the ratio of bleeds to strokes seen in the pivotal DOAC vs. warfarin trials in patients with clinical AF. Prior research has concluded that patients place a higher emphasis on stroke prevention than on bleeding. Further research is needed to identify the characteristics that will help identify patients with device-detected AF who will receive the greatest benefit from DOAC treatment.

Towards a new classification of atrial fibrillation detected after a stroke or a transient ischaemic attack

Globally, up to 1·5 million individuals with ischaemic stroke or transient ischaemic attack can be newly diagnosed with atrial fibrillation per year. In the past decade, evidence has accumulated supporting the notion that atrial fibrillation first detected after a stroke or transient ischaemic attack differs from atrial fibrillation known before the occurrence of as stroke. Atrial fibrillation detected after stroke is associated with a lower prevalence of risk factors, cardiovascular comorbidities, and atrial cardiomyopathy than atrial fibrillation known before stroke occurrence. These differences might explain why it is associated with a lower risk of recurrence of ischaemic stroke than known atrial fibrillation. Patients with ischaemic stroke or transient ischaemic attack can be classified in three categories: no atrial fibrillation, known atrial fibrillation before stroke occurrence, and atrial fibrillation detected after stroke. This classification could harmonise future research in the field and help to understand the role of prolonged cardiac monitoring for secondary stroke prevention with application of a personalised risk-based approach to the selection of patients for anticoagulation.

Ignored Role of Paroxysmal Atrial Fibrillation in the Pathophysiology of Cryptogenic Stroke in Patients with Patent Foramen Ovale and Atrial Septal Aneurysm

The association between cryptogenic stroke (CS) and patent foramen ovale (PFO) with or without atrial septal aneurysm (ASA) has been a debate for decades in terms of pathophysiologic processes and clinical courses. This issue has become more interesting and complex, because of the concerns associating the CS with so-called normal variant pathologies of interatrial septum, namely ASA and PFO. While there is an anatomical pathology in the interatrial septum, namely PFO and ASA, the embolic source of stroke is not clearly defined. Moreover, in patients with PFO and CS, the risk of recurrent stroke has also been associated with other PFOunrelated factors, such as hyperlipidemia, body mass index, diabetes mellitus, and hypertension, leading to the difficulty in understanding the pathophysiologic mechanism of CS in patients with PFO and/or ASA. Theoretically, the embolic source of cryptogenic stroke in which PFO and/or ASA has been involved can be categorized into three different anatomical locations, namely PFO tissue and/or ASA tissue itself, right or left atrial chambers, and venous vascular territory distal to the right atrium, i.e., inferior vena cava and lower extremity venous system. However, the possible role of paroxysmal atrial fibrillation associated with PFO and/or ASA as a source of cryptogenic stroke has never been mentioned clearly in the literature. This review aims to explain the association of cryptogenic stroke with PFO and/or ASA in a comprehensive manner, including anatomical, clinical, and mechanistic aspects. The potential role of paroxysmal atrial fibrillation and its contribution to clinical course have been also discussed in a hypothetical manner to elucidate the pathophysiology of CS and support further treatment modalities.

[Tactics of anticoagulant therapy in patients with cardiac implantable electronic devices and subclinical atrial fibrillation: A review]

Screening for atrial fibrillation (AF) has attracted considerable attention recently. Of special interest are patients with cardiac implantable electronic devices (CIEDs) that allow for recording episodes of atrial arrhythmias of various durations, including asymptomatic ones, in which case they are referred to as subclinical atrial fibrillation (SCAF). The available data suggest that the risk of thromboembolic events varies between patients with SCAF and clinically overt AF. As of today, the question regarding anticoagulant therapy in patients with SCAF remains unresolved. The article presents an overview of previous and ongoing studies on this issue, as well as current guidelines on anticoagulant use in patients with SCAF and CIEDs.

Cost-effectiveness of an insertable cardiac monitor in a high-risk population in the US

BACKGROUND

Insertable cardiac monitors (ICMs) are a clinically effective means of detecting atrial fibrillation (AF) in high-risk patients, and guiding the initiation of non-vitamin K oral anticoagulants (NOACs). Their cost-effectiveness from a US clinical payer perspective is not yet known. The objective of this study was to evaluate the cost-effectiveness of ICMs compared to standard of care (SoC) for detecting AF in patients at high risk of stroke (CHADS₂ ≥ 2), in the US.

METHODS

Using patient data from the REVEAL AF trial (n = 393, average CHADS₂ score = 2.9), a Markov model estimated the lifetime costs and benefits of detecting AF with an ICM or with SoC (specifically intermittent use of electrocardiograms and 24-h Holter monitors). Ischemic and hemorrhagic strokes, intra- and extra-cranial hemorrhages, and minor bleeds were modelled. Diagnostic and device costs, costs of treating stroke and bleeding events and medical therapy-specifically costs of NOACs were included. Costs and health outcomes, measured as quality-adjusted life years (QALYs), were discounted at 3% per annum, in line with standard practice in the US setting. One-way deterministic and probabilistic sensitivity analyses (PSA) were undertaken.

RESULTS

Lifetime per-patient cost for ICM was $31,116 versus $25,330 for SoC. ICMs generated a total of 7.75 QALYs versus 7.59 for SoC, with 34 fewer strokes projected per 1000 patients. The model estimates a number needed to treat of 29 per stroke avoided. The incremental cost-effectiveness ratio was $35,528 per QALY gained. ICMs were cost-effective in 75% of PSA simulations, using a $50,000 per QALY threshold, and a 100% probability of being cost-effective at a WTP threshold of $150,000 per QALY.

CONCLUSIONS

The use of ICMs to identify AF in a high-risk population is likely to be cost-effective in the US healthcare setting.

Implantable loop recorders in patients with atrial fibrillation

INTRODUCTION

Implantable loop recorders (ILRs) provide practitioners with high-quality electrocardiographic data over an extended monitoring period. These data can guide the diagnosis and management of patients with atrial fibrillation (AF).

AREAS COVERED

This review summarizes the available evidence and consensus statements supporting the use of ILRs in the detection of AF, as well as monitoring of patients with known AF. Future directions for research are also discussed.

