Use of color Doppler echocardiography to assess the development of valvular regurgitation in Standardbred trotters

M-Mode Echocardiographic Measurements of Interventricular Septum, Left Ventricular Internal Diameter, and Left Ventricular Free-Wall Thickness in Normal Horses-A Meta-Analytical Study

The purpose of this study was to provide a systematic meta-analysis on echocardiographic measurements in normal Thoroughbred and Standardbred horses. The current systematic meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). All the available published papers on the reference values of echocardiographic assessment via M-mode echocardiography were searched, and fifteen studies were finally selected for analysis. In both fixed and random effect, the confidence interval (CI) for the interventricular septum (IVS) was 2.8-3.1 and 4.7-7.5; for the left ventricular free-wall (LVFW) thickness, it was 2.9-3.2 and 4.2-6.7; and for the left ventricular internal diameter (LVID), it was -5.0-4.6 and -10.0--6.7, respectively. For IVS, the Q statistic, I-squared, and tau-squared were 925.3, 98.1, and 7.9, respectively. Similarly, for LVFW, all the effects were on the positive side of zero, with a range of 1.3-68.1. The CI indicated a significant variation among the studies (fixed, 2.9-3.2; random, 4.2-6.7). The z-values of LVFW for fixed and random effects were, respectively, 41.1 (p < 0.001) and 8.5 (p < 0.001). However, the Q statistic was 886.6 (p < 0.001). Moreover, the I-squared was 98.08, and the tau-squared was 6.6. By contrast, the effects of LVID fell on the negative side of zero, (2.8-83.9). The present meta-analysis provides an overview of the echocardiographic measurements of cardiac diameters in healthy Thoroughbred and Standardbred horses. The meta-analysis indicates variations in results among different studies. This result should be considered when evaluating a horse for heart disease and each case should be evaluated independently.

Association between Cardiac Auscultation and Echocardiographic Findings in Warmblood Horses

Heart murmurs are detected frequently when auscultating horses and certain murmurs can usually be linked to specific valvular regurgitations. Limited information exists about the accuracy of these broad rules in warmblood horses and the influence of grade of the regurgitation and dimensional changes on murmur intensity. This study aims to clarify the accuracy of cardiac auscultation in warmblood horses and the influence of the grade of regurgitation and dimensional changes on the loudness of the murmur. In this retrospective study, 822 warmblood horses presented for cardiac examination in a large equine referral center in northern Germany underwent a thorough cardiac auscultation. In total, 653 of these revealed one or more heart murmurs. Most common auscultatory findings were left-sided systolic murmurs (68%) or left-sided diastolic murmurs (15%). On 635 of these horses, an echocardiographic examination was performed, revealing regurgitations of the mitral valve as the most common valvular regurgitation (77%) followed by regurgitations of the aortic valve (23%). Thirty-one percent of horses that underwent echocardiographic examination displayed dimensional changes of one or more compartments of the heart, with the left atrium being most affected (21%), followed by the left ventricle (13%). The main goal of this study was to link certain auscultatory findings with results of the echocardiographic examinations, trying to determine whether auscultation and echocardiography agreed on the valve affected, as well as to find out if loudness of the murmur coincided with grade of regurgitation and presence of dimensional changes. Agreement between auscultation and cardiac ultrasound was substantial (Kappa 0.74) if one or more murmurs and regurgitations were present and almost perfect (Kappa 0.94) if only one murmur and one regurgitation were found. Auscultation was particularly well suited for detection of left-sided systolic and diastolic murmurs, with 87% of left-sided systolic murmurs being caused by a mitral valve regurgitation and 81% of left-sided diastolic murmurs originating from an aortic valve regurgitation. We found a fair agreement between the grade of regurgitation and the respective murmur. Association was particularly good between mild regurgitations and low-grade murmurs, while differentiation between moderate to severe regurgitation based upon the loudness of the murmur was less reliable. Dimensional changes were usually linked to more severe regurgitations and higher-grade murmurs. However, a direct correlation between murmur intensity and the presence or severity of dimensional changes, independent of the grade of valvular regurgitation, could not be established in this cohort of horses.

