The equine cardiovascular system, particularly the heart, is fundamental to maintaining the health and performance of horses. The heart is responsible for pumping oxygenated blood throughout the body, supporting vital functions and physical activity. In horses, the heart's structure and function are adapted to meet the demands of both rest and exertion, with notable features such as a large cardiac output and efficient blood circulation. Conditions affecting the equine heart, such as arrhythmias, valvular diseases, and myocardial disorders, can significantly impact a horse's well-being and athletic capability. This page aggregates peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of the equine heart, as well as diagnostic and therapeutic approaches to managing cardiac health in horses.
Farag AMM, Ibrahim HMM.Donkey (Equus asinus), the cheapest form of agricultural power in Egypt, is used principally as draught or pack animals and may also be ridden, or used for threshing, raising water, milling, and other work. The aim of the present study was to provide B-mode and M-mode echocardiographic reference ranges from a sample of population of donkeys (E. asinus) based on the probability theory and statistics. In the present study, B-mode and 2-dimensional guided M-mode echocardiography were performed on 44 clinically healthy donkeys (E. asinus) (22 males and 22 females), without any neither clinical nor...
Ibrahim HMM, Abouelnasr KS, Hamed MA, Eltayesh RA, El-Khodery SA.The aim of the present study was to assess and compare the changes of the echocardiographic dimensions and cardiac function indices after epidural injection of xylazine or dexmedetomidine in clinically healthy donkeys. In an experimental prospective randomized cross-over study, 10 healthy adult donkeys were injected with saline solution, xylazine (0.20 mg kg), and dexmedetomidine (0.005 mg kg) into the epidural space between the second and third coccygeal vertebrae. Echocardiographic dimensions as well as cardiac function indices were assessed using a 2-3.9 MHz sector transducer, at the l...
Vernemmen I, De Clercq D, Decloedt A, Vera L, Van Steenkiste G, van Loon G.The number of atrial premature depolarisations (APDs) is a known risk factor for atrial fibrillation (AF) recurrence in humans. Objective: To evaluate if the number of APDs over a 24-h period 5 days post cardioversion predicts AF recurrence within 1 year in horses, taking the multifactorial nature of AF into account. Methods: Retrospective case series. Methods: Eighty horses met these inclusion criteria: first AF episode, no AF recurrence within 5 days post cardioversion, cardioversion by transvenous electrical cardioversion (TVEC), 24-h ECG recording and echocardiographic examination 5 da...
Rassoli A, Fatouraee N, Guidoin R, Zhang Z.Bioprosthetic heart valves still have poor long-term durability due to calcification and mechanical failure. The function and performance of bioprostheses is known to depend on the collagen architecture and mechanical behavior of the target tissue. So it is necessary to select an appropriate tissue for such prostheses. In this study, porcine, equine, and bovine pericardia were compared histologically and mechanically. The specimens were analyzed under light microscopy. The planar biaxial tests were performed on the tissue samples by applying synchronic loads along the axial (fiber direction) a...
Vera L, Campos Arias D, Muylle S, Stergiopulos N, Segers P, van Loon G.Arterial rupture in horses has been observed during exercise, after phenylephrine administration or during parturition (uterine artery). In human pathophysiological research, the use of computer models for studying arterial hemodynamics and understanding normal and abnormal characteristics of arterial pressure and flow waveforms is very common. The objective of this research was to develop a computer model of the equine arterial circulation, in order to study local intra-arterial pressures and flow dynamics in horses. Morphologically, large differences exist between human and equine aortic arc...
Caivano D, Corda A, Rishniw M, Giorgi ME, Parpaglia MLP, Conti MB, Porciello F, Birettoni F.Equine cardiovascular structures and function are routinely assessed by transthoracic echocardiography. Recently, investigators have described the echocardiographic visualization of equine pulmonary vein ostia. In companion animals, the right pulmonary vein (RPV) to right pulmonary artery (RPA) ratio has been used as an index to estimate the severity of cardiac diseases resulting in left ventricular volume overload. We sought to assess the feasibility of measuring RPV and RPA dimensions, and sought to provide various previously examined RPV and RPA variables in clinically healthy horses that c...