EXPERT OPINION

ILRs are the gold standard for detecting AF, providing superior diagnostic yield compared to other modes of ambulatory electrocardiography monitoring. Both experimental evidence and consensus statements support the use of ILRs in clinical settings where the diagnosis of AF may significantly change management, or where a high degree of sensitivity is needed. ILRs may also be used to monitor patients following AF ablation. More evidence is needed to better inform how ILR-detected AF should change management.

Consumer-Led Screening for Atrial Fibrillation: Frontier Review of the AF-SCREEN International Collaboration

The technological evolution and widespread availability of wearables and handheld ECG devices capable of screening for atrial fibrillation (AF), and their promotion directly to consumers, has focused attention of health care professionals and patient organizations on consumer-led AF screening. In this Frontiers review, members of the AF-SCREEN International Collaboration provide a critical appraisal of this rapidly evolving field to increase awareness of the complexities and uncertainties surrounding consumer-led AF screening. Although there are numerous commercially available devices directly marketed to consumers for AF monitoring and identification of unrecognized AF, health care professional-led randomized controlled studies using multiple ECG recordings or continuous ECG monitoring to detect AF have failed to demonstrate a significant reduction in stroke. Although it remains uncertain if consumer-led AF screening reduces stroke, it could increase early diagnosis of AF and facilitate an integrated approach, including appropriate anticoagulation, rate or rhythm management, and risk factor modification to reduce complications. Companies marketing AF screening devices should report the accuracy and performance of their products in high- and low-risk populations and avoid claims about clinical outcomes unless improvement is demonstrated in randomized clinical trials. Generally, the diagnostic yield of AF screening increases with the number, duration, and temporal dispersion of screening sessions, but the prognostic importance may be less than for AF detected by single-time point screening, which is largely permanent, persistent, or high-burden paroxysmal AF. Consumer-initiated ECG recordings suggesting possible AF always require confirmation by a health care professional experienced in ECG reading, whereas suspicion of AF on the basis of photoplethysmography must be confirmed with an ECG. Consumer-led AF screening is unlikely to be cost-effective for stroke prevention in the predominantly young, early adopters of this technology. Studies in older people at higher stroke risk are required to demonstrate both effectiveness and cost-effectiveness. The direct interaction between companies and consumers creates new regulatory gaps in relation to data privacy and the registration of consumer apps and devices. Although several barriers for optimal use of consumer-led screening exist, results of large, ongoing trials, powered to detect clinical outcomes, are required before health care professionals should support widespread adoption of consumer-led AF screening.

How should I treat patients with subclinical atrial fibrillation and atrial high-rate episodes? Current evidence and clinical importance

Long-term and continuous ECG monitoring using cardiac implantable electronic devices and insertable cardiac monitors has improved the capability of detecting subclinical atrial fibrillation (AF) and atrial high-rate episodes. Previous studies demonstrated a high prevalence (more than 20%) in patients with cardiac implantable electronic devices or insertable cardiac monitors. Subclinical AF and atrial high-rate episodes are often suspected as the cause of prior or potential future ischemic stroke. However, the clinical significance is still uncertain, and the evidence is limited. This review aims to present and discuss the current evidence on the clinical impact of subclinical AF and atrial high-rate episodes. It focuses particularly on the association between the duration of the episodes and major clinical outcomes like thromboembolic events. As subclinical AF and atrial high-rate episodes are presumed to be associated with ischemic strokes, detection will be particularly important in patients with cryptogenic stroke and in high-risk patients for thromboembolism. In this context, it is also interesting whether there is a temporal relationship between the detection of subclinical AF and atrial high-rate episodes and the occurrence of thromboembolic events. In addition, the review will examine the question whether there is a need for a therapy with oral anticoagulation.

Estimated incidence of previously undetected atrial fibrillation on a 14-day continuous electrocardiographic monitor and associated risk of stroke

Aims

There is uncertainty about whether and how to perform screening for atrial fibrillation (AF). To estimate the incidence of previously undetected AF that would be captured using a continuous 14-day ECG monitor and the associated risk of stroke.

Methods and results

We analysed data from a cohort of patients &gt;65 years old with hypertension and a pacemaker, but without known AF. For each participant, we simulated 1000 ECG monitors by randomly selecting 14-day windows in the 6 months following enrolment and calculated the average AF burden (total time in AF). We used Cox proportional hazards models adjusted for CHA2DS2-VASc score to estimate the risk of subsequent ischaemic stroke or systemic embolism (SSE) associated with burdens of AF &gt; and &lt;6 min. Among 2470 participants, the median CHA2DS2-VASc score was 4.0, and 44 patients experienced SSE after 6 months following enrolment. The proportion of participants with an AF burden &gt;6 min was 3.10% (95% CI 2.53–3.72). This was consistent across strata of age and CHA2DS2-VASc scores. Over a mean follow-up of 2.4 years, the rate of SSE among patients with &lt;6 min of AF was 0.70%/year, compared to 2.18%/year (adjusted HR 3.02; 95% CI 1.39–6.56) in those with &gt;6 min of AF.

Conclusions

Approximately 3% of individuals aged &gt;65 years with hypertension may have more than 6 min of AF detected by a 14-day ECG monitor. This is associated with a stroke risk of over 2% per year. Whether oral anticoagulation will reduce stroke in these patients is unknown.

What to do with device-detected atrial high-rate episodes: Summary of the evidences

Cardiac implanted electronic devices (CIEDs), that perform atrial sensing via an atrial electrode, commonly detect self-terminating atrial arrhythmias. Nomenclature of these arrhythmias is defined as atrial high-rate episodes (AHREs) and subclinical atrial fibrillation (SCAF). We have provided a comprehensive summation of the trials regarding the incidence and adverse outcomes of AHREs. The reported incidence of AHRE varies considerably (approximately 10% to %70) between studies depending on the definition of AHRE, duration of follow-up and the clinical profile of the population. There is increasing evidence related with the association between AHREs' and stroke and/or systemic embolism. However, risk of stroke and/or systemic embolism seems to be less than the risk associated with clinical AF. There is still lack of sufficient evidence related with oral anticoagulation (OAC) in patients with AHRE to reduce thromboembolic risk. Although, the strongest association of OAC treatment with reduction in stroke has been reported to be observed among patients with device detected SCAF episodes of >24 hours; it is still questionable whether AHRE is a direct cause of thromboembolic event or just a marker of increased risk. Results of ongoing randomized clinical trials (NOAH-AFNET 6 and ARTESIA) will provide robust evidence on effect of OAC therapy on AHREs. This article is protected by copyright. All rights reserved.

