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Introduction: Alternatives for out-of-clinic heart rate (HR) measurement are required to optimise the management of atrial fibrillation (AF) in dogs. Additionally, the presence of circadian variation (CV) in HR in pet dogs remains unknown. We aimed to identify the number and duration of spot-checks required for an accurate estimation of 24-hour HR in canine AF. Circadian variation in HR was examined in healthy dogs and dogs with AF, and spot-check-derived HR was compared with a CV-derived gold standard., Materials and Methods: Ambulatory electrocardiogram data from healthy dogs and dogs with AF were retrospectively analysed. Heart rate was calculated from the entire recording and pre-defined periods (spot-checks) of one hour to 30 and 60 s in duration. Circadian variation in HR was determined by cosinor analysis. Bias and limits of agreement of means and median HR with mesor HR were determined by correlation and Bland-Altman analysis., Results: Circadian variation in HR was identified not only in 18/22 healthy dogs and 14/21 AF dogs but only on ambulatory electrocardiogram recordings. Four-hourly spot-checks provided the most accurate estimate of mesor HR in healthy dogs (bias of the median over 30 s 7.70, limits of agreement 7.48), whereas, in dogs with AF, four, six and eight-hourly spot-checks provided reliable estimates of mesor HR (bias within -1.29 and -29.5)., Conclusions: Four, six and eight-hourly HR spot-checks can estimate 24-hourly HR in dogs with AF. There was CV in HR in most healthy pet dogs and dogs with AF. Spot-check protocols cannot identify CV in HR., Competing Interests: Conflict of Interest Statement The authors do not have any conflicts of interest to disclose., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Wired ambulatory monitoring of the electrocardiogram (ECG) is an established method used by researchers and clinicians. Recently, a new generation of wireless, compact, and relatively inexpensive heart rate monitors have become available. However, before these monitors can be used in scientific research and clinical practice, their feasibility, validity, and reproducibility characteristics have to be investigated. Therefore, we tested how two wireless heart rate monitors (i.e., the Ithlete photoplethysmography (PPG) finger sensor and the Cortrium C3 ECG monitor perform against an established wired reference method (the VU-AMS ambulatory ECG monitor). Monitors were tested on cross-instrument and test-retest reproducibility in a controlled laboratory setting, while feasibility was evaluated in protocolled ambulatory settings at home. We found that the Cortrium and the Ithlete monitors showed acceptable agreement with the VU-AMS reference in laboratory setting. In ambulatory settings, assessments were feasible with both wireless devices although more valid data were obtained with the Cortrium than with the Ithlete. We conclude that both monitors have their merits under controlled laboratory settings where motion artefacts are minimized and stationarity of the ECG signal is optimized by design. These findings are promising for long-term ambulatory ECG measurements, although more research is needed to test whether the wireless devices' feasibility, validity, and reproducibility characteristics also hold in unprotocolled daily life settings with natural variations in posture and activities., (© 2021 Society for Psychophysiological Research.)

P wave centric ambulatory electrocardiographic (ECG) monitoring has emerged as an important tool aiding the diagnosis of arrhythmias. However, their efficacy and user experience in infants and young children are not well established. A retrospective study was performed to detail clinical and user experience of ECG monitoring using the Carnation Ambulatory Monitor (CAM) patch (Bardy Diagnostics Inc., Seattle, WA) in patients less than 10 kg. Additionally, 2 different monitor locations (over the sternum and horizontal over the left axilla) were assessed to address the optimal placement in these patients. A total of 33 CAM reports from 25 patients, aged 0 to15 months were included in the study. Mean patient age was 4.2 months ± 5.0 and mean weight was 5.3 kg ± 2.4. Thirty-six percent of patients (9/25) had known congenital heart disease. Indications for monitoring included: tachyarrhythmia (15/33, 45%), bradyarrhythmia (6/33, 18%), ectopic rhythm (9/33, 27%), cardiac tumor (1/33, 1%), and prolonged QT interval (1/33, 1%). All CAM reports showed clear, identifiable P waves which were diagnostic and lead to changes in medical management for 30% of patients (e.g., medication adjustments or discharge from cardiology care). We found the upright placement over the sternum performed better than the horizontal placement over the left axilla for small infants and children less than 10 kg. A P wave centric single-lead ECG monitor is helpful in providing accurate diagnostics tracings in infants and small children aiding in their clinical management.

The aim of this study was to validate the measurements of the beat intervals taken at rest by the Omegawave ® device by comparing them to an ambulatory electrocardiogram system. For this purpose, the electrocardiogram was digitally processed, time-aligned, and scrutinized for its suitable use as gold-standard. Rest measurements were made for 10 minutes on 5 different days to 10 men and 3 women (24.8±5.05 years; 71.82±11.02 kg; 174.35±9.13 cm). RR intervals were simultaneously recorded using the Omegawave device and a Holter electrocardiogram. The processing of Holter electrocardiogram signals included the detrending of baseline noise and a high-pass filtering for emphasizing the QRS complexes and attenuating the T waves. After obtaining the RR intervals from the electrocardiogram, those from the Omegawave device were automatically aligned to them with cross-correlation digital processing techniques and compared to check whether both measurements could be considered superimposable. A Bland-Altman analysis was applied to the 5 measurements made for all subjects. The Omegawave device exhibited very strong agreement with a quality-controlled Holter electrocardiogram. Deviations not exceeding 25 ms could be expected in 95% of the cases, which is within manageable ranges both for clinical practice and for sports., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)

