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Topic:Cardiovascular Health
Cardiovascular health in horses encompasses the study of the heart and blood vessels, focusing on their structure, function, and associated disorders. The equine cardiovascular system is responsible for the circulation of blood, delivering oxygen and nutrients to tissues, and removing waste products. Research in this area includes the examination of cardiac anatomy, the electrophysiology of the heart, and common cardiovascular conditions such as arrhythmias, valvular diseases, and heart murmurs. Diagnostic tools such as echocardiography, electrocardiography, and cardiac biomarkers are utilized to assess cardiovascular function and detect abnormalities. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological mechanisms, diagnostic approaches, and therapeutic strategies related to cardiovascular health in horses.
Immediate and persistent complete heart block following a horse kick. Nonpenetrating chest trauma has been reported to cause acute and transient disorders of impulse formation and propagation, including intraventricular conduction delay and heart block. We report a case of immediate and sustained complete heart block following blunt chest injury.
Detomidine-propofol anesthesia for abdominal surgery in horses. To evaluate propofol for induction and maintenance of anesthesia, after detomidine premedication, in horses undergoing abdominal surgery for creation of an experimental intestinal adhesion model. Methods: Prospective study. Methods: Twelve horses (424 +/- 81 kg) from 1 to 20 years of age (5 females, 7 males). Methods: Horses were premedicated with detomidine (0.015 mg/kg i.v.) 20 to 25 minutes before induction, and a propofol bolus (2 mg/kg i.v.) was administered for induction. Propofol infusion (0.2 mg/kg/min i.v.) was used to maintain anesthesia. The infusion rate was adjusted to maintain an...
Dissecting aortic aneurysm in a horse. A case of dissecting aortic aneurysm in a 4-year-old male thoroughbred horse is reported. The horse had a history of inflammation in the right thigh and a fever 2 weeks before sudden death. At necropsy, aortic aneurysms were observed from the aortic valve to the aortic arch, spreading over a distance of 40 cm. An irregular rupture of the intima of the ascending aorta was located in the cardiac side of a ramification to the tunica branchiocephalicus communis. An intramural haematoma, apparent on the cut surface and in the pericardium, had caused cardiac tamponade and sudden death.
Effects of extrathoracic airway obstruction on intrathoracic pressure and pulmonary artery pressure in exercising horses. To determine whether dorsal displacement of the soft palate (DDSP) results in pulmonary artery hypertension and leads to increases in transmural pulmonary artery pressure (TPAP); to determine whether pulmonary hypertension can be prevented by prior administration of furosemide; and to determine whether tracheostomy reduces pulmonary hypertension. Methods: 7 healthy horses. Methods: Horses were subjected to 3 conditions (control conditions, conditions after induction of DDSP, and conditions after tracheostomy). Horses were evaluated during exercise after being given saline (0.9% NaCl) solution ...
Metabolic effects of nitric oxide synthase inhibition during exercise in the horse. The effect of nitric oxide synthase (NOS) inhibition during exercise on lactate production was investigated in five Thoroughbred horses. A standard exercise test (SET), consisting of three canters (approximately 55 per cent VO2max), with walking and trotting between each canter, was performed twice (control and test, in random order) by each horse. Nphi-nitro-L-arginine methyl ester (L-NAME; 20 mg kg-1), a competitive inhibitor of NOS, induced a significant increase (P < 0.05) in plasma lactate [5.7 (2.9) vs 11.8 (3.8) mmol L-1], which continued to increase despite administration of L-argin...
Field exercise testing for assessing fitness in French standardbred trotters. This review considers standardized exercise testing which is, routinely used for French Trotters in the field. Track testing provides a more limited range of measurements than treadmill testing, but has the advantage of being performed in the horse's natural environment. Various measurements such as heart rate during exercise and blood lactate concentration after exercise may be measured on the track and lead to the calculation of physiological variables such as V200 (velocity corresponding to a 200 bpm heart rate) and V4 (velocity corresponding to a 4 mmol/L blood lactate concentration). V4 i...
V(O2) recovery kinetics in the horse following moderate, heavy, and severe exercise. At the onset of exercise, horses exhibit O2 uptake (VO2) kinetics that are qualitatively similar to those of humans. In humans, there is a marked dissymmetry between on- and off-kinetics for VO2. This investigation sought to formally characterize the off-transient (recovery) VO2 kinetics in the horse within the moderate (M), heavy (H), and severe (S) exercise domains. Six horses were run on a high-speed treadmill at M, H, and S exercise intensities (i.e., that speed which yielded approximately 50, 85, 100% peak VO2, respectively, on the maximal incremental test). The time courses for the recov...
