Cardiovascular variables in eventing and endurance horses over a season.

INTRODUCTION: The objectives of this study were to describe the changes in clinical cardiovascular examination variables over a competition season in groups of competitive eventing and endurance horses and to compare these findings to non-competitive controls of the same breeds. ANIMALS: This study included two eventing horses, 11 endurance horses, and 13 eventing and seven endurance control breed-matched horses. MATERIALS AND METHODS: Cardiovascular examinations were performed before starting the competition season, in the middle and at the peak/end of the competition season. Examinations included auscultation of the heart; M-mode echocardiographic measurements and calculated values; left atrial, pulmonary artery, and aortic diameters; color flow Doppler; exercise electrocardiograms (ECG) measuring peak heart rates and quantifying premature complexes; and 24-h continuous ECGs quantifying premature complexes per hour. RESULTS: Auscultation, echocardiograms, arrhythmias during exercise, and 24-h continuous ECGs did not change significantly throughout the season (p > 0.05 for all variables). CONCLUSION: Cardiovascular examination variables of eventing and endurance horses throughout a competition season are reported here for the first time. Although the present study did not reveal significant changes, data should be interpreted carefully as only a small number of horses were examined.

Atrial fibrillation management in a breeding stallion.

A 20-year-old warmblood breeding stallion presented to a University practice for semen collection and evaluation was incidentally diagnosed with atrial fibrillation (AF). Electrocardiogram recordings during breeding revealed inappropriately rapid tachycardia and occasional ventricular premature depolarizations/aberrant ventricular conduction. Transvenous electrical cardioversion was performed. After successful cardioversion the horse displayed supraventricular ectopy and atrial contractile dysfunction and was administered sotalol hydrochloride in an attempt to decrease the risk of AF recurrence. Supraventricular ectopy and echocardiographic evidence of atrial dysfunction gradually improved and normalized over 6 months. No direct adverse effects of the chronic anti-arrhythmic treatment were observed and libido and semen quality were unaffected. AF recurred 6 months after cardioversion and sotalol therapy was continued to control the ventricular ectopy/aberrant ventricular conduction during semen collection. Considerations regarding pathologic arrhythmias and inappropriately high heart rates in breeding stallions with AF may be similar to those in riding horses. Sotalol hydrochloride was a safe anti-arrhythmic drug in the management of this case.

Exercising arrhythmias and sudden cardiac death in horses: Review of the literature and comparative aspects.

Arrhythmias are common in equine athletes during and immediately after exercise. Many of these rhythm variations are not clinically relevant. In horses, a link between different exercising arrhythmias and poor performance or between exercising arrhythmias and sudden cardiac death (SCD) is strongly suspected but not fully understood or proven. SCD during races or competitions is rare, but has catastrophic consequences for the safety of the human partner and public perceptions of welfare during equestrian sports. This review summarises current knowledge of equine exercise arrhythmias and their implications in SCD and compares existing principles and recommendations for equine subjects with those for human athletes.

Accuracy and Precision of Noninvasive Blood Pressure in Normo-, Hyper-, and Hypotensive Standing and Anesthetized Adult Horses.

BACKGROUND: Blood pressure is relevant to the diagnosis and management of many medical, cardiovascular and critical diseases. The accuracy of many commonly used noninvasive blood pressure (NIBP) monitors and the accuracy of NIBP measurements in hypo- and hypertensive standing horses has not been determined. HYPOTHESIS/OBJECTIVES: The objective of this study was to investigate the accuracy of an oscillometric BP monitor in standing horses before and during pharmacologically induced hyper- and hypotension and to compare results in standing and anesthetized horses. ANIMALS: Eight standing mares from a research herd (SG) and eight anesthetized horses from a hospital population (AG). METHODS: Prospective experimental and observational studies. Invasive blood pressure (IBP) and NIBP, corrected to heart level, were measured simultaneously. In the SG hyper- and hypotension were induced by administration of phenylephrine (3 µg/kg/min IV for 15 minutes) and acepromazine (0.05 mg/kg IV), respectively. In the AG NIBP and IBP were recorded during regular hospital procedures. RESULTS: There was a significant correlation between mean NIBP and IBP in standing (R = 0.88, P < .001) and anesthetized horses (R = 0.81, P < .001). The mean bias (lower, upper limit of agreement) was 16.4(-16.1, 48.9) mmHg for mean BP in the SG and 0.5(-22.3, 23.2) mmHg in the AG. The NIBP device was capable of identifying the increase and decrease in BP in all horses, but in the SG significant correlation between NIBP and IBP was only detected for the normotensive phase. CONCLUSION AND CLINICAL IMPORTANCE: While the evaluated oscillometric BP device allowed estimation of BP and adequately differentiated marked trends, the accuracy and precision were low in standing horses.