Background: Wrist-worn heart rate (HR) monitors are increasingly popular. A paucity of data exists on their accuracy in atrial fibrillation (AF) in ambulatory patients. We sought to assess the HR accuracy of two commercially available smart watches [SW] (Fitbit Charge HR [FB] and Apple Watch Series 3 [AW]) compared with Holter monitoring in an ambulant patient cohort., Methods: Thirty-two participants ≥18 years referred for 24-hour Holter monitoring were prospectively recruited. Each participant was randomly allocated to wear either a FB or AW along with their Holter monitor., Results: Across all devices, 53,288 heart rate values were analysed from 32 participants. Twenty wore the AW (17 had persistent AF and 3 had sinus rhythm [SR]) while 12 participants wore the FB (9 in persistent AF and 3 in SR). Participants in SR demonstrated strong agreement compared to Holter monitoring (bias <1 beat, limits of agreement [LoA] -11 to 11 beats). In AF, both devices underestimated HR measurements (bias -9 beats, LoA -41 to 23). The degree of underestimation was more pronounced when HR > 100 bpm (bias of -28 beats for HR range 100-120 bpm, -48 for 120-140 bpm, and -69 for >140 bpm) compared to a slower HR (bias of -6 for HR range 80-100 bpm, <1 for 60-80 bpm, and -1 for <60 bpm)., Conclusion: In ambulatory patients, smartwatches underestimated HR in AF particularly at HR ranges >100 bpm. Further improvements in device technology are needed before integrating them into the clinical management of rate control in AF., (Copyright © 2019. Published by Elsevier B.V.)

Implantable loop recorders (ILR) are utilized for long-term rhythm monitoring. Typical placement of the Medtronic Reveal LINQ along the left parasternal border may compromise the quality and/or feasibility of future imaging studies. We sought to evaluate the utility of placing an ILR in the left anterior axillary position and the impact on the quality of cardiac imaging. We reviewed patients from May 2017 to June 2018 who had placement of a Reveal LINQ device in the left anterior axillary position. Demographic, procedural, and clinical data were collected via retrospective review. Cardiac magnetic resonance imaging (MRI) studies were reviewed for image quality after ILR placement. Eight patients met inclusion criteria for this study (median age 6 years, 50% female). Six patients (75%) had an ILR placed in the operating room, while all others were placed in the electrophysiology lab. All patients demonstrated acceptable R waves for diagnostic evaluation (median = 0.85 mV, range 0.24-1.7 mV). Cardiac MRI was obtained in 7 patients following ILR placement with diagnostic image quality and no adverse events. One device was explanted 28 days after placement due to concern for possible infection. No other devices required removal or revision (median follow up duration 11 months, IQR 8-13.5). ILR placement in the left anterior axillary position can record adequate signals in pediatric patients. In addition, axillary ILR device position may allow for completion of cardiac imaging, particularly cardiac MRI, without significant artifacts which is critical for patients with congenital heart disease.

This study was designed to examine the RR interval signal qualities of a Holter device and a heart rate chest belt monitor at rest and during exercise. Ten healthy individuals completed five low- to high-intensity activities while simultaneously using the medilog ® AR12plus  Holter monitor and the Polar H10 heart rate monitor. The RR interval signal quality was based on the quantification of the missing RR intervals and RR interval detection errors. Therefore, both measurement systems were compared against visual inspection of the raw electrocardiography signal. The missing and wrong R-wave peak detections were counted manually for both measurement systems. RR interval signal quality was defined as the relative number of correctly detected RR intervals. Overall, RR interval signal qualities of 94.6% and 99.6% were demonstrated for the medilog ® AR12plus  and the Polar H10. During the high-intensity activities, the RR interval signal quality of the medilog ® AR12plus  dropped to 89.8%, whereas the Polar H10 maintained a signal quality of 99.4%. The correlation between both systems was high (r = 0.997, p > 0.001). The excellent RR interval signal quality during low- to moderate-intensity activities in the medilog ® AR12plus  and during low- to high-intensity activities in the Polar H10 demonstrates both measurement systems' validity for the detection of RR intervals throughout a wide range of activities. A simple chest strap such as the Polar H10 might be recommended as the gold standard for RR interval assessments if intense activities with strong body movements are investigated.

Background: Recent advances in wearable technology make continuous cardiorespiratory monitoring possible, with potential applications in assessment of cardiopulmonary patients, healthy subjects and athletes. The aim of the present study was to qualitatively and quantitatively evaluate a new wearable device (Learn Inspire Free Entertain = L.I.F.E.) by embedding in a compression shirt a 12‑lead ECG system and 5 respiratory sensors., Methods: Thirty cardiorespiratory patients and ten healthy subjects were studied for 24 h during their usual life activities. In 8 healthy subjects, simultaneous measurements of the device and of an ergo-spirometer were performed during different levels of ventilation in five different body positions. The quality of ECG signals in terms of measurability of heart rate, P wave, QRS complex and ST segment, was analyzed by four expert cardiologists/respiratory physiologists using an arbitrary 1-5 scale. The sum of the respiratory signals was used to calculate the respiratory rate, inspiratory time and relative changes of tidal volume. These parameters were compared to ergo-spirometer measurements., Results: Median quality value was >3 for heart rate, QRS complex, ST segment and P wave (except in L3, aVL, aVF, V1 and V2 leads). Median quality of respiratory traces was >4 in patients and between 3 and 4 in healthy subjects. The respiratory monitoring of respiratory rate and inspiratory time was accurate in all body positions. Tidal volumes were underestimated due to a high level of ventilation., Conclusions: The L.I.F.E. device provides an accurate continuous monitoring of cardiorespiratory signals during the 24 h both in normal subjects and cardiorespiratory patients., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Aims: Diagnostic ambulatory electrocardiogram (AECG) monitoring is widely used for evaluating syncope/collapse. In Europe, two sets of practice guidelines [National Institute for Health and Clinical Excellence (NICE) and European Society of Cardiology (ESC)] provide recommendations concerning optimal selection of AECG devices. However, whether practising physicians' select AECGs based on published guidelines is unclear. This study examined AECG use by Emergency Department (EDs) physicians and cardiologists in two European countries: Germany (D) and United Kingdom (UK)., Methods and Results: A quantitative survey was undertaken in which 177 respondents participated (ED: UK 33, Germany 40; Cardiology: UK 54, Germany 50). The choice of AECG technology varied by specialty. Thus, among EDs, despite patients having daily symptoms, 20% (UK), 31% (D) of respondents chose an AECG other than Holter monitor. Conversely, when monitoring for infrequent events (

