Topic:Cardiac
The cardiac system in horses encompasses the heart and associated structures responsible for blood circulation and overall cardiovascular function. Equine cardiac health is essential for maintaining optimal performance and well-being. The equine heart, a muscular organ, pumps oxygenated blood throughout the body, supporting various physiological processes. Common cardiac concerns in horses include arrhythmias, murmurs, and heart failure. Diagnostic tools such as electrocardiography (ECG), echocardiography, and cardiac biomarkers are employed to assess heart function and detect abnormalities. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathology, and diagnostic approaches related to equine cardiac health.
Twenty-four hour continuous transvenous temporary right ventricular pacing in healthy horses. The ability to perform transvenous temporary cardiac pacing (TV-TP) is critical to stabilize horses with symptomatic bradyarrhythmias. Reports of successful TV-TP in horses are limited, and only briefly describe short-term pacing. Objective: To describe temporary, medium-term (24 h) transvenous right ventricular pacing in awake horses using a bipolar torque-directed pacing catheter. Methods: Six healthy adult institutional teaching horses. Methods: Prospective experimental study with 2 immediately successive TV-TP lead placements in each horse with a target location of the RV apex. One place...
Effect of Hypotension and Dobutamine on Gastrointestinal Microcirculations of Healthy, Anesthetized Horses. Horses undergoing abdominal exploratory surgery are at risk of hypotension and hypoperfusion. Normal mean arterial pressure is used as a surrogate for adequate tissue perfusion. However, measures of systemic circulation may not be reflective of microcirculation. This study measured the mean arterial pressure, cardiac index, lactate, and four microcirculatory indices in six healthy, anesthetized adult horses undergoing elective laparotomies. The microcirculatory parameters were measured at three different sites along the gastrointestinal tract (oral mucosa, colonic serosa, and rectal mucosa) wi...
Low-dose sugammadex reverses moderate rocuronium-induced neuromuscular block in horses. Neuromuscular block (NMB) during general anaesthesia has an implicit risk of inadvertent residual NMB during recovery. Reversal of NMB is commonly encouraged to decrease this risk, and has historically been performed with neostigmine/atropine, two agents with important cardiac and gastrointestinal side effects. Sugammadex is a new selective relaxant binding agent that can reverse rocuronium-induced NMB efficiently and without these complications. Recommended doses are possibly cost-prohibitive. Objective: To measure the recovery time from rocuronium-NMB after administration of low-dose sugamma...
Evaluation of the Audicor Acoustic Cardiography Device as a Diagnostic Tool in Horses with Mitral or Aortic Valve Insufficiency. Mitral and aortic valve insufficiencies have been commonly reported in horses. The objective of this study was to establish the use of acoustic cardiography (Audicor®) in horses with aortic (AI) or mitral valve insufficiency (MI). A total of 17 healthy horses, 18 horses with AI, and 28 horses with MI were prospectively included. None of the horses was in heart failure. Echocardiography and Audicor® analyses were conducted. Electromechanical activating time (EMAT), rate-corrected EMATc, left ventricular systolic time (LVST), rate-corrected LVSTc, and intensity and persistence of the third and...
Postmortem magnetic resonance imaging findings of tricuspid atresia with ventricular and atrial septal defects and subvalvular pulmonic stenosis in a Japanese native Noma horse. The necropsy of a 2-day-old Noma horse that died of weakness showed an enlarged cardiac base and a narrow cardiac apex, suggesting cardiac malformation. The excised heart underwent imaging to investigate its luminal structure. On three-dimensional magnetic resonance imaging, the right atrium and right ventricle were discontinuous. The right atrium communicated with the left atrium and the left ventricle communicated with the right ventricle. The lumen narrowed near the pulmonary artery valve. Since the same findings were observed on gross examination, the foal was diagnosed with tricuspid atre...
Effect of physiological and pharmacological stress on heart rate, blood pressure, and echocardiographic measurements in healthy Warmblood horses. Echocardiographic measurements are important prognostic indicators but might be influenced by heart rate and blood pressure. This is particularly important when comparing repeated examinations. Objective: To determine the effect of physiological stress at mildly increased heart rates and pharmacological challenge using IV administration of N-butylscopolammonium bromide and metamizol sodium on heart rate, blood pressure, and echocardiographic measurements. Methods: Twenty healthy Warmblood horses. Methods: Randomized crossover study. Horses were examined echocardiographically by 2-dimensional, ...
