Comparing human and animal antimicrobial usage: a critical appraisal of the indicators used is needed

Comparisons between antimicrobial usage (AMU) in humans and food-producing animals are regularly made. The accuracy of such comparisons depends on the indicators used to quantify AMU. Indicators for AMU quantitatively relate use data (the numerator) to population data (the denominator). The denominator should be a proxy for the population at risk in a certain period when comparing the exposure of different populations to antimicrobials. Denominators based on numbers of animals slaughtered, such as the commonly used population correction unit, do not consider the time at risk of antimicrobial treatment. Production-based indicators underestimate animal AMU. Additionally, production-based indicators are fundamentally different from indicators used to quantify human AMU. Using such indicators to compare human and animal AMU therefore leads to biased results. More caution should be taken in selecting the indicator to quantify AMU when comparing AMU in food-producing animals and humans.

Structural and electro-anatomical characterization of the equine pulmonary veins: implications for atrial fibrillation

INTRODUCTION/OBJECTIVES

Spontaneous pulmonary vein (PV) activity triggers atrial fibrillation (AF) in humans. Although AF frequently occurs in horses, the origin remains unknown. This study investigated the structural and electro-anatomical properties of equine PVs to determine the potential presence of an arrhythmogenic substrate.

ANIMALS, MATERIALS AND METHODS

Endocardial three-dimensional electro-anatomical mapping (EnSite Precision) using high-density (HD) catheters was performed in 13 sedated horses in sinus rhythm. Left atrium (LA) access was obtained retrogradely through the carotid artery. Post-mortem, tissue was harvested from the LA, right atrium (RA), and PVs for histological characterization and quantification of ion channel expression using immunohistochemical analysis.

RESULTS

Geometry, activation maps, and voltage maps of the PVs were created and a median of four ostia were identified. Areas of reduced conduction were found at the veno-atrial junction. The mean myocardial sleeve length varied from 28 ± 13 to 49 ± 22 mm. The PV voltage was 1.2 ± 1.4 mV and lower than the LA (3.4 ± 0.9 mV, P < 0.001). The fibrosis percentage was higher in PV myocardium (26.1 ± 6.6 %) than LA (14.5 ± 5.0 %, P = 0.003). L-type calcium channel (CaV1.2) expression was higher in PVs than LA (P = 0.001). T-type calcium channels (CaV3.3), connexin-43, ryanodine receptor-2, and small conductance calcium-activated potassium channel-3 was expressed in PVs.

CONCLUSIONS

The veno-atrial junction had lower voltages, increased structural heterogeneity and areas of slower conduction. Myocardial sleeves had variable lengths, and a different ion channel expression compared to the atria. Heterogeneous properties of the PVs interacting with the adjacent LA likely provide the milieu for re-entry and AF initiation.

Seasonality of antimicrobial use in Dutch food-producing animals

Due to globally increasing antimicrobial resistance (AMR), it is pivotal to understand factors contributing to antimicrobial use (AMU) to enable development and implementation of AMR-reducing interventions. Therefore, we explored seasonal variations of systemic AMU in food-producing animals in the Netherlands. Dutch surveillance data from January 2013 to December 2018 from cattle, pig, and broiler farms were used. AMU was expressed as the number of Defined Daily Dosages Animal per month (DDDA/animal-month) per farm by animal sector, antimicrobial line (first, second, and third), antimicrobial class, and farm type. Seasonality of AMU was analyzed using Generalized Additive Models (GAMs) with DDDA/animal-month as outcome variable, and year and month as independent variables. Year and month were modelled as smooth terms represented with penalized regression splines.Significant seasonality of AMU was found in the cattle and pig sectors, but not in broilers. Significant seasonality of AMU was found mainly for first-line antimicrobials. In the cattle sector, a significant increase during winter was found for the use of amphenicols (an increase of 23.8%) and long-acting macrolides (an increase of 3.4%). In the pig sector, seasonality of AMU was found for pleuromutilins (p < 0.001) with an increase of 20% in October-November. The seasonality of pleuromutilins was stronger in sows/piglets (an increase of 47%) than in fattening pigs (16% increase). Only in fattening pigs, the use of amphenicols showed a significant seasonality with an increase of 11% during winter (P < 0.001). AMU in cattle and pig sectors shows seasonal variations likely caused by seasonality of diseases. In broilers, no AMU seasonality was observed, possibly due to the controlled environment in Dutch farms. In the context of the one health concept, future studies are necessary to explore whether this seasonality is present in other populations and whether it has implications for antimicrobial resistance in humans through the food chain.

A walk in the PARC: developing and implementing 21st century chemical risk assessment in Europe

Current approaches for the assessment of environmental and human health risks due to exposure to chemical substances have served their purpose reasonably well. Nevertheless, the systems in place for different uses of chemicals are faced with various challenges, ranging from a growing number of chemicals to changes in the types of chemicals and materials produced. This has triggered global awareness of the need for a paradigm shift, which in turn has led to the publication of new concepts for chemical risk assessment and explorations of how to translate these concepts into pragmatic approaches. As a result, next-generation risk assessment (NGRA) is generally seen as the way forward. However, incorporating new scientific insights and innovative approaches into hazard and exposure assessments in such a way that regulatory needs are adequately met has appeared to be challenging. The European Partnership for the Assessment of Risks from Chemicals (PARC) has been designed to address various challenges associated with innovating chemical risk assessment. Its overall goal is to consolidate and strengthen the European research and innovation capacity for chemical risk assessment to protect human health and the environment. With around 200 participating organisations from all over Europe, including three European agencies, and a total budget of over 400 million euro, PARC is one of the largest projects of its kind. It has a duration of seven years and is coordinated by ANSES, the French Agency for Food, Environmental and Occupational Health & Safety.

Use of a new antimicrobial consumption monitoring system (Vet-AMNet): Application to Dutch dairy sector over a 9-year period

Introduction

The urgency of preventing the increase of antimicrobial resistance has been emphasized by international authorities such as the World Health Organization, European Medicines Agency, and World Organization for Animal Health. Monitoring systems capable of reporting antimicrobial consumption data are regarded as a crucial pillar of this fight. The Vet-AMNet system was developed to collect and analyze national antimicrobial consumption data in Portuguese dairy farms to support the veterinary authority in stewardship actions and to assist both veterinarians and farmers in daily decisions related to antimicrobials.

Methods

To evaluate the robustness of the system and other identified critical success factors, it was used to analyze antimicrobial consumption data available from the Dutch dairy cow sector over the period from 2012 to 2020. The data previously used for publications by the Netherlands Veterinary Medicines Institute (SDa) were imported and pre-processed by the Vet-AMNet system according to the SDa's standard operating procedure and the Dutch metrics to measure antimicrobial consumption were calculated.

Results

By comparing the outputs with the figures generated by the system established in the Netherlands, the Portuguese system was validated. Antimicrobial consumption data from the Dutch dairy sector during the 9-year period will be presented in unpublished graphs and tables, where each molecule's pharmaceutical formulation, pharmacotherapeutic group and line of choice will be related and discussed, illustrating the evolution of sectorial antimicrobial consumption against a background of a strong national antimicrobial policy initiated by public-private cooperation and supported by legislation.

The prevalence and clinical significance of a reduced ventricular ejection fraction in asymptomatic young elite endurance athletes

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Health and Medical Research Council of Australia

Background

Ventricular ejection fraction (EF) is the most widely used parameter to evaluate ventricular systolic function. Endurance athletes presenting with a reduced ventricular EF often raise the question of an underlying dilated or arrhythmogenic cardiomyopathy. The clinical significance of a reduced EF in athletes remains to be elucidated.

Purpose

To investigate the prevalence and clinical significance of a reduced EF in asymptomatic endurance athletes.

Methods

Two hundred eighteen asymptomatic young elite endurance athletes were evaluated at baseline. Cardiac magnetic resonance imaging (CMR) was performed to assess cardiac volumes, left ventricular and right ventricular EF (LVEF and RVEF), mass and fibrosis. Athletes with reduced EF (ATrEF) were defined as those having LVEF&lt;50% and/or RVEF&lt;45%. Ventricular systolic and diastolic function were assessed by trans-thoracic echocardiography. A 12-lead ECG and 24-hour holtermonitoring assessed electrical alterations and arrhythmias. In 145 athletes, LV and RV contractile reserve was evaluated by exercise CMR. Cardiopulmonary testing was performed in all athletes to measure maximal oxygen uptake (VO2max).

