Topic:Heart
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.
Preliminary investigation of orally administered benazepril in horses with left-sided valvular regurgitation. Despite the paucity of data available, orally administered angiotensin-converting enzyme (ACE) inhibitors are empirically used in horses with valvular regurgitation. Objective: Evaluate the echocardiographic and hormonal changes in response to oral benazepril in horses with left-sided valvular regurgitation. Methods: Prospective, randomised double-blind, placebo-controlled trial. Methods: Horses with mitral valve (MR) and/or aortic valve regurgitation (AR) received oral benazepril (n = 6) at a dosage of 1 mg/kg q 12 h or a placebo (n = 5) for 28 days. Echocardiography was performed before drug...
Double outlet right ventricle with subpulmonary ventricular septal defect (Taussig-Bing anomaly) and other complex congenital cardiac malformations in an American Quarter Horse foal. A 4-week-old American Quarter Horse colt presented with a recent history of diarrhea and decreased activity level. On initial physical examination, the animal was bright and alert and major findings were limited to a loud systolic heart murmur radiating widely over both sides of the thorax. While in the hospital, the clinical condition of the foal warranted further imaging to determine the cause and extent of cardiac disease. A variety of congenital cardiac malformations were identified during echocardiographic examination and autopsy, including a double outlet right ventricle and a subpulmona...
Antiarrhythmic Effects of Combining Dofetilide and Ranolazine in a Model of Acutely Induced Atrial Fibrillation in Horses. Antiarrhythmic compounds against atrial fibrillation (AF) often have reduced efficacy and may display cardiac and/or noncardiac toxicity. Efficacy can be improved by combining 2 compounds with distinct mechanisms, and it may be possible to use lower doses of each compound, thereby reducing the likelihood of adverse side effects. The purpose of this study was to investigate whether the effective doses of dofetilide and ranolazine can be reduced if the drugs are combined. Dofetilide, ranolazine, and a combination of these were administered in 4 incremental dosing regimens to horses with acutely ...
Agreement between Electrocardiogram and Heart Rate Meter Is Low for the Measurement of Heart Rate Variability during Exercise in Young Endurance Horses. Analysis of the heart rate variability (HRV) gains more and more importance in the assessment of training practice and welfare in equine industry. It relies on mathematical analyses of reliably and accurately measured variations in successive inter-beat intervals, measured as RR intervals. Nowadays, the RR intervals can be obtained through two different techniques: a heart rate meter (HRM) or an electrocardiogram (ECG). The agreement and reliability of these devices has not been fully assessed, especially for recordings during exercise. The purpose of this study was to assess the agreement of ...
Right ventricular function during pharmacological and exercise stress testing in horses. The disproportionate rise of pulmonary artery pressure compared to systemic blood pressure during exercise can lead to detrimental right ventricular remodelling in endurance athletes. Horses may act as an extreme model of these athletic cardiovascular adaptations, as they show a three fold increase in pulmonary pressures during exercise. Right ventricular function was examined in ten healthy horses using post-exercise and pharmacological stress echocardiography in a randomised cross-over design. Exercise testing was performed on a treadmill while pharmacological testing was performed using an ...
Expression of various sarcomeric tropomyosin isoforms in equine striated muscles. In order to better understand the training and athletic activity of horses, we must have complete understanding of the isoform diversity of various myofibrillar protein genes like tropomyosin. Tropomyosin (TPM), a coiled-coil dimeric protein, is a component of thin filament in striated muscles. In mammals, four TPM genes (TPM1, TPM2, TPM3, and TPM4) generate a multitude of TPM isoforms via alternate splicing and/or using different promoters. Unfortunately, our knowledge of TPM isoform diversity in the horse is very limited. Hence, we undertook a comprehensive exploratory study of various TPM i...
Estimates of heritability of atrial fibrillation in the Standardbred racehorse. The number of Standardbred racehorses admitted to the Ontario Veterinary College Teaching Hospital (Guelph, Canada) for treatment of atrial fibrillation (AF) has been on the rise since the early 1990s. A small number of sires have been contributing to a large proportion of cases, indicating there may be a genetic predisposition to the arrhythmia in this breed. Objective: The objectives of this study were to determine the heritability of AF in Standardbred horses and whether heritability of the arrhythmia differs across gaits and/or sexes. Methods: Heritability study based on retrospective revi...