Two-dimensional, M-mode and left atrial velocity echocardiographic measurements in healthy Norwegian-Swedish Coldblooded Trotters

INTRODUCTION

The Norwegian-Swedish Coldblooded Trotter (NSCT) is an important breed in Norwegian and Swedish harness racing. In spite of this, little is known about its cardiac measurements and factors that may influence these. The aims of this study were to establish reference intervals (RI) for a series of conventional echocardiographic variables, primarily of the left heart, in NSCTs in race training and to evaluate any effects age, gender, estimated body weight (EBW), number of starts and racing performance may have on these.

ANIMALS

Sixty-three apparently healthy NSCTs in race training.

METHODS

Observational study, convenience sampling. All horses were examined unsedated in their normal stabling environment. Auscultatory and echocardiographic examinations were performed. Means, standard deviations, medians and confidence intervals of the RI limits were used to summarize the data. The relationship between selected echocardiographic variables and age, gender, EBW, racing performance and number of starts were explored using linear regression analyses.

RESULTS

Reference intervals were determined for routinely used echocardiographic variables. Data for left atrial velocity were also obtained. Increasing age, number of starts and money earned significantly increased all cardiac measurements. Males had significantly higher ventricular measurements than females. Great vessel measurements increased with increasing EBW. Horses with faster recorded racing times had generally significantly increased cardiac measurements. Clinically insignificant valvular regurgitation was a common finding, particularly at the tricuspid and pulmonary valves.

CONCLUSIONS

The RIs described and the factors that may affect these will assist clinicians in interpreting echocardiograms of NSCTs with suspected cardiac disease or poor performance.

Abnormalities detected at pre-purchase examination of National Hunt racehorses presented at sale

BACKGROUND

Few studies are available concerning prevalences of abnormalities in the Thoroughbred horse population.

OBJECTIVES

Determine the prevalence of commonly observed abnormalities in a National Hunt Thoroughbred population using results of pre-purchase examinations conducted at Thoroughbred sales venues.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

Veterinary pre-purchase examination certificates for 13,603 3- and 4-year-old Thoroughbred National Hunt horses from Tattersalls Ireland, Goffs Ireland and Doncaster Bloodstock Sales Ltd. (DBS) Sales were analysed. All conditions noted by the veterinarians were recorded to determine the prevalence of abnormalities.

RESULTS

Abnormalities were recorded in 73.6% of horses; 12.0% had abnormalities likely to prejudice their use for racing. Metacarpal/metatarsal exostoses and tarsal-plantar desmitis affected 17.1 and 19.4% of the sample respectively, while 9.9% were found to make abnormal respiratory noises and 5.3% had recurrent laryngeal neuropathy. Age, year of birth and sex significantly affected the prevalence of many abnormalities (P<0.001). The proportions of horses sold differed significantly between horses with and without some abnormalities, with unaffected horses significantly more likely to be sold (e.g., prejudicial findings present vs. non-prejudicial/none, 38.1% vs. 77.6% respectively, P<0.001). A range of abnormalities significantly negatively affected the price at sale (P<0.001). Significantly higher proportions of horses in the lower price categories had multiple abnormalities (P<0.001).

MAIN LIMITATIONS

The study consisted only of horses entered into store horse sales and presented for sale. Horses kept for racing or breeding purposes or horses withdrawn prior to the panel veterinary pre-purchase examination were not included. The upper respiratory tract was only examined endoscopically in horses found to have an abnormal respiratory noise.

CONCLUSIONS

A large proportion of 3- and 4-year-old Thoroughbred National Hunt horses intended for sale are affected by abnormalities. The prevalence of many abnormalities increases with age and certain abnormalities are viewed negatively by purchasers, affecting sale of the horse and achieved sale price.

Examination of Horses with Cardiac Disease

Despite advances, increased convenience, and availability of echocardiography and other diagnostic techniques in equine cardiology, a comprehensive history and clinical examination still forms the essential first step in any cardiac evaluation. This article summarizes the approach to the cardiac examination at rest, highlighting key areas for the clinician to assess, and stressing the importance of context for assessing the significance of any abnormalities detected. Ancillary techniques, such as blood pressure measurement and the laboratory assessment of cardiac disease in the horse, are also introduced.