Results

Thirty-one ATrEF (14.2%) were compared to 187 athletes with a preserved EF (ATpEF). ATrEF were more frequently males (93 vs 77% male, p=0.033) but did not differ from ATpEF with regard to age (18.8±2.1 vs 18.3±2.1 years, p=0.25). Ten athletes had an isolated reduced LVEF, 10 had an isolated reduced RVEF and 11 had both a reduced LVEF and RVEF. ATrEF had similar end-diastolic volumes and cardiac mass but differed by higher end-systolic volumes.

Peak exercise LVEF and RVEF determined by exercise CMR remained lower in ATrEF (68±3 vs 73±4% and 62±6 vs 69±5%, p&lt;0.001) but contractile reserve was greater (ΔLVEF 18±5 vs 14±4% and ΔRVEF 19±5 vs 15±5%, p&lt;0.01).

A reduced EF was not associated with lower exercise capacity, in fact VO2max was higher in ATrEF than in ATpEF (65±6 vs 62±9mL/kg/min, p=0.020) and the percentage of predicted VO2max by the Wasserman equation were similar (151±14 vs 149±21%, p=0.533).

Fibrosis was present in 3 ATrEF and 18 ATpEF (9.7 vs 9.6%, p=0.993) and was isolated to the RV hinge-points in all but 3 ATpEF who had midmyocardial LV lateral wall fibrosis. LV systolic strain (-17.5±2.0 vs -19±2.1%, p&lt;0.001) was lower in ATrEF whereas RV free wall systolic strain (-24.9±3.7 vs -25.1±3.5%, p=0.776) was similar. Diastolic function was normal in all ATrEF and ATpEF. Pathologic T-wave inversions were present in 2 ATrEF and 13 ATpEF (6.5 vs 7%, p=0.999). Ventricular premature beats (VPB) were infrequent but more prevalent in ATrEF than in ATpEF (2[0-18] vs 1[0-2]/24h, p=0.025; 16.1 vs 2.7% &gt;100/24h, p=0.006).

Conclusion

A reduced ventricular EF is common in asymptomatic young elite endurance athletes, is more frequent in males but is not associated with structural, functional or electrical abnormalities apart from a minor excess in VPB.

Comparison of different antimicrobial use indicators and antimicrobial resistance data in food-producing animals

Objectives

To explore the effects of using different indicators to quantify antimicrobial usage (AMU) in livestock and compare outcomes with antimicrobial resistance (AMR) data.

Methods

Three indicators were used to quantify AMU, two indicators in which the denominator varied: defined daily doses per average mass of the animals present per year (DDD/AY) and defined daily doses per population correction unit (DDD/PCU) and one in which the numerator varied: milligrams of active ingredient per PCU (mg/PCU). AMU was compared with antimicrobial resistance data from the national monitoring programme from 2013 to 2018 with the proportion of Escherichia coli isolates fully susceptible to a predefined panel of antimicrobials for the broiler, dairy cattle and pig farming livestock sectors in the Netherlands.

Results

The ranking of livestock sectors differs between sectors when using different indicators to express AMU. Dairy cattle rank lowest when expressing AMU in DDD/AY, followed by pigs and broilers corresponding to the rankings of the sectors for AMR. When changing the denominator to PCU, the ranking in AMU is reversed: use ranks highest in dairy cattle and lowest broilers.

Conclusions

Using different denominators in AMU indicators has a major impact on measured use. This might result in misinterpretation of effects of interventions on AMU and the associations of AMU with AMR across animal sectors. From an epidemiological perspective, indicators that take into account time at risk of exposure to antimicrobials are to be preferred and reflect the AMR risk most accurately.

Assessing the impact of education in atrial fibrillation: A systematic review

Funding Acknowledgements

Type of funding sources: None.

Background

Atrial Fibrillation (AF) is the most common heart rhythm disorder. Patient education is recommended as part of comprehensive AF management. Despite this the impact of education alone on outcomes in AF populations is unknown.

Purpose

The aim of this study was to describe the impact of education on clinically relevant outcomes in patient with AF including mortality, hospital admissions, emergency department presentations, stroke and quality of life. 

Methods

The authors searched Pubmed, Embase, CINAHL, Cochrane database and Psycinfo from inception until September 2019. Studies were included if they were prospective and of randomized controlled or observational design with a minimum follow-up 3 months and published in English.

Results

A total of 1667 studies were screened with 37 undergoing full text review and 6 meeting eligibility criteria. There was a total of 588 participants with a mean age of 65.63 ± 11.05 and 60.71% were male. A meta-analysis was unable to be performed due to heterogeneity in reporting of outcomes. Two studies examined the impact of education on mortality with no impact evident from either intervention. The impact of education on hospitalisations (all cause – 3 studies, cardiovascular – 1 study and AF - 2 studies) was explored in five studies with no impact on this outcome from any intervention. Similarly, there was no impact of education on emergency department presentations, except for one study in which a video was used in addition to standardised education. There was no impact on stroke from two studies exploring this outcome. There was no evidence of impact of education on general or AF specific quality of life.

Conclusions

There is little evidence to suggest that educational interventions to date have significantly impacted on death, hospitalisations, emergency department presentations or quality of life in AF populations. There is an urgent need to identify optimal modes and components of educational interventions to improve patient outcomes and reduce health care burden in AF.

Development and validation of a questionnaire to assess knowledge in patients with Atrial Fibrillation

Funding Acknowledgements

Type of funding sources: None.

OnBehalf

Centre for Heart Rhythm Disorders

Background

Education is critical to empower individuals to self-monitor and manage their condition. Significant variability exists in the provision of education for atrial fibrillation (AF), whilst individual patient factors including health literacy and education level attainment may impact on knowledge levels. Objective assessment of knowledge  may help to target education to areas of need, and result in improved patient outcomes.

Objective

To describe the development and validation of a knowledge questionnaire for AF.

Methods

A multidisciplinary expert team of healthcare professionals developed the questionnaire, in conjunction with consumers, with question content based upon areas deemed most critical to AF and related self-management. The multiple choice questionnaire consists of 20 items, each worth 5 points, to give a total score out of 100. The questionnaire assesses five domains specific to AF: general knowledge, complications, medications, risk factors and action. The questionnaire was developed in English. The questionnaire was tested on 10 randomly selected patients with AF for face validity and 19 healthcare professionals for content validity. The final version was completed by 454 individuals with AF. Exploratory factor analysis was used to determine construct validity with factor loadings of 0.40 and above considered acceptable. Reliability was assessed using Cronbach’s alpha, with a value greater than 0.7 acceptable.

Results

Face and content validity were considered acceptable, after minor changes to wording. The cohort of 454 individuals with AF had a mean age of 66.9 ± 12 years and 43% were female. Mean (SD) total score was 57.7 ± 15.8. Exploratory factor analysis was undertaken using the principal components method. This resulted in a Kaiser–Meyer–Olkin Measure of Sampling Adequacy of .64 and a Bartlett"s Test of Sphericity being significant at 0.00. Seven factors were selected and analysed using principal component analysis with varimax rotation. All items loaded on one of the seven factors. Internal consistency demonstrated a Cronbach’s alpha of 0.65.

Conclusion

The Atrial Fibrillation Knowledge Questionnaire is a valid measure to assess knowledge in individuals with AF.

Quality evaluation of patient educational resources for catheter ablation of atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

The prevalence of atrial fibrillation (AF) is increasing rapidly with growing utilisation of catheter ablation (CA) as a treatment strategy. Education of individuals undertaking this procedure is diverse, with varying degrees of information provided and little standardisation. Many individuals utilise the internet as an educational resource. However, there is limited regulation of online patient information.

Aims

The purpose of this study was to evaluate the quality of web based  patient education resources for patients undergoing CA in the management of AF.

