Science‐in‐brief: Equine Cardiology Virtual Retreat June 2020

An Equine Cardiology virtual research retreat was organised by the University of Pennsylvania's New Bolton Center Cardiology and Ultrasound Group. This retreat was generously supported by Boehringer Ingelheim and Gaeltec. The goal was to present research, lines of investigation or innovative clinical initiatives to facilitate knowledge sharing and develop new ideas, collaborations and working groups. Fifty researchers and scientists from eight different countries met virtually over 3 days in June 2020 (Table S1). Twenty-one abstracts were presented and each day breakout groups discussed topics related to equine cardiology. Preliminary results were presented by Celia Marr (Rossdales Equine Hospital and Diagnostic Centre) and JoAnn Slack (University of Pennsylvania), following on from work by Katharyn Mitchell (University of Zurich)1 on the use of heart rate variability (HRV) tools to improve the detection of arrhythmias in exercising ECGs, with the use of objective measures or graphical representations such as Poincaré plots and HRV variables. Much was discussed about the need for a consensus on the definitions of arrhythmias—what constitutes an atrial (APC) or ventricular premature complex (VPC) and how they are diagnosed at high heart rates (HR) and during exercise, when ECG quality is frequently affected by motion artefacts and multiple leads are not available. It was agreed that equine-specific standards for ECG recording, analysis and interpretation are needed for both clinical and research purposes. This will be a focus of this arrhythmia-working group, headed by JoAnn Slack. Kamalan Jeevaratnam (University of Surrey) described the use of complexity estimator algorithms to analyse ECGs of horses in sinus rhythm. Horses with historical paroxysmal atrial fibrillation (AF) showed less complexity than healthy horses. These computer-generated analyses may provide an additional diagnostic tool for evaluation of horses in which paroxysmal AF is suspected.2 Sian Durward-Akhurt (University of Minnesota) is currently using whole genome sequencing of horses with AF, to identify putative arrhythmia-causing mutations in candidate genes with the long-term goal to develop a genetic test that can identify horses at risk of arrhythmia development. The research group from the University of Copenhagen (Helena Carstensen, Rikke Buhl) is investigating the effect of training and AF on structural and electrical atrial remodelling3 that may decrease the likelihood of cardioversion success, and increase the risk of AF reoccurrence after conversion. Much of the discussion in the AF breakout session focused on the potential role of atrial tachycardia (AT) in AF development, with the hypothesis that AT can lead to AF in some horses. In addition, it was emphasised that classifying supraventricular arrhythmias too specifically (without electrophysiological information) should be avoided. Gunther van Loon (University of Ghent) proposed classifying supraventricular arrhythmias broadly (similar to what is done in human medicine). It was also emphasised that the use of a 12-lead ECG is important to try and determine the origin of APCs (left or right atrium) which might aid in guiding any future therapeutic interventions (particularly with respect to EP mapping and ablation of arrhythmogenic foci).4-6 In addition, the AF breakout group discussed the use of implantable loop recorders in horses. Data from the University of Copenhagen shows that this might be a promising (although currently expensive) tool to detect sustained AF7 and paroxysmal AF in poorly performing horses by collecting ECG data over longer periods (weeks or months). Work on developing goal-orientated protocols for cardiac and cardiorespiratory imaging is currently underway at both the University of Zurich (Christina Eberhardt) and Texas A&M University (Kari Bevevino). Both groups reiterated that the proposed protocols are not intended to replace a complete echocardiographic evaluation or experts in cardiology. It is the aim of investigators interested in POCUS to define standards of training, indications and diagnostic accuracy with the goal of making medical care accessible while maintaining or improving standards of care in general and specialty practice. Rachel Jago and Jenny Brown (University of Edinburgh) are using two-dimensional speckle tracking (2DST) to define left ventricular (LV) twist mechanics of the Thoroughbred (TB) racehorse at rest, while Celia Marr discussed how the technique can be used to identify subtle abnormalities of ventricular function in a field setting. Colin Schwarzwald (University of Zurich) showed that the pulmonary artery distensibility index is not superior to static measurements of the pulmonary artery diameter for diagnosis of pulmonary hypertension, while investigators from Edinburgh also reported on the feasibility and repeatability of the LV and right ventricular (RV) volume calculation by three-dimensional echocardiography (3DE). A breakout group discussion focused on advanced echocardiographic techniques. Colour-coded TDI and 2DST are generally perceived as “black box technologies” that are based on proprietary algorithms influenced by various filter settings and post-processing tools. While the body of literature on advanced echocardiography methods in horses is increasing, the benefit in routine clinical use of these techniques is yet to be defined. Currently, TDI is used by small animal cardiologists to characterise ventricular diastolic function, while 2DST is