Cardiac/Cardiovascular Conditions Affecting Sport Horses

Cardiac murmurs are not uncommonly detected in the equine athlete. Although most are benign in nature, differentiation and quantification of murmurs due to valvular regurgitation are important for prognosis and recommendations. Arrhythmias can be associated with structural disease or occur independently and may range in severity from minimal clinical effect to poor performance to presenting a safety risk to rider and horse. This article discusses commonly encountered cardiac conditions in the sport horse. Physical examination, diagnostic approach, valvular disease, and arrhythmias with an impact on performance or ridden safety are discussed.

The heart remains the core: cardiac causes of poor performance in horses compared to human athletes

Cardiac remodelling occurs in response to exercise and is generally beneficial for athletic performance due to the increase in cardiac output. However, this remodelling also may lead to an increased prevalence of cardiac murmurs and arrhythmias. In most cases, these are not considered to be significant. However, in some cases, there may be potentially deleterious consequences. Whilst sudden cardiac death (SCD) is a rare occurrence, the consequences are catastrophic for both the horse and potentially the rider or driver. Furthermore, the sudden death of a horse in the public arena has negative connotations in regards to public perception of welfare during equestrian sports. Prediction of which individuals might be susceptible to potential deleterious effects of exercise is a focus of interest in both human and equine athletes but remains a challenge because many athletes experience cardiac murmurs and exercise-induced arrhythmias that are clinically irrelevant. This review summarises the effects of exercise on cardiac remodelling in the horse and the potential effects on athletic performance and SCD. The use of biomarkers and their future potential in the management of athletic horses is also reviewed.

Relationships between body dimensions, body weight, age, gender, breed and echocardiographic dimensions in young endurance horses

BACKGROUND

The heart's physiological adaptation to aerobic training leads to an increase in heart chamber size, and is referred to as the Athlete's heart. However, heart dimensions are also related to body weight (BWT), body size, growth and (in some species) breed. There are few published data on the relationships between heart dimensions and growth or aerobic training in Arabian and Arabian-related endurance horses. Therefore the objective of the present study was to describe the influence of body dimensions (body length (BL), thoracic circumference (TC), withers height (WH)), BWT, age, gender, breed (purebred Arabians, part-bred Arabians, Anglo-Arabians, and Others) and the initiation of endurance training on echocardiographic measurements in competition-fit endurance horses aged 4 to 6 years.

RESULTS

Most left atrial (LA) and left ventricular (LV) dimensions increased with age, whereas LA and LV functional indices did not. Although there was no gender difference for LV dimensions, females had larger LA dimensions. In terms of breed, Anglo-Arabians had the largest LV dimensions. Regression models indicated that the included explanatory factors had a weak influence on heart dimensions. Age, body dimensions, breed and gender showed the most consistent influence on LA dimensions, whereas BWT, breed and kilometres covered in competition showed the most consistent influence on LV dimensions.

CONCLUSION

The increase in echocardiographic dimensions with age indicates on-going growth in our population of 4 to 6 year-old horses. We also observed small changes associated with the initiation of endurance training. Morphometric dimensions had a greater influence on LA dimensions, whereas LV dimensions were also influenced (albeit weakly) by parameters associated with exercise intensity. These results may therefore reflect early adaptations linked to the initiation of endurance training.

Recommendations for management of equine athletes with cardiovascular abnormalities

Murmurs and arrhythmias are commonly detected in equine athletes. Assessing the relevance of these cardiovascular abnormalities in the performance horse can be challenging. Determining the impact of a cardiovascular disorder on performance, life expectancy, horse and rider or driver safety relative to the owner's future expectations is paramount. A comprehensive assessment of the cardiovascular abnormality detected is essential to determine its severity and achieve these aims. This consensus statement presents a general approach to the assessment of cardiovascular abnormalities, followed by a discussion of the common murmurs and arrhythmias. The description, diagnosis, evaluation, and prognosis are considered for each cardiovascular abnormality. The recommendations presented herein are based on available literature and a consensus of the panelists. While the majority of horses with cardiovascular abnormalities have a useful performance life, periodic reexaminations are indicated for those with clinically relevant cardiovascular disease. Horses with pulmonary hypertension, CHF, or complex ventricular arrhythmias should not be ridden or driven.