Methods

A cross-sectional observational study was performed to obtain all freely accessible online educational resources designed to inform AF patients about CA. from inception until 1st October 2019. Three search engines were used: Google, Yahoo! and Bing, using the search terms "atrial fibrillation" and "catheter ablation" combined with "patient information and patient education" in English and Spanish. The Patient Education Materials Assessment Tool (PEMAT) is a validated tool used to evaluate web-based patient education materials as well as  printable tools. The PEMAT score objectively measures the understandability and actionability of printable tools for audio-visual material.

Results

A total of 17 websites and 15 printable tools were included in the analysis. Non-government organizations developed 19% of materials and 75% were created by private or university hospitals. Nineteen materials (59.3%) were rated as highly understandable and 25 materials (21%) were rated as highly actionable, whilst ten materials had an actionability of 0% (6 websites and 4 printable tools).  Less than a half of the materials evaluated were highly rated by the PEMAT score, with a total of 7 websites (41%) and 7 printable tools (46,6%) scoring &gt;70%.

Conclusion

The overall understandability of educational CA material was high, whilst improvement of actionability is warranted. The addition of summaries, visual aids and tools such as checklists may improve quality. These findings have significant implications for developing new patient educational material for CA in AF.

Incidence of new-onset atrial fibrillation after cavotricuspid isthmus ablation for isolated typical atrial flutter: a systematic review and meta-analysis

Funding Acknowledgements

Type of funding sources: None.

Background

There is a lack of consensus guidelines regarding the continuation of anticoagulant therapy following cavotricuspid isthmus (CTI) ablation for typical atrial flutter.  This is despite a significant number of patients developing new-onset atrial fibrillation (AF) following the procedure.  Furthermore, a summary of Kaplan-Meier estimates for drug-free, arrhythmia-free survival has never been reported.

Purpose

 To estimate the incidence of drug-free, new-onset AF stratified by rhythm monitoring strategy in patients undergoing  CTI ablation for isolated typical atrial flutter.

Methods

PubMed, Embase and MEDLINE databases were searched to identify relevant studies. Only studies where anti-arrhythmic drugs were discontinued post-ablation and that accounted for patient censoring by reporting results in the form of time to event data were included.  Data was extracted from published Kaplan-Meier curves using a digitizing software and confidence intervals for the survivor function were estimated based on the number at risk at the time point of interest. Results were pooled in a random effects model using the DerSimonian-Laird estimator.

Results

 Thirteen relevant studies incorporating 1712 patients (79 % male, mean age 63.2 +/-11.2 years,  LVEF 55.2 +/-10.8%) were identified. The estimated  freedom from  new-onset atrial fibrillation was 89.7% (95% CI: 80.3-90.1%) at 1 year and 86.2% (95% CI: 78.4-94.0%) at 2 years in patients undergoing predominantly symptom –based monitoring, 74.6% (95%CI: 67.0-82.3%) at 1 year and 69.5% (95%CI: 63.5-75.6%) at 2 years  in patients undergoing regular clinic follow-up with periodic Holter monitoring and 51.4% (95% CI: 41.8-61.0%) at 1 year and 22.7% (95% CI: 8.7% - 36.6%) at 2 years in patients with implantable loop recorders.

Conclusion

 With the advent of implantable loop recorders, it is apparent that most patients with isolated atrial flutter manifest new-onset AF following CTI ablation and the merits of discontinuing anticoagulation must be carefully considered in this population.  Symptom-based monitoring likely severely underestimates the incidence of new-onset AF and may lead to adverse outcomes, particularly in patients with a high risk of stroke.

Cardiorespiratory fitness and electroanatomical remodelling in patients with atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Introduction

Atrial fibrillation (AF) is the most common clinically-relevant arrhythmia. Its initiation and maintenance is linked to the presence cardiovascular risk factors such as hypertension and obesity. Higher cardiorespiratory fitness (CRF) has been associated with a better prognosis. However, specific electroanatomical features associated with baseline CRF have not been described. 

Purpose

Compare electroanatomical substrate across exercise capacity levels in patients with AF

Methods

Patients referred for de novo AF radiofrequency ablation at the Centre for Heart Rhythm Disorders from August 2017 until June 2020 were screened for inclusion and CRF was evaluated in metabolic equivalents (METs) by a symptom-limited maximal treadmill exercise test using the standard Bruce protocol prior to ablation. Predicted CRF was calculated based on established equations and patients were categorized according to the percentage of predicted CRF achieved; low (&lt;85%), adequate (85-100%) and high (&gt;100%). Total mean and regional peak-to-peak bipolar voltages, percent of low voltage areas (% LVA), conduction velocity (CV) and percent of complex fractionated electrograms (% CFE) in sinus rhythm were compared across groups. 

Results

There were no between-group differences in baseline characteristics, medication use or echocardiographic features. Total mean voltage was significantly lower in the low CRF group compared to both adequate and high CRF. Compared to the high CRF group, roof (3.25 ± 1.2 mV vs 1.9 ± 1.3 mV, p &lt; 0.05), posterior (3.8 ± 1.8 mV vs 1.7 ± 0.9 mV, p &lt; 0.001) and inferior mean voltages (3.4 ± 2 mV vs 1.6 ± 0.7 mV, p &lt; 0.05) were significantly lower in the low CRF group (figure 1A). Furthermore, compared with the adequate CRF group, mean voltages were significantly lower in the posterior (3.7 ± 1.5 mV vs 1.7 ± 0.9 mV, p &lt; 0.001), inferior (3.4 ± 1 mV vs 1.6 ± 0.7 mV, p &lt; 0.001) and lateral (4.2 ± 2.2 mV vs 2.1 ± 1.4 mV, p &lt; 0.05) walls of the low CRF group. Anterior and septal mean voltages were not significantly different across CRF groups (P for trend = 0.07, 0.3 and 0.15, respectively). Conduction velocities were not significantly different across groups. The inferior %LVA was significantly higher in the low CRF (5.6 ± 6%) compared to adequate CRF group (23 ± 18%) (p &lt; 0.05) (figure 1B). Total and regional % CFE was higher in the low CRF compared to adequate and high CRF.

Conclusion

Participants in the lower baseline CRF category showed significant reductions in regional voltages along with higher fractionation with preserved conduction velocities. Research on the effect of physical activity and CRF on left atrial arrhythmogenic substrate is required.

Abstract Figure. Global and regional mV and % LVA by CRF

Cardiorespiratory fitness and left atrial strain in atrial fibrillation: A comparative study

Funding Acknowledgements

Type of funding sources: None.

Background

Atrial fibrillation (AF) is the most common clinically relevant arrhythmia, and its occurrence is associated with pathological left atrial (LA) remodelling. In these patients, low cardiorespiratory fitness (CRF) is associated with increased AF recurrence. Speckle tracking derived LA strain (LAS) permits chamber function quantification and provides angle-independent and highly reproducible measurements of chamber deformation. However, the relationship between CRF and LA function, amongst AF patients is poorly understood. 

Purpose

To compare LA function amongst AF patients stratified by cardiorespiratory fitness. 

Methods

Consecutive AF patients referred for treadmill exercise stress test (EST) and transthoracic echocardiogram (TTE) between March and December 2020 were screened for inclusion. Treadmill EST was symptom limited and age and gender predicted CRF was calculated with conventional formulas. Speckle tracking software was used to obtain LAS from apical 4 and 2 chamber views and mean measurements for LASr and LASb were calculated. Those achieving &lt;100% (low CRF) and ≥100% (high CRF) of predicted CRF were compared. 

Results

After exclusions, 141 patients in sinus rhythm were included in the analysis. Baseline characteristics were not significantly different between groups. Ejection fraction (63.6 ± 4.7% vs 64.8 ± 8.4%, p = 0.3) and LA volume index (33.1 ± 6.9 vs 31.4 ± 9.4 mL/m2, p = 0.3) were not different between groups. Both LASr (22.9% ± 7.4% vs 27.6% ± 11.4%, p = 0.02) and LASb (8.2% ± 4.7% vs 12.1% ± 6.8%, p = 0.004) (figure 1) were significantly higher in the fitter group. 

Conclusion

Patients with higher CRF showed improved LA function as per strain measurement in the absence of AF. The relationship between CRF and left atrial function warrants further research.

Abstract Figure. LASr and LASb by CRF

Sudden cardiac death related to physical exercise and sports in the young: a nationwide cohort study of Australia

Funding Acknowledgements

Type of funding sources: None.

