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.
Physiologic effects of anesthesia induced and maintained by intravenous administration of a climazolam-ketamine combination in ponies premedicated with acepromazine and xylazine. To examine the physiologic and pharmacokinetic effects of a technique of total intravenous anesthesia in ponies. Methods: 6 healthy ponies. Methods: Ponies were premedicated with acepromazine (0.03 mg/kg of body weight, IV) and xylazine (1.0 mg/kg, IV). Two minutes later, anesthesia was induced with ketamine (2.0 mg/kg, IV) followed by climazolam (0.2 mg/kg, IV). Anesthesia was maintained for 120 minutes by an infusion of climazolam (0.4 mg/kg/h) and ketamine (6.0 mg/kg/h). Oxygen (5 L/min) was supplemented. 20 minutes after the infusion was stopped sarmazenil (0.04 mg/kg, IV) was administered...
[Use of a mix of lidocaine and butorphanol as a caudal epidural anesthesia in a mare]. Loss of rear motor control is the main limiting factor in the use of caudal epidural anesthesia in the horse. In man and laboratory animals, a small dose of an opiate combined with a local anesthetic enhances analgesia without impairing motor function. Thus, the amount of local anesthetic administered may be reduced. Butorphanol is an opiate widely used in horses. It has a good margin of safety and few cardiorespiratory effects. The effects of lidocaine (0.25 mg/kg) and lidocaine-butorphanol (0.25 mg/kg, and 0.04 mg/kg, respectively) were compared in 2 groups of 5 healthy unsedated mares. Hors...
Nitric oxide and exercise in the horse. 1. The effects of exercise on the production rate of nitric oxide (NO) in exhaled air (VNO) and the effects of inhaled NO (80 p.p.m.) on cardiovascular and respiratory parameters were investigated in five Throughbred horses. 2. The concentration of NO ([NO]) in exhaled air collected from within the nasal opening was lower when collected at a high flow rate of 80 l min-1 than at a low flow rate of 20 l min-1: when trotting at 3.7 m s-1 the values were 0.78 +/- 0.15 and 1.23 +/- 9.14 p.p.b., respectively, and when cantering at 9 m s-1 the values were 1.69 +/- 0.31 and 2.25 +/- 0.32 p.p.b., respe...
Pulmonary vascular pressures of strenuously exercising thoroughbreds after administration of phenylbutazone. To determine the effects of phenylbutazone administration on heart rate and right atrial and pulmonary vascular pressures in Thoroughbreds during rest and during exercise performed at maximal heart rate. Methods: 7 healthy, exercise-conditioned Thoroughbreds. Methods: Horses were studied on 3 occasions: without medication [control], after i.v. administration of phenylbutazone (4.4 mg/kg of body weight) at 12-hour intervals for 2 days and a final dose given 1 hour before exercise, and after i.v. administration of phenylbutazone for 2 days in the same manner, but with the final dose given 24 hou...
Comparison of antinociceptive, cardiovascular, and respiratory effects, head ptosis, and position of pelvic limbs in mares after caudal epidural administration of xylazine and detomidine hydrochloride solution. To examine and compare effects of 2 alpha 2-adrenergic receptor agonists, xylazine and detomidine, administered into the sacrococcygeal epidural space to induce safe and effective perineal analgesia on cardiovascular and respiratory functions, head ptosis, and position of pelvic limbs in healthy mares. Methods: 8 healthy mares. Methods: Blood samples were drawn and systemic hemodynamics were determined, including cardiac output and pulmonary arterial, systemic arterial, and right atrial pressures. Two-way ANOVA with repeated measures was used to detect significant (P < 0.05) differences bet...
Minimal redistribution of pulmonary blood flow with exercise in racehorses. We determined the spatial distribution of pulmonary blood flow at rest and during increasing levels of exercise (34, 59, and 90% of maximal oxygen consumption) in Thoroughbred racehorses (n = 4) using 15-microns fluorescent microspheres. After the horses were killed, the lungs were flushed free of blood, removed, air-dried at total lung capacity, and sliced into isogravitational planes, which were sampled in a systematic fashion for three-dimensional reconstruction. The fluorescence was measured for quantification of blood flow. Mean pulmonary blood flow heterogeneity (expressed as a coefficie...