Behavioral observations, heart rate and cortisol monitoring in horses following multiple oral administrations of a cannabidiol containing paste (part 2/2). As a remedy against stress and anxiety, cannabidiol (CBD) products are of increasing interest in veterinary medicine. Limited data is available describing the actual effectiveness of CBD in horses. The aim of this study (part 2 of 2) was to analyze stress parameters via behavioral observation, heart rate monitoring and assessment of blood and saliva cortisol levels in healthy horses treated repeatedly with a CBD containing paste. Twelve horses were randomly assigned to a treatment or a control group. Two pastes were orally administered in a double-blinded study design, one paste containing CBD...
Successful caudal vena cava and pulmonary vein isolation in healthy horses using 3D electro-anatomical mapping and a contact force-guided ablation system. Recently, treatment of equine atrial tachycardia by three-dimensional electro-anatomical mapping (3D EAM) and radiofrequency catheter ablation (RFCA) has been described. Myocardial sleeves in the caudal vena cava and pulmonary veins are a potential trigger for initiation and perpetuation of atrial tachycardia and atrial fibrillation in the horse. Isolation of these myocardial sleeves by RFCA may be an effective treatment for these arrhythmias. Objective: To describe the feasibility of 3D EAM and RFCA to isolate caudal vena cava and pulmonary veins in adult horses using 3D mapping and a contact...
Behavioral observations, heart rate and heart rate variability in horses following oral administration of a cannabidiol containing paste in three escalating doses (part 1/2). Cannabidiol (CBD) products have been proposed to exert stress- and anxiety-relieving effects in animals. Despite the increasing popularity of CBD for veterinary use, the available research detailing the effects of CBD in horses is limited. The aim of this study (part 1 of 2) was to analyze stress parameters via behavioral observations and heart rate monitoring in healthy horses following single oral administration of a CBD containing paste in different doses. Study products were two pastes for oral administration, one containing CBD and one containing no active ingredient. Pastes were applied ...
Prolonged hyperinsulinemia increases the production of inflammatory cytokines in equine digital lamellae but not in striated muscle. Hyperinsulinemia is the key feature of equine metabolic syndrome (EMS) which leads to debilitating sequelae. Hyperinsulinemia-associated laminitis (HAL) is one of the major sequelae of EMS, although the pathophysiological mechanisms are not well elucidated. Using an equine model, we hypothesized that expression of inflammatory markers would be increased in digital lamellae and striated muscle following prolonged hyperinsulinemia. Healthy Standardbred horses (5.4 ± 1.9 years) were alternately assigned to a prolonged euglycemic-hyperinsulinemic clamp (pEHC) or control group (n = 4 per group...
Development of a three-dimensional computer model of the equine heart using a polyurethane casting technique and in vivo contrast-enhanced computed tomography. Insight into the three-dimensional (3D) anatomy of the equine heart is essential in veterinary education and to develop minimally invasive intracardiac procedures. The aim was to create a 3D computer model simulating the in vivo anatomy of the adult equine heart. Methods: Ten horses and five ponies. Methods: Ten horses, euthanized for non-cardiovascular reasons, were used for in situ cardiac casting with polyurethane foam and subsequent computed tomography (CT) of the excised heart. In five anaesthetized ponies, a contrast-enhanced electrocardiogram-gated CT protocol was optimized to image th...
Muscarinic acetylcholine receptors M2 are upregulated in the atrioventricular nodal tract in horses with a high burden of second-degree atrioventricular block. Second-degree atrioventricular (AV) block at rest is very common in horses. The underlying molecular mechanisms are unexplored, but commonly attributed to high vagal tone. Unassigned: To assess whether AV block in horses is due to altered expression of the effectors of vagal signalling in the AV node, with specific emphasis on the muscarinic acetylcholine receptor (M) and the G protein-gated inwardly rectifying K (GIRK4) channel that mediates the cardiac current. Unassigned: Eighteen horses with a low burden of second-degree AV block (median 8 block per 20 h, IQR: 32 per 20 h) were assign...
Large animal ventilator-integrated volumetric capnography generates clinically acceptable values of physiologic dead space in anesthetized healthy adult horses. To evaluate the agreement between the Tafonius large animal ventilator-integrated volumetric capnography (vCap) software and the Respironics NICO noninvasive cardiac output monitor reference system. Methods: Data were collected from 56 healthy adult horses undergoing general anesthesia. Methods: Animals were placed under general anesthesia and connected to the Tafonius large animal ventilator circle system. A flow partitioning device with CO2 and flow sensors was utilized to couple the endotracheal tube to the NICO monitor. Tafonius CO2 and flow sensors are incorporated into the Y-piece of the...