Effects of hypoxia on endocrine and metabolic responses to anaesthesia in ponies. Some metabolic and endocrine effects of hypoxaemia were studied during halothane anaesthesia in six ponies. Each was anaesthetised twice; on one occasion a 20-minute period of hypoxaemia (arterial oxygen tension between 4.4 and 5.8 [mean 5.3] kPa) was imposed during 120 minutes of anaesthesia. On the second occasion arterial oxygen tension was maintained above 17 kPa throughout. Routine cardiovascular monitoring was performed and blood samples were taken to measure haematocrit, cortisol, insulin, glucose and lactate. Anaesthesia was associated with hypotension in both groups (mean ABP 7.0 kPa...
Locomotor, cardiocirculatory and metabolic adaptations to training in Andalusian and Anglo-Arabian horses. The effects of two training programmes in 20 Andalusian and 12 Anglo-Arabian horses were evaluated by an increasing intensity work test at velocities of 4, 5, 6, 7 and 8 m sec(-1). Heart rate was monitored and blood samples were drawn at rest and after each velocity to analyse packed cell volume, haemoglobin concentration, plasma lactate and potassium levels. Furthermore, the programmes were video-taped and stride length, duration and frequency, stance (restraint and propulsion), swing phase durations and stride vertical component were measured. The training protocol of the Andalusian horses p...
Cardiovascular and metabolic adaptations in horses competing in cross-country events. The cardiovascular and metabolic response to two cross-country events (CC*: preliminary level and CC*** advanced level) were analysed in 8 male eventing horses (4 Anglo-Hunter and 4 Anglo-Arabian). This study focused on the establishment of the main metabolic pathways involved in the muscle energy resynthesis during the competitions. Heart rate (HR) was recorded throughout the CC events. Jugular venous blood samples were withdrawn before the warm-up period, immediately after the competitions and at 5 and 10 min in the recuperation period. The following haematological parameters were studied: r...
Effects of inhaled dry powder ipratropium bromide on recovery from exercise of horses with COPD. The present study evaluated ventilatory, cardiovascular and metabolic parameters during recovery from strenuous exercise in horses suffering from a crisis of chronic obstructive pulmonary disease (COPD) and to determine whether ipratropium dry powder inhalation (DPI) before exercise has an effect on these parameters. When 6 saddle horses, affected with COPD, developed airway obstruction, they inhaled placebo and ipratropium (2400 microg/horse), the order being randomly chosen. Pulmonary function tests were then recorded 15 min after inhalation. Following these tests, the horses underwent a str...
Effects of intravenously administered glycopyrrolate in anesthetized horses. The purpose of this study was to determine the heart rate (HR) and blood pressure (BP) effect of glycopyrrolate in anesthetized horses with low HR ( 5 beats/min within 10 min), glycopyrrolate (same dose) was administered. Heart rate increased by > 5 beats/min in 3 out of 9 horses following the initial glycopyrrolate treatment. Overall changes in HR and mean BP were not significantly different, while systolic and diastolic BP increased significantly (P 5 beats/min, which was significant. A significant increase in BP was produced following treatment with 2.5 micrograms/kg BW, but not followi...
Hemodynamic effects of thyroidectomy in sedentary horses. To investigate hemodynamic effects of thyroidectomy in horses at rest. Methods: 6 healthy aged Quarter Horse mares. Methods: Horses were monitored for 5 months before and 4 weeks after thyroidectomy and for an additional 4 weeks after administration of thyroid hormone supplement (2.5 microg of thyroxine/kg of body weight, PO, q 12 h, and 0.6 microg of triiodothyronine/kg, PO, q 12 h). Responses to thyroid-stimulating hormone (TSH) were measured before and 4 weeks after thyroidectomy. Other variables monitored daily were resting rectal temperature (T), heart rate (HR), respiratory rate (RR), an...
The cardiopulmonary effects of clenbuterol when administered to dorsally recumbent halothane-anaesthetised ponies–failure to increase arterial oxygenation. Clenbuterol (0.8 microg kg(-1) intravenously) was investigated in ponies (small horses) anaesthetised with acepromazine, detomidine and thiopentone, then halothane in oxygen alone (hyperoxic group) or with nitrous oxide (hypoxic group). Following instrumentation, ponies were placed in dorsal recumbency for 60 minutes, clenbuterol (both groups) or a saline control (hyperoxic group) given, and cardiopulmonary parameters monitored for a further 60 minutes. In the hyperoxic group, clenbuterol administration resulted in a transitory (<five minutes) 15 per cent fall in arterial blood pressure and...