Assessment of autonomic nervous function by power spectral analysis of heart rate variability in the horse. We studied power spectral analysis of heart rate (HR) variability in the horse, with the hypothesis that the quantitative information provided by the spectral analysis of HR variability reflects the interaction between sympathetic and parasympathetic regulatory activities. For this purpose, electrocardiogram, blood pressure (BP) and respiratory (Resp) waveform were simultaneously recorded from Thoroughbred horses (3-5 years old) and analyzed by power spectrum. There were two major spectral components at low-frequency (LF) and high-frequency (HF) bands for HR variability. The peak of Resp varia...
Cardiopulmonary effects of desflurane in ponies, after induction of anaesthesia with xylazine and ketamine. Cardiopulmonary parameters were measured in 12 ponies (small horses) before anaesthesia and, following induction with xylazine and ketamine, during maintenance of anaesthesia with desflurane. In six of the ponies (group A) anaesthesia was maintained for three hours with desflurane at an end-tidal concentration of 7.4 per cent. In the other six ponies (group B), anaesthesia was maintained in the same way for one hour and then the effects of end-tidal desflurane concentrations of 7.4 per cent and 9.6 per cent with and without artificial ventilation were investigated. In group A ponies the arteri...
Cardiorespiratory, endocrine and metabolic changes in ponies undergoing intravenous or inhalation anaesthesia. Six Welsh gelding ponies (weight 246 +/- 6 kg) were premedicated with 0.03 mg/kg of acepromazine intravenously (i.v.) followed by 0.02 mg/kg of detomidine i.v. Anaesthesia was induced with 2 mg/kg of ketamine i.v. Ponies were intubated and lay in left lateral recumbency. On one occasion anaesthesia was maintained for 2 h using 1.2% halothane in oxygen. The same group of ponies were anaesthetized 1 month later using the same induction regime and anaesthesia was maintained with a combination of detomidine, ketamine and guaiphenesin, while the ponies breathed oxygen-enriched air. Electrocardiogra...
Effects of altered FIO2 on maximum VO2 in the horse. Although the horse is considered an elite athlete with a specific VO2max some 2-4 times higher than man, maximal O2 transport is compromised both by moderately severe arterial desaturation and by failure to extract all O2 from blood perfusing exercising muscle. This prompted the present study to ascertain whether correction of arterial desaturation would proportionally augment VO2max and, if so, would O2 extraction behave in a manner predicted by diffusional transport limitation. Six two year old thoroughbreds were exercised to VO2max on a treadmill each on three separate occasions breathing g...
Effects of transporting horses facing either forwards or backwards on their behaviour and heart rate. The effects of transporting horses facing either forwards or backwards were compared by transporting six thoroughbred horses in pairs in a lorry on one journey facing in the direction of travel, and on another journey facing away from the direction of travel, over a standard one-hour route. Heart rate monitors were used to record their heart rate before, during and after the journey and the horses' behaviour was recorded by scan sampling each horse every other minute. The average heart rate was significantly lower (P < 0.05) when the horses were transported facing backwards, and they also t...
Phenylbutazone increases right atrial pressure and heart rate of running horses. The effect of inhibition of cyclooxygenase activity on the hemodynamic response to exertion was examined in 6 horses. Rates of O2 consumption and CO2 production and carotid, pulmonary arterial, and right atrial pressures were measured while the horses performed a standardized exercise test on a treadmill after treatment with phenylbutazone or a placebo. Phenylbutazone (8.8 mg/kg p.o. for 2 days and 4.4 mg/kg i.v. 60 min before exertion) abolished the exertion-induced increases in plasma 6-ketoprostaglandin F1 alpha and thromboxane B2 concentrations, confirming inhibition of cyclooxygenase acti...