Blood-Based Markers for Skeletal and Cardiac Muscle Function in Eventing Horses before and after Cross-Country Rides and How They Are Influenced by Plasma Volume Shift. Horses competing in cross-country tests are subjected to high physical demands. Within the scope of this prospective longitudinal study, blood values of 20 elite eventing horses were examined before and after two- to four-star cross-country rides. The aim was to find out whether blood-based markers for skeletal muscle and cardiac muscle function change after cross-country exercise. Parameters that provide information about fluid balance, muscle enzymes, metabolites and cardiac muscle-specific markers were investigated. We developed an approach to eliminate the concentration changes caused by r...
Effects of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses. Pregnancy affects maternal hemodynamics. The changes in autonomic nervous system activity for hemodynamics adaptation in pregnant horses are still unclear. Thus, this study aimed to examine the effect of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses. Unassigned: A total of 23 Thai native crossbred mares without any cardiac abnormalities were included in this study. The animals were assigned into two groups, a non-pregnant mare group (n =12) and a pregnant mare group (n = 11). Electrocardiogram recordings (paper speed = 25 mm/s and calibrati...
Treatment of a Paroxysmal Atrioventricular Block by Implantation of a Bipolar, Single-Chamber Cardiac Pacemaker in a Donkey. A two-year-old donkey presented with recurrent syncope. Electrocardiography revealed periods without any atrioventricular conduction and without any ventricular escape rhythm with a duration of up to one minute. Finally, atrioventricular conduction resumed spontaneously with a preceding ventricular escape beat. Laboratory tests and echocardiography identified no reversible cause. The diagnosis of a paroxysmal atrioventricular block (PAVB) was made. Therefore, a single-chamber cardiac pacemaker was implanted under general anesthesia. The device was programmed in the VVI mode to prevent further ...
Cardiac Changes after Lactate-Guided Conditioning in Young Purebred Arabian Horses. Cardiac adaptation to conditioning in horses was evaluated after empirical training based on trainers' experience. Twelve purebred Arabian horses, aged (mean ± SD) 28.42 ± 3.75 months, which did not perform any type of exercise prior to the research, were submitted to treadmill conditioning for six weeks. The conditioning program was based on the velocity run by the horse at which the blood lactate concentration, determined in an incremental exercise test (IET), reached 2 mmol/L (V). The velocity at which the blood lactate concentration reached 4 mmol/L (V) was also determined. The echocardi...
Risk of anesthesia-related complications in draft horses: a retrospective, single-center analysis. To report anesthetic-related complications and determine risks associated with anesthesia in draft horses. Methods: Retrospective study. Methods: A total of 401 anesthetic records for draft horse breeds that underwent general anesthesia from January 2010 through December 2020 were reviewed; horses euthanized during general anesthesia were excluded. Methods: Demographics, perioperative drugs used, procedure type and duration, time to extubation, number of attempts to stand, use of sling in recovery and perioperative morbidity and mortality were investigated. Morbidity and mortality statistical ...
Electrical impedance tomography to measure lung ventilation distribution in healthy horses and horses with left-sided cardiac volume overload. Left-sided cardiac volume overload (LCVO) can cause fluid accumulation in lung tissue changing the distribution of ventilation, which can be evaluated by electrical impedance tomography (EIT). Objective: To describe and compare EIT variables in horses with naturally occurring compensated and decompensated LCVO and compare them to a healthy cohort. Methods: Fourteen adult horses, including university teaching horses and clinical cases (healthy: 8; LCVO: 4 compensated, 2 decompensated). Methods: In this prospective cohort study, EIT was used in standing, unsedated horses and analyzed for convent...
Appraising the Welfare of Thoroughbred Racehorses in Training in Queensland, Australia: The Incidence, Risk Factors and Outcomes for Horses after Retirement from Racing. There is international public concern regarding retirement of racehorses, including the reason for retirement and the outcome for horses after racing. However, there are currently no prospective studies investigating these factors. A recent independent inquiry in Queensland, Australia, highlighted that the true outcomes for horses after retirement from racing are largely unknown. Furthermore, there are currently no measures to monitor the outcome for racehorses and their welfare once they have left the care of the trainer. This study investigated these gaps in knowledge through a weekly survey...
The effects of flumazenil on ventilatory and recovery characteristics in horses following midazolam-ketamine induction and isoflurane anaesthesia. Flumazenil antagonises the actions of benzodiazepines. There has been no prior research specifically investigating this anaesthetic reversal agent for horses. Objective: To determine the effects of flumazenil administration in horses on (a) ventilatory parameters after midazolam-ketamine induction and maintenance with isoflurane in oxygen and on (b) the characteristics of recovery from general anaesthesia. Methods: Blinded, randomised, crossover experiment. Methods: Six horses were randomly assigned to receive high-dose flumazenil (F , 20 µg/kg), low-dose flumazenil (F , 10 µg/kg) and sali...