Equine Cardiovascular Therapeutics. Heart disease can be defined as any abnormality of the heart whether it is a cardiac dysrhythmia or structural heart disease, either congenital or acquired. Heart failure occurs when a cardiac abnormality results in the inability of the heart to pump enough blood to meet the body's needs. Heart disease can be present without leading to heart failure. Heart failure, however, is a consequence of heart disease. There are 4 main areas where the clinician can intervene to improve cardiac output with heart failure: preload, afterload, myocardial contractility, and heart rate.
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 recurrenc...
Antibodies against Apicomplexa protozoa and absence sarcocysts in heart tissues from horses in southern Brazil. Sarcocystis spp., Neospora spp., and Toxoplasma gondii are Apicomplexa protozoa that can infect horses. This study aimed to investigate the occurrence of antibodies against Sarcocystis spp., Neospora spp., and T. gondii in horses slaughtered in southern Brazil. The presence of histological lesions, tissue cysts, and Sarcocystis spp. DNA in the hearts of these horses was also investigated. A total of 197 paired serum and heart samples were evaluated by serology and direct microscopic examination; 50 of these samples were subjected to histopathological and PCR analyses. Antibodies against at lea...
Third-Degree Atrioventricular Block and Collapse Associated with Eosinophilic Myocarditis in a Horse. Third-degree atrioventricular block (AVB) and primary inflammatory myocarditis are uncommon findings in horses. The horse of this report presented for collapse at rest and was found to have multiple cardiac arrhythmias, most notably 3rd-degree AVB. The horse was subsequently diagnosed with eosinophilic myocarditis on necropsy, a rare form of myocarditis not previously reported in horses. Despite extensive testing, an etiologic agent could not be identified, illustrating the difficulty in identifying a specific cause of myocarditis in horses.
Treatment of supraventricular tachycardia in a horse. To describe the treatment of persistent supraventricular tachycardia (SVT) in a young horse in endurance training. Methods: A 6-year-old Arab gelding in endurance training presented for a dysrhythmia and decreased performance. SVT was diagnosed and conversion to a normal sinus rhythm was achieved following administration of a constant rate infusion of amiodarone. However, reversion to SVT occurred shortly after initiation of ridden exercise. A second attempt to convert the dysrhythmia with amiodarone failed, but normal sinus rhythm was achieved with transvenous electrical cardioversion (TVEC)....
Cardiac findings in Quarter Horses with heritable equine regional dermal asthenia. OBJECTIVE To compare biomechanical and histologic features of heart valves and echocardiographic findings between Quarter Horses with and without heritable equine regional dermal asthenia (HERDA). DESIGN Prospective case-control study. ANIMALS 41 Quarter Horses. PROCEDURES Ultimate tensile strength (UTS) of aortic and mitral valve leaflets was assessed by biomechanical testing in 5 horses with HERDA and 5 horses without HERDA (controls). Histologic evaluation of aortic and mitral valves was performed for 6 HERDA-affected and 3 control horses. Echocardiography was performed in 14 HERDA-affected...
Exercise-Induced Cardiac Remodeling: Lessons from Humans, Horses, and Dogs. Physical activity is dependent upon the cardiovascular system adequately delivering blood to meet the metabolic and thermoregulatory demands of exercise. Animals who regularly exercise therefore require a well-adapted heart to support this delivery. The purpose of this review is to examine cardiac structure, and the potential for exercise-induced cardiac remodeling, in animals that regularly engage in strenuous activity. Specifically, we draw upon the literature that has studied the "athlete's heart" in humans, horses, and dogs, to enable the reader to compare and contrast cardiac remodeling i...
Echocardiographic Assessment of Left Ventricular Function in Healthy Horses and in Horses with Heart Disease Using Pulsed-Wave Tissue Doppler Imaging. Assessment of left ventricular (LV) function by tissue Doppler imaging (TDI) is not well established in horses with heart disease. Objective: To describe the use of pulsed-wave (PW) TDI for the assessment of LV function, establish reference intervals, investigate effects of mitral regurgitation (MR), aortic regurgitation (AR), and primary myocardial disease (MD), and provide proof of concept for the use of PW TDI in Warmblood horses with heart disease. Methods: Thirty healthy horses, 38 horses with MR, 25 with AR, 8 with MD. Methods: Echocardiograms were retrospectively analyzed. Reference int...