Gómez-Torres FA, Ballesteros-Acuña LE, Ruíz-Sauri A.The cardiac nodes are the source of the electrical impulse that is transmitted to the heart, the aim of this work is study the histological and morphometric characteristics of the different components of the sinus and atrioventricular nodes in horses and dogs that help to know the physiopathology of these nodes. A group of ten horse hearts and five dog hearts were used. The region of the sinus and atrioventricular nodes was sectioned serially, and the block of tissue removed for study. The samples were assessed using a morphometric analysis with the Image-Pro Plus 7.1 software and the acquisit...
Gehlen H, Schlaga A.Several studies have shown the effect of training on myocardial deformation parameters in human athletes. The aim of this prospective, longitudinal study was echocardiographic evaluation of myocardial velocities and deformation in horses during the first year of training. Twelve Standardbred yearlings were examined using tissue Doppler imaging (TDI) and two-dimensional speckle tracking (2D-ST) during the first year of race training (short axis of left and right ventricle). The first examination was performed before the beginning of training (n = 12). At the last time point, horses were fully ...
Mao J, Rassoli A, Tong Y, Rouse EN, Le-Bel G, How D, Germain L, Fatouraee N, Zhang Z, Reed RR, Guidoin R.Transcatheter aortic valve implantation (TAVI) has gained considerable acceptance in the past decade due to its lower risks than conventional open-heart surgery. However, the deformation and delamination of the leaflets during the crimping procedure have raised questions about the durability and long-term serviceability of the pericardium tissue from which the leaflets are made. The collagen architecture, wall thickness and mechanical properties of donkey pericardium were investigated to assess its suitability as an alternative material for the manufacture of heart valves. Coupons sampled from...
Vernemmen I, De Clercq D, Decloedt A, Schauvliege S, Taeymans Y, De Wolf D, van Loon G.This report describes a rare case of an aorto-cardiac fistula in a six-year-old French Warmblood mare presented with atrial fibrillation, decreased performance, ventral oedema, bounding arterial pulsation and pathological jugular venous pulse. A 2.7-cm-diameter fistula connected the right aortic sinus of Valsalva to the right atrium. Atrial fibrillation was likely due to volume overload of the right heart due to left-to-right shunting. The horse was treated by percutaneous transcatheter closure of the fistula delivered under general anaesthesia using a transarterial approach. The operation was...
Molesan A, Wang M, Sun Q, Pierce V, Desideri R, Palmer S, Todhunter R, Kelly K.Postmortem evaluation of racehorses has focused primarily on musculoskeletal injuries; however, horses also die suddenly on the track (sudden death [SD]). Although cardiac conditions are frequently suspected as a cause of death, SD racehorses are often autopsy negative; however, previous studies have been limited due to inconsistent or insufficient cardiac sampling and lack of controls. SD in New York (NY) and Maryland (MD) racehorses was evaluated in an observational case vs control study comparing clinical information, postmortem evaluation including cardiac dissection, and cardiac conductio...
Redpath A, Bowen M.Many cardiac therapeutics lack significant evidence of benefit in the horse, and in many cases their use is based on extrapolation of evidence from other species. In recent years there has been a push to develop a better understanding of both the pharmacodynamics and pharmacokinetics of these drugs. Recent data have described the use of antiarrhythmic agents including sotalol, flecainide, and amiodarone. Data about the use of ACE inhibitors in the management of congestive heart failure are encouraging and support their use in certain cases, wheras evidence for other medicines, such as pimobend...
Durando MM.Horses have a high prevalence of resting arrhythmias, cardiac murmurs, and valvular regurgitation, and training can increase the prevalence. This makes it challenging for equine veterinarians who are asked to evaluate horses for poor performance to determine the clinical relevance of some findings. In addition, cardiac disease has the potential to cause collapse or sudden death, putting both the horse and rider at risk. Further diagnostics, such as echocardiograms and resting and exercising ECGs can help to sort out the impact of an abnormality found on resting physical examination. However un...
van Loon G.Arrhythmias are common in horses. Sinus arrhythmia and first- and second-degree atrioventricular block are frequently found physiologic arrhythmias, but should immediately disappear after stress or exercise. Atrial premature depolarizations are usually not associated with poor performance, but are a potential trigger for atrial fibrillation. Atrial fibrillation results in an abnormal ventricular response during exercise and poses a risk for collapse in some horses. This arrhythmia can usually be treated by quinidine sulfate or transvenous electrical cardioversion. Ventricular premature depolar...