Adaptations to daily exercise in hot and humid ambient conditions in trained thoroughbred horses. The objectives of this study were to: 1) determine the effects of heat and high relative humidity (RH) on the clinical and physiological responses of horses during and after daily exercise training and 2) determine whether repeated exposure to, and exercise in, the heat would result in improved thermal tolerance (heat acclimation). Six trained Thoroughbred horses completed 1 h of submaximal exercise in cool, dry conditions (CD) and during a daily 4 h period of exposure to high heat and humidity (HH, room temperature = 33-35 degrees C, RH = 80-85%) for 22 days. Rectal temperature (Tre) and hear...
Redistribution of cardiac output in response to heat exposure in the pony. Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues in 4 ponies at rest in thermoneutral (16 degrees C/60% RH) and mildly hot (41 degrees C/34% RH) environments. In response to heat stress there were increases in cardiac output (2-fold), respiratory frequency (5-fold), blood flow to the skin of the body (3-fold), and limbs (50%), respiratory muscles (2-fold) and the upper respiratory tract (3-fold). Ponies were able to maintain body temperature in the hot environment by increasing blood flow to the tissues involved in heat dissipation, while blood ...
Equine coronary hemodynamics during brief coronary occlusions at three levels of collateral function. Adult-grade ponies were surgically instrumented with a Doppler flow probe and pneumatic cuff occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium, anterior interventricular vein, and, in some animals, the LAD. Conscious-animal studies were begun 2 wk after surgery. Measured variables included regional left ventricular systolic function, end-diastolic wall thickness, oxygen extraction, lactate extraction, and hydrogen ion release. Changes in collateral perfusion were de...
Laparoscopic anatomy of the abdomen in dorsally recumbent horses. To provide an accurate and detailed description of the laparoscopic anatomy of the abdomen of horses positioned in dorsal recumbency and to compare those observations with laparoscopic anatomy of standing horses. The effects of laparoscopy and positional changes on arterial blood pressure and blood gas values also were investigated. Methods: Descriptive anatomic study. Methods: Laparoscopy was performed on 6 horses (2 mares, 2 geldings, and 2 stallions) to record the normal laparoscopic anatomy of the abdomen in dorsal recumbency. Methods: Feed was withheld from all horses for 36 hours. Horses...
Pulmonary capillary pressure during exercise in horses. The object of this study was to relate pulmonary capillary pressure to arterial and wedge pressures during exercise. Pulmonary vascular pressures were measured in six standardbred horses exercising at speeds equivalent to 75, 90, and 100% of maximal heart rate. Vascular pressures were measured with transducer-tip catheters and expressed relative to esophageal pressure. Pulmonary capillary pressure was estimated by the arterial-occlusion technique modified for exercise. Mean pulmonary arterial, capillary and wedge pressures increased from 30.5 +/- 6.3, 17.8 +/- 4.3, and 13.4 +/- 1.6 mmHg, respe...
Cardiopulmonary effects of medetomidine in sheep and in ponies. Medetomidine was administered intravenously to six sheep at 5, 10 and 20 micrograms kg-1 and to one horse and four ponies at 5 and 10 micrograms kg-1. In both species medetomidine resulted in significant decreases in heart rate and cardiac output and, initially, in an increase in arterial blood pressure. In the ponies this increase in blood pressure was followed by a significant and prolonged decrease, but in the sheep the secondary decrease in blood pressure was not statistically significant. In the sheep, the three doses of medetomidine resulted in profound and significant decreases in arter...
Evaluation of propofol for general anesthesia in premedicated horses. To evaluate selected hemodynamic, respiratory, and behavioral responses to propofol in horses premedicated with xylazine or detomidine. Methods: Xylazine (0.5 and 1.0 mg/kg of body weight) was administered IV on different days to each of 6 horses prior to IV administration of propofol (2 mg/kg). In a second group of 6 horses, detomidine (15 and 30 micrograms/kg) was similarly studied. Methods: 2 groups of 6 mature healthy horses. Methods: Rectal temperature, heart and respiratory rates, arterial blood gas tensions, and direct arterial blood pressures were recorded before and at fixed intervals...