The convergence between wearable and medical device technologies is a natural progression. Miniaturization has allowed the design of small, compact monitoring systems that can record physiological signals over longer periods of time. Thus, the potential for these devices to expand the understanding of disease progression and patients' clinical status is very high. The accuracy of these devices, however, is dependent upon the computer algorithms utilized in the analysis of the large volume of physiological data monitored and/or recorded by the devices. Automated interpretation of the data by these new technologies, therefore, necessitates closer examination by regulatory organizations. The current requirements for the validation of novel Ambulatory ECG (A-ECG) annotation algorithms are based on the AAMI/ANSI-EC57 and IEC60601-2-47 Standard. These standards are being updated, but they rely on a very limited set of digitized ECG recordings from a couple of ECG databases built in the first half of the 70's. These reference signals are obsolete. We are developing a validation tool for computerized methods designed to detect and monitor cardiac activities based on body-surface ECGs. We will rely on a set of existing digital high-resolution 12‑lead A-ECG recordings acquired in cardiac patients and healthy individuals. These ECG signals include a large and unique set of electrocardiographic events. This tool is being qualified by the Center for Devices and Radiological Health of the United States Food and Drug Administration (FDA) as a Medical Device Development Tool (MDDT). This document provides insights into the design of the M.A.D.A.E. database, its functionalities, and its ultimate role in enabling the next generations of automatic interpretation of ECG signals., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Introduction: FDA has established initiatives to characterize clinical and non-clinical biomarkers to enable more precise prediction of proarrhythmia risk based upon knowledge of drug effect on multiple cardiac ion channels (Colatsky et al., 2016). The FDA has recently demonstrated superiority of early ventricular repolarization interval (JTp) in differentiating pure hERG block from multi-channel block in human subjects. Preclinical studies often acquire a single lead ECG, whereas FDA measurements of JTp were derived ​from a spatial vectorcardiogram computed using multiple leads. This study compares QT subintervals derived from single lead vs. spatial magnitude (SM) ECG and contrasts information obtained from multilead and single lead ECGs in the canine model., Methods: Four beagle dogs were instrumented with 3-lead Holter monitors to acquire continuous surface ECG recordings for three consecutive days. A 24-h baseline recording was obtained on day 1 followed by administration of dofetilide on day 2 and atropine and dofetilide on day 3. Lead II and SM ECGs were automatically analyzed using the AE-1010 Rhythm Express™ (RE) software (VivaQuant, St. Paul, MN USA) without manual intervention or editing of the results (auto). Five-minute averages of beat-to-beat intervals measured on each lead were compared for agreement assessed by Bland-Altman (BA) statistics and consistency measured as the repeatability standard deviation (SD) from 5-min intervals. The fully automated results were screened by an operator (semi-automated) and compared to automated results., Results: JTp and TpTe measured using SM lead are less sensitive to changes in posture and respiration related changes in T-wave morphology. The 24-h repeatability SD of 5-min subintervals for JTp and TpTe over the three days was improved by 15.4% and 15.5% respectively with the highest improvements of 23.3% for JTp on day 2 and 25.3% for TpTe on day 3. Drug induced changes in QTcV, QRS, RR, and PR intervals were qualitatively similar between the SM lead and Lead II and in close agreement based on BA statistics. Semi-automated and automated measurements from SM Lead were in close agreement based on BA statistics., Discussion: Single lead ECG is adequate for PR, RR, QRS, and QT, but produces different and more variable results when assessing QT subintervals relative to the SM lead. Close agreement between automated and semi-automated measurements demonstrates Rhythm Express accuracy and the potential to streamline interval analysis., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background and Purpose: This scientific statement provides an interprofessional, comprehensive review of evidence and recommendations for indications, duration, and implementation of continuous electro cardiographic monitoring of hospitalized patients. Since the original practice standards were published in 2004, new issues have emerged that need to be addressed: overuse of arrhythmia monitoring among a variety of patient populations, appropriate use of ischemia and QT-interval monitoring among select populations, alarm management, and documentation in electronic health records., Methods: Authors were commissioned by the American Heart Association and included experts from general cardiology, electrophysiology (adult and pediatric), and interventional cardiology, as well as a hospitalist and experts in alarm management. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Authors were assigned topics relevant to their areas of expertise, reviewed the literature with an emphasis on publications since the prior practice standards, and drafted recommendations on indications and duration for electrocardiographic monitoring in accordance with the American Heart Association Level of Evidence grading algorithm that was in place at the time of commissioning., Results: The comprehensive document is grouped into 5 sections: (1) Overview of Arrhythmia, Ischemia, and QTc Monitoring; (2) Recommendations for Indication and Duration of Electrocardiographic Monitoring presented by patient population; (3) Organizational Aspects: Alarm Management, Education of Staff, and Documentation; (4) Implementation of Practice Standards; and (5) Call for Research., Conclusions: Many of the recommendations are based on limited data, so authors conclude with specific questions for further research., Competing Interests: The American Heart Association makes every effort to avoid any actual or potential conflicts of interest that may arise as a result of an outside relationship or a personal, professional, or business interest of a member of the writing panel. Specifically, all members of the writing group are required to complete and submit a Disclosure Questionnaire showing all such relationships that might be perceived as real or potential conflicts of interest., (© 2017 American Heart Association, Inc.)