Prevalence of exercise-associated arrhythmias in normal performing dressage horses

REASONS FOR PERFORMING STUDY

Exercise-associated arrhythmias are important differentials when evaluating poor performance sport horses. However, most studies of arrhythmias have been conducted in racehorses and therefore there is a paucity of knowledge concerning the prevalence and significance of exercise-associated arrhythmias in riding horses.

OBJECTIVES

The objective of this study was to examine the prevalence of arrhythmias, particularly supraventricular premature complex (SVPCs) and ventricular premature complex (VPCs), associated with exercise in normal performing dressage horses.

METHODS

In total, 21 normal performing dressage horses, aged 5-16 years (mean 9 years), were examined clinically and echocardiographically to detect the prevalence of valvular regurgitation. Electrocardiographic (ECG) examinations were performed during rest and during a standardised dressage exercise programme, as well as during recovery period 1 h after exercise. All ECG recordings were analysed for presence and frequency of arrhythmias and arrhythmias were correlated with HR. Mean HR for walk, trot, canter and for specific dressage movements, as well as maximum HR was calculated. Fisher's exact test was used to test for associations between arrhythmias, valvular regurgitation, age and gender.

RESULTS

SVPCs occurred rarely during rest, but occurred during exercise in 6 (28.6%), and in 13 (61.9%) horses during recovery period. Most horses had ≤ 3 SVPCs. Ventricular premature complex were seen in one horse, which developed twice during exercise. Mild valvular regurgitation was seen in 11 (52%) of the horses. No significant associations between arrhythmia and age, gender or valvular regurgitation were observed.

CONCLUSIONS

Reference values for normal performing dressage horses are presented for the first time, demonstrating that arrhythmias occur infrequently during exercise and recovery. Maximum HR in dressage horses is low compared to both showjumping and racehorses. Studies of dressage horses with moderate to severe valvular regurgitation at rest or poor performance are needed to further elucidate the significance of cardiac arrhythmias.

Effect of light exercise on valvular regurgitation in Standardbred trotters

REASONS FOR PERFORMING STUDY

Although valvular regurgitation is diagnosed frequently by colour Doppler echocardiography in racehorses at rest, there is currently no information about the effect of exercise on valvular regurgitation.

OBJECTIVES

To investigate the effect of light exercise on valvular regurgitation in a population of trotters.

METHODS

Standardbred trotters (n = 73) were examined by resting auscultation and echocardiography, of which 50 fullfilled the criteria of the study. Of these, 4 had reduced performance according to the trainers and were not included in the statistical analyses. Horses that showed valvular regurgitations diagnosed by colour Doppler echocardiography at rest, were light exercised and the regurgitant valves were then re-examined by colour Doppler echocardiography.

RESULTS

Of the 46 horses, 41 (89%) had one or more valvular regurgitations at rest with tricuspid regurgitation present in 83% of horses, mitral regurgitation 46%, pulmonary regurgitation 37% and aortic regurgitation 57%. After exercise, one or more valvular regurgitation persisted for 23 of the 41 horses (56%). The regurgitation decreased significantly for mitral, pulmonary and aortic valves; the mitral regurgitation persisted for 21% of the horses, pulmonary regurgitation persisted for 6% and aortic regurgitation persisted after exercise for 23 % with regurgitation diagnosed at rest. Half of those with tricuspid regurgitation at rest still had tricuspid regurgitation after exercise.

CONCLUSIONS

The results of this study showed that the majority of small valvular regurgitations disappear after light exercise. However, the severity of tricuspid regurgitation increased in 4 horses. Furthermore, these horses were not performing satisfactorily according to the trainers.

POTENTIAL RELEVANCE

Studies in man have shown that severity after exercise suggests pathological regurgitation. The present study indicates that echocardiographic examination of valvular regurgitation after exercise might be a relevant examination in horses. However, more studies are needed to evaluate the effect of strenuous exercise on valvular regurgitation in horses.