Reef VB.Arrhythmias detected on prepurchase examination should be confirmed with an ECG. Exercising ECG determines if the arrhythmia is overdriven during exercise or is a safety concern. An echocardiogram is needed in all horses with a grade 3/6 or louder mid to late systolic, holosystolic, or pansystolic murmur or any holodiastolic decrescendo murmur to identify the cardiac abnormality and its hemodynamic impact. Most horses with arrhythmias and murmurs have a normal performance career and life expectancy and are insurable. Risks for sudden death and congestive heart failure associated with the commo...
Bonagura JD.Equine heart diseases can be categorized with morphologic, etiologic, and physiologic diagnoses and classified anatomically as diseases of the pericardium, myocardium, valves (endocardium), and great vessels. An appreciation of normal and pathologic physiology is a key to understanding diagnosis and therapy of heart disease. Pathophysiologic diagnoses include arrhythmias, congestive heart failure, and pulmonary hypertension. Heart rhythm disturbances can occur in isolation or with structural disease. Heart failure stems from arterial filling owing to insufficient cardiac output. Pulmonary hype...
Decloedt A.Pericardial, myocardial, and great vessel diseases are relatively rare in horses. The clinical signs are often nonspecific and vague, or related to the underlying cause. Physical examination usually reveals tachycardia, fever, venous distension or jugular pulsation, a weak or bounding arterial pulse, ventral edema, and abnormal cardiac auscultation such as arrhythmia, murmur, or muffled heart sounds. The prognosis depends on the underlying cause and the disease progression, and ranges from full recovery to poor prognosis for survival. This article focuses on the etiology, diagnosis, prognosis,...
Marr CM.Degenerative myxomatous disease is common and is associated with aging. Poor prognostic indicators for equine aortic regurgitation specifically include ventricular ectopy, increased pulse pressure, and hyperkinetic pulses. Valvular prolapse is a functional abnormality diagnosed echocardiographically, about which knowledge is limited. A better understanding of its role in valvular regurgitation is needed. Infective endocarditis presents with fever and other systemic signs accompanying valvular regurgitation. The prognosis is poor, warranting aggressive therapy. Other forms of valvular disease o...
Schwarzwald CC.This article provides an overview on the principles of transthoracic echocardiography in horses. Indications for echocardiography, equipment, and technical considerations are discussed and a systematic approach for a complete echocardiographic examination in horses is described. Methods for assessment of chamber dimensions, allometric scaling of measurements, assessment of systolic and diastolic ventricular function, assessment of atrial function, hemodynamic assessment, and evaluation of valvular regurgitation are explained, focusing on traditional 2-dimensional (2D), motion-mode, and Doppler...
Scansen BA.Congenital heart disease (CHD) represents a small proportion of horses undergoing clinical evaluation; however, both simple and complex defects occur during cardiac development leading to many unique malformations. This article reviews cardiac development and the fetal circulation, describes the morphologic method and the sequential segmental approach to CHD analysis, presents a summary of CHD in horses, and offers an overview of lesions that should be considered during evaluation of horses suspected to have CHD. For many forms of equine CHD, therapies are limited because cardiac interventions...
Siwinska N, Michalek M, Zak A, Slowikowska M, Noszczyk-Nowak A, Niedzwiedz A, Paslawska U.Precise understanding of the dimensions of the vascular lumina is essential for accurate interpretation of cardiac vessels imaging. To the authors' best knowledge, this is the first study focusing on the ultrasound measurement of the right coronary artery (RCA) in the horse. The aim of this study was to determine both the ultrasonographic range of the normal diameter and lumen area of the RCA in horses and the influence of gender, age and level of training on the RCA dimensions. An additional aim of the study was to assess intra- and inter-observer repeatability of the collected measurements. ...
Gehlen H, Shety T, El-Zahar H, Hofheinz I.Cardiac biomarkers are important tools for monitoring disease progress and can monitor progression of therapy. Endothelin-1 (ET-1) has been studied for its use as a cardiac biomarker in human and small animal medicine while in horses with cardiac disease it has not been evaluated yet. The objective of the present study was to determine the concentration of plasma ET-1 in healthy horses and compare it with ET-1 concentration in horses with cardiac disease during rest and after exercise. Fifty four horses admitted to the Equine Clinic of Free University of Berlin were used in the present study, ...