Circulating biomarkers, echocardiographic parameters, and incident subclinical atrial fibrillation in patients with diabetes and hypertension

BACKGROUND

Long-term rhythm monitoring (LTRM) can detect undiagnosed atrial fibrillation (AF) in patients at high risk of AF and stroke. Biomarkers and echocardiographic parameters could, however, help identify patients benefitting most from LTRM. The aim of this study was to investigate, whether circulating biomarkers of cardiac and vascular function (brain natriuretic peptide (BNP), cardiac troponin I (cTnI), copeptin, and mid-regional proadrenomedullin (MR-proADM)) and echocardiographic parameters were associated with incident subclinical AF (SCAF) in a population at high risk of stroke in the presence of AF. For this purpose, we investigated individuals ≥65 years of age with hypertension and diabetes mellitus, but no history or symptoms of AF or other cardiovascular disease (CVD).

METHODS

We included 82 consecutive patients (median age 71.3 years (IQR 67.4-75.1)). All patients received an insertable cardiac monitor (ICM) and were followed for a median of 588 days (IQR 453-712). On the day of ICM implantation, a comprehensive echocardiogram and blood samples were obtained.

RESULTS

During a median follow-up of 588 days (IQR: 453-712 days), incident SCAF occurred in 17 patients (20.7%) with a median time to first-detected episode of 91 days (IQR 41-251 days). MR-proADM (median 0.87 nmol/L (IQR 0.76-1.02) vs 0.78 nmol/L (IQR 0.68-0.98)) and copeptin (median 13 pmol/L (IQR 9-17) vs 8 pmol/L (IQR 4-18)) levels were insignificantly higher in patients with incident SCAF. BNP and cTnI concentrations and echocardiographic parameters were similar in the two groups.

CONCLUSIONS

MR-proADM, BNP, cTnI, copeptin, and several echocardiographic parameters were not associated with incident SCAF in this cohort of patients with hypertension and diabetes, but without any underlying CVD.

Age and Sex Specific Prevalence of Clinical and Screen-Detected Atrial Fibrillation in Hospitalized Patients

BACKGROUND

The prevalence of atrial fibrillation (AF) is high in older patients. The present study aimed to estimate the age and sex specific prevalence of clinical and screen-detected atrial fibrillation (AF) in hospitalized patients.

METHODS

The STAR-FIB cohort study was a prospective cohort study recruiting participants from a large source population of hospitalized patients aged 65-84 years. The estimated size of the source population was 26,035 (95% CI 25,918-26,152), and 795 consenting patients without clinical AF were included in the cohort study after stratification by sex and age (49.2% females; mean age 74.7 years). Patients in the cohort study underwent three seven-day Holter ECGs in intervals of two months to screen for AF.

RESULTS

In the source population, the estimated prevalence of clinical AF was 22.2% (95% CI 18.4-26.1), 23.8% for males (95% CI 20.9-26.6) and 19.8% for females (95% CI 17.3-22.4; p for difference between sexes, 0.004). There was a linear trend for an increase in the prevalence of clinical AF with increasing age, overall and in both sexes. In the cohort study, AF was newly diagnosed in 38 patients, for an estimated prevalence of screen-detected AF of 4.9% overall (95% CI 3.3-6.6), 5.5% in males (95% CI 3.2-7.8) and 4.0% in females (95% CI 2.0-6.0; p for difference between sexes, 0.041). The estimated prevalence of screen-detected AF in the source population was 3.8% overall, 4.2% in males and 3.2% in females.

CONCLUSION

In a large hospital-based patient population aged 65-84 years, the prevalence of clinical AF and of screen-detected AF was 22.2% and 3.8%, respectively, and significantly higher in males than females.

Optimizing indices of AF susceptibility and burden to evaluate AF severity, risk and outcomes

Atrial fibrillation (AF) has heterogeneous patterns of presentation concerning symptoms, duration of episodes, AF burden, and the tendency to progress towards the terminal step of permanent AF. AF is associated with a risk of stroke/thromboembolism traditionally considered dependent on patient-level risk factors rather than AF type, AF burden, or other characterizations. However, the time spent in AF appears related to an incremental risk of stroke, as suggested by the higher risk of stroke in patients with clinical AF vs. subclinical episodes and in patients with non-paroxysmal AF vs. paroxysmal AF. In patients with device-detected atrial tachyarrhythmias, AF burden is a dynamic process with potential transitions from a lower to a higher maximum daily arrhythmia burden, thus justifying monitoring its temporal evolution. In clinical terms, the appearance of the first episode of AF, the characterization of the arrhythmia in a specific AF type, the progression of AF, and the response to rhythm control therapies, as well as the clinical outcomes, are all conditioned by underlying heart disease, risk factors, and comorbidities. Improved understanding is needed on how to monitor and modulate the effect of factors that condition AF susceptibility and modulate AF-associated outcomes. The increasing use of wearables and apps in practice and clinical research may be useful to predict and quantify AF burden and assess AF susceptibility at the individual patient level. This may help us reveal why AF stops and starts again, or why AF episodes, or burden, cluster. Additionally, whether the distribution of burden is associated with variations in the propensity to thrombosis or other clinical adverse events. Combining the improved methods for data analysis, clinical and translational science could be the basis for the early identification of the subset of patients at risk of progressing to a longer duration/higher burden of AF and the associated adverse outcomes.