Background

Sudden cardiac death (SCD) during physical exercise is uncommon but devastating.

Purpose

We aimed to determine risk factors, causes and circumstances of sports and exercise-related SCD in the young in Australia.

Methods

We retrospectively reviewed the National Coronial Information System (NCIS) registry for deaths in Australia relating to cardiovascular disease (CVD) in cases aged 10 to 35 years between 2000-2016. Included cases had been undertaking sports or physical exercise at time of event. We collected baseline demographics and circumstances of death including location, type of physical exercise, whether the event was witnessed, and engagement of bystander cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) use prior to ambulance arrival.

Results

Over a 17-year period, 1,925 SCD cases were identified of which 110 cases (6%) related to sports/physical exercise were included in final analysis. Median age was 27 years (interquartile range [IQR] 21-32 years) with most being male (92%). Median BMI was 27 kg/m2 (IQR, 23-30) with 13 cases (12%) occurring in active athletes. Most common causes were coronary artery disease (CAD; 37%) and sudden arrhythmic death syndrome (SADS; 20%). Australian Rules Football (24%), running/jogging (14%) and soccer (14%) were the most frequently practiced at time of event. Prior symptoms were present in 39% (chest pain 37%, presyncope/syncope 26%). Most were witnessed (87%) with bystander CPR in 70%. AED use prior to ambulance arrival was 8%.

Conclusions

This study demonstrates the high occurrence of CAD and SADS in exercise-related SCD in the young. Although events were commonly witnessed, an AED was seldom used prior to ambulance arrival highlighting an important opportunity to improve outcomes in the post-arrest chain of survival.

Greater cardiorespiratory fitness reduces incidence of atrial fibrillation: a meta-analysis

Funding Acknowledgements

Type of funding sources: None.

Introduction

 Atrial Fibrillation (AF) is the most common sustained cardiac arrhythmia affecting 1-2% of the global population, with the prevalence of AF increasing dramatically over the past two decades. Although low levels of cardiorespiratory fitness (CRF) and physical activity are predictive of cardiovascular disease onset and mortality, only recently has this emerged as a potential risk factor for AF.

Purpose

The aim of this meta-analysis was therefore to quantify the relationship between CRF, measured by a symptom limited exercise stress test, and incident AF. We hypothesised that there would be an inverse relationship between CRF and the incidence of AF.

Methods

The systematic literature review was conducted using PUBMED, MEDLINE and EMBASE databases, with seven studies meeting the inclusion criteria. A random-effects meta-analysis was then used to compare the multivariate risk estimates of the lowest CRF group from each cohort with the group of the highest CRF.

Results

Data from 206,925 individuals (55.8% males) was used for analysis with a mean age of 55 ± 2.5 years and a mean follow-up period of 10.3 ± 5 years. The total number of AF events across the studies was 19,913. The overall pooled risk of AF in the high-CRF group versus the low-CRF group showed a significant lower risk of incident AF in those with high-CRF (OR: 0.52, 95% CI, 0.44-0.605, p &lt; 0.001). There was evidence of statistical heterogeneity between the studies (I2 = 81%, p &lt; 0.001). AF incidence rates demonstrated an overall decline in rates across the CRF quartiles from low to high. The mean incidence rate for low-CRF was 21 ± 13.4 compared to 6.9 ± 0.7 per 1000 person-years for the high CRF group (p = 0.03).

Conclusion

There is an inverse association between a lower CRF and an increased risk of AF, with a higher level of CRF protective against AF. This study highlights that low-CRF may be an additional risk factor for AF along with already other established lifestyle-based risk factors such as obesity and hypertension. Exercise interventions should be promoted as a primary prevention strategy in those at risk of developing AF with known risk factors. Future studies are warranted to identify the mechanism(s) through which improved CRF confers a reduction in AF incidence.

Abstract Figure. AF risk between high and low-CRF

Implications of presenting to hospital with AF: the REVIEW AF study

Background

There is a growing burden of hospitalizations due to atrial fibrillation (AF). The implications of hospitalisation to the individual with AF has not been well characterized.

Purpose

To characterise the consequences of presenting to hospital with AF.

Methods

Individuals presenting to the emergency department (ED) of three hospitals in South Australia from March 2013 to February 2014 with a primary diagnosis of AF were enrolled. Based on coding and individual electronic medical record review all re-presentations over follow up were characterised as: 1) AF related; 2) cardiovascular related (excluding AF); or 3) all other causes. Mortality over follow up was also determined.

Results

The study cohort comprised of 437 individuals with an AF related index presentation. Mean age was 69±15 years and 49.9% were male. Individuals were followed for a mean of 3.7±0.4 years. There were 2304 unplanned presentations over follow up. The percentage of the study cohort who presented to the ED or were admitted to hospital over follow up is detailed in Figure 1. Compared to individuals who did not have a hospital admission for AF over follow up, those who were readmitted for AF were more likely to be hypertensive (63.2% vs 49.3%, p&lt;0.001); and have a higher CHA2DS2-VASc score (3.2±1.8 vs 2.7±1.9, p=0.002) and HAS-BLED score (2.0±1.0 vs 1.5±1.1, p&lt;0.001). A total of 71 individuals (16.2%) died during the follow-up period (annual mortality rate of 3.78%).

Conclusions

A hospital presentation with a primary diagnosis of AF identifies individuals at high risk of repeat hospitalisations and death. Urgent studies are needed to improve management of this high-risk cohort.

Figure 1. Repeat hospital presentations in AF

Funding Acknowledgement

Type of funding source: None

Opportunities to reduce the risk of stroke in AF: the REVIEW AF study

Background

Stroke is one of the most devastating complications of atrial fibrillation (AF) and is associated with poor patient outcomes. Recent registry data has demonstrated improved use of stroke prevention therapy with the advent of direct-acting oral anticoagulants, but little data exists in the Australian health care setting.

Purpose

To examine the use of oral anticoagulant therapy in a cohort of individuals presenting to the emergency department (ED) due to AF.

Methods

A total of 437 consecutive individuals who presented to the ED with a primary diagnosis of AF to three tertiary hospitals in our city in South Australia between March 2013 and March 2014 were included. Data were collected retrospectively from electronic medical record review. CHA2DS2-VASc and HAS-BLED scores were calculated and any documented contraindications to the use of oral anticoagulation (OAC) taken in to consideration.

Results

Mean age was 69±15 years and 49.9% were male. A total of 244 (55.8%) individuals had a prior diagnosis of AF at index presentation. 179 (73.4%) of these individuals recorded a CHA2DS2-VASc score of ≥2. A total of 124 of these individuals were appropriately anticoagulated (69.3%) whilst 37 individuals were not treated with OAC and did not have a documented contraindication (20.7%). Anticoagulation status was unknown in 18 individuals due to a lack of documentation (10.0%). A CHA2DS2-VASc score of 0 was recorded in 25 individuals with a prior diagnosis of AF at index presentation with 3 individuals (12%) inappropriately overtreated with OAC. The remaining 193 individuals (44.2%) presented with a first episode of AF. In 129 (66.8%) of these individuals a CHA2DS2-VASc score of ≥2 was recorded and only 10 individuals had a documented contraindication to the use of OAC. In 119 (61.7%) individuals there were no documented contraindications to the use of OAC. In 74 (62.2%) of these presentations OAC was not commenced, whilst in 45 (37.8%) individuals OAC was prescribed.

Conclusions

Significant opportunity exists to improve the use of stroke prevention therapy in AF. Despite repeated opportunities to commence this therapy within the hospital setting, it remains frequently underutilised in individuals at high risk of stroke.

Funding Acknowledgement

Type of funding source: None

Hinge point fibrosis in athletes is not associated with structural, functional or electrical consequences: a comparison between young and middle-aged elite endurance athletes

Background

The health benefits of extensive endurance training have been debated due to the report of myocardial fibrosis (MF), arrhythmias and temporary post-race cardiac impairment in middle-aged and veteran athletes. The extent of these changes is unknown in elite young athletes.

Purpose

To assess the prevalence of MF and its structural, functional and electrical impact in highly trained young endurance athletes (YA, 15–23 years) as compared to middle-aged athletes (MA, 30–50 years). We hypothesised that MF would be more frequent in MA and associated with more structural, functional and electrical abnormalities.