Purpose: Athletes and members of the public increasingly rely on wearable HR monitors to guide physical activity and training. The accuracy of newer, optically based monitors is unconfirmed. We sought to assess the accuracy of five optically based HR monitors during various types of aerobic exercise., Methods: Fifty healthy adult volunteers (mean ± SD age = 38 ± 12 yr, 54% female) completed exercise protocols on a treadmill, a stationary bicycle, and an elliptical trainer (±arm movement). Each participant underwent HR monitoring with an electrocardiogaphic chest strap monitor (Polar H7), forearm monitor (Scosche Rhythm+), and two randomly assigned wrist-worn HR monitors (Apple Watch, Fitbit Blaze, Garmin Forerunner 235, and TomTom Spark Cardio), one on each wrist. For each exercise type, HR was recorded at rest, light, moderate, and vigorous intensity. Agreement between HR measurements was assessed using Lin's concordance correlation coefficient (rc)., Results: Across all exercise conditions, the chest strap monitor (Polar H7) had the best agreement with ECG (rc = 0.996) followed by the Apple Watch (rc = 0.92), the TomTom Spark (rc = 0.83), and the Garmin Forerunner (rc = 0.81). Scosche Rhythm+ and Fitbit Blaze were less accurate (rc = 0.75 and rc = 0.67, respectively). On treadmill, all devices performed well (rc = 0.88-0.93) except the Fitbit Blaze (rc = 0.76). While bicycling, only the Garmin, Apple Watch, and Scosche Rhythm+ had acceptable agreement (rc > 0.80). On the elliptical trainer without arm levers, only the Apple Watch was accurate (rc = 0.94). None of the devices was accurate during elliptical trainer use with arm levers (all rc < 0.80)., Conclusion: The accuracy of wearable, optically based HR monitors varies with exercise type and is greatest on the treadmill and lowest on elliptical trainer. Electrode-containing chest monitors should be used when accurate HR measurement is imperative.

Background: Although continuous electrocardiographic (ECG) monitoring is ubiquitous in hospitals, monitoring practices are inconsistent. We evaluated implementation of American Heart Association practice standards for ECG monitoring on nurses' knowledge, quality of care, and patient outcomes., Methods and Results: The PULSE (Practical Use of the Latest Standards of Electrocardiography) Trial was a 6-year multisite randomized clinical trial with crossover that took place in 65 cardiac units in 17 hospitals. We measured outcomes at baseline, time 2 after group 1 hospitals received the intervention, and time 3 after group 2 hospitals received the intervention. Measurement periods were 15 months apart. The 2-part intervention consisted of an online ECG monitoring education program and strategies to implement and sustain change in practice. Nurses' knowledge (N=3013 nurses) was measured by a validated 20-item online test, quality of care related to ECG monitoring (N=4587 patients) by on-site observation, and patient outcomes (mortality, in-hospital myocardial infarction, and not surviving a cardiac arrest; N=95 884 hospital admissions) by review of administrative, laboratory, and medical record data. Nurses' knowledge improved significantly immediately after the intervention in both groups but was not sustained 15 months later. For most measures of quality of care (accurate electrode placement, accurate rhythm interpretation, appropriate monitoring, and ST-segment monitoring when indicated), the intervention was associated with significant improvement, which was sustained 15 months later. Of the 3 patient outcomes, only in-hospital myocardial infarction declined significantly after the intervention and was sustained., Conclusions: Online ECG monitoring education and strategies to change practice can lead to improved nurses' knowledge, quality of care, and patient outcomes., Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01269736., (© 2017 American Heart Association, Inc.)

Background: There are conflicting data on the influence of meal intake on the QT interval., Methods: Ten healthy subjects were studied before and after a standardized breakfast and lunch with a sequence of supine resting, standing and exercise. Data collection was performed using a 12-lead Holter with semi-automated analysis. QT correction was performed using Fridericia (QTcF) correction formula and a subject-specific method based on individual QT/RR-regression (QTcI)., Results: Meal intake induced significant changes in HR (p<0.001), but not in QTcF (p=0.512) or QTcI (p=0.739). Postural analysis showed only significant differences in supine position for HR (p=0.010), not when standing or during exercise., Conclusion: Food intake induced an increase in heart rate limited to supine position. Using QTcF and QTcI no QTc changes were found., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Symptoms that may be caused by arrhythmia are common in pediatric outpatient departments, though it remains challenging to reveal paroxysmal tachycardia. This investigation evaluated prospectively the quality and diagnostic yield of a newly available handheld patient-activated event recorder (ER) in children. In 226 children (pts) aged 0-17 years with or without congenital heart defects, pacemaker/ICDs or arrhythmia, a lead-I ER ECG was created. ER ECGs were recorded by pressing the patients' thumbs on the device and were analyzed in comparison with a lead-12 ECG, as gold standard. Event recording and data transmission were possible in all cases. ECG quality of the ER showed a high accordance in measuring heart rate (ICC = 0.962), duration of QRS complexes (κ = 0.686), and PR interval (ICC = 0.750) (p < 0.001) although P wave detection remained challenging (p = 0.120). 36 % (n = 82) of the pts had heart rhythm disturbances. The ER yielded 92 % sensitivity in diagnosing supraventricular tachycardia plus 77 % sensitivity and 92 % specificity in identifying abnormal ECGs. In children, the application of the tested ER was suitable. ECGs of good quality could be performed and transmitted easily, and also complex arrhythmia analysis was possible. This ER is an excellent diagnostic device for the detection and exclusion of tachycardia in children.