Cardiac Mean Electrical Axis in Thoroughbreds-Standardization by the Dubois Lead Positioning System. Different methodologies for electrocardiographic acquisition in horses have been used since the first ECG recordings in equines were reported early in the last century. This study aimed to determine the best ECG electrodes positioning method and the most reliable calculation of mean cardiac axis (MEA) in equines. Methods: We evaluated the electrocardiographic profile of 53 clinically healthy Thoroughbreds, 38 males and 15 females, with ages ranging 2-7 years old, all reared at the São Paulo Jockey Club, in Brazil. Two ECG tracings were recorded from each animal, one using the Dubois lead posi...
Recoarctation After Norwood I Procedure for Hypoplastic Left Heart Syndrome: Impact of Patch Material. The development of recoarctation after the Norwood I procedure is a known complication in patients with hypoplastic left heart syndrome (HLHS). Methods: We reviewed data on 194 consecutive patients with HLHS who underwent the Norwood I procedure between 2000 and 2015. All patients who survived until the second stage of the procedure were included. Recoarctation was defined by the need for intervention, either catheter based or surgical. The aim of our study was to determine if the patch material used for the initial arch reconstruction had an influence on the development of recoarctation. Resu...
The effects of ephedrine on intramuscular blood flow and other cardiopulmonary parameters in halothane-anesthetized ponies. To evaluate the effect of ephedrine on intramuscular blood flow and hemodynamic parameters during equine anesthesia. Methods: Prospective experimental study. Methods: Six healthy adult Welsh Mountain ponies (five males, one female, mean weight: 267 kg, range: 213-347 kg). Methods: Halothane-anesthetized ponies received an IV bolus of ephedrine (0.1 mg kg), followed 30 minutes later by a second IV ephedrine injection (0.2 mg kg). Changes in intramuscular blood flows (IMBF) in upper and lower triceps brachii were measured by laser Doppler flowmetry. Cardiopulmonary measurements were made at inte...
Transcutaneous direct current cardioversion in a foal with lone atrial fibrillation. There are rare published reports of atrial fibrillation (AF) in foals, all of which are associated with structural heart disease or within the adaptive period of newborns. This report describes a 3-month-old Thoroughbred filly with AF and a structurally normal heart on echocardiography. Medical cardioversion of the foal's AF was attempted with three 20mg/kg doses of quinidine sulfate therapy without success. Timed, transcutaneous, direct current cardioversion was successfully performed using adhesive patches on the midthorax in conjunction with intravenous procainamide at a total dose of 20mg/...
Relationships between body dimensions, body weight, age, gender, breed and echocardiographic dimensions in young endurance horses. 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 (...
[Heart disease in sports horses: Current recommendations of the 2014 ACVIM / ECEIM consensus statement]. Heart murmurs and arrhythmias are common in horses. Assessment of their clinical relevance concerning health, performance, safety and longevity of sports horses is of highest importance. A comprehensive cardiovascular examination is crucial for diagnosis and assessment of the severity of disease. Recently, an expert panel of the American College of Veterinary Internal Medicine (ACVIM) and the European College of Equine Internal Medicine (ECEIM) developed a consensus statement containing recommendations for sports horses with heart disease. This article summarizes the most relevant recommendati...
Autopsy imaging for cardiac tamponade in a Thoroughbred foal. Autopsy imaging (Ai), postmortem imaging before necropsy, is used in human forensic medicine. Ai was performed using computed tomography (CT) for a 1-month-old Thoroughbred foal cadaver found in a pasture. CT revealed pericardial effusion, collapse of the aorta, bleeding in the lung lobe, gas in the ventricles and liver parenchyma, and distension of the digestive tract. Rupture in the left auricle was confirmed by necropsy; however, it was not depicted on CT. Therefore, Ai and conventional necropsy are considered to complement each other. The cause of death was determined to be traumatic cardi...
Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables. Echocardiographic assessment of left atrial (LA) size and function in horses is not standardized. Objective: The aim of this study was to establish reference intervals for echocardiographic indices of LA size and function in Warmblood horses and to provide proof of concept for allometric scaling of variables and for the clinical use of area-based indices. Methods: Thirty-one healthy Warmblood horses and 91 Warmblood horses with a primary diagnosis of mitral regurgitation (MR) or aortic regurgitation (AR). Methods: Retrospective study. Echocardiographic indices of LA size and function were meas...
Cardiac and Respiratory Disease in Aged Horses. Respiratory and cardiac diseases are common in older horses. Advancing age is a specific risk factor for cardiac murmurs and these are more likely in males and small horses. Airway inflammation is the most common respiratory diagnosis. Recurrent airway obstruction can lead to irreversible structural change and bronchiectasis; with chronic hypoxia, right heart dysfunction and failure can develop. Valvular heart disease most often affects the aortic and/or the mitral valve. Management of comorbidity is an essential element of the therapeutic approach to cardiac and respiratory disease in older e...
Left Ventricular Function After Prolonged Exercise in Equine Endurance Athletes. Prolonged exercise in human athletes is associated with transient impairment of left ventricular (LV) function, known as cardiac fatigue. Cardiac effects of prolonged exercise in horses remain unknown. Objective: To investigate the effects of prolonged exercise on LV systolic and diastolic function in horses. Methods: Twenty-six horses competing in 120-160Â km endurance rides. Methods: Cross-sectional field study. Echocardiography was performed before and after rides, and the following morning, and included two-dimensional echocardiography, anatomical M-mode, pulsed-wave tissue Doppler imaging...
Analytical validation and establishment of reference intervals for a ‘high-sensitivity’ cardiac troponin-T assay in horses. Cardiac troponin-I assays have been validated in horses.'High-sensitivity' cardiac troponin assays are now the standard in human cardiology. Objective: Appropriately validate the'high-sensitivity' cardiac Troponin-T (hscTnT) assay for clinical use in horses, establish reference intervals, determine the biological variation, and demonstrate assay utility in selected clinical cases. Methods: Analytical validation of the Roche hscTnT assay included within- and between-run precision, linear dose response, limit of quantitation (LoQ), stability, and comparison with cTn-I (iSTAT). Reference interval...
Pulmonary atresia with intact ventricular septum and hypoplastic right ventricle in an Arabian foal. Pulmonary atresia with intact ventricular septum, rudimentary tricuspid valve, hypoplastic right ventricle, and right-to-left atrial shunting were identified in a four-day-old, male Arabian foal with clinical signs of cyanotic heart disease. Pulmonary blood flow was apparently derived from a ductus arteriosus. Echocardiographic evaluation revealed the majority of cardiac abnormalities and also findings compatible with right-sided congestive heart failure. Congenital cardiac defects have a high incidence in this breed, and this is the first description of this combination of congenital cardiac ...
Atrial Premature Depolarization-Induced Changes in QRS and T Wave Morphology on Resting Electrocardiograms in Horses. The electrocardiographic differentiation between atrial (APDs) and ventricular (VPDs) premature depolarizations is important. P wave prematurity and normal QRS and T wave morphology generally are used as discriminating criteria for APDs. Objective: The aim of this study was to determine whether P, Q, R, S, and T wave amplitude, PQ interval, QRS and P wave duration and P and T wave morphology differ between APDs and sinus beats. To determine the relationship between the RR coupling interval and the change in S wave amplitude between sinus beats and APDs. Methods: Case-control study. From a modi...
Effects of Age, Exercise Duration, and Test Conditions on Heart Rate Variability in Young Endurance Horses. Although cardiac recovery is an important criterion for ranking horses in endurance competitions, heart rate variability (HRV) has hardly ever been studied in the context of this equestrian discipline. In the present study, we sought to determine whether HRV is affected by parameters such as age, exercise duration and test site. Accordingly, HRV might be used to select endurance horses with the fastest cardiac recovery. The main objective of the present study was to determine the effects of age, exercise duration, and test site on HRV variables at rest and during exercise and recovery in young...