Methods

We prospectively assessed 197 YA and 34 MA. All had ECG, maximal oxygen consumption (VO2max) testing, cardiac magnetic resonance imaging (CMR), echocardiography and 24h-holter. Indexed left ventricular and right ventricular end diastolic volume (LVEDVi, RVEDVi), ejection fraction (LVEF, RVEF), left ventricular mass (LVMi), and MF defined as delayed gadolinium enhancement were assessed by CMR. LV and RV free wall strain (LVSL, RVfwSL) were assessed by 2D speckle tracking echocardiography. Ventricular premature beats (VPB) and non-sustained ventricular tachycardia (nsVT) were assessed by 24h-holter.

Results

YA and MA (18±2 vs 38±5 years [p&lt;0.01]; 78% vs 80% male [p=0.99]) with an elite level of fitness (VO2max 61±8 vs 54±10 mL/min/kg [p&lt;0.01]; % predicted VO2max 150±20 vs 158±30 [p=0.02]) had a large variance in LV and RV remodelling (Figure 1). MF was seen in 28 athletes (12.5%) and more prevalent in MA than in YA (23.5 vs 10.5%, p=0.048). MF was limited to the hinge points in all 8 MA with MF and 17 YA. 3 YA had LV lateral wall subepicardial MF. 27 of 187 (14.4%) male athletes had MF compared to 1 of 50 (2%) female athletes (p=0.01).

MF+ MA(A) and YA(B) as well as MF− MA(C) and YA(D) had similar structural remodelling (LVEDVi 110±14 vs 118±14 vs 113±19 vs 110±16 mL/m2; RVEDVi 120±14 vs 128±17 vs 117±19 vs 125±23mL/m2; LVMi 77±11 vs 83±14 vs 81±14 vs 77±15g/m2, p&gt;0.05). LVEF, LVSL and RVSL were similar (59±3 vs 58±5 vs 61±6 vs 58±6%; −18.8±2 vs −18.8±2 vs −19.8±2 vs −19.3±2%; −26.3±2.4 vs −24.4±2.4; −26.3±3 vs −25.8±3.5% respectively, p&gt;0.05). LVEF &lt;50% was seen in 19 (8.2%) athletes (0 [0%] vs [5%] 1 vs 1 [3.8%] vs 17 [9.6%]; p=0.51). RVEF was higher in D compared to C without further differences between groups (54±4 vs 54±6 vs 53±6 vs 57±5, p=0.005). RVEF&lt;45% was seen 21 (9.1%) athletes (0 [0%] vs 1 [5%] vs 0 [0%] vs 20 [11.3%]; p=0.14). Abnormal T-wave inversion was similar (12.5 vs 5 vs 7.4 vs 6.2%, p=0.93) as was the prevalence of &gt;100VPB/24h (12.5 vs 5 vs 11.1 vs 5.1%, p=0.42). 2 athletes had nsVT, both in D. All had similar exercise capacity (% predicted VO2max 157±26 vs 152±15 vs 147±24 vs 158±32%; p=0.11).

Conclusion

Hinge-point fibrosis was more prevalent in MA, possibly due to repeated hemodynamic stress during exercise, but is not associated with structural, functional or electrical consequences.

Figure 1. Cardiac remodelling in elite athletes

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds voor Wetenschappelijk Onderzoek (FWO)

Impact of sensing vector on insertable cardiac monitor detection of P and R wave amplitude

Background

P-wave visibility is useful for diagnosis of atrial arrhythmias via insertable cardiac monitors (ICM).

Purpose

To compare the sensing capability of ICM with different vector length: Medtronic REVEAL LINQ (45mm) vs. Biotronik Biomonitor BMIII (75mm).

Methods

We accessed de-identified remote monitoring transmissions from n=40 patients with BMIII from Biotronik for comparison with n=80 gender- and body mass index (BMI)-matched patients with REVEAL LINQ. Digital measurement of calibrated ICM electrograms was performed using DigitizeIt© (V2.3.3, Germany) of 5 consecutive P-QRS complexes by 3 investigators independently. P-wave amplitude was measured from baseline to peak and R-wave amplitude was measured from peak-to-peak. Further, we evaluated the impact of BMI on P-wave visibility.

Results

Patients in both groups are well matched for gender and BMI (53% male, mean BMI 26.7 kg/m2; both p=NS). P-wave and R-wave amplitude were 89% & 20% larger in the BMIII vs. LINQ (0.072±0.039 vs. 0.038±0.022mV, p=0.0001; & 0.83±0.42 vs. 0.69±0.45mV, p=0.095 respectively; Figure). Consequently, the P/R-wave ratio was 44% greater for the BMIII (p=0.002). Multivariate regression analysis showed that increasing BMI, female gender and LINQ were independently associated with lower P-wave amplitude (all P&lt;0.001). Inter-operator reproducibility of P-wave measures was very good (ICC 0.91, P&lt;0.001).

Conclusion

The longer ICM sensing vector of BMIII yielded considerable larger P-wave amplitude than LINQ, that was not impacted by increasing BMI. Better P-wave visibility may improve clinical decision-making after device-detected arrhythmias while further studies are needed to determine its impact on clinical outcomes.

P-wave visibility comparison of ICMs

Funding Acknowledgement

Type of funding source: None

Monitoring of Farm-Level Antimicrobial Use to Guide Stewardship: Overview of Existing Systems and Analysis of Key Components and Processes

The acknowledgment of antimicrobial resistance (AMR) as a major health challenge in humans, animals and plants, has led to increased efforts to reduce antimicrobial use (AMU). To better understand factors influencing AMR and implement and evaluate stewardship measures for reducing AMU, it is important to have sufficiently detailed information on the quantity of AMU, preferably at the level of the user (farmer, veterinarian) and/or prescriber or provider (veterinarian, feed mill). Recently, several countries have established or are developing systems for monitoring AMU in animals. The aim of this publication is to provide an overview of known systems for monitoring AMU at farm-level, with a descriptive analysis of their key components and processes. As of March 2020, 38 active farm-level AMU monitoring systems from 16 countries were identified. These systems differ in many ways, including which data are collected, the type of analyses conducted and their respective output. At the same time, they share key components (data collection, analysis, benchmarking, and reporting), resulting in similar challenges to be faced with similar decisions to be made. Suggestions are provided with respect to the different components and important aspects of various data types and methods are discussed. This overview should provide support for establishing or working with such a system and could lead to a better implementation of stewardship actions and a more uniform communication about and understanding of AMU data at farm-level. Harmonization of methods and processes could lead to an improved comparability of outcomes and less confusion when interpreting results across systems. However, it is important to note that the development of systems also depends on specific local needs, resources and aims.

Association of antimicrobial usage with faecal abundance of aph(3')-III, ermB, sul2 and tetW resistance genes in veal calves in three European countries

BACKGROUND

High antimicrobial use (AMU) and antimicrobial resistance (AMR) in veal calves remain a source of concern. As part of the EFFORT project, the association between AMU and the abundance of faecal antimicrobial resistance genes (ARGs) in veal calves in three European countries was determined.

METHODS

In 2015, faecal samples of veal calves close to slaughter were collected from farms located in France, Germany and the Netherlands (20 farms in France, 20 farms in the Netherlands and 21 farms in Germany; 25 calves per farm). Standardized questionnaires were used to record AMU and farm characteristics. In total, 405 faecal samples were selected for DNA extraction and quantitative polymerase chain reaction to quantify the abundance (16S normalized concentration) of four ARGs [aph(3')-III, ermB, sul2 and tetW] encoding for resistance to frequently used antimicrobials in veal calves. Multiple linear mixed models with random effects for country and farm were used to relate ARGs to AMU and farm characteristics.

RESULTS

A significant positive association was found between the use of trimethoprim/sulfonamides and the concentration of sul2 in faeces from veal calves. A higher weight of calves on arrival at the farm was negatively associated with aph(3')-III and ermB. Lower concentrations of aph(3')-III were found at farms with non-commercial animals present. Furthermore, farms using only water for the cleaning of stables had a significantly lower abundance of faecal ermB and tetW compared with other farms.