Background: Atrial fibrillation (AF) is estimated to account for approximately every fifth ischemic stroke. In routine clinical practice, detection of undiagnosed, clinically silent AF represents a major diagnostic challenge, and in up to 30% of patients with ischemic stroke, AF remains undetected. The MonDAFIS study has been designed to quantify the diagnostic yield and clinical relevance of systematic electrocardiogram (ECG) monitoring for patients with acute ischemic stroke during the subsequent in hospital stay., Study Design: A prospective randomized multicenter study in 3,470 patients with acute ischemic stroke or transient ischemic attack and without known AF on hospital admission. Over a period of approximately 2years, patients will be enrolled in about 30 German-certified stroke units and randomized 1:1 to receive either usual stroke unit diagnostic procedures for detection of AF (control group) or usual stroke unit diagnostic procedures plus standardized and centrally analyzed Holter ECG recording for up to 7days in hospital (intervention group). Results of the ECG core laboratory analysis will be provided to the patients and treating physicians. All patients will be followed up for treatment and cardiovascular outcomes at 6, 12, and 24months after enrollment., Outcomes: The primary outcome of the randomized MonDAFIS study is the proportion of patients who receive anticoagulation therapy 12months after the index stroke. Secondary outcomes include the number of stroke patients with newly detected AF in hospital and the rate of recurrent stroke, major bleedings, myocardial infarction, or death 6, 12, and 24months after the index event. MonDAFIS will also explore patient-reported adherence to anticoagulants, the clinical relevance of short atrial tachycardia, or excessive supraventricular ectopic activity as well as cost-effectiveness of prolonged, centrally analyzed ECG recordings., Conclusion: MonDAFIS will be the largest study to date to evaluate whether a prolonged and systematic ECG monitoring during the initial in hospital stay has an impact on secondary stroke prevention. In addition, prognosis as well as adherence to medication up to 2 years after the index stroke will be analyzed. The primary results of the MonDAFIS study may have the potential to change the current guidelines recommendations regarding ECG workup after ischemic stroke., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Nowadays several diagnostic tools are available to investigate cardiovascular symptoms like palpitations, dizziness and syncope: ECG Holter (or ambulatory ECG, AECG), external and implantable event/loop recorders. Despite this technological burden, many diagnoses are still missed. In the meantime, we are facing an increasing use of implantable devices for cardiac pacing/defibrillation (CIED), which have rapidly evolved from simple pacing/shock boxes to devices including several diagnostic features. However, these functions are not adequately exploited in current clinical practice and several redundant diagnostic tests, like AECG, are still prescribed to CIED carriers, leading to an increase of costs and a delay in final diagnosis. This review is aimed at identifying the current role of AECG in CIED carriers in view of this technological improvement. First, we will briefly present the indications for AECG according to current guidelines. We will then provide a direct comparison of the different diagnostic features provided by AECG (and event/loop recorders) versus automatic diagnostic CIED to highlight the respective pros and cons. This will serve to carefully discuss these indications in view of the results of recent studies on CIED carriers, highlighting the need for proper implantation and follow-up. Eventually, we will provide useful hints to properly analyse AECG in CIED carriers, considering the different behaviours according to the implemented algorithms. We will conclude by suggesting updated indications for AECG., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Many patients suffer from palpitations or dizziness/presyncope. These patients are often referred for Holter ECG (24 hour), although the sensitivity for detecting arrhythmias is low. A new method, short intermittent regular and symptomatic ECG registrations at home, might be a convenient and more sensitive alternative also suitable for primary health care. In this case report we present a patient who had contacted health care several times during a seven year period for paroxysmal palpitations. Routine examination with 24 hour Holter ECG and event recorder did not result in a diagnosis. Using intermittent handheld ECG registration at home, a paroxysmal supraventricular arrhythmia was diagnosed. Further investigation revealed that the patient had a concealed Wolff-Parkinson-White (WPW) syndrome.

Background and Purpose: Extended cardiac monitoring immediately after acute ischemic stroke (AIS) increases paroxysmal atrial fibrillation (PAF) detection, but its reliability for detection or exclusion of longer term paroxysmal PAF is unknown. We evaluated the positive and negative predictive value (PPV and NPV) of AF detection early after AIS, for PAF confirmation 90 days later., Methods: We investigated 49 patients within 7 days of AIS for PAF according to current guidelines; 23 patients received 7 days of additional noninvasive cardiac event monitoring with an R-test device early after their stroke (ISRCTN 97412358). Ninety days after AIS, everyone underwent 7 days of cardiac event monitoring. We calculated the PPV and NPV of immediate PAF detection through extended cardiac event monitoring and through any investigative modality, for the presence of PAF on the 90-day event monitor., Results: PAF detected by a 7-day event monitor within 2 weeks of AIS had a PPV of 100% (95% confidence interval, 72%-100%) for PAF confirmation after 90 days. NPV after 7 days of event monitoring was 64% (95% confidence interval, 35%-87%). PAF detected early through any modality had a PPV of 100% (95% confidence interval, 76%-100%). However, the NPV in the absence of R-test monitoring was only 42% (95% confidence interval, 28%-58%)., Conclusions: AF detection through any means immediately after stroke holds strong PPV for confirmation after 90 days, justifying treatment decisions on early monitoring alone. However, failure to identify AF through early monitoring has only modest NPV even after 7 days of monitoring; repeated investigation is desirable., (© 2014 American Heart Association, Inc.)

The goal of treatment for atrial fibrillation (AF) is often to control symptoms. It remains unclear whether targets for treatment such as AF rate or AF burden are correlated with AF symptom severity. Two hundred eighty-six patients completed a questionnaire of their general health and well-being, including a detailed AF symptom assessment immediately followed by a 7-day continuous monitor. AF characteristics assessed from the monitor included AF burden, AF rate, sinus rhythm rate, frequency and severity of pauses, and premature atrial contraction or premature ventricular contraction burden. Characteristics were analyzed separately for patients with paroxysmal or persistent AF. Symptom severity was assessed using the University of Toronto Atrial Fibrillation Severity Scale. Monitor characteristics were compared with AF symptom severity. The mean age of the cohort was 61.8 years and the majority of subjects were male (65.4%). Co-morbidities included hypertension (64.5%), sleep apnea (38.4%), congestive heart failure (19.6%), and diabetes (16.4%). In those with persistent or paroxysmal AF, there were no significant predictors of AF symptom severity. Specifically, heart rate in AF or sinus rhythm, AF burden, or premature atrial contraction or premature ventricular contraction burden was not predictive of AF symptom severity. After adjusting for potential cofounders (including age, gender, and co-morbidities), these findings persisted. In conclusion, there is no value in using AF monitor characteristics to predict symptoms in patients with AF., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: This study looked to assess the care pathway and diagnostic yield in patients who received an implantable loop recorder (ILR) after an "initial phase of the diagnostic work-up" (initial work-up) or after a "full evaluation" of unexplained syncope., Methods and Results: Physicians classified the timing of an ILR implant in 514 patients as either following an "initial work-up" (n=128; 25%) or "full evaluation" (n=386; 75%). Patients with an "initial work-up" underwent a median (IQ range) of 8 (6-14) tests prior to ILR implant compared to 14 (10-21) tests after "full evaluation" (p<0.0001). Hospitalization and injury before implant were less common in patients with an "initial work-up": 53 vs. 75%, p<0001, and 23% vs. 39%, p<0.001, as were visits to specialists, e.g. neurologist, 32% vs. 50%, p<0.001. At one year after implant, the syncope recurrence rate was 32% in the initial work-up group and 36% in the full evaluation group, and the incidence of recurrences with an ILR-guided diagnosis was 52% and 75% respectively. Diagnoses were cardiac in 90% after "initial work-up" vs. 79% after "full evaluation"., Conclusions: Patients who only underwent an "initial work-up" had fewer investigations and a lower incidence of injury or hospitalization. The diagnostic yield from the ILR was high in both groups. Patients in both groups underwent more investigations than suggested in the ESC guidelines and could have benefitted from limiting the initial evaluation before an ILR is implanted., (© 2013.)

