Sudden death in racing Thoroughbred horses: An international multicentre study of post mortem findings

Lyle, C. H.; Uzal, Francisco A.; McGorum, Bruce; Aida, Hitoshi; Blissitt, Karen J.; Case, James T.; Charles, JA; Gardner, Ian A.; Horadagoda, N. U.; Kusano, Keigo; Lam, Kenneth K.H.; Pack, Jung-Sun; Parkin, T. D. H.; Slocombe, R. F.; Stewart, Brian D.; Boden, Lisa

doi:10.1111/j.2042-3306.2010.00164.x

Cited by 100 publications

(173 citation statements)

References 16 publications

(15 reference statements)

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“…Third, might a third form of breathlessness, “chest tightness”, which is associated with inflammatory processes [5,30,31], arise independently or in association with other pathophysiological conditions [3,32,33,34,35]? Fourth, what, if any, impact might use of bitless bridles have on the ease of airflow through the upper respiratory tract [22,36,37,38,39]; the degrees of exercise-induced hypoxaemia, hypercapnia and/or acidaemia [24,25,26,27,28,29]; and the occurrence and severity of lower respiratory tract pathophysiology [3,38,40,41], and thus breathlessness? Fifth, in light of these observations, how significant might breathlessness be as an animal welfare issue in exercising horses?…”

Section: Introductionmentioning

confidence: 99%

Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles

Mellor

Beausoleil

2017

Animals

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Simple SummaryHorses have superior athletic capabilities due largely to their exceptional cardiorespiratory responses during exercise. This has particular relevance to horses’ potential to experience breathlessness, especially when their athletic performance is reduced by impaired respiratory function. Breathlessness, incorporating three types of unpleasant experiences, has been noted as of significant animal welfare concern in other mammals. However, the potential for breathlessness to occur in horses as usually ridden wearing bitted bridles has not yet been evaluated in detail. Accordingly, key physiological responses to exercise and the consequences of impaired respiratory function are outlined. Then the physiological control of breathing and the generation of the aversive experiences of breathlessness are explained. Finally, the potential for horses with unimpaired and impaired respiratory function to experience the different types of breathlessness is evaluated. This information provides a basis for considering the circumstances in which breathlessness may have significant negative welfare impacts on horses as currently ridden wearing bitted bridles. Potential beneficial impacts on respiratory function of using bitless bridles are then discussed with emphasis on the underlying mechanisms and their relevance to breathlessness. It is noted that direct comparisons of cardiorespiratory responses to exercise in horses wearing bitless and bitted bridles are not available and it is recommended that such studies be undertaken.AbstractHorses engaged in strenuous exercise display physiological responses that approach the upper functional limits of key organ systems, in particular their cardiorespiratory systems. Maximum athletic performance is therefore vulnerable to factors that diminish these functional capacities, and such impairment might also lead to horses experiencing unpleasant respiratory sensations, i.e., breathlessness. The aim of this review is to use existing literature on equine cardiorespiratory physiology and athletic performance to evaluate the potential for various types of breathlessness to occur in exercising horses. In addition, we investigate the influence of management factors such as rein and bit use and of respiratory pathology on the likelihood and intensity of equine breathlessness occurring during exercise. In ridden horses, rein use that reduces the jowl angle, sometimes markedly, and conditions that partially obstruct the nasopharynx and/or larynx, impair airflow in the upper respiratory tract and lead to increased flow resistance. The associated upper airway pressure changes, transmitted to the lower airways, may have pathophysiological sequelae in the alveolae, which, in their turn, may increase airflow resistance in the lower airways and impede respiratory gas exchange. Other sequelae include decreases in respiratory minute volume and worsening of the hypoxaemia, hypercapnia and acidaemia commonly observed in healthy horses during strenuous exercise. These and other factors are implica...

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Section: Introductionmentioning

confidence: 99%

Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles

Mellor

Beausoleil

2017

Animals

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“…Furthermore, the clinical interpretation of analysis results is challenged by limited knowledge of the clinical significance of various arrhythmias [1]. Both supraventricular and ventricular premature beats have raised concerns in equine cardiology as potential initiators of atrial fibrillation [2] and fatal ventricular arrhythmias [3]. In recent years, studies have therefore investigated the occurrence of premature beats in healthy horses [4–8], horses with poor performance [9, 10], and in both clinical [11, 12] and experimental settings [13].…”