CONCLUSION

A positive association was found between the use of trimethoprim/sulfonamides and the abundance of sul2 in faeces in veal calves. Additionally, other relevant risk factors associated with ARGs in veal calves were identified, such as weight on arrival at the farm and cleaning practices.

70Autonomic dysfunction in atrial fibrillation (AF) patients: absent vasomotor reflex to decreased cardiac venous return during af in comparison to sinus rhythm; implications for earlier rhythm control

Funding Acknowledgements

Dr Malik is supported by an Australian Postgraduate Award Scholarship from the University of Adelaide.

OnBehalf

Centre for Heart Rhythm Disorders, University of Adelaide & Royal Adelaide Hospital

Background

A bi-directional relationship exists between AF and the autonomic nervous system (ANS). Patients with AF studied in sinus rhythm (SR) have impaired vasomotor responses to decreased cardiac volume. Whether autonomic dysfunction worsens during AF itself, is unknown. 

Purpose

We examined haemodynamic responses to lower body negative pressure (LBNP) in patients with persistent AF compared to AF studied in SR. LBNP decreases cardiac volume, deactivates atrial stretch receptors and induces a reflex to maintain blood pressure by increasing systemic vascular resistance (SVR). 

Methods

21 consecutive patients with paroxysmal or persistent AF were studied; during AF (n = 8) or SR (n = 13). Anti-arrhythmic and anti-hypertensives were withheld for 5 half-lives. Patients underwent LBNP using a custom-made chamber sealing both lower limbs. Negative pressure at sham (-0 mmHg), low (-20 mmHg) and high level (-40 mmHg) was applied for 5 minutes each. Finger photo plethysmography was used for beat-beat-blood pressure. Computation of SVR during AF is not feasible with this method. Therefore, the right forearm was used to perform venous occlusion plethysmography (VOP); non-invasive, well validated with LBNP and impervious to AF: to estimate forearm blood flow (FBF) and SVR (inversely proportional). 

Results

Baseline characteristics and responses to LBNP are presented in Table 1. MAP was maintained, and HR rose slightly, in the SR group. MAP and HR decreased in the AF group. VOP demonstrates a reduction in FBF in the SR group (vasoconstriction); whereas the vasomotor response to LBNP was absent during AF. Figure 1 (Panels A-C). 

Conclusion

The presence of AF is associated with autonomic dysfunction from impaired cardiac volume regulation. This novel finding may contribute to the known risk of falls and syncope due to AF. Further studies are needed to evaluate whether abnormal cardiac reflexes are involved in atrial remodelling and AF progression.

Table 1 Baseline Characteristics During AF During SR P Value Age 65 ± 5 59 ± 3 0.4 AAD & Anti-HTN medications withheld (%) 75 85 0.6 Resting mean arterial pressure (MAP) 109 ± 9 93 ± 6 0.1 Resting heart rate (HR) 94 ± 6 60 ± 4 0.0001* Haemodynamic response to LBNP % Δ MAP due to LBNP -9 ± 5 +0.5 ± 3 0.2 % Δ HR due to LBNP -6 ± 3 +5 ± 3 0.03* % Δ FBF due to LBNP +75 ± 59 -27 ± 8 0.02* AAD Anti-arrhthmic. HTN: Hypertension. Mean +/- SEM.

Abstract Figure. Vasomotor response to LBNP: in AF vs SR

P1428The outcome of atrial fibrillation ablation in patients undergoing radiofrequency ablation, guided by novel indices incorporating force, time and power

Background

Ablation index (AI) and Lesion Size Index (LSI) are novel parameters that incorporates contact force, time, and power in a weighted formula. Recent studies have shown that such indices predict lesion size and durability of pulmonary vein isolation (PVI). However, the outcomes of ablation guided by indices of force-time-power, such as PV reconnections and atrial fibrillation recurrence, have not been well characterised.

Objectives

To determine the association between indices of force-time-power and acute PV reconnections, procedure and fluoroscopy time and AF recurrence in patients undergoing radiofrequency PVI.

Methods

PUBMED and EMBASE were searched using the terms "catheter ablation" AND "Ablation index" OR "Contact force" OR "Force time integral" OR "lesion size" from inception through 22 May 2019. Studies reporting the procedure time, ablation time, fluoroscopy time, and incidence of AI acute and late reconnection and AF recurrence were included.

Result

 Six studies were included in this study with 530 patients, which n = 416 were paroxysmal AF and 114 non-paroxysmal AF. All procedural characteristics (procedure, radiofrequency, and fluoroscopy times) were similar between AI guided and non-AI guided ablation (p &gt; 0.05). Two studies comparing mean PV reconnections in AI guided vs. AI Blinded. Two studies compared minimum AI in reconnected vs. non-reconnected PV segments. Acute PV segment reconnection was associated with a lower minimum AI vs. non-reconnection. In 3 studies reporting AI guided vs. AI blinded ablations, AI was associated with an increased freedom from AF after average follow-up of 12 months.

Conclusions

Radiofrequency ablation guided by AI/LSI was associated with lower acute PV reconnection rates and improved AF freedom after PVI. There was no difference in fluoroscopy, ablation or procedure time with the use of these novel parameters.

Abstract Figure.

Practical applications of studies on the TSH receptor and TSH receptor autoantibodies

Studies on the TSH receptor (TSHR) have numerous practical applications in vitro and in vivo. For example human monoclonal autoantibodies (MAbs) to the TSHR are useful reagents for in vitro diagnostics. Measurement of TSHR autoantibodies (TRAbs) is helpful in diagnosis and management of autoimmune thyroid disease. Currently available highly sensitive and specific assays to measure TRAbs use the human TSHR MAb M22 instead of the TSH. Furthermore, preparations of the human TSHR MAb M22 are useful as the World Health Organisation International Standard for thyroid stimulating antibody and for calibration of the assays for measuring TRAbs. Preparations of thermostabilised TSHR extracellular domain have recently become available and this is likely to have an impact on improvements in specificity testing for TRAb assays. In addition the stable TSHR preparations have practical application for specific immunoadsorption of patient serum TRAbs. Human TSHR MAbs also have promising prospects as new therapeutics. Autoantibodies with TSHR antagonistic activities are "natural" inhibitors of TSHR stimulation and are expected to be helpful in controlling TSHR activity in patients with Graves' disease, Graves' ophthalmopathy and thyroid cancer.

Measurement of Total Starch in Cereal Products by Amyloglucosidase-α-Amylase Method: Collaborative Study

American Association of Cereal Chem- ists/AOAC collaborative study was conducted to evaluate the accuracy and reliability of an enzyme assay kit procedure for measurement of total starch in a range of cereal grains and products. The flour sample is incubated at 95°C with thermostable α-amylase to catalyze the hydrolysis of starch to maltodextrins, the pH of the slurry is adjusted, and the slurry is treated with a highly purified amyloglucosidase to quantitatively hydrolyze the dextrins to glucose. Glucose is measured with glucose oxidase-peroxidase reagent. Thirty-two collaborators were sent 16 homogeneous test samples as 8 blind duplicates. These samples included chicken feed pellets, white bread, green peas, high- amylose maize starch, white wheat flour, wheat starch, oat bran, and spaghetti. All samples were analyzed by the standard procedure as detailed above; 4 samples (high-amylose maize starch and wheat starch) were also analyzed by a method that requires the samples to be cooked first in dimethyl sulfoxide (DMSO). Relative standard deviations for repeatability (RSDr) ranged from 2.1 to 3.9%, and relative standard deviations for reproducibility (RSDr) ranged from 2.9 to 5.7%. The RSDr value for high amylose maize starch analyzed by the standard (non-DMSO) procedure was 5.7%; the value

P5 Clinical utility of stress echocardiography in remote indigenous and non-indigenous populations: a 10-year study in central Australia

Background

Central Australia is a vast, geographical region spanning some 830,000 square kilometres. It is the most populous Indigenous region in Australia (44%) and a great distance from tertiary centres (1,500km). Non-invasive testing is important in this setting due to the high prevalence of cardiovascular disease and long-distance travel required for coronary angiography, the latter with significant logistical, financial, and cultural barriers. Although stress echocardiography has been extensively validated as a long-term prognostic tool in selected populations, we are not aware of prior studies in remote Indigenous and non-Indigenous individuals.