Background: There are innumerous indicators to assure the quality of a service. However, medical competence and the proper performance of a procedure determine its final quality. The Brazilian Society of Cardiac Arrhythmias recommends minimum parameters necessary to guarantee the excellence of ambulatory electrocardiographic monitoring services., Objective: To recommend minimum medical competences and the information required to issue a Holter monitoring report., Methods: This study was grounded in the concept of evidence-based medicine and, when evidence was not available, the opinion of a writing committee was used to formulate the recommendation. That committee consisted of professionals with experience on the difficulties of the method and management in providing services in that area., Results: The professional responsible for the Holter monitoring analysis should know cardiovascular pathologies and have consistent formation on electrocardiography, including cardiac arrhythmias and their differential diagnoses. The report should be written in a clear and objective way. The minimum parameters that comprise a Holter report should include statistics of the exam, as well as quantification and analysis of the rhythm disorders observed during monitoring., Conclusion: Ambulatory electrocardiographic monitoring should be performed by professionals knowledgeable about electrocardiographic analysis, whose report should comprise the minimum parameters mentioned in this document.

Remote device management involves remote follow-up (which replace periodic in-clinic device interrogations for assessing device function), remote monitoring (with unscheduled transmissions of alerts such as atrial fibrillation), and patient-initiated interrogations (that are initiated manually due to a perceived or real clinical event). This article overviews the different aspects related to these functions.

The implantable diagnostic monitor, or loop recorder (ILR) is a subcutaneous monitor capable of continuous ECG monitoring up to 3 years. It is an elegant investigative tool for the assessment of patients with recurrent, unexplained syncope in whom an arrhythmic cause needs to be excluded, and is now increasingly utilised very early in the diagnostic work-up of these patients, in line with current guidelines. This review examines the evidence underpinning these recommendations as well as the relevant clinical trials evaluating the use of the ILR in syncope. Continued research will be needed to validate its role as a first line investigation in a sub-select of syncopal patients, especially with the addition of remote monitoring capabilities., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The current study evaluates the validity of the PEP computed from a fixed value for the Q-wave onset to R-wave peak (QR) interval and an R-wave peak to B-point (RB) interval that is estimated from the R-peak to dZ/dt-min peak (ISTI) interval. Ninety-one subjects participated in a 90min laboratory experiment in which a variety of often employed physical and mental stressors were presented and 31 further subjects participated in a structured 2hour ambulatory recording in which they partook in natural activities that induced large variation in posture and physical activity. PEP, QR interval, and ISTI were scored and rigorously checked by interactive inspection. Across the very diverse laboratory and ambulatory conditions the QR interval could be approximated by a fixed interval of 40ms but 95% confidence intervals were large (25.5 to 54.5ms). Multilevel analysis showed that 79% to 81% of the within and between-subject variation in the RB interval could be predicted by the ISTI with a simple linear regression equation. However, the optimal intercept and slope values in this equation varied significantly across subjects and study setting. Bland Altman plots revealed a large discrepancy between the estimated PEP using the R-wave peak and dZ/dt-min peak and the actual PEP based on the Q-wave onset and B-point. We conclude that the PEP estimated from a fixed QR interval and the ISTI could be a useful addition to the psychophysiologist's toolbox, but that it cannot replace the actual PEP to index cardiac sympathetic control., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: T-wave alternans (TWA) has been associated with increased vulnerability to ventricular tachyarrhythmias and sudden cardiac death. However, both random (white) noise and (patho)physiologic processes (ie, premature ventricular contractions and heart and respiration rates) may hamper TWA estimation and therefore lessen its clinical utility for risk stratification., Objective: To investigate the effect of random noise and certain (patho)physiologic processes on the estimation of TWA by using the fast Fourier transform method and to develop methods to overcome these potential sources of error., Methods: We used a combination of human electrocardiogram data and computer simulations to assess the effects of a premature ventricular contraction and random and colored noise on the accuracy of TWA estimation., Results: We quantitatively demonstrate that replacing a "bad" beat with an odd/even median beat is a more accurate approach than replacing it with the overall average or the overall median beat. We also show that phase resetting may have a significant effect on alternans estimation and that estimation of alternans by using frequencies >0.4922 cycles/beat in a 128-point fast Fourier transform provides the most accurate approach for estimating the alternans when phase resetting is likely to occur. In addition, our data demonstrate that the number of indeterminate TWA tests due to high levels of noise can be reduced when the alternans voltage exceeds a new higher threshold. Furthermore, the amplitude of random noise has a significant effect on alternans estimation and the alternans voltage threshold should be adjusted for noise levels >1.8 μV. Finally, we quantitatively demonstrate that colored noise may lead to a false-positive or a false-negative result. We propose methods to estimate the effect of these (patho)physiologic processes on the alternans estimation in order to determine whether a TWA test is likely to be a true positive or a true negative., Conclusion: This study introduces novel methods to overcome potential sources of error in the estimation of TWA. These methods may improve the utility of TWA either for ambulatory monitoring or for clinical risk stratification for ventricular arrhythmias and sudden cardiac death., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

