In the latest virtual issue of the Equine Veterinary Journal leading researchers shed light on advancements in the cardiac physiology, diagnostic techniques and management of various conditions, including atrial fibrillation (AF). This virtual issue is free to read until 7 January 2026.
Guest edited by Laura Nath and Vicky Savage, the collection of 20 papers includes a comprehensive editorial and is aimed at giving readers a deeper understanding of current progress in equine cardiology, while also highlighting the need for further equine specific diagnostic tools and additional research.
The collection explores:
- Atrial fibrillation (AF), the most common cause of poor performance in the equine athlete. This is a multifactorial and complex arrhythmia and this collection discusses the significant advancements in the diagnosis and management of atrial fibrillation (AF) in recent years
- The high prevalence of cardiac arrhythmias in exercising horses, with a need for further validated, equine-specific electrophysiological tools. In particular, the use of continuous cardiac rhythm monitoring is explored using implantable loop recorders (ILRs) to overcome the limitations of short ECG recording duration. These devices have been used clinically to successfully identify atrial fibrillation in standardbred racehorses with intermittent poor performance. The feasibility of a wearable ECG device as an effective approach for obtaining field-based recordings is also discussed
- The association of peak heart rate with the presence of arrhythmias. A maximal effort with a heart rate exceeding 200 BPM is required when assessing horses for cardiac arrhythmias to evaluate the influence of fluctuations in autonomic tone and the impact of fatigue. Increasing HRV (heart rate variability) in peak exercise and recovery periods is associated with cardiac arrhythmia, whilst lameness can lower HRV indices. Arrhythmias occur in up to 56% of event horses in the cross-country phase with greater prevalence of arrhythmias at higher divisions of the sport, likely reflecting the greater physical effort required at this level
- Association between cardiac arrhythmias and other conditions, specifically the relationship between upper respiratory obstructions and ectopic/re-entrant rhythms that can occur during any exercise phase. In addition, the association between AF and an increased risk of exercise-induced pulmonary hemorrhage, with supporting observed physiological changes, is discussed, highlighting an area that requires further investigation
The relationship between atrial premature depolarisations and atrial fibrillatory rate (AFR) to assess AF recurrence risk in horses, supporting the ability to predict the likelihood of AF recurrence before initiating treatment.
- Structural cardiac differences, including the presence of accessory leaflets in the atrioventricular valves in 39/40 valves studied provide further information to aid diagnostic interpretation. Knowledge of anatomical variants is important when implementing advanced imaging techniques, including three-dimensional echocardiography
- Advancing techniques in electro-anatomical mapping focusing on the pulmonary veins, where the presence of muscle sleeves of myocardial tissue in pulmonary vein ostia, with the presence of adrenergic and non-adrenergic nerve fibres within the muscle sleeves, suggests this tissue has the potential to trigger arrhythmias. The gross and histological structure of pulmonary veins has been assessed using 3D electro-anatomical mapping and subsequently to identify and guide ablation of the arrhythmogenic tissue in standing horses. These techniques demonstrate that trans-septal puncture is preferable to the carotid approach and that isolation of both the caudal vena cava and pulmonary veins is achievable
Laura Nath said: “This collection highlights important and exciting work and improves our understanding of arrhythmogenic mechanisms, diagnosis of arrhythmias and recognition of cardiac pathology in both clinical and research settings.” Fellow guest editor, Vicky Savage said: “We are delighted with this collection which brings strong, evidence-based practical support to equine vets to enable them to provide patients with a more advanced service for diagnosis and management of cardiac disorders.”
The virtual issue is available here.