Purpose

To determine whether stress echocardiography can adequately risk stratify and quantify the long-term prognosis of Indigenous and non-Indigenous individuals in remote Central Australia.

Methods

Consecutive individuals undergoing stress echocardiography in Central Australia between 2007 and 2017 were included. Exercise or dobutamine stress echocardiography was performed and reported via standard protocols.  Individuals were followed up for the primary outcome of all-cause mortality.

Results

One thousand and eight patients (54% Indigenous, 63% dobutamine stress) were included. Indigenous patients were younger, more likely to be female, and had a greater prevalence of cardiometabolic comorbidities (p &lt; 0.05 for all). Overall, 797 (79%) patients had no abnormality during rest or stress echocardiography, with no difference according to ethnicity (p &gt; 0.05).  After a mean follow up of 3.5 ± 2.4 years, 54 (5%) of patients were deceased; 127 (14%) patients underwent revascularization and were censored from follow-up. In patients with a normal test, annual mortality averaged 1.3% over 5 years of follow up, with annual mortality being significantly higher in Indigenous compared to non-Indigenous individuals (2.0% vs 0.6% respectively). Individuals with either ischemia or scar had a significantly worse long-term outcome compared to those with a normal test (Figure). In multivariate analyses, increasing age (HR 1.04 [95% CI 1.01-1.08]), chronic kidney disease (HR 4.83 [1.79-13.02]), and lack of ACEI/ARB use (HR 0.19 [95% CI 0.09-0.42]) were associated with all-cause mortality. Although Indigenous ethnicity was a univariate predictor of mortality, this association was attenuated and non-significant in multivariate analyses.

Conclusion

Indigenous patients in remote Central Australia with a normal stress echocardiogram had a significantly higher annual rate of mortality compared to their non-Indigenous counterparts. However, this association may be in large part due to comorbid conditions. A normal test in Indigenous individuals was still able to adequately risk-stratify and identify a lower risk group of patients in whom ongoing local medical management and focusing on cardiometabolic risk factor reduction is likely to be appropriate.

Abstract P5 Figure. Kaplan Meier survival curve

P3794MOODS: a novel risk score to identify patients with atrial fibrillation and sleep apnoea

Background

Sleep-disordered breathing (SDB) is an important risk factor for developing atrial fibrillation (AF), and treatment of concomitant SDB can improve AF rhythm outcomes. Diagnosis of SDB requires sleep studies which can pose a significant time and resource burden. We sought to develop a prediction score based on clinical characteristics that can help identify AF patients who require further assessment for SDB.

Methods

Prospectively-collected data for 442 consecutive patients treated for AF from 2009 to 2017 were analysed. All patients were considered candidates for rhythm-control and therefore referred for sleep studies. The diagnosis of SDB was confirmed using in-lab polysomnography and classified using the apnoea-hypopnoea-index (AHI), with cut-offs of ≥15/hr and ≥30/hr indicating moderate-to-severe and severe SDB respectively. Patients treated up to 2015 formed the derivation cohort (n=311) and the remainder (n=113) formed the validation cohort. Multivariate logistic regression analysis was used to identify clinical variables predictive of moderate-to-severe SDB. A risk score model was developed based on regression coefficients and tested using receiver-operating-characteristics analyses on the validation cohort.

Results

Overall, mean age was 60±11 years, mean body mass index (BMI) was 30±5 kg/m2 and 69% were men. The prevalence of moderate-to-severe SDB was 33.7%. There were no significant differences in baseline characteristics between the derivation and validation cohorts. Male gender (score=1), overweight (BMI: 25–29 kg/m2, score=2), obesity (BMI≥30 kg/m2, score=3), diabetes (score=1), and stroke (score=2) were significantly independently predictive of moderate-to-severe SDB and formulated the score. The score performed well to predict moderate-to-severe SDB with a C-statistic of 0.73 (95% CI: 0.67–0.79, P<0.001) in the derivation cohort, and 0.67 (95% CI: 0.57–0.77, P<0.001) in the validation cohort. As a rule-out test, a score of ≤3 had a negative predictive value of 77% for moderate-to-severe SDB (91% for severe SDB). A score of ≥4 had an intermediate positive likelihood ratio (PLR) of 2 for moderate-to-severe SDB (2.2 for severe SDB), while a score of ≥5 had a high PLR of 6.5 and 6.8 for moderate-to-severe SDB and severe SDB respectively.

Sensitivity and specificity table

Conclusion

A novel risk score comprising clinical characteristics can identify patients with AF likely to benefit from further assessment for SDB. Application of this model may aid optimise resource utilisation and facilitate timely patient care.

P5657Fibrosis detected by late-gadolinium enhancement cardiac MRI is associated with atrial fibrillation and poorer ablation outcome: A meta-analysis

Background

Fibrosis is a hallmark of atrial fibrillation (AF) substrate. Recent data suggests that fibrosis detected by late-gadolinium enhancement (LGE) cardiac MRI (CMR) can predict AF. However, this relationship is not well described.

Objective

To delineate the association of cardiac fibrosis detected by LGE CMR with AF prevalence, AF recurrence after catheter ablation.

Methods

PubMed, Embase, Web of Science and Ovid MEDLINE were searched through November 2018, using the keywords: LGE AND Fibrosis AND CMR AND AF. Inclusion criteria: 1. LGE CMR of left atrial (LA LGE), ventricular wall (LV LGE) or right ventricular wall (RV LGE); 2. Studies reporting AF or recurrent arrhythmia after ablation; 3. Patient ≥18 years; and 4. ≥50 participants. Included studies were pooled in a random effects meta-analysis and reported as: mean difference (MD); unadjusted risk ratios (RR); adjusted hazard ratios (HR); and 95% confidence intervals (95% CI).

Results

After exclusions, we identified 9 studies (2,307 patients [65.9% males, 34.1% females]) conducted between 2003 and 2015 for LGE and AF. Fibrosis was present in 666 (35.1%) and detected by LV LGE in 7 (78%) and RV LGE in 2 (22%). The presence of AF was higher in patients positive for ventricular LGE than those negative, trending towards significance (RR: 1.51, 95% CI: 0.94–2.45, p=0.09). Pooled LV fibrosis associated with AF progression (RR [NPAF vs. PAF]: 2.2, 95% CI: 1.22–3.94, p=0.009). We identified 8 studies (2,041 patients [65.8% males, 34.2% females]) conducted between 2006 and 2016 reporting LGE and AF recurrence after catheter ablation, with fibrosis detected in 644 (31.6%) by LA LGE in 8 (88.9%, biased towards one centre). After 17.8±14.2 follow-up years, atrial fibrosis was significantly greater in recurrent AF than controls (MD: 4.97%, 95% CI: 1.23–8.7, p<0.01), and predicted 16% increased risk of AF recurrence (RR: 1.16, 95% CI: 1.07–1.26, p<0.05).

Conclusion

Myocardial fibrosis detected by LGE associates with prevalence and progress of AF and is predictive of AF recurrence post ablation. This further supports the proarrhythmic role of fibrosis and selection of patients for ablation therapy based on LGE.

P1234Weight fluctuation demonstrates residual atrial arrhythmogenic substrate despite final weight loss in a chronic sheep model: implications for epicardial fat and fibrofatty infiltrates

Background

Obesity-mediated epicardial adipose tissue (EAT) expansion drives fat cell infiltration which forms the unique substrate for atrial fibrillation (AF). The LEGACY study showed the benefits of weight loss but an attenuated response with weight fluctuation. How fluxes in weight impacts the atrial substrate in not known.

Objective

To investigate EAT and the atrial substrates due to weight fluctuation, with comparison to stable obesity.

Methods

We studied 24 sheep in 3 equal groups over 80 weeks: 1. Obesity induced by high calorie diet fed ad libitum; 2. Weight fluctuation induced by 20-week cycle of weight gain/loss (20:20:20:20); and 3. Lean controls fed quality hay to maintain baseline weight. All sheep underwent: daily weight measurement; haemodynamic and imaging assessments (cardiac MRI; dual-energy X-ray absorptiometry; and matrix assisted laser desorption infrared lipid imaging); electrophysiological studies and electroanatomic mapping; histological and structural analysis. Evaluations included: atrial voltage, conduction velocity, and refractoriness (7 sites, 2 cycle lengths), electrogram fractionation, EAT volume, fibro-fatty infiltration, myolysis of myocytes, and spatial distribution of intra-atrial lipids.