A growing trend among clinical studies is the use of heart rate monitors (HRMs) for assessment of heart rate variability (HRV). These instruments offer a convenient alternative to traditional electrocardiographs (ECGs) for recording and processing of R-R data. Reports on the validity of such systems are, however, conflicting. This study aimed to assess the validity of a commercial HRM on a large study sample, with emphasis on gender and age. Simultaneous recordings of R-R intervals were conducted with the Polar RS800 HRM and a 3-lead ECG on 341 individuals. Data editing was performed with individually designated software for each instrument. Agreement on SDNN, RMSSD, and HF- and LF power was assessed with intraclass correlations (ICCs), standard errors of measurement (SEMs) and Bland and Altman plots. The HRM was not able to identify 18 observations with non-sinus beats. For men, agreement between instruments ranged from good to excellent (ICC ≥ 0.8) on all HRV measures, and SEMs were generally small. For women the results were weaker, with unacceptable agreement between instruments on SDNN. Women over 60 years did not reach a critical ICC value of 0.75 on any of the HRV measures. Bland and Altman plots demonstrated that the RS800 generally overestimated HRV, and that uncertainty increased with higher values. Since the Polar system did not identify errors satisfactorily, or return valid values of HRV for certain groups, it is concluded that, whenever possible, traditional ECGs should be used for both gathering and editing of HRV data.

Background: T-wave alternans (TWA) is a well-documented noninvasive electrocardiographic (ECG) method useful for identifying patients at risk for sudden cardiac death (SCD)., Objective: The purpose of this study was to evaluate whether the long-term average TWA activity on Holter monitoring provides prognostic information in patients with chronic heart failure., Methods: Twenty-four-hour Holter ECGs from 650 ambulatory patients with mild-to-moderate chronic heart failure were analyzed in the study. Average TWA activity was measured by using a fully automated multilead technique, and 2 indices were proposed to quantify TWA: an index quantifying the average TWA activity in the whole recording (IAA), which was used to define a positive/negative TWA test, and an index quantifying the average TWA activity at heart rates between 80 and 90 beats/min (IAA(90))., Results: Patients were divided into TWA positive (TWA+) and TWA negative (TWA-) groups by setting a cut point of 3.7 μV for IAA, corresponding to the 75th percentile of the distribution of IAA in the population. After a median follow-up of 48 months, the survival rate was significantly higher in the TWA- group for cardiac death and SCD (p = .017 and p = .001, respectively). Multivariate Cox proportional hazards analysis revealed that both TWA+ and IAA(90) were associated with SCD with hazard rates of 2.29 (p = .004) and 1.07 per μV (p = .046), respectively., Conclusion: The average TWA activity measured automatically from Holter ECGs predicted SCD in patients with mild-to-moderate chronic heart failure., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

This consensus guideline was prepared on behalf of the International Society for Holter and Noninvasive Electrocardiology and is cosponsored by the Japanese Circulation Society, the Computers in Cardiology Working Group on e-Cardiology of the European Society of Cardiology, and the European Cardiac Arrhythmia Society. It discusses the electrocardiographic phenomenon of T-wave alternans (TWA) (i.e., a beat-to-beat alternation in the morphology and amplitude of the ST-segment or T-wave). This statement focuses on its physiological basis and measurement technologies and its clinical utility in stratifying risk for life-threatening ventricular arrhythmias. Signal processing techniques including the frequency-domain Spectral Method and the time-domain Modified Moving Average method have demonstrated the utility of TWA in arrhythmia risk stratification in prospective studies in >12,000 patients. The majority of exercise-based studies using both methods have reported high relative risks for cardiovascular mortality and for sudden cardiac death in patients with preserved as well as depressed left ventricular ejection fraction. Studies with ambulatory electrocardiogram-based TWA analysis with Modified Moving Average method have yielded significant predictive capacity. However, negative studies with the Spectral Method have also appeared, including 2 interventional studies in patients with implantable defibrillators. Meta-analyses have been performed to gain insights into this issue. Frontiers of TWA research include use in arrhythmia risk stratification of individuals with preserved ejection fraction, improvements in predictivity with quantitative analysis, and utility in guiding medical as well as device-based therapy. Overall, although TWA appears to be a useful marker of risk for arrhythmic and cardiovascular death, there is as yet no definitive evidence that it can guide therapy., (Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

The 2009 ESC guideline emphasizes active risk stratification and the diagnostic strategy of prolonged ECG monitoring using an implantable loop recorder. The initial evaluation aims at establishing a prima vista diagnosis or at least a diagnostic hypothesis and risk stratification according to ECG criteria and clinical findings. Carotid sinus massage as a diagnostic procedure remains controversial. Electrophysiological study for evaluation of suspected arrhythmogenic syncope is of decreasing relevance. The loop recorder enables documentation of the rhythm during a subsequent syncope. Neurological work-up is not routinely recommended. A standardized evaluation minimizes the rate of unexplained syncopes. Therapeutic decisions include ICD or pacemaker, as indicated in cases of arrhythmogenic syncope or carotid sinus syncope, and mostly general measures in case of other reflex syncopes.

Statistical, spectral, multi-resolution and non-linear methods were applied to heart rate variability (HRV) series linked with classification schemes for the prognosis of cardiovascular risk. A total of 90 HRV records were analyzed: 45 from healthy subjects and 45 from cardiovascular risk patients. A total of 52 features from all the analysis methods were evaluated using standard two-sample Kolmogorov-Smirnov test (KS-test). The results of the statistical procedure provided input to multi-layer perceptron (MLP) neural networks, radial basis function (RBF) neural networks and support vector machines (SVM) for data classification. These schemes showed high performances with both training and test sets and many combinations of features (with a maximum accuracy of 96.67%). Additionally, there was a strong consideration for breathing frequency as a relevant feature in the HRV analysis.