Gastrointestinal ultrasonography of normal Standardbred neonates and frequency of asymptomatic intussusceptions.

BACKGROUND: Ultrasonographic appearance of the gastrointestinal (GI) tract of equine neonates has not been completely described. OBJECTIVES: To describe (1) sonographic characteristics of the GI segments in normal nonsedated equine neonates, (2) intra- and interobserver variation in wall thickness, and (3) the sonographic appearance of asymptomatic intussusceptions, and (4) to compare age and sonographic findings of foals with and without asymptomatic intussusceptions. ANIMALS: Eighteen healthy Standardbred foals ≤5 days of age. METHODS: Prospective, cross-sectional blinded study. Gastrointestinal sonograms were performed stall-side. Intraobserver variability in wall thickness measurements was determined by calculating the coefficient of variation (CV). The Bland-Altman method was used to assess interobserver bias. Student's t-test and Fisher's exact test were used to test the association among presence of intussusceptions, age, and selected sonographic findings. RESULTS: The reference ranges (95% predictive interval) for wall thickness were 1.6-3.6 mm for the stomach, 1.9-3.2 mm for the duodenum, 1.9-3.1 mm for the jejunum, 1.3-2.2 mm for the colon, and 0.8-2.7 mm for the cecum. Intraobserver wall thickness CV ranged from 8 to 21% for the 2 observers for 5 gastrointestinal segments. The interobserver bias for wall thickness measurements was not significant except for the stomach (0.14 mm, P < .05) and duodenum (0.29 mm, P < .05). Diagnostic images of mural blood flow could not be obtained. Asymptomatic intussusceptions were found in 10/18 neonates. Associations between sonographic variables or age and the presence of intussusceptions were not found. CONCLUSIONS AND CLINICAL IMPORTANCE: Sonographic characteristics of the GI tract of normal Standardbred neonates can be useful in evaluating ill foals. Asymptomatic small intestinal intussusceptions occur in normal Standardbred neonates.

The effects of hypohydration on central venous pressure and splenic volume in adult horses.

BACKGROUND: Central venous pressure (CVP) is used in many species to monitor right-sided intravascular volume status, especially in critical care medicine. HYPOTHESIS: That hypohydration in adult horses is associated with a proportional reduction in CVP. ANIMALS: Ten healthy adult horses from the university teaching herd. METHODS: In this experimental study, horses underwent central venous catheter placement and CVP readings were obtained by water manometry. The horses were then deprived of water and administered furosemide (1 mg/kg IV q6h) for up to 36 hours. Weight, CVP, vital signs, PCV, total protein (TP), and serum lactate were monitored at baseline and every 6 hours until a target of 5% decrease in body weight loss was achieved. The spleen volume was estimated sonographically at baseline and peak volume depletion. Linear regression analysis was used to assess the association of CVP and other clinical parameters with degree of body weight loss over time. RESULTS: There was a significant association between CVP and decline in body weight (P < .001), with a decrease in CVP of 2.2 cmH(2)O for every percentage point decrease in body weight. Other significant associations between volume depletion and parameters measured included increased TP (P = .007), increased serum lactate concentration (P = .048), and decreased splenic volume (P = .046). There was no significant association between CVP and vital signs or PCV. CONCLUSIONS AND CLINICAL IMPORTANCE: These findings suggest that CVP monitoring might be a useful addition to the clinical evaluation of hydration status in adult horses.