Relation of Antecedent Symptoms to the Likelihood of Detecting Subclinical Atrial Fibrillation With Inserted Cardiac Monitors

Atrial fibrillation (AF) comes to attention clinically during an evaluation of symptoms, an evaluation of its adverse outcomes, or because of incidental detection during a routine examination or electrocardiogram. However, a notable number of additional individuals have AF that has not yet been clinically apparent or suspect-subclinical AF (SCAF). SCAF has been recognized during interrogation of pacemakers and defibrillators. More recently, SCAF has been demonstrated in prospective studies with long-term monitors-both external and implanted. The REVEAL AF trial enrolled a demographically "enriched" population that underwent monitoring for up to 3 years with an insertable cardiac monitor. SCAF was noted in 40% by 30 months. None of these patients had AF known before the study; however, some had nonspecific symptoms common to patients with known AF. The current study assessed whether patients with versus without such symptoms were more likely to have SCAF detected. We found that only palpitations had an association with AF detection when controlling for other baseline symptoms (hazard ratio 1.61 (95% confidence interval 1.12 to 2.32; p = 0.011). No other prescreening symptoms evaluated were associated with an increased likelihood of SCAF detection although patients without detected SCAF had an even higher frequency of symptoms than those with detected SCAF. Thus, REVEAL AF demonstrated that the presence of palpitations is associated with an increased likelihood of SCAF whereas other common symptoms are not; and, symptoms, per se, may more likely be consequent to associated disorders than they are a direct consequence of SCAF.

Atrial fibrillation and stroke: how much atrial fibrillation is enough to cause a stroke?

PURPOSE OF REVIEW

The association between atrial fibrillation and stroke is firmly established, and anticoagulation reduces stroke risk in patients with atrial fibrillation. However, the role of anticoagulation in very brief durations of atrial fibrillation (subclinical atrial fibrillation) is an area of controversy.

RECENT FINDINGS

Stroke risk increases alongside burden of atrial fibrillation. Ongoing trials will clarify if 24 h or less of atrial fibrillation on extended monitoring necessitates lifelong anticoagulation. Trials examining empiric anticoagulation for individuals with ESUS did not demonstrate benefit over antiplatelet agents. However, hypothesis-generating sub-analyses suggest that certain at-risk groups may benefit. Atrial cardiopathy is associated with subclinical atrial fibrillation and research examining anticoagulation after ESUS in this population is underway.

SUMMARY

Stroke risk increases alongside burden of ectopic atrial activity. However, this risk may in part be because of prothrombotic dysfunction associated with atrial cardiopathy in addition to the arrhythmia itself. The minimal amount of subclinical atrial fibrillation to warrant anticoagulation for stroke prevention, and how this may be modified by the total duration of monitoring, will be clarified by the results of ongoing clinical trials. Currently research will also help identify whether a select group of ESUS patients who have structural and electrophysiological markers of atrial cardiopathy warrant anticoagulation for secondary prevention.

Atrial Fibrillation in Patients with Embolic Stroke of Undetermined Source during 3 Years of Prolonged Monitoring with an Implantable Loop Recorder

BACKGROUND

 Undocumented atrial fibrillation (AF) is suspected as a main stroke cause in patients with embolic stroke of undetermined source (ESUS), but its prevalence is largely unknown. This prospective study therefore aimed at delineating the prevalence of AF in patients with ESUS using continuous cardiac monitoring by implantable loop recorder (ILR) with daily remote interrogation over a period of 3 years and its clinical consequences, including recurrent stroke.

METHODS

 In consecutive patients with an ESUS diagnosis after complete work-up, an ILR was implanted and followed by daily remote monitoring until AF was detected or a follow-up of at least 3 years was completed. Additionally, the ILR was interrogated in-hospital in 6-month intervals.

RESULTS

 A total of 123 patients (74 male, mean age 65 ± 9 years) were enrolled and completed the 3 years study period. AF was detected in 51 patients (41.4%). In 43 of the 51 AF positive patients (84%) oral anticoagulation was established. Recurrent strokes occurred in 18 patients (14.6%) of this ESUS population, 9 of these patients being AF positive (17.6% of the AF-positive patients) and 9 being AF negative (12.5% of AF-negative patients). Patients with AF were slightly older than patients without AF (63.1 ± 8.8 vs. 67.5 ± 9.6 years, p = 0.12). Other parameters such as CHA₂DS₂-VASc score, infarct localization, micro- and macroangiopathy, carotid or aortic plaques, or stroke recurrence were not significantly different between groups.

CONCLUSION

 In ESUS patients, early implantation of an ILR with cardiac monitoring and remote transmission over a 3-year period detected AF in 41.4% and resulted in oral anticoagulation in 84% of these patients.

The Link Between CHA2DS2-VASc Score and Thromboembolic Risk in Patients Without Known Atrial Fibrillation: Are We Missing a Silent Culprit?

Stroke is a leading cause of morbidity and mortality. The majority of strokes are ischemic and a subset of these are due to atrial fibrillation (AF). Other etiologies include a variety of cardiovascular disorders. The CHA₂DS₂-VASc score is a validated stroke prediction tool for patients with non-valvular AF. However, it has also been shown to predict increased risk for stroke or thromboembolism in the absence of AF. Given how common subclinical AF (SCAF) is when looked for in patients with elevated CHA₂DS₂-VaSc scores who are not known to have AF, (especially when implanted monitors are used), the stroke/thromboembolism risk that has been associated with CHA₂DS₂-VASc scores absent known AF may be an overestimate of the true risk due to the likely presence of SCAF in some of the subjects included. This has not yet been adequately addressed in the literature. Finally, the risk of a left atrial thromboembolic event is a consequence of the altered atrial anatomy and physiology (atrial cardiomyopathy) that may result from comorbid disorders and AF itself, or, additively from both - whether or not the AF has been already recognized clinically.

Predictors of Atrial Fibrillation During Long-Term Implantable Cardiac Monitoring Following Cryptogenic Stroke

Background

Following cryptogenic stroke, guidelines recommend cardiac monitoring for occult atrial fibrillation (AF). We aimed to evaluate predictors of AF during long‐term implantable cardiac monitoring.

Methods and Results

We studied 293 consecutive patients who underwent implantable cardiac monitor implant (Medtronic LINQ) following hospitalization for cryptogenic stroke at the University of Rochester Medical Center from January 2013 to September 2018. Multivariable Cox proportional hazards regression modeling was used to identify predictors of AF during long‐term monitoring. At 36 months of follow‐up, the cumulative rate of implantable cardiac monitor–detected AF events was 32% in the total study population. Multivariable analysis identified age ≥70 years as the most powerful predictor of the development of AF events during follow‐up (hazard ratio, 2.28 [95% CI, 1.39–3.76]; P=0.001). Replacing age with the CHA₂DS₂‐VASc (congestive heart failure, hypertension, age, diabetes mellitus, stroke, vascular disease, age, sex category) score resulted in a weaker association, for which each 1‐point increment in the CHA₂DS₂‐VASC score was associated with an 18% increased risk of developing AF (95% CI, 1.00–1.38; P=0.047). Consistent results were shown using Kaplan–Meier analysis by age and by the CHA₂DS₂VASc score.