Wiśniewska M, Janczarek I, Wilk I, Wnuk-Pawlak E.The aim of the study was to evaluate the effect of music therapy on changes in the level of parameters describing heart rate (HR) and heart rate variability (HRV) as excitability indicators in geriatric horses. The study involved 20 warmblood geriatric horses, aged 20 years or more. Animals were kept in two identical stables in one facility. Horses from stable No. 1 were considered the experimental group, whereas horses from stable No. 2 constituted a control group. The experiment consisted in playing relaxation new age music to the horses in the experimental group for 28 days use special so...
Lorello O, Ramseyer A, Burger D, Gerber V, Navas de Solis C.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. Methods: This study included two eventing horses, 11 endurance horses, and 13 eventing and seven endurance control breed-matched horses. 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 he...
Scopa C, Palagi E, Sighieri C, Baragli P.To manage a stressful stimulus animals react both behaviorally and physiologically to restore the homeostasis. In stable horses, a stressful stimulus can be represented by social separation, riding discomfort or the presence of novel objects in their environment. Although Heart Rate Variability is a common indicator of stress levels in horses, the behavioral mechanisms concurrently occurring under stressful conditions are still unknown. The sudden inflation of a balloon was administered to 33 horses. Video-recording of self-directed behaviors (snore, vacuum chewing, snort, head/body shaking) a...
Nardelli M, Lanata A, Valenza G, Sgorbini M, Baragli P, Scilingo EP.This paper reports on a novel real time index designed to assess the quality of electrocardiographic (ECG) traces recorded in a group of five horses during a submaximal treadmill test procedure. During the experimental protocol two ECG monitoring systems were simultaneously applied to the animals. The first system was equipped with textile electrodes while the second one with standard red-dot electrodes. The procedure comprised four phases with an increased treadmill velocity, specifically, Walk 1, Trot 1, Trot 2 and Gallop. Three signal quality levels have been fixed according to the amount o...
Broux B, De Clercq D, Vera L, Ven S, Deprez P, Decloedt A, van Loon G.Heart rate variability (HRV) parameters, and especially RMSSD (root mean squared successive differences in RR interval), could distinguish atrial fibrillation (AF) from sinus rhythm(SR) in horses, as was demonstrated in a previous study. If heart rate monitors (HRM) automatically calculating RMSSD could also distinguish AF from SR, they would be useful for the monitoring of AF recurrence. The objective of the study was to assess whether RMSSD values obtained from a HRM can differentiate AF from SR in horses. Furthermore, the impact of artifact correction algorithms, integrated in the analyses ...
DiVincenzo MJ, Bonagura JD, Rings L, Burns TA, Cianciolo RE, Kohnken R.An 8-month-old Hanoverian gelding was presented with a history of cardiac murmurs that were not apparent as a foal nor reported at the time of castration. Major echocardiographic findings included mitral valvular thickening, functional stenosis, and mitral regurgitation of sufficient severity to cause diastolic and systolic cardiac murmurs, left-sided volume overload, and pulmonary hypertension. Due to the hemodynamic severity of the lesion and poor prognosis for future performance and longevity, euthanasia was elected. On gross postmortem examination, there was focal fibrous epicarditis affec...
Slack JA, McGuirk SM, Erb HN, Lien L, Coombs D, Semrad SD, Riseberg A, Marques F, Darien B, Fallon L, Burns P, Murakami MA, Apple FS, Peek SF.The cardiac biomarkers cardiac troponin T (cTnT) and I (cTnI) and the cardiac isoenzyme of creatine kinase (CKMB) are used extensively in human medicine to diagnose and provide valuable prognostic information in patients with ischemic, traumatic, and septic myocardial injury. We designed a study to establish normal values for these markers in healthy, neonatal foals and to compare them with values obtained from septic neonates in a referral hospital population. The 25th, 50th, 75th, and 95th percentiles for cTnI and CKMB in the healthy-foal population were 0.08, 0.14, 0.25, 0.49 ng/mL and 1.4,...