Physical Preparation Strategies of Professional Jockeys. Kiely, M, Warrington, G, McGoldrick, A, and Cullen, S. Physical preparation strategies of professional jockeys. J Strength Cond Res 36(11): 3184-3189, 2022-Professional horse racing is a physically demanding sport. The aim of the study was to examine the physical preparation strategies of jockeys for racing. A questionnaire was developed and validated which comprised of 4 sections; (a) background information, (b) making weight and current associated exercise habits, (c) current physical activity practices, and (d) jockey perceptions of strength and conditioning (S&C) and current practices....
Hypertrophic cardiomyopathy in a Clydesdale gelding. A 7-year-old Clydesdale gelding was referred with a history of progressive lethargy and ventral oedema. The horse developed diarrhoea after treatment with antibiotics by the referring veterinarian. History, clinical signs, imaging and laboratory findings were consistent with hypertrophic cardiomyopathy complicated by antibiotic-associated colitis. Progression of clinical signs prompted euthanasia and the antemortem diagnosis of hypertrophic cardiomyopathy was confirmed at postmortem examination. Conclusions: Primary HCM is reported as rare in horses, but specific descriptions are lacking. The ...
Effect of sotalol on heart rate, QT interval, and atrial fibrillation cycle length in horses with atrial fibrillation. Based on its pharmacokinetic profile and electrophysiological effects in healthy horses, sotalol potentially could be used as a long-term PO antiarrhythmic drug in horses. Objective: To evaluate the effect of sotalol on heart rate (HR), QT interval, atrial fibrillatory rate, and success of cardioversion in horses with naturally occurring chronic atrial fibrillation (AF). Methods: Twenty-eight horses referred for transvenous electrical cardioversion of AF were treated with 2 mg/kg sotalol PO q12h for 3 days before cardioversion, and 13 horses underwent the same protocol without sotalol administ...
Prolonged hyperinsulinemia affects metabolic signal transduction markers in a tissue specific manner. Insulin dysregulation is common in horses although the mechanisms of metabolic dysfunction are poorly understood. We hypothesized that insulin signaling in striated (cardiac and skeletal) muscle and lamellae may be mediated through different receptors as a result of receptor content, and that transcriptional regulation of downstream signal transduction and glucose transport may also differ between tissues sites during hyperinsulinemia. Archived samples from horses treated with a prolonged insulin infusion or a balanced electrolyte solution were used. All treated horses developed marked hyperin...
Sarcocystis fayeri in skeletal muscle of horses with neuromuscular disease. Recent reports of Sarcocystis fayeri-induced toxicity in people consuming horse meat warrant investigation on the prevalence and molecular characterization of Sarcocystis spp. infection in horses. Sarcocysts in skeletal muscle of horses have been commonly regarded as an incidental finding. In this study, we investigated the prevalence of sarcocysts in skeletal muscle of horses with neuromuscular disease. Our findings indicated that S. fayeri infection was common in young mature horses with neuromuscular disease and could be associated with myopathic and neurogenic processes. The number of in...
Risk factors for recurrence of atrial fibrillation in horses after cardioversion to sinus rhythm. Although atrial fibrillation (AF) can be successfully treated in horses, recurrence occurs frequently. In humans, atrial function after cardioversion can predict recurrence. Objective: To examine the prognostic value of atrial mechanical function at 24 hours after cardioversion and other potential predictor variables for AF recurrence in horses. Methods: 117 horses treated for AF at 4 referral centers. Methods: Retrospective study. Inclusion criteria were successful cardioversion, echocardiography at 24 hours after cardioversion and ≥4 months follow-up. To determine factors associated with A...
The influence of age on serum concentrations of cardiac troponin I: results in rats, monkeys, and commercial sera. Cardiac troponins serve as serum biomarkers of myocardial injury. The current study examined the influence of age on serum concentrations of cardiac troponin I (cTnI). An ultrasensitive immunoassay was used to monitor cTnI concentrations in Sprague-Dawley (SD) rats and Erythrocebus patas monkeys of different ages. The mean cTnI concentrations were highest in 10-day-old rats compared to 25-, 40-, and 80-day-old SD rats. Cardiomyocyte remodeling was apparent in hearts from 10-day-old SD rats as evident by hypercellularity, irregularly shaped nuclei, and moderate numbers of myocytes undergoing mi...