Conclusions

Cryptogenic stroke patients continue to develop AF episodes during 36 months of implantable cardiac monitoring following the index event. Age is the most powerful predictor of occult AF in this population.

Detection of Previously Unrecognized (Subclinical) Atrial Fibrillation

Atrial fibrillation (AF) has been associated with increased morbidity and mortality, even when symptoms are absent and the arrhythmia is unrecognized (e.g., subclinical AF [SCAF]). Despite substantial evidence demonstrating an association between AF and adverse outcomes, the role of mass screening for previously unrecognized SCAF, such that its individual and population risks may be reduced by prophylactic therapy, remains uncertain. Many AF screening strategies exist, from pulse palpation and single-use devices to implanted cardiac monitors; however, existing guidelines are insufficient in specifying who to screen and for how long. In general, higher age, more (and more severe) comorbidities, and longer monitoring periods are associated with greater detection of SCAF. Herein we review the significance of previously unrecognized SCAF and current status of SCAF detection methods. We then propose a clinical approach to help clinicians incorporate AF screening into their practice. In conclusion, we report that SCAF may not be rare, that inserted cardiac monitors have the highest yield of SCAF detection, that clinical concern regarding SCAF is appropriate, but that evidence for therapy mandates is still being collected.

Comprehensive Evaluation of Rhythm Monitoring Strategies in Screening for Atrial Fibrillation

Background:

Stroke is an increasing health problem worldwide. Atrial fibrillation (AF) is a major risk factor for stroke, and the attention given to AF screening is rising, as new monitoring technologies emerge. We aimed to evaluate the performance of a large panel of screening strategies and to assess population characteristics associated with diagnostic yield.

Methods:

Individuals with stroke risk factors but without AF were recruited from the general population to undergo screening with an implantable loop recorder. New-onset AF lasting ≥6 minutes was adjudicated by senior cardiologists. After continuous monitoring for >3 years, complete day-to-day heart rhythm data sets were reconstructed for every participant, including exact time of onset and termination of all AF episodes. Random sampling was applied to assess the sensitivity and negative predictive value of screening with various simulated screening strategies compared with the implantable loop recorder. The diagnostic yield across strategies and population subgroups was compared by use of nonparametric tests.

Results:

The rhythm data sets comprised 590 participants enduring a total of 659 758 days of continuous monitoring and 20 110 AF episodes. In these data, a single 10-second ECG yielded a sensitivity (and negative predictive value) of 1.5% (66%) for AF detection, increasing to 8.3% (67%) for twice-daily 30-second ECGs during 14 days and to 11% (68%), 13% (68%), 15% (69%), 21% (70%), and 34% (74%) for a single 24-hour, 48-hour, 72-hour, 7-day, or 30-day continuous monitoring, respectively. AF detection further improved when subsequent screenings were performed or when the same monitoring duration was spread over several periods compared with a single period (eg, three 24-hour monitorings versus one 72-hour monitoring; P <0.0001 for all comparisons). The sensitivity was consistently higher among participants with age ≥75 years, male sex, CHADS 2 score >2, or NT-proBNP (N-terminal pro-B-type natriuretic peptide) ≥40 pmol/L and among participants with underlying ≥24-hour AF episodes compared with shorter AF ( P <0.0001 for all screening strategies).

Conclusions:

In screening for AF among participants with stroke risk factors, the diagnostic yield increased with duration, dispersion, and number of screenings, although all strategies had low yield compared with the implantable loop recorder. The sensitivity was higher among participants who were older, were male, or had higher NT-proBNP.

Registration:

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02036450 .

Screening for atrial fibrillation in high-risk nursing home residents

Background

Various methods have been implemented for screening of patients for atrial fibrillation (AF), but the yield has generally been low. Targeting high-risk patients may improve detection of asymptomatic AF, which could be of value if appropriate treatment could be initiated before a potential thromboembolic event.

Objective

The purpose of this study was to test screening of high-risk nursing home residents having ≥2 risk factors for AF and no previous history of AF using a smartphone-based electrocardiographic (ECG) monitoring device to determine whether it is an accurate, easy-to-use method of screening for asymptomatic AF.

Methods

Study participants had ≥2 risk factors, consisting of age ≥75 years, female sex, obstructive sleep apnea, peripheral vascular disease, diabetes mellitus, obesity, hypertension, and congestive heart failure. Using the monitoring device, 30-second heart rhythm recordings were obtained on 4 different occasions. All tracings were reviewed by a cardiologist and, if uncertain, by an electrophysiologist. The nursing facility was notified of any diagnosis of AF, prompting further evaluation by the primary physician.

Results

Of the 245 residents screened, 18 (7.4%) had a diagnostic tracing for AF, 15 (83.3%) of whom had AF on the initial screen. There were no significant differences in demographics or individual risk factors between residents with and those without AF.

Conclusion

Intermittent ECG screening of high-risk nursing home residents using a simple, handheld device provided a diagnostic yield in our population comparable to that observed in past studies. Such screening of high-risk individuals can aid in the early diagnosis of AF and initiation of appropriate treatment.

Rhythm monitoring strategies in patients at high risk for atrial fibrillation and stroke: A comparative analysis from the REVEAL AF study

BACKGROUND

Reducing atrial fibrillation (AF)-related stroke requires timely AF diagnosis, but the optimal monitoring strategy is unknown.

OBJECTIVE

We used insertable cardiac monitor (ICM) data from the REVEAL AF study to compare AF detection rates by various short-term continuous monitoring (STM) strategies.