Burger D, Vidondo B, Gerber V, Deillon D, Müller A, Scheidegger M, Käser R, Ramseyer A.Fatigue and related injuries to the musculoskeletal system are among the most frequent reasons for the withdrawal of high-level eventing horses from the sport. The safety of both horse and rider is very important, and early detection of fatigue is crucial. Objective: To investigate elite eventing horses in competitive events focusing on biomechanical, cardiovascular and metabolic variables across the cross-country test and to identify their potential associations with fatigue. Methods: Prospective observational exploratory field study. Methods: Observations on 54 cross-country tests of 33 hors...
Hilwig RW.Electrocardiograms were obtained from normal horses and from horses with cardiac or other organic disease that affected the cardiac rhythm. Tracings were obtained from a base-apex bipolar monitor lead, with the negative electrode attached to the skin in the right jugular furrow and the positive electrode attached to the skin on the ventral medline, beneath the apex of the heart. Each arrhythmia was discussed relative to importance and probable cause.
Gelzer AR, Moïse NS, Vaidya D, Wagner KA, Jalife J.Atrial fibrillation (AF) is common in healthy horses. We studied the temporal organization of AF to test the hypothesis that the arrhythmia is governed by a high degree of periodicity and therefore is not random in the horse. Further, we surmised that concealed conduction of AF impulses in the AV node results in an inverse relationship between AF frequency and ventricular frequency. Results: Fast Fourier transform (FFT) analysis of atrial activity was done on signal-averaged ECGs (n = 11) and atrial electrograms (n = 3) of horses with AF at control (C), after quinidine sulfate (22 mg/kg by mou...
Durando MM.Horses have a high prevalence of resting arrhythmias, cardiac murmurs, and valvular regurgitation, and training can increase the prevalence. This makes it challenging for equine veterinarians who are asked to evaluate horses for poor performance to determine the clinical relevance of some findings. In addition, cardiac disease has the potential to cause collapse or sudden death, putting both the horse and rider at risk. Further diagnostics, such as echocardiograms and resting and exercising ECGs can help to sort out the impact of an abnormality found on resting physical examination. However un...
Young LE.Our recent data have confirmed that maximum oxygen delivery in racing Thoroughbreds is positively correlated to left ventricular mass measured by echocardiography. A similar, but weaker relationship also exists between left ventricular mass and Timeform performance rating in commercial racehorses. The relationship of the Thoroughbred heart to racing success and the special problems that selective breeding for aerobic capacity have had in this species are reviewed in this article.
Young LE, Scott GR.In order to assess the reliability and repeatability of transthoracic echocardiography for detecting serial changes in cardiac function in horses, day to day variability of a number of echocardiographic indices of ventricular function were studied. The variables investigated were, from 2-dimensional (2-D) and M-mode echocardiography - aortic diameter in systole (Aos), pulmonary artery diameter in systole (Pas), left ventricular internal diameter in systole (LLVIDs) and diastole (LLVIDd), and left ventricular fractional shortening (%FS) and estimated ejection fraction (EF). From pulsed Doppler ...
Weixler VHM, Kuschnerus K, Romanchenko O, Ovroutski S, Cho MY, Berger F, Sigler M, Sinzobahamvya N, Photiadis J, Murin P.The aim was to report mid-term performance of decellularized equine pericardium used for repair of various congenital heart defects in the pediatric population. Methods: A retrospective review of all patients undergoing patch implantation between 2016 - 2020 was performed. Patch quality, surgical handling, hemostasis and early patch-related complications were studied on all patients. Mid-term performance was observed in patients with ≥12 months follow-up and intact patch at discharge (without reoperation/stent implantation). Results: A total of 201 patients with median age of 2.5 years [inte...
Sarazan RD, Starke WA, Krause GF, Garner HE.The cardiovascular effects of detomidine and xylazine were compared in six chronically instrumented, conscious ponies. Ponies were instrumented with a micromanometer in the left ventricular chamber, a Doppler flow probe on a coronary artery and sonomicrometer crystals in the left ventricular free wall. Heart rate, ventricular systolic pressure, stroke work, dP/dtmax, minute work and coronary blood flow were measured for 4 h following intravenous injection of detomidine at several doses or xylazine at 1.1 mg/kg. Both drugs caused a profound hypertensive response at 15 s post-injection. The magn...