Results

The Table shows the group differences. Compared to reference controls, obesity demonstrated: Increased atrial volume and pressure, abnormal atrial electrical properties, expanded EAT and ensuing fibro-fatty infiltrations, and myolysis of myocytes. Despite comparable weight and EAT with controls, weight fluctuation resulted in extensive and severe fibro-fatty infiltrations, and twofold greater myolysis that persisted. Moreover, characteristic profiles and abundance of lipid species in the atrial myocardium were noted on further evaluation. More importantly, EAT and fibro-fatty infiltrates strongly correlated with increased atrial volume and pressure; with only fibro-fatty infiltrates correlating with fractionated electrograms (r=0.71, p<0.001) and conduction slowing (r=−0.59, p=0.006). Similarly, atrial myolysis exhibited significant correlations with atrial enlargement and haemodynamics, and electrical substrates (p<0.05 for all).

Conclusions

Obesity induces fibro-fatty replacement of atrial myocytes and deterioration of contractile units, which may drive impaired electrical remodeling. Despite final weight loss, weight fluctuation demonstrates residual electro-structural, fibro-fatty and contractile substrates.

P2561Withdrawal of simulated obstructive sleep apnea partially reverses atrial arrhythmogenic substrate in rats

Background

Obstructive sleep apnea (OSA) is associated with structural alterations of the left atria (LA) and increased occurrence of atrial fibrillation (AF). Obstructive respiratory events lead to intermittent hypoxia (IH) and ineffective inspiration against the occluded upper airways, which result in intrathoracic and cardiac transmural pressure changes. Data on reversibility of LA-structural remodeling processes after withdrawal of OSA are still missing.

Objectives

Aim of the study was to develop a novel AF animal model mimicking intrathoracic pressure changes in addition to IH and to analyze the effect of OSA-withdrawal on atrial remodeling reversibility.

Method

In sedated rats (2% isoflurane), IH (n=9) was applied by intermittent increase in the respiratory dead volume. Standardized obstructive respiratory events were induced by defined intermittent negative upper airway pressure (INAP = inverse CPAP) applied via a customized mask connected to a negative pressure device (n=9). One minute of IH or INAP was followed by a rest period of nine minutes for four hours every second day. Rats with comparable anesthesia were used as controls (CTR). After three weeks, the animals were sacrificed. To analyze atrial structural remodeling reversibility, additional INAP-rats (n=5) were sacrificed after INAP-withdrawal of three weeks and compared to respective CTR (n=7).

Result

Blood pressure was not affected by IH or INAP. Intermittent desaturation and post-apneic hyperventilation were comparable in INAP- and IH-rats, but INAP-rats showed significantly higher breathing efforts during apneas compared to IH-rats. LA connexin43 (Cx43) protein expression assessed by quantitative immunofluorescence was reduced in both groups compared to CTR (0.77±0.07% in CTR vs. 0.45±0.06% in IH, p=0.02; CTR vs. 0.39±0.06% in INAP, p=0.005). However, LA interstitial fibrosis content (7.03±0.58% vs. CTR, p=0.01) and LA myocyte diameters (13.23±0.34μm vs. CTR, p=0.03) were increased in INAP-rats, but not in IH-rats. This was associated with longer inducible AF-durations in INAP-rats (11.65±4.43s vs. 0.72±0.33s in CTR, p=0.03) but not in IH-rats (1.28±0.33s vs. CTR, p=0.31). Three weeks of INAP-withdrawal (INAP-W) normalized interstitial fibrosis content (INAP-W vs. CTR, p=0.50) and LA-myocyte diameter (INAP-W vs. CTR, p=0.31). However, LA Cx43 protein expression remained low after three weeks of INAP withdrawal and inducible AF-episodes were still prolonged compared to respective CTR.

Conclusion

Application of INAP in rats mimics important components of OSA beyond IH and allows the study of an arrhythmogenic substrate in the atrium independent of the development of risk factors. In our model, withdrawal of INAP resulted in partial reversibility of structural LA remodeling but was not sufficient to abolish inducible AF-episodes completely. Future clinical studies are warranted to determine the anti-arrhythmic effect of isolated sleep apnea treatment in AF-patients.

Acknowledgement/Funding

Else Kröner-Fresenius-Stiftung, SFB-TRR219-M02/S-02

P2498Exercise capacity and all-cause mortality in remote Indigenous and non-Indigenous populations

Background

Exercise capacity is a powerful predictor of all-cause mortality. However, its association with Indigenous populations in Central Australia, who face disproportionate health burdens, is unclear. Given the isolation from tertiary centers, exercise testing could provide useful local risk-stratification.

Purpose

To characterize the association of exercise capacity with all-cause mortality in Indigenous and non-Indigenous individuals in remote Central Australia.

Methods

Demographic, medication, and all-cause mortality data were prospectively collected from patients undergoing exercise stress tests from 2007–2017.

Results

A total of 3,414 patients (34% Indigenous) were included. At 4.8±2.9 years of follow-up, 86 (2.5%) deaths had occurred. Each 1-MET increase in exercise capacity conferred a 14% lower risk for mortality among Indigenous individuals (HR 0.86, 95% CI 0.79–0.94) and 20% lower risk for mortality among non-Indigenous individuals (HR 0.80, 95% CI 0.73–0.89) after adjusting for age, comorbidities, and medications. Mortality risk reduction for each 1-MET increase in exercise capacity was similar (p=0.32) for Indigenous and non-Indigenous individuals.

Conclusions

Exercise capacity is a significant predictor of all-cause mortality in Indigenous and non-Indigenous individuals. These findings have important clinical implications towards exercise capacity for risk-stratification and preventative importance of physical activity.

P2843Impact of bipolar vector orientation and inter-electrode spacing on electrograms during human atrial fibrillation

Background

In patients with atrial fibrillation (AF), local atrial bipolar electrograms (EGM) are clinically used to determine peak-to-peak voltage (Vpp), dominant frequency (DF) and Shannon Entropy (ShEn) for electroanatomical substrate characterization and substrate-based ablation. The effect of bipolar vector orientation and inter-electrode spacing on these EGM-derived measures during AF is unclear.

Methods

To quantify the impact of bipolar vector orientation and inter-electrode spacing, bipolar EGM (10,496 and 20,968 atrial sites, respectively) were reconstructed from unipolar EGM recorded with an array of 18 electrodes in 14 patients with persistent AF. We compared Vpp, DF and ShEn between any two adjacent bipolar vectors with a difference of 45 degree. Vpp, DF and ShEn values were ranked into different classes from highest to lowest value. To quantify the effect of inter-electrode spacing, bipolar EGM were constructed from electrodes spaced 4mm, 8mm, and 12mm apart, respectively.

Results

First, bipolar vector orientation significantly impacts Vpp (maximal difference: 1.341±2.169 mV vs. 0.595±0.652 mV; p<0.01) and the percentage of atrial low voltage areas (Vpp<0.05mV) (maximal difference: 62.31% vs. 32.54%). Bipolar vector orientation also influences DF (maximal difference: 8.547±2.971 Hz vs. 6.360±1.077 Hz; p<0.01) and ShEn (maximal difference: 4.898±0.488 vs. 4.120±0.650; p<0.01) measurements. Second, inter-electrode spacing affects Vppincreasing from 0.854±1.299 mV to 1.013±1.302 mV for 4mm, and 12mm, respectively (p<0.01). The percentage of atrial low voltage areas differed between 53.77% and 42.03% for 4mm and 12mm, respectively. Furthermore, inter-electrode spacing alters DF (maximal difference: 7.316±2.239 Hz vs. 7.234±2.124 Hz; p<0.01) and ShEn (maximal difference: 4.364±0.714 vs. 4.514±0.624; p<0.01) measurements.

Conclusions

Bipolar vector orientation and inter-electrode spacing both significantly affect bipolar EGM-derived measures that may result in significant uncertainty around the electroanatomical substrate characterization in AF patients, which should be considered in the development of future mapping catheter tools and algorithms.