METHODS AND RESULTS

Patients without known AF, but with CHADS₂ scores ≥3 (or = 2 with ≥1 additional AF risk factor) received an ICM for AF detection. One-time STM strategies were assessed by computing AF incidence at 1, 2, 7, 14, and 30 days post-ICM insertion. Repeated STM strategies (quarterly 24-hour, 48-hour, 7-day, or monthly 24-hour monitoring) were modeled by randomly selecting day(s) within a 30-day window around each nominal evaluation date over a 1-year period (simulated 10,000 times). Endpoints included AF ≥6 minutes, AF ≥1 hour, and daily AF burden ≥1 and ≥ 5.5 hours. The impact of compliance on AF detection was evaluated using daily compliance rates of 85%, 75%, 65% and 55% during follow-up months 1-3, 4-6, 7-9, and 9-12, respectively. Based on data from 385 patients (71.5 ± 9.9 years; CHADS₂ score 3.0 ± 1.0) the incidence of AF ≥6 minutes via ICM at 12 months was 27.1% (95% CI, 22.5-31.5%). This exceeded the range of estimated rates from all modeled one-time and repeated STM strategies (0.8% for 24-hour Holter monitoring to 10.6% for quarterly 7-day monitoring). Findings were similar for all AF endpoints. Modeled non-compliance reduced AF detection by 4.5% to 22.9%.

CONCLUSIONS

Most AF episodes detected via ICMs would go undetected via conventional STM strategies, thus preventing optimal prophylaxis for adverse consequences.

Incidence and predictors of atrial fibrillation episodes as detected by implantable loop recorder in patients at risk: From the LOOP study

BACKGROUND

Recent studies have suggested a high prevalence of subclinical atrial fibrillation (AF) in various patient populations, and interest in AF screening has increased. However, knowledge about episode duration is scarce, and risk factors for short or long subclinical AF episodes have yet to be recognized. The aim of the study was to assess AF by long-term continuous screening and to investigate predictors of episodes lasting ≥6 minutes, ≥5.5 hours, or ≥24 hours, respectively.

METHODS

A total of 597 patients aged ≥70 years and diagnosed with ≥1 of hypertension, diabetes, previous stroke, or heart failure were recruited from the general population to receive implantable loop recorder with remote monitoring. Exclusion criteria included history of AF or cardiac implantable electronic device. AF episodes were adjudicated by senior cardiologists.

RESULTS

During 40 (37; 42) months of continuous monitoring, AF was detected in 209 (35%) of the patients. The cumulative incidences at 3 years were 33.8% (30.2%-37.8%), 16.1% (13.4%-19.4%), and 5.7% (4.1%-7.9%) for AF episodes lasting ≥6 minutes, ≥5.5 hours, and ≥24 hours, respectively. Slower resting sinus rate and higher body mass index, N-terminal prohormone of brain natriuretic peptide, and troponin T at baseline were independently associated with AF detection. Addition of these markers to a model of sex, age, and comorbidities improved prediction of AF episodes ≥24 hours (time-dependent area under the receiver operating characteristic curve 79% vs 65%, P = .037).

CONCLUSIONS

A considerable burden of previously unknown AF was detected when long-term monitoring was applied in at-risk patients. Biomarkers were associated with AF incidence and improved prediction of long AF episodes.

Hypertension and Arrhythmias

Hypertension is the most common cardiovascular risk factor and underlies heart failure, coronary artery disease, stroke, and chronic kidney disease. Hypertensive heart disease can manifest as cardiac arrhythmias. Supraventricular and ventricular arrhythmias may occur in the hypertensive patients. Atrial fibrillation and hypertension contribute to an increased risk of stroke. Some antihypertensive drugs predispose to electrolyte abnormalities, which may result in atrial and ventricular arrhythmias. A multipronged strategy involving appropriate screening, aggressive lifestyle modifications, and optimal pharmacotherapy can result in improved blood pressure control and prevent the onset or delay progression of heart failure, coronary artery disease, and cardiac arrhythmias.

Should This Patient Be Screened for Atrial Fibrillation?: Grand Rounds Discussion From Beth Israel Deaconess Medical Center

Atrial fibrillation (AFib) is the most common type of cardiac arrhythmia, affecting 2.7 million to 6.1 million persons in the United States. Although some persons with AFib have no symptoms, others do. For those without symptoms, AFib may be detected by 12-lead electrocardiogram (ECG), single-lead monitors (such as ambulatory blood pressure monitors and pulse oximeters), or consumer devices (such as wearable monitors and smartphones). Pulse palpation and heart auscultation also may detect AFib. In a systematic review, screening with ECG identified more new cases of AFib than no screening. Atrial fibrillation is an important cause of stroke, and without anticoagulant treatment, patients with AFib have approximately a 5-fold increased risk for stroke. The U.S. Preventive Services Task Force reviewed the benefits and harms of ECG screening for AFib in adults aged 65 years or older and found inadequate evidence that ECG identifies AFib more effectively than usual care. This conclusion is in contrast to guidelines from the European Society of Cardiology and the National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand, which found that active screening for AFib in patients older than 65 years may be useful. Here, 2 cardiologists discuss the risks and benefits of screening for AFib, if and when they would recommend screening, and whether they would recommend anticoagulation for a patient with screen-detected AFib.

Searching for Atrial Fibrillation Poststroke: A White Paper of the AF-SCREEN International Collaboration

Cardiac thromboembolism attributed to atrial fibrillation (AF) is responsible for up to one-third of ischemic strokes. Stroke may be the first manifestation of previously undetected AF. Given the efficacy of oral anticoagulants in preventing AF-related ischemic strokes, strategies of searching for AF after a stroke using ECG monitoring followed by oral anticoagulation (OAC) treatment have been proposed to prevent recurrent cardioembolic strokes. This white paper by experts from the AF-SCREEN International Collaboration summarizes existing evidence and knowledge gaps on searching for AF after a stroke by using ECG monitoring. New AF can be detected by routine plus intensive ECG monitoring in approximately one-quarter of patients with ischemic stroke. It may be causal, a bystander, or neurogenically induced by the stroke. AF after a stroke is a risk factor for thromboembolism and a strong marker for atrial myopathy. After acute ischemic stroke, patients should undergo 72 hours of electrocardiographic monitoring to detect AF. The diagnosis requires an ECG of sufficient quality for confirmation by a health professional with ECG rhythm expertise. AF detection rate is a function of monitoring duration and quality of analysis, AF episode definition, interval from stroke to monitoring commencement, and patient characteristics including old age, certain ECG alterations, and stroke type. Markers of atrial myopathy (eg, imaging, atrial ectopy, natriuretic peptides) may increase AF yield from monitoring and could be used to guide patient selection for more intensive/prolonged poststroke ECG monitoring. Atrial myopathy without detected AF is not currently sufficient to initiate OAC. The concept of embolic stroke of unknown source is not proven to identify patients who have had a stroke benefitting from empiric OAC treatment. However, some embolic stroke of unknown source subgroups (eg, advanced age, atrial enlargement) might benefit more from non-vitamin K-dependent OAC therapy than aspirin. Fulfilling embolic stroke of unknown source criteria is an indication neither for empiric non-vitamin K-dependent OAC treatment nor for withholding prolonged ECG monitoring for AF. Clinically diagnosed AF after a stroke or a transient ischemic attack is associated with significantly increased risk of recurrent stroke or systemic embolism, in particular, with additional stroke risk factors, and requires OAC rather than antiplatelet therapy. The minimum subclinical AF duration required on ECG monitoring poststroke/transient ischemic attack to recommend OAC therapy is debated.

