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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.
[Circulatory and respiratory effects of ketamine in horses anesthetized with halothane]. Ketamine (0.3 mg/kg) administered intravenously to 12 halothane anesthetized horses caused a significant respiratory depression during ten minutes when respiration was spontaneous. Significant hemodynamic effects were not observed except for cardiac index. Clinical application was also discussed. Ketamine (0.3 mg/kg) administered intravenously to 12 halothane anesthetized horses caused a significant respiratory depression during ten minutes when respiration was spontaneous. Significant hemodynamic effects were not observed except for cardiac index. Clinical application was also discussed.
Systemic distribution of blood flow in ponies during 1.45%, 1.96%, and 2.39% end-tidal isoflurane-O2 anesthesia. Effects of 1.1, 1.5, and 1.8 minimal alveolar concentration (MAC) isoflurane-O2 (1.45%, 1.96%, and 2.39% end-tidal isoflurane, respectively) anesthesia on cardiac output, blood pressure, and blood flow to the brain, thyroid glands, adrenal glands, kidneys, and splanchnic organs were examined in 9 healthy isocapnic adult ponies. Tissue blood flows were studied using 15-micron diameter radionuclide-labeled microspheres that were injected into the left ventricle, and comparisons were made with data obtained from ponies in the conscious state. Isoflurane anesthesia caused dose-related reduction in...
Mitral valvular insufficiency associated with ruptured chordae tendineae in three foals. Mitral valvular insufficiency associated with ruptured chordae tendineae was diagnosed in 3 foals with signs of congestive heart failure, which were believed to be secondary to the development of pulmonary hypertension associated with the valvular insufficiency. The septal leaflet of the mitral valve was affected in all 3 foals, and foal 2 also had ruptured chordae tendineae associated with the caudal mitral valve leaflet. Bacterial endocarditis and myocardial necrosis were associated with the ruptured chordae tendineae in foals 3 and 2, respectively. Idiopathic rupture was considered in foal ...
Temporal effects of halothane and isoflurane in laterally recumbent ventilated male horses. Cardiopulmonary function was monitored in 6 non-medicated, healthy male horses, anesthetized with halothane or isoflurane in O2 at a constant dose (1.2 times the minimum alveolar concentration). Horses were exposed once to each anesthetic agent, and a minimum of 2 weeks separated anesthetic exposures. All horses were studied in left lateral recumbency, and ventilation was mechanically controlled to induce a PaCO2 of 35 to 45 mm of Hg and an inspiratory peak airway pressure of 18 to 22 cm of H2O. After 1 hour of horse preparation, constant conditions were begun. With duration of anesthesia, car...
Echocardiographic detection of tricuspid atresia in two foals. M-mode, 2-dimensional, and contrast echocardiographic studies were used to detect tricuspid atresia in 2 foals. M-mode echocardiographic findings included a small right ventricle, large left ventricle, large mitral valve excursion, large left atrium (foal 2), dropout of the cranial aspect of the aortic root, and a thick band of echoes in the tricuspid valve region. These findings were confirmed by 2-dimensional echocardiography. In addition, a large right atrium, persistent foramen ovale, ventricular septal defect, and large mitral valve apparatus were imaged. One foal also had a thick right a...
In vitro calibration and surgical implantation of electromagnetic blood flow transducers for measurement of left coronary blood flow and cardiac output in the pony. Electromagnetic flow transducers were implanted via left thoracotomy in 8 ponies (122.7 to 263.6 kg) around the main pulmonary and left main coronary arteries for continuous measurement of mean and pulsatile blood flow. Flow transducers were calibrated in vitro with a gravity flow system. The mean +/- SE pulmonary flow was 73.1 +/- 5.1 ml/kg of body weight/min. Left coronary flow was 0.95 +/- 0.07 ml/kg/min (1.3% of cardiac output) and was not believed to be an accurate measurement. This was caused by the inability to implant a zero-flow occluder, requiring the use of minimum flow during systo...
Equine endotoxemia: cardiovascular, eicosanoid, hematologic, blood chemical, and plasma enzyme alterations. Ponies with electromagnetic blood flow transducers implanted around the main pulmonary and left main coronary arteries, were used to evaluate effects of chronic sublethal endotoxin on cardiac output (CO), stroke volume, and left coronary blood flow (LCBF). Plasma thromboxane (TX), as indicated by TXB2, prostacyclin as indicated by 6-keto-prostaglandin (PG) F1 alpha, and hematologic and blood chemical values also were evaluated. Over 24 hours, 2 groups of ponies were given progressively increasing IV and intraperitoneal doses of Escherichia coli lipopolysaccharide (LPS) at 0, 6, 12, and 18 hour...