occasionally used to help identifying preclinical systolic dysfunction in patients with borderline measurements of fractional shortening or ejection fraction. Our knowledge of TDI and 2DST in horses suggests that these might be the most useful clinical applications in this species as well.8-10 Three-dimensional echocardiography in horses is in its infancy and limited by the large dimensions of horses’ hearts, leading to low recording frame rates. Current experience suggests that 3DE might be useful for quantification of chamber dimensions, measurement of the regurgitant orifice of insufficient valves and the size of septal defects,11 and characterisation of structural valvular abnormalities. Annelies Decloedt (University of Ghent) presented data associating valvular regurgitations with arrhythmia burden during exercise tests. Mild and severe aortic regurgitation were associated with VPCs, while APCs were not associated with any valvular regurgitation. This information supports the need for exercise testing when evaluating horses with aortic regurgitation. Fe ter Woort (Equine Sports Medicine Practice) discussed her work on technology validation12 while Laura Nath (University of Adelaide) presented investigations into sudden death (SD) and its relationship to myocardial fibrosis in Thoroughbred racehorses in Victoria, Australia using historical and post-mortem results. The focus of one breakout session was the development of a centralised equine cardiology database or repository. Katharyn Mitchell presented an overview of the current logistics, considerations and goals of such a project. It was proposed that for any database to be successful, ECG and Echocardiography standards would be needed. Ease of data input, and good quality, complete data sets were considered additionally needed attributes of a cardiology database. Katharyn Mitchell agreed to continue the work on this project, in conjunction with other interested parties. Claire Underwood (University of Pennsylvania) presented the results of the 2020 Equine Echocardiography Survey, which was conducted as a follow-up to a 2014 survey on the same topic. Left atrial assessment in right parasternal image planes, LA areas and tissue Doppler imaging for assessment of LV diastolic function have been adopted by a larger number of clinicians since 2014. However, similar to the 2014 survey, it was rare for more than 50% of respondents to be using the same location and timing to measure a certain cardiac structure. The need for echocardiographic standards was discussed in a breakout group discussion. Etienne Coté (University of Prince Edward Island) and John Bonagura (North Carolina State University) both joined the discussion to report on a collaboration between the Cardiology group of the American College of Veterinary Internal Medicine (ACVIM) and the American Society of Echocardiography (ASE), with the goal to leverage the ASE standards approach in developing new echocardiography standards for dogs and cats. They suggested including equine standards as part of this ACVIM-ASE initiative. This was considered a great opportunity for the equine cardiology group. Claire Underwood, Colin Schwarzwald and Virginia Reef (University of Pennsylvania) accepted the task of establishing contact with the ACVIM-ASE standards group, setting up an expert committee and initiating this project. The concept of coupling mobile health and big data analytics to test and implement an injury and exercise associated death prevention program for equine athletes was presented by Cris Navas (University of Pennsylvania). Steps to assess the feasibility of the program, accuracy of devices and evaluate candidate variables are needed before the program can be established. The devices, duration, timing, processing and potential applications of HRV analyses in sports medicine was the centre of discussion of a breakout session. It was proposed that this modality has many potential applications that deserve attention and advances in wearables and artificial intelligence methods can be expected to pave the way to achievable injury prevention programmes in future. Tiago Afonso (University of Saskatchewan) raised the topic of angiotensin converting enzyme inhibitors (ACEI) and the possibility of rebound renin release and angiotensin II production after temporary or incomplete ACEI. In addition, the usefulness of aldosterone monitoring to detect ACEI breakthrough was discussed as a topic of future study. Katharyn Mitchell also presented the topic of myocardial dysfunction in critically ill horses. Studies using advanced imaging methods (TDI, 2DST) to detect and monitor myocardial dysfunction are proposed, particularly concerning fluid responsiveness, with the aim to reduce morbidity and mortality in critically ill horses by early recognition of myocardial dysfunction. The global pandemic forced an online meeting and despite the limitations of virtual interactions, active and dynamic discussions occurred. The presence of clinicians, researchers, internists, sports medicine specialists and cardiologists brought different perspectives and created an open, rich dialogue with frequent strong, respectful and productive inputs. Potential collaborations and calls for action were generated, particularly involving the development of standards for equine ECGs, echocardiography, and exercise associated deaths and injuries. This group hopes to continue and expand activities in equine cardiology research. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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