Atrial high-rate episodes: prevalence, stroke risk, implications for management, and clinical gaps in evidence

Self-terminating atrial arrhythmias are commonly detected on continuous rhythm monitoring, e.g. by pacemakers or defibrillators. It is unclear whether the presence of these arrhythmias has therapeutic consequences. We sought to summarize evidence on the prevalence of atrial high-rate episodes (AHREs) and their impact on risk of stroke. We performed a comprehensive, tabulated review of published literature on the prevalence of AHRE. In patients with AHRE, but without atrial fibrillation (AF), we reviewed the stroke risk and the potential risk/benefit of oral anticoagulation. Atrial high-rate episodes are found in 10-30% of AF-free patients. Presence of AHRE slightly increases stroke risk (0.8% to 1%/year) compared with patients without AHRE. Atrial high-rate episode of longer duration (e.g. those >24 h) could be associated with a higher stroke risk. Oral anticoagulation has the potential to reduce stroke risk in patients with AHRE but is associated with a rate of major bleeding of 2%/year. Oral anticoagulation is not effective in patients with heart failure or survivors of a stroke without AF. It remains unclear whether anticoagulation is effective and safe in patients with AHRE. Atrial high-rate episodes are common and confer a slight increase in stroke risk. There is true equipoise on the best way to reduce stroke risk in patients with AHRE. Two ongoing trials (NOAH-AFNET 6 and ARTESiA) will provide much-needed information on the effectiveness and safety of oral anticoagulation using non-vitamin K antagonist oral anticoagulants in patients with AHRE.

Passive Detection of Atrial Fibrillation Using a Commercially Available Smartwatch

Importance

Atrial fibrillation (AF) affects 34 million people worldwide and is a leading cause of stroke. A readily accessible means to continuously monitor for AF could prevent large numbers of strokes and death.

Objective

To develop and validate a deep neural network to detect AF using smartwatch data.

Design, Setting, and Participants

In this multinational cardiovascular remote cohort study coordinated at the University of California, San Francisco, smartwatches were used to obtain heart rate and step count data for algorithm development. A total of 9750 participants enrolled in the Health eHeart Study and 51 patients undergoing cardioversion at the University of California, San Francisco, were enrolled between February 2016 and March 2017. A deep neural network was trained using a method called heuristic pretraining in which the network approximated representations of the R-R interval (ie, time between heartbeats) without manual labeling of training data. Validation was performed against the reference standard 12-lead electrocardiography (ECG) in a separate cohort of patients undergoing cardioversion. A second exploratory validation was performed using smartwatch data from ambulatory individuals against the reference standard of self-reported history of persistent AF. Data were analyzed from March 2017 to September 2017.

Main Outcomes and Measures

The sensitivity, specificity, and receiver operating characteristic C statistic for the algorithm to detect AF were generated based on the reference standard of 12-lead ECG-diagnosed AF.

Results

Of the 9750 participants enrolled in the remote cohort, including 347 participants with AF, 6143 (63.0%) were male, and the mean (SD) age was 42 (12) years. There were more than 139 million heart rate measurements on which the deep neural network was trained. The deep neural network exhibited a C statistic of 0.97 (95% CI, 0.94-1.00; P < .001) to detect AF against the reference standard 12-lead ECG-diagnosed AF in the external validation cohort of 51 patients undergoing cardioversion; sensitivity was 98.0% and specificity was 90.2%. In an exploratory analysis relying on self-report of persistent AF in ambulatory participants, the C statistic was 0.72 (95% CI, 0.64-0.78); sensitivity was 67.7% and specificity was 67.6%.

Conclusions and Relevance

This proof-of-concept study found that smartwatch photoplethysmography coupled with a deep neural network can passively detect AF but with some loss of sensitivity and specificity against a criterion-standard ECG. Further studies will help identify the optimal role for smartwatch-guided rhythm assessment.

Changes in Management Following Detection of Previously Unknown Atrial Fibrillation by an Insertable Cardiac Monitor (from the REVEAL AF Study)

The REVEAL AF study demonstrated a high incidence of previously undetected atrial fibrillation (AF) using insertable cardiac monitors (ICMs) in patients with risk factors for AF and stroke. This analysis evaluated whether ICM monitoring led to changes in clinical management after AF detection. Patients with CHADS₂ scores ≥3 (or =2 with ≥1 additional AF risk factor) but no history of AF received an ICM and were followed 18 to 30 months. Physicians recorded changes in clinical management in response to AF detection at scheduled (every 6 months) and unscheduled follow-up visits. Changes in clinical management included oral anticoagulation, rhythm or rate control pharmacotherapy, cardioversion, ablation, and cardiac subspecialist referral. In 387 patients who met inclusion criteria and received an ICM, AF was found in 115. A change in clinical management was taken in 87 patients with AF (76%). In 80 of these 87, a change was taken at the first visit after AF detection. In total, 31 patients (27%) with AF had ≥2 visits at which changes in clinical management were taken. The most common change was initiation of oral anticoagulation (n = 73, 63% of patients with AF). Patients with a change in clinical management at the first visit after AF detection tended to have longer AF episodes and a higher maximal daily AF burden compared with AF patients for whom no change was taken (longest episode: 52 vs 28 minutes; maximal daily AF burden:112 vs 23 minutes). Changes in management more frequently occurred at visits where patients reported AF-compatible symptoms (65% vs 46% of visits, p = 0.01). In conclusion, ICM monitoring to identify AF guides both immediate and long-term patient management in a population at high risk for stroke.