Effects on the intramuscular blood flow and cardiopulmonary function of anaesthetised ponies of changing from halothane to isoflurane maintenance and vice versa. The effects on intramuscular blood flow and cardiopulmonary parameters of changing from anaesthesia with halothane to isoflurane and vice versa were investigated in six ponies (small horses). Anaesthesia was induced with xylazine, ketamine and diazepam, maintained for one hour with halothane at an end tidal concentration of 1 per cent and then with isoflurane at 1.5 per cent for a further hour (halo/iso). On another occasion the order in which the volatile agents were administered was reversed (iso/halo). After one hour of anaesthesia the mean (sd) arterial blood pressure (MAP) and cardiac out...
Effect of regular training on the myocardial and plasma concentrations of taurine and alpha-amino acids in thoroughbred horses. Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 +/- 1.2 mumol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 +/- 0.9 and 7.7 +/- 0.69 mumol/g wet weight for glutam...
Characterisation of the cardiovascular pharmacology of medetomidine in the horse and sheep. Medetomidine was administered to sheep and horses at a dose rate of 5 microg kg(-1) (i.v.). Heart rate and blood pressure were recorded. Medetomidine induced bradycardia and a biphasic blood pressure response consisting of a transient hypertension followed by hypotension. Administration of prazosin (an alpha1 adrenoceptor antagonist; 100 microg kg(-1), i.v.) had no effect on the cardiovascular response to medetomidine (5 microg kg(-1), i.v.), but inhibited the cardiovascular response of methoxamine (an alpha1 adrenoceptor agonist; 75 microg kg(-1), i.v.). L-659,066 (an alpha2 adrenoceptor anta...
Intensity-dependent effects of acute submaximal exercise on the pharmacokinetics of bromsulphalein in horses. To determine the effects of acute exercise on hepatic blood flow by studying hepatic clearance of bromsulphalein for several submaximal exercise intensities. Methods: 8 adult Standardbred mares. Methods: Horses were subjected to 4 submaximal exercise intensities (resting and 40, 60, and 80% maximal oxygen consumption). After horses had been running at the required treadmill speed for 1 minute, bromsulphalein (BSP; 5 mg/kg of body weight, IV) was administered during a 45- to 60-second period, and horses continued at the desired speed for an additional 15 minutes. Blood samples were collected at...
Effects of dopamine, dobutamine, dopexamine, phenylephrine, and saline solution on intramuscular blood flow and other cardiopulmonary variables in halothane-anesthetized ponies. To evaluate the effect on intramuscular blood flow (IMBF) and hemodynamic variables of 4 antihypotensive agents given during anesthesia. Methods: 8 ponies. Methods: Halothane-anesthetized ponies (n = 6) positioned in lateral recumbency received, on separate occasions, infusions of each of the following 4 agents in serially increasing dosages or saline solution: phenylephrine hydrochloride (0.25, 0.5, 1, and 2 microg/kg of body weight), dopamine (2.5, 5, 10, and 20 microg/kg), dobutamine (1, 2.5, 5, and 10 microg/kg), and dopexamine (0.5, 1, 5, and 10 microg/kg). Changes in IMBF (by laser-Doppl...
Hepatic blood flow in horses during the recuperative period from maximal exercise. To determine effects of walking or standing on hepatic blood flow of horses after brief, intense exercise. Methods: 6 adult Thoroughbreds (4 mares, 2 geldings). Methods: Horses were preconditioned on a treadmill to establish uniform level of fitness. Once fit, treadmill speed causing each horse to exercise at 120% of maximal oxygen consumption was determined and used in simulated races at 14-day intervals. In a three-way crossover study, horses were exercised at a speed inducing 120% of maximal oxygen consumption until fatigued or for a maximum of 2 minutes. Three interventions were studied: r...
Comparison of two techniques for total intravenous anesthesia in horses. To characterize responses associated with two 1-hour total intravenous anesthesia techniques in horses. Methods: 6 mature, healthy mares. Methods: Each horse was anesthetized 3 times. Treatment order was determined by a series of Latin squares. After baseline measurements and instrumentation, horses were given xylazine (XYL) i.v.; anesthesia was induced 5 minutes later with 10% guaifenesin given i.v., then either ketamine (KET) or propofol (PRO) was given i.v. After anesthesia induction, each horse received an infusion of XYL and either KET or a low or high dose of PRO. Cardiopulmonary variabl...
Effects of buprenorphine on cardiovascular and pulmonary function in clinically normal horses and horses with chronic obstructive pulmonary disease. To evaluate the cardiovascular and respiratory effects of buprenorphine administered intravenously in clinically normal horses and horses with chronic obstructive pulmonary disease (COPD). Methods: 5 clinically normal horses and 5 horses with COPD that were in partial clinical remission (period A) or were having an acute attack of airway obstruction (period B). Methods: Pulmonary function testing, arterial blood gas analysis, and arterial blood pressure measurements were performed before and after a single intravenous bolus of buprenorphine (3 microg/kg of body weight). Respiratory rate (f), t...