Time-related responses of spontaneously breathing, laterally recumbent horses to prolonged anesthesia with halothane. Cardiovascular and respiratory functions were serially evaluated in ten healthy, fasting, spontaneously breathing, laterally recumbent adult horses during five hours of constant 1.06% alveolar halothane (equivalent to 1.2 times the minimum alveolar concentration for horses). Mean carotid arterial pressure was about 25% higher after one hour of constant-dose halothane than after 30 minutes of constant-dose (P less than 0.05), and remained increased throughout the study. Mean carotid arterial pressure peaked after 90 minutes, and was about 30% higher than at 30 minutes. Total peripheral vascular...
Echocardiographic evaluation of equine aortic insufficiency. Echocardiographic evaluation of 23 horses with aortic insufficiency was performed, using M-mode (n = 23) and 2-dimensional real-time echocardiography (n = 14 of 23). Echocardiograms were evaluated for abnormalities of aortic and mitral valves and alterations in motion of these valves. Changes in left ventricular chamber size and function, as well as aortic root size, were evaluated. The presence of other cardiac disease was also evaluated. Horses with aortic insufficiency had significant increases (P less than 0.01) in mean values of left ventricular chamber size, aortic root diameter, and sho...
Mixed venous oxygen tension as an estimate of cardiac output in anesthetized horses. The relationship between mixed venous O2 tension and cardiac output was studied in six anesthetized horses breathing 100% O2. Cardiac output, O2 consumption, mean arterial pressure, heart rate, and arterial and venous blood gases were measured after administration of xylazine or dobutamine to horses in lateral, sternal, and dorsal recumbencies. After approximately 3 hours, Escherichia coli endotoxin was administered while horses were in dorsal recumbency, and all measurements were repeated. Relationships between cardiac index (CI) and PVO2, heart rate, mean arterial pressure, jugular PVO2, and...
Transmural coronary vasodilator reserve and flow distribution during maximal exercise in normal and splenectomized ponies. 1. Transmural distribution of myocardial blood flow was studied using 15 micron diameter radionuclide-labelled microspheres in six normal ponies and nine splenectomized ponies at rest, and during maximal exercise performed without as well as with adenosine infusion (3 microM kg-1 min-1). The splenectomized ponies were also studied during submaximal exercise performed at 75% of the workload. 2. Maximal exertion in normal ponies increased heart rate (348%), mean arterial blood pressure (40.9%), rate-pressure product (563%), arterial O2 content (43.2%), and mean pulmonary artery pressure (247%). ...
Skeletal muscle perfusion during prolonged 2.03% end-tidal isoflurane-O2 anesthesia in isocapnic ponies. Effects of 1.55 minimum alveolar concentration isoflurane O2 anesthesia (2.03% end-tidal isoflurane) on blood flow in the up-(nondependent) and down-(dependent) positioned skeletal muscles were studied at 60, 120, and 180 minutes in 6 healthy isocapnic ponies in right lateral recumbency on a nonpadded hardwood floor. Measurements were made, using 15-micron diameter radionuclide-labeled microspheres injected into the left ventricle, and comparisons were made with data obtained from ponies in the conscious state. Isoflurane administration caused a sharp reduction in cardiac output and systemic p...
Left ventricular hypertrophy in chronically hypertensive ponies. Systemic arterial hypertension is associated with equine laminitis, a disease precipitated by gross over-ingestion of carbohydrates. We examined the hearts from nine chronically hypertensive (161 +/- 11/99 +/- 6 mmHg) laminitic ponies and nine normotensive (128 +/- 2/76 +/- 3 mmHg) ponies postmortem for signs of left ventricular hypertrophy. The hypertensive ponies had hearts which were significantly larger (7.77 +/- 0.26 g/kg bodyweight (BW) vs. 5.67 +/- 0.22 g/kg BW), as well as increased combined left ventricle and septum weight (4.99 +/- 0.21 g/kg BW vs. 3.67 +/- 0.20 g/kg BW) and left ven...
Cardiovascular effects of intravenous sodium penicillin, sodium cefazolin, and sodium citrate in awake and anesthetized horses. Sodium penicillin, sodium cefazolin, and sodium citrate were administered to six adult horses on separate occasions, when awake and during anesthesia. The order of administration was randomized and studies were separated by a minimum of 7 days. Arterial blood pressure decreased significantly (less than 0.05) from control 5 minutes after intravenous (IV) sodium penicillin in awake and anesthetized horses. Systolic arterial blood pressure remained significantly (less than 0.05) decreased 10 minutes after IV sodium penicillin in anesthetized horses. Sodium cefazolin and sodium citrate did not sig...
Cardiovascular drugs. Their pharmacology and use in horses. Knowledge of the dosage, rate and route of administration, and potential side effects of drugs used to treat cardiac disease in horses has been refined. The judicious use of these drugs can increase exercise capacity, improve health, and potentially prolong life. Currently, antiarrhythmics (quinidine, lidocaine), positive inotropies (digoxin), and diuretics (furosemide) are the primary agents used to treat cardiovascular disease in horses. The development of newer drugs (verapamil, milrinone, bumetanide) and their usefulness in therapy for horses with cardiovascular disease require further inv...