[Oximetry in veterinary anesthesia: the continuous determination of mixed venous oxygen saturation in dogs and horses]. The continuous fiberoptical measurement of the mixed venous partial oxygen saturation is described. It is an enrichment of the diagnostical possibilities in veterinary medicine. In the horse it is of great interest, because disturbances of the pulmonary gas exchange and the myocardial function are common in the anaesthetised horse, and reliable methods of assessing the cardiac output are rare. Using this monitoring technique in nearly 100 equine high risk patients facilitated insight into the complex changes of the pulmonary, cardiac and circulatory function in the anaesthetised horse. The reg...
Effects of inhalation anesthetic agents on response of horses to three hours of hypoxemia. To study the effects of inhalation anesthetic agents on the response of horses to 3 hours of hypoxemia. Methods: Controlled crossover study. Methods: Five healthy adult horses. Methods: Horses were anesthetized twice: once with halothane, and once with isoflurane in O2. Anesthetized horses were positioned in left lateral recumbency. Constant conditions for the study began at 2 hours of anesthesia. A constant agent dose of 1.2 minimum alveolar concentration, PaO2 of 50 +/- 5 mm of Hg, and PaCO2 of 45 +/- 5 mm of Hg were maintained for 3 hours. Circulatory measurements were made at 0.5, 1, 2, an...
Computerized ECG recording in horses during a standardized exercise test. In the horse, it is important to make a reliable ECG recording during exercise as cardiac arrhythmia is one of the possible causes of poor performance. The purpose of the present study was to obtain a satisfactory, standardized method for ECG recording by computer during a standardized treadmill exercise test and to evaluate the procedure both in healthy and in diseased horses. Ten experienced healthy research horses were used to develop and adapt the original method (for humans) of computerized ECG recording with the Cardio Perfect software program and to obtain reference values for heart rat...
Cardiovascular and pulmonary effects of sevoflurane anesthesia in horses. The effects of 1.0, 1.5, and 2.0 minimum alveolar concentration (MAC) of sevoflurane on hemodynamic, pulmonary and blood chemistry variables were measured during spontaneous and controlled ventilation in healthy horses. Sevoflurane was the only anesthetic drug administered to the horses. In a dose-dependent manner, sevoflurane significantly decreased (P < .05) mean arterial blood pressure, cardiac output, and stroke volume. There was a progressive decrease in peripheral vascular resistance and an increase in heart rate as the concentration of sevoflurane was increased, but the differences w...
Analgesic, hemodynamic, and respiratory effects of caudal epidurally administered xylazine hydrochloride solution in mares. To examine effects of 0.25 mg of xylazine/kg of body weight diluted to a total volume of 6 ml/450 kg with sterile 0.9% NaCl, administered into the epidural space of the sacrococcygeal joint on perineal analgesia, sedation, ataxia, and respiratory and cardiovascular function in standing mares. Methods: Randomized, blinded study, using xylazine (treatment) and 0.9% NaCl (controls). At least 2 weeks elapsed between the treatments. Methods: Eight healthy mares. Methods: Blood samples were drawn. Systemic hemodynamics were determined, including cardiac output and pulmonary arterial, systemic arteri...
Evaluation of five common induction protocols by comparison of hemodynamic responses to surgical manipulation in halothane-anesthetized horses. To determine whether hemodynamic responses of halothane-anesthetized horses undergoing surgical procedures depended on anesthetic induction protocols used, and to determine whether hemodynamic responses to surgical manipulation could be detected. Methods: Prospective experimental study without controls. Methods: 36 clinically normal horses. Methods: Horses were allotted to 5 groups according to anesthetic induction protocol: acepromazine/guaifenesin/thiamylal, acepromazine/guaifenesin/ketamine, xylazine/guaifenesin/thiamylal, xylazine/guaifenesin/ketamine, and xylazine/diazepam/ketamine. Anest...
Multiple congenital cardiac anomalies and idiopathic thoracic aortitis in a horse. An echocardiographical and clinical pathological investigation of the rapid loss of weight by a yearling thoroughbred filly revealed an atrial septal defect, a ventricular septal defect and hyperfibrinogenaemia. A post mortem examination confirmed the cardiac abnormalities and revealed a severe thoracic aortitis. It is proposed that the idiopathic thoracic aortitis contributed to the horse's compromised cardiovascular homoeostasis.