Kiryu K, Nakamura T, Kaneko M, Oikawa M, Yoshihara T.Twenty thoroughbred race horses were selected for postmortem cardiopathological study of sudden cardiac death; ten of the twenty horses died suddenly. In order to define accurately the morphological changes observed in these ten hearts, ten other thoroughbred race horses considered to have normal hearts were selected as a control group and studied by postmortem coronary angiography. Of the ten horses that died suddenly, eight were witnessed to have died either during or shortly after training or racing. The death was instantaneous except in one horse, which showed ventricular tachycardia and d...
Reef VB, Clark ES, Oliver JA, Donawick WJ.A permanent, transvenous, atrioventricular, sequential pacing system was implanted successfully in a 7-year-old Quarter Horse gelding with complete heart block. The transvenous atrial and ventricular electrodes were placed in their respective positions in the heart, using real-time, 2-dimensional echocardiography. The horse was able to return successfully to competition as a show horse.
Patteson MW, Cripps PJ.Auscultation was used to examine 545 horses for cardiac murmurs and some arrhythmias. The most significant finding was the high prevalence of right-sided holosystolic or pansystolic plateau-type murmurs compatible with a diagnosis of tricuspid regurgitation in National Hunt racing Thoroughbreds of all ages (16.4%). This condition was found in 4.7% of flat-racing Thoroughbreds, 3.7% of non-racing Thoroughbreds and Thoroughbred crosses, and in none of the ponies examined. High prevalences of left-sided early systolic murmurs (53%), left-sided early diastolic murmurs (23%), right-sided early dias...
Swanson CR, Muir WW, Bednarski RM, Skarda RT, Hubbell JA.The hemodynamic changes induced by constant infusions of dopamine or dobutamine (each 3, 5, and 10 micrograms/kg/min) were observed in halothane-anesthetized horses. Left ventricular dp/dt and cardiac output were increased in horses given dobutamine at dosage of 3 micrograms/kg/min and in those given either of the drugs at dosages of 5 and 10 micrograms/kg/min. Concomitant increases in systemic arterial blood pressure occurred at lower infusion dosage rates of dobutamine than those of dopamine and were modulated by dosage-related changes in peripheral vascular resistance that were different be...
Ebert LC, Schön CA, Ruder TD, Thali MJ, Hatch GM.Horse kicks are rare incidents-especially, if they end in fatality. In this case, a 13-year-old girl collapsed 3 minutes after sustaining a kick to the chest from a pony. Resuscitation attempts were unsuccessful. Postmortem computed tomography and magnetic resonance imaging were performed before autopsy.Imaging revealed a 3-cm long laceration of the left ventricle and a large pericardial effusion. Using segmentation techniques, the amount of blood inside the pericardium was determined. These findings correlated well with the autopsy findings. Pericardial tamponade was determined at autopsy to ...
Scheffer CW, Robben JH, Sloet van Oldruitenborgh-Oosterbaan MM.A method for the continuous monitoring of the electrocardiogram (ECG) of horses at rest and during exercise was evaluated in five healthy horses. The horses spent 24 hours in a loose box and performed a standardised exercise test on a treadmill during this period. Two bipolar leads were recorded, lead 1 between the xiphoid and the left withers, and lead 2 between the left ventral thorax and the left dorsal thorax, using disposable electrodes. The quality of the ECGs enabled both an 'operator-controlled' and an automatic analysis to be made. Lead 1 was the most stable during exercise and lead 2...
Weber JM, Dobson GP, Parkhouse WS, Wheeldon D, Harman JC, Snow DH, Hochachka PW.This study characterizes the effects of exercise on the cardiac output (Q) and the metabolic rate (VO2) of trained Thoroughbred racehorses. Heart rate, Q, and arteriovenous (a-v)O2 difference were measured at rest and at three levels of submaximal treadmill exercise (1.6 m/s walk and 3-4 m/s trot at 6% incline, and 6.5 m/s horizontal canter). Heart rate and (a-v)O2 difference were also measured during maximal exercise (12.5 m/s gallop, 5% incline) to obtain an estimate of maximum O2 uptake (VO2max). The walk, trot, and canter represented 25, 45, and 55% VO2max. Mean heart rate went from 48.9 (...