Right atrioventricular atresia and ventricular septal defect in a foal. Right atrioventricular atresia with a ventricular septal defect, a rare congenital cardiac anomaly of either animals or man, was diagnosed in a one week old Arabian foal. The foal had been weak and cyanotic since birth, sometimes becoming dyspneic when stressed. Necropsy revealed a dilated and hypertrophied left ventricle with the right ventricle being small. The right atrioventricular valve was absent. The right and left ventricles communicated via a septal defect which was located immediately adjacent to the aortic valve.
Regional distribution of brain blood flow during maximal exertion in splenectomized ponies. It has been reported in exercising ponies that O2 supply to all regions of the brain increased primarily due to a large increment in CaO2 and it was implied that this may reflect a generalized increase in brain metabolism during strenuous exercise. Splenectomy ameliorates the rise in CaO2 observed with exercise in ponies. Thus, the objective of the present study was to examine changes in regional brain blood flow and O2 supply of splenectomized ponies with sub-maximal and maximal exercise and to compare these data with previous observations in normal ponies. It was reasoned that in the absence...
Isoflurane anesthesia for equine colic surgery. Comparison with halothane anesthesia. Isoflurane was compared with halothane as an anesthetic agent for emergency colic surgery in a series of 38 juvenile and adult horses. After presurgical stabilization with fluids and supportive medications, anesthesia was induced by intravenous xylazine and/or diazepam followed by ketamine. Anesthesia was maintained with isoflurane or halothane in oxygen with controlled ventilation. Heart rates (HR), arterial blood gases, mean arterial pressures (MAP), rate pressure products (RPP), requirements for cardiovascular support medications, and recovery times to standing were compared using nonparame...
Role of carotid chemoreceptors and pulmonary vagal afferents during helium-oxygen breathing in ponies. Our purpose was to assess compensatory breathing responses to airway resistance unloading in ponies. We hypothesized that the carotid bodies and hilar nerve afferents, respectively, sense chemical and mechanical changes caused by unloading, hence carotid body-denervated (CBD) and hilar nerve-denervated ponies (HND) might demonstrate greater ventilatory responses when decreasing resistance. At rest and during treadmill exercise, resistance was transiently reduced approximately 40% in five normal, seven CBD, and five HND ponies by breathing gas of 79% He-21% O2 (He-O2). In all groups at rest, He...
The effect of lateral and dorsal recumbency on cardiopulmonary function in the anaesthetised horse. The effect of lateral and dorsal recumbency on cardiopulmonary function in six anaesthetised horses were compared. Cardiac output/kg, stroke volume/kg, alveolar ventilation, venous admixture, pulmonary shunt and blood-gas values were determined. From lateral to dorsal recumbency cardiac output/kg decreased non-significantly. A significant increase in pulmonary shunt occurred. A positive correlation between body mass and pulmonary shunt in dorsal recumbency was found. Alveolar ventilation increased significantly in dorsal recumbency when breathing air compared to oxygen.
Systemic and centrally mediated angiotensin II effects in the horse. The primary aim of the study was to evaluate the potential value of intravenous (i.v.) infusion of angiotensin II (AII) for phonocardiographic differential diagnosis of equine valvular insufficiency. Ten-minute AII infusions at 4.5-33 pmol kg-1 min-1 induced clear-cut dose-dependent rises in systemic arterial blood pressure (aBP), whereas the pulmonary aBP remained largely unaffected. It implies that i.v. infusion of AII at about 10 pmol kg-1 min-1 could be a valuable tool for the acoustic differentiation between mitral and tricuspid valvular dysfunction in the horse. The infusion at, and abov...
Effects of xylazine on equine intestinal vascular resistance, motility, compliance, and oxygen consumption. Isolated jejunal segments were perfused at a constant blood flow rate to determine simultaneously the effects of xylazine on intestinal vascular resistance, motility, compliance, and oxygen consumption in 12 anesthetized ponies. Xylazine was infused into the artery perfusing the intestinal segment (group 1), or into the jugular vein as a single IV bolus (group 2), or 3 times as IV boluses repeated at 10-minute intervals (group 3). Dose-response curves in group 1 indicated a biphasic response to the drug with vasoconstriction, increased motility, and increased oxygen consumption at lower doses ...
Evaluation for veterinary use of the Chiltern box: a device for home electrocardiographic monitoring. The Chiltern Box is a small electrocardiograph designed for home monitoring of human patients. Its veterinary application has been investigated in the dog, the cat and the horse. It has been useful in the diagnosis of previously undiagnosed dysrhythmias in dogs showing signs of exercise intolerance and syncope.