Section: Introductionmentioning

confidence: 99%

Appropriate threshold levels of cardiac beat-to-beat variation in semi-automatic analysis of equine ECG recordings

et al. 2016

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BackgroundAlthough premature beats are a matter of concern in horses, the interpretation of equine ECG recordings is complicated by a lack of standardized analysis criteria and a limited knowledge of the normal beat-to-beat variation of equine cardiac rhythm. The purpose of this study was to determine the appropriate threshold levels of maximum acceptable deviation of RR intervals in equine ECG analysis, and to evaluate a novel two-step timing algorithm by quantifying the frequency of arrhythmias in a cohort of healthy adult endurance horses.ResultsBeat-to-beat variation differed considerably with heart rate (HR), and an adaptable model consisting of three different HR ranges with separate threshold levels of maximum acceptable RR deviation was consequently defined. For resting HRs <60 beats/min (bpm) the threshold level of RR deviation was set at 20%, for HRs in the intermediate range between 60 and 100 bpm the threshold was 10%, and for exercising HRs >100 bpm, the threshold level was 4%. Supraventricular premature beats represented the most prevalent arrhythmia category with varying frequencies in seven horses at rest (median 7, range 2–86) and six horses during exercise (median 2, range 1–24).ConclusionsBeat-to-beat variation of equine cardiac rhythm varies according to HR, and threshold levels in equine ECG analysis should be adjusted accordingly. Standardization of the analysis criteria will enable comparisons of studies and follow-up examinations of patients. A small number of supraventricular premature beats appears to be a normal finding in endurance horses. Further studies are required to validate the findings and determine the clinical significance of premature beats in horses.

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“…A presumptive cause of death was made in 25% (67/268) of cases and death remained unexplained in 22% (58/268) of cases (Lyle et al 2011). Sudden death can be attributed to a variety of causes.…”

Section: Discussionmentioning

confidence: 99%

“…Sudden death can be attributed to a variety of causes. Causes of sudden death and the lesions found in cases of exercise-related sudden death are similar in different racing jurisdictions (Lyle et al 2011). Although fatal musculoskeletal injuries have a low prevalence, milder forms of these injuries have a high prevalence (Stover 2003).…”

Section: Discussionmentioning

confidence: 99%

“…These fatalities include sudden deaths that occur while racing or training and horses that are euthanized due to catastrophic injuries (Boden et al 2005, Lyle et al 2011. Reported causes of death in Thoroughbred horses associated with racing or training include catastrophic musculoskeletal injury (CMI), acute abdominal crisis (colic), other major causes of death included respiratory, digestive and multi-organ system disorders (Johnson et al 1994).…”

Section: Introductionmentioning

confidence: 99%

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A retrospective study of causes for mortality of Thoroughbred horses in Caracas, Venezuela (2008-2012)

2018

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The aim of this study was to describe the causes of death in Thoroughbred horses at the Racetrack “La Rinconada”, in Caracas (Venezuela) during 2008-2012. This study was conducted in a cohort of all Thoroughbred horses that died or were subjected to euthanasia. Data was collected retrospectively. Only horses for which a full necropsy report was available were included in the study. The carcass and all internal organs of each horse were examined and representative samples of tissues with abnormalities were collected in 10% neutral buffered formalin and processed for histopathological examination. Samples were collected for bacteriological or virological examination when indicated in gross examination. A descriptive statistical analysis was performed. A total of 532 Thoroughbred horses were examined post-mortem. Of these horses, 44% were females and 56% males. In general musculoskeletal injuries and dilaceration occurred specifically at higher frequency. The total year and horses dead for descriptive statistical analysis was to mean 106.4 and median 125; Standard Deviation: 47.82573; variation (Standard Deviation): 2287.3, population (Standard Deviation): 42.77663 and variance (Standard Deviation): 18229.84. In conclusion we identify and describe the causes of death in Thoroughbred Race Horses in Caracas, Venezuela. In order of importance the causes of death were principally skeletal muscle injuries resulting in fractures euthanasia, abdominal crisis were mostly bowel twists and gastric rupture andrespiratory pathologies such as the pneumonia, pleuritis presented a significant number of cases of pulmonary hemorrhage induced by exercise. Finally the multisystem pathologies were presented in low cases.

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Sudden death in racing Thoroughbred horses: An international multicentre study of post mortem findings

Abstract: SummaryReasons for performing study: To improve the understanding of exercise related sudden death in Thoroughbred racehorses.

Cited by 100 publications

References 16 publications

Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles

Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles

Appropriate threshold levels of cardiac beat-to-beat variation in semi-automatic analysis of equine ECG recordings

A retrospective study of causes for mortality of Thoroughbred horses in Caracas, Venezuela (2008-2012)

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