Thayer JF, Hahn AW, Pearson MA, Sollers JJ, Johnson PJ, Loch WE.High heart rate variability (HRV) has been associated with more efficient autonomic control, allowing more responsivity and sensitivity to changing environmental demands. Previous results from spectral analysis of interbeat intervals of equine heart rate (HR) indicated increased HRV, reflecting more effective vagal control of the heart. This study focuses on characterizing equine HR and HRV during increasing then decreasing physical demand. A non-invasive ambulatory monitoring system continuously records HR and HRV as horses exercise on a high speed equine treadmill at increasing then decreasi...
Marr CM, Reef VB, Reimer JM, Sweeney RW, Reid SW.Two-dimensional and M-mode echocardiograms were recorded from 41 horses before they were successfully treated for atrial fibrillation. In addition, these examinations were performed in a subgroup of 20 horses after treatment, and the results were compared with pretreatment values. Atrial fibrillation in this group of horses was associated with a reduction of mean left ventricular fractional shortening (mean 31% +/- 5.24%), and 22 of the 41 horses were below the reference range. The remaining mean M-mode variables were within the normal reference range, although 12 horses had increased left ven...
Divers TJ, Kraus MS, Jesty SA, Miller AD, Mohammed HO, Gelzer AR, Mitchell LM, Soderholm LV, Ducharme NG.Six adult horses were administered sodium monensin, 1.0-1.5 mg/kg, via gastric gavage. Anorexia and/or diarrhea occurred within 24 hr after monensin administration in all 6 horses. Cardiac disease and dysfunction were evaluated by both elevations in heart rate, echocardiography, and an increase in serum concentrations of cardiac troponin I (cTnI), occurred in 4 horses. The development and severity of cardiac disease was likely affected by the monensin dose, vehicle (water or corn oil) mixed with monensin, and/or whether the monensin was administered to fed or fasted horses. Initial increases i...
Rossi TM, Kavsak PA, Maxie MG, Pearl DL, Pyle WG, Physick-Sheard PW.Human cardiac troponin I (cTnI) assays have been used in equine medicine, often without prior analytical validation for equine use. In the absence of appropriate validation, the clinical significance of assay results is uncertain and can lead to misdiagnosis. We followed the American Society for Veterinary Clinical Pathology guidelines and investigated linearity, precision, limit of quantification (LoQ), and comparative recovery for 6 commercial cTnI assays developed for use in human medicine. Clinically acceptable linearity was observed in assays A-D, whereas assay E did not detect equine cTn...
Van Der Vekens N, Decloedt A, Sys S, Ven S, De Clercq D, van Loon G.Cardiac troponin I (cTnI) is a marker for detection of myocardial damage in horses. Many cTnI assays exist and medical studies have shown that the clinical performance of assays differs. The aim of this study was to compare two different cTnI assays in horses. Serum samples were taken from 23 healthy horses (group 1) and 72 horses with cardiac disease (group 2). Cardiac troponin I was determined using assay 1 in laboratory A (limit of detection, LOD, 0.03 ng/mL) and assay 2 in laboratories B and C (LOD 0.01 ng/mL). In group 1, a median cTnI concentration of <0.03 (<0.03-0.04) ng/mL and <0....
Hammond A, Sage W, Hezzell M, Smith S, Franklin S, Allen K.Heart rate variability (HRV) analysis measures the inter-beat interval variation of successive cardiac cycles. Measurement of these indices has been used to assess cardiac autonomic modulation and for arrhythmia identification in exercising horses. Objective: To report HRV indices during submaximal exercise, strenuous exercise and recovery, and explore relationships with clinical conditions (arrhythmias, lameness, equine gastric ulcer syndrome [EGUS], lower airway inflammation and upper respiratory tract obstructions [URTOs]) in Thoroughbred racehorses. Methods: Retrospective, observational cr...
Buhl R, Ersbøll AK, Eriksen L, Koch J.To evaluate the incidence and development of valvular regurgitation and its effect on racing performance in Standardbred trotters from 2 to 3.5 years of age. Methods: Longitudinal observational study. Methods: 103 horses. Methods: Horses were examined via echocardiographic imaging 4 times at 6-month intervals. Two-dimensional and M-mode echocardiographic examinations were performed in each horse, and color Doppler imaging was used to detect and evaluate regurgitant blood flow at each valve. Results: For all cardiac valves, the frequency of valvular regurgitation increased significantly during ...