Shear-induced platelet activation and platelet-neutrophil aggregate formation by equine platelets. To determine whether platelets become activated and form platelet-platelet or platelet-neutrophil aggregates, or both, when subjected to shear. Methods: Blood obtained from 3 Thoroughbreds. Methods: Blood, with PCV adjusted to 32 (low hematocrit) or 60 (high hematocrit)%, was subjected to shear rates of 11.25, 22.5, 45, 90, 225, and 750/s for 3 minutes by use of a cone-plate viscometer. Flow cytometric techniques were used to identify activated platelets, platelet-platelet aggregates, and platelet-neutrophil aggregates. Results: Shear resulted in decreased platelet count, increased mean platel...
Effects of hypercapnia on endocrine and metabolic responses to anaesthesia in ponies. Some metabolic and endocrine effects of hypercapnia were studied in six ponies during halothane anaesthesia with neuromuscular blockade and controlled ventilation. Each was anaesthetised twice, once with a 40-minute-period of hypercapnia (10 kPa) and once when normocapnia (5.3 kPa) was maintained throughout two hour's anaesthesia. Routine cardiovascular monitoring was performed and blood samples were taken for assay of cortisol, insulin, glucose, lactate, muscle and liver enzymes and total protein. Anaesthesia induced hypotension and lacticacidaemia which were slightly ameliorated during hyper...
Blood-gas measurements adjusted for temperature at three sites during incremental exercise in the horse. Rectal temperature (Tre) is often used to adjust measurements of blood gases, but these adjusted measurements may not approximate temperatures during intense exercise at main sites of gas exchange: muscle and lung. To evaluate differences in blood gases between sites, temperatures (T) were measured with thermocouples in the rectum (re), in mixed venous blood (v), in gluteal muscle (mu), and on the skin (sk) in seven Arabian horses as they underwent an incremental exercise test on a treadmill. Blood samples were drawn from the carotid artery and pulmonary artery (mixed venous) 30 s before each ...
Temporal effects of an infusion of dobutamine hydrochloride in horses anesthetized with halothane. To evaluate temporal hemodynamic effects of dobutamine in horses anesthetized with halothane. Methods: 8 adult Thoroughbreds. Methods: Anesthesia was induced by i.v. administration of romifidine and ketamine and maintained using halothane in oxygen. After 60 minutes, dobutamine was administered i.v. for 60 minutes at 4 micrograms/kg of body weight/min. Measurements of left ventricular function were obtained by transesophageal echocardiography and cardiac catheterization. Results: Mean, systolic, diastolic, aortic, pulmonary arterial, and left and right ventricular end-diastolic and systolic pr...
Cardiovascular effects of surgical castration during anaesthesia maintained with halothane or infusion of detomidine, ketamine and guaifenesin in ponies. Sixteen colts were premedicated with acepromazine and anaesthesia was induced with detomidine and ketamine. Ponies were randomly allocated to receive halothane (HAL) or infusion of detomidine, ketamine and guaiphenesin (DKG) to maintain anaesthesia. Heart and respiratory rate, ECG, mean arterial blood pressure (MABP), cardiac index (CI), blood gases and plasma cortisol, ketamine and guaiphenesin were measured. Surgical castration took place between 45 and 75 min and anaesthesia lasted 90 min. MABP with DKG was significantly higher than with HAL, and, with HAL, MABP increased from pre-surgery (...
Haemodynamic effects of a sixty minute infusion of dopamine hydrochloride in horses anaesthetised with halothane. To describe the haemodynamic effects of a 60 min infusion of dopamine 4 microg/kg bwt/min during halothane anaesthesia, 7 mature Thoroughbred horses were studied. The infusion began 1 h after induction of anaesthesia by romifidine (100 microg/kg) and ketamine (2.2 mg/kg bwt). Throughout the period of dopamine infusion and for 30 min after its discontinuation, the horses were ventilated by intermittent positive pressure to maintain PaCO2 between 4.6-5.4 KPa. Inspired halothane concentration was adjusted to maintain an end tidal halothane concentration of 0.9%. Haemodynamic variables were measur...
Glomerular filtration rate, effective renal plasma flow, blood pressure and pulse rate in the equine neonate during the first 10 days post partum. The aim of this study was to determine glomerular filtration rate (GFR), effective renal plasma flow (RPF) and filtration fraction (FF) values in Pony foals during the first 10 days post partum in order to assess any age-related changes and the reliability of the single injection inulin/p-aminohippurate (PAH) method. Arterial blood pressure and pulse rate were determined in Pony and Thoroughbred (TB) foals during the first 10 days post partum to establish age-related changes, differences between breeds and possible interrelationships with GFR and RPF. Inulin and PAH were injected intravenously...