The third meeting of the International Society for Holter and Noninvasive Electrocardiology working group was convened in Lund, Sweden, in June 2010 to consider the key clinical challenge of developing electrocardiographic (ECG) criteria for identification of the global subendocardial ischemia that results from subtotal occlusion of either the left main coronary artery or its equivalent. The participants considered the specific abnormalities typical of global subendocardial ischemia on the presenting ECG and outlined further studies to establish the optimal quantitative ECG criteria. Subgroups on Electrocardiology, Myocardial Imaging, and Coronary Intervention met separately to establish priorities on their topic and then joined together in a final session of the entire working group. The principles for a retrospective and then a prospective study were identified, and a writing group was formed., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Endomyocardial biopsy remains the gold standard of diagnosis of acute cellular rejection after heart transplantation. However, routine biopsies are of major inconvenience to patients and are also risky and costly. In the present research we considered possibility of non-invasive diagnosis of acute cellular rejection in patients after orthotopic heart transplantation. Results of research are based on studying 34 endomyocardial biopsys in combination with Holter monitoring and ECHO findings in 21 heart recipients. It is demonstrated that case follow-up with Holter monitoring and ECHO is mandatory for diagnosis of acute cellular rejection and optimal treatment tactics.

Background: A prolongation of the corrected QT interval (QTc) in the routine ECG of otherwise healthy neonates has been suspected to be a risk factor for sudden infant death. None of the studies published so far differentiated between awake and sleeping neonates., Objective: This study was designed to find possible differences of the QTc when neonates were asleep or awake, and to provide guide values for neonatal QTc in 24-h ECGs., Methods: Hundred neonates (51 male, 49 female, age 2-11 days) underwent ambulatory ECG with defined lead positions. The QT interval was measured constantly in three different leads, and the corrected QT interval was calculated using Bazett's formula. We compared the QTc obtained during sleep with the QTc obtained from wake periods., Results: The heart rate was significantly higher when the neonates were awake, and when awake higher in girls than in boys. While there was no statistically significant difference between the QTc when the babies were awake or asleep in leads 1 and 3, this reached the level of mathematical significance in the most cranio-caudal lead 2., Conclusion: Changes of the corrected QT interval in neonates seems to be dependent on the lead position of ambulatory ECGs, and could be found only in one lead. Guide values for the sleeping and awake neonate are provided.

Background: Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C) Diagnostic Task Force Criteria (TFC) proposed in 1994 are highly specific but lack sensitivity. A new international task force modified criteria to improve diagnostic yield. A comparison of diagnosis by 1994 TFC versus newly proposed criteria in 3 patient groups was conducted., Methods and Results: In new TFC, scoring by major and minor criteria is maintained. Structural abnormalities are quantified and TFC highly specific for ARVD/C upgraded to major. Furthermore, new criteria are added: terminal activation duration of QRS > or = 55 ms, ventricular tachycardia with left bundle-branch block morphology and superior axis, and genetic criteria. Three groups were studied: (1) 105 patients with proven ARVD/C according to 1994 TFC, (2) 89 of their family members, and (3) 39 patients with probable ARVD/C (ie, 3 points by 1994 TFC). All were screened for pathogenic mutations in desmosomal genes. Three ARVD/C patients did not meet the new sharpened criteria on structural abnormalities and thereby did not fulfill new TFC. In 62 of 105 patients with proven ARVD/C, mutations were found: 58 in the gene encoding Plakophilin2 (PKP2), 3 in Desmoglein2, 3 in Desmocollin2, and 1 in Desmoplakin. Three patients had bigenic involvement. Ten additional relatives (11%) fulfilled new TFC: 9 (90%) were female, and all carried PKP2 mutations. No relatives lost diagnosis by application of new TFC. Of patients with probable ARVD/C, 25 (64%) fulfilled new TFC: 8 (40%) women and 14 (56%) carrying pathogenic mutations., Conclusions: In this first study applying new TFC to patients suspected of ARVD/C, 64% of probable ARVD/C patients and 11% of family members were additionally diagnosed. ECG criteria and pathogenic mutations especially contributed to new diagnosis. Newly proposed TFC have a major impact in increasing diagnostic yield of ARVD/C.

Background: Current methods for detecting atrial fibrillation (AF) have limited diagnostic yield. Continuous monitoring with automatic arrhythmia detection and classification may improve detection of symptomatic and asymptomatic AF and subsequent patient treatment. The study purpose was to quantify the performance of the first implantable leadless cardiac monitor (ICM) with dedicated AF detection capabilities., Methods and Results: Patients (n=247) with an implanted ICM (Reveal XT, Medtronic Inc, Minneapolis, Minn) who were likely to present with paroxysmal AF were selected. A special Holter device stored 46 hours of subcutaneously recorded ECG, ICM markers, and 2 surface ECG leads. The ICM automatic arrhythmia classification was compared with the core laboratory classification of the surface ECG. Of the 206 analyzable Holter recordings collected, 76 (37%) contained at least 1 episode of core laboratory classified AF. The sensitivity, specificity, positive predictive value, and negative predictive value for identifying patients with any AF were 96.1%, 85.4%, 79.3%, and 97.4%, respectively. The AF burden measured with the ICM was very well correlated with the reference value derived from the Holter (Pearson coefficient=0.97). The overall accuracy of the ICM for detecting AF was 98.5%., Conclusions: In this ICM validation study, the dedicated AF detection algorithm reliably detected the presence or absence of AF and the AF burden was accurately quantified. The ICM is a promising new diagnostic and monitoring tool for the clinician to treat AF patients independently of symptoms. Long-term studies are needed to evaluate the clinical benefits of the technology.