Cost-effectiveness of an insertable cardiac monitor in a high-risk population in the UK

Objective

To evaluate the cost-effectiveness of insertable cardiac monitors (ICMs) compared with standard of care (SoC) for detecting atrial fibrillation (AF) in patients at high risk of stroke (CHADS₂ >2), using a UK National Health Service (NHS) perspective.

Methods

Using patient characteristics and clinical data from the REVEAL AF trial, a Markov model assessed the cost-effectiveness of detecting AF with an ICM compared with SoC. Costs and benefits were extrapolated across modelled patient lifetime. Ischaemic and haemorrhagic strokes, intracranial and extracranial haemorrhages and minor bleeds were modelled. Diagnostic and device costs were included, plus costs of treating stroke and bleeding events and costs of oral anticoagulants (OACs). Costs and health outcomes, measured as quality-adjusted life years (QALYs), were discounted at 3.5% per annum. One-way deterministic and probabilistic sensitivity analyses (PSA) were undertaken.

Results

The total per-patient cost for ICM was £13 360 versus £11 936 for SoC (namely, annual 24 hours Holter monitoring). ICMs generated a total of 6.50 QALYs versus 6.30 for SoC. The incremental cost-effectiveness ratio (ICER) was £7140/QALY gained, below the £20 000/QALY acceptability threshold. ICMs were cost-effective in 77.4% of PSA simulations. The number of ICMs needed to prevent one stroke was 21 and to cause a major bleed was 37. ICERs were sensitive to assumed proportions of patients initiating or discontinuing OAC after AF diagnosis, type of OAC used and how intense the traditional monitoring was assumed to be under SoC.

Conclusions

The use of ICMs to identify AF in a high-risk population is cost-effective for the UK NHS.

Incidence of Previously Undiagnosed Atrial Fibrillation Using Insertable Cardiac Monitors in a High-Risk Population: The REVEAL AF Study

Importance

In approximately 20% of atrial fibrillation (AF)-related ischemic strokes, stroke is the first clinical manifestation of AF. Strategies are needed to identify and therapeutically address previously undetected AF.

Objective

To quantify the incidence of AF in patients at high risk for but without previously known AF using an insertable cardiac monitor.

Design, Setting, and Participants

This prospective, single-arm, multicenter study was conducted from November 2012 to January 2017. Visits took place at 57 centers in the United States and Europe. Patients with a CHADS2 score of 3 or greater (or 2 with at least 1 additional risk factor) were enrolled. Approximately 90% had nonspecific symptoms potentially compatible with AF, such as fatigue, dyspnea, and/or palpitations.

Exposures

Patients underwent monitoring with an insertable cardiac monitor for 18 to 30 months.

Main Outcomes and Measures

The primary end point was adjudicated AF lasting 6 or more minutes and was assessed at 18 months. Other analyses included detection rates at points from 30 days to 30 months and among CHADS2 score subgroups. Median time from insertion to detection and the percentage of patients subsequently prescribed oral anticoagulation therapy was also determined.

Results

A total of 446 patients were enrolled; 233 (52.2%) were male, and the mean (SD) age was 71.5 (9.9) years. A total of 385 patients (86.3%) received an insertable cardiac monitor, met the primary analysis cohort definition, and were observed for a mean (SD) period of 22.5 (7.7) months. The detection rate of AF lasting 6 or more minutes at 18 months was 29.3%. Detection rates at 30 days and 6, 12, 24, and 30 months were 6.2%, 20.4%, 27.1%, 33.6%, and 40.0%, respectively. At 18 months, AF incidence was similar among patients with CHADS2 scores of 2 (24.7%; 95% CI, 17.3-31.4), 3 (32.7%; 95% CI, 23.8-40.7), and 4 or greater (31.7%; 95% CI, 22.0-40.3) (P = .23). Median (interquartile) time from device insertion to first AF episode detection was 123 (41-330) days. Of patients meeting the primary end point, 13 (10.2%) had 1 or more episodes lasting 24 hours or longer, and oral anticoagulation therapy was prescribed for 72 patients (56.3%).

Conclusions and Relevance

The incidence of previously undiagnosed AF may be substantial in patients with risk factors for AF and stroke. Atrial fibrillation would have gone undetected in most patients had monitoring been limited to 30 days. Further trials regarding the value of detecting subclinical AF and of prophylactic therapies are warranted.

Trial Registration

clinicaltrials.gov Identifier: NCT01727297.

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.

Extended Cardiac Monitoring in Patients With Severe Sleep Apnea and No History of Atrial Fibrillation (The Reveal XT-SA Study)

Atrial fibrillation (AF) is a risk factor for ischemic stroke and reported to be associated with severe obstructive sleep apnea (OSA). The aim of this study was to determine the occurrence of newly detected AF in patients with severe OSA and no previous history of AF. Prospective observational study included patients with severe OSA (Apnea-Hypopnea Index [AHI] ≥ 30) and no history of AF. Primary outcome was detection of AF lasting ≥10 seconds. Patients were subjected to 2 24-hour Holter monitors, and if no AF was detected, implanted with a Medtronic Reveal XT implantable loop recorder. Follow-up was done every 6 months for a total of 3years. Implantable loop recorder was explanted if the primary outcome was detected (AF) or the battery was exhausted. Of the 31 patients enrolled, 6 withdrew participation in the study before implantation. Mean age was 57 ± 10years, mean body mass index was 35 ± 6; 52% male patients. Hypertension 56% and coronary artery disease 24%. Mean AHI was 55 ± 18. AF was detected in 5 patients (20%). AF mean duration was 4.8hours (range 20 seconds to 15.3 hours). Mean time to diagnosis was 11 ± 7 months. Male gender was predictive for AF detection (p = 0.04). Continuous positive airway pressure therapy was used by 96% of patients with 68% total adherence. Mean follow-up was 27 months. In conclusion, extended cardiac monitoring of patients with severe OSA may facilitate the identification of newly detected AF.