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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.
Diagnostic value of contrast echocardiography in the horse. M-mode echocardiography is a safe and practical means of using ultrasound to evaluate the dynamic movements of cardiac structures. The technique can be refined by using a simple contrast medium in the form of carbon dioxide mixed with heparinised blood to provide a strong echogenic result. This technique was employed in a series of 15 normal conscious standing horses and in three animals with specific cardiac defects. In the clinical cases it was possible to confirm the diagnosis and differentiate between a congenital septal defect and mitral regurgitation. The method was found to be safe and ...
Cardiovascular and respiratory effects of acetylpromazine and xylazine on halothane-anesthetized horses. Circulatory and respiratory effects of intravenously administered acetylpromazine (0.033 and 0.067 mg/kg) and xylazine (0.5 and 1.0 mg/kg) were studied in drug cross-over fashion in eight laterally recumbent horses anesthetized only with halothane (1.06%, end-tidal) in O2. Both doses of acetylpromazine caused a significant and sustained elevation in cardiac output via a rise in stroke volume. Xylazine produced an initial significant fall in cardiac output followed by a return to control levels. Halothane anesthesia did not prevent xylazine-related atrioventricular conduction block. All treatme...
A hemodynamic model for anaphylactic shock. The treatment of cardiovascular collapse and anaphylactic shock is largely empiric. A simple animal model was developed to evaluate the hemodynamic alterations in anaphylaxis. Eight adult New Zealand white rabbits of both sexes were studied. All animals weighed 3.8 kg to 5.3 kg. Sensitization was accomplished with a 2-mL subcutaneous dose of horse serum followed in two days with a 2-mL intravenous (IV) dose. At least 14 days elapsed after the IV dose before a 1-mL challenge dose of horse serum was given. On the day of the challenge dose, a femoral arterial catheter, arterial temperature probe,...
Comparison of echocardiographic and autopsy measurements of cardiac dimensions in the horse. This study was initiated to determine the accuracy of M-mode echocardiography in measuring left ventricular dimensions and estimating heart weights in horses. Left ventricular free wall and interventricular septal thickness and left ventricular external and internal diameters were measured and heart weights estimated from the echocardiograms of 47 horses. Autopsy measurements of the same parameters were then recorded. Statistical comparison of the data demonstrated: (1) Systolic measurements of wall thickness more closely resembled the heart in death than the diastolic measurements; (2) good c...
Echocardiography. Diagnostic ultrasound permits the clinician to image the beating heart, quantitate cardiac dimensions, identify specific congenital and acquired cardiac lesions, and estimate the degree of cardiac compensation and muscle failure that accompanies a specific lesion. The M-mode (motion) echocardiogram and two-dimensional echocardiogram are complementary studies that have proved useful for identification of cardiac septal defects, endocarditis, pericardial effusion, intracardiac shunting, cardiomegaly, and heart muscle failure. Appreciation of the technique and basic knowledge of the types of info...
Diagnostic radiology and nuclear cardiology. Their use in assessment of equine cardiovascular disease. Survey thoracic radiography, although limited by physical considerations in the adult horse, can supply clinically useful information about changes in cardiac size and function. The radiographic features of cardiomegaly, altered pulmonary circulation, pulmonary edema, and pleural effusion as manifested in the horse are discussed. Nuclear cardiology can be performed in the standing horse. The initial transit of a radioactive tracer through the central circulation provides information about cardiac chamber size, efficiency of ventricular contraction, valvular competence, and presence of intracar...
Evaluation of the equine cardiovascular system. A thorough examination of the cardiovascular system is an integral part of a physical examination in the horse. The normal equine cardiovascular parameters are discussed, with an emphasis on auscultatory findings. The availability and application of other diagnostic techniques are discussed based upon findings of the physical examination.
Equine heart disease. An overview. The clinician must appreciate unique aspects of equine cardiovascular physiology in order to distinguish normal variation from a pathophysiologic state. Cardiovascular problems in the horse include auscultation of cardiac murmurs, identification of cardiac arrhythmias, and recognition of congestive heart failure. A cardiac data base including history, general and cardiovascular examination, and resting and postexercise electrocardiogram are necessary to evaluate most horses for significant heart disease. Additional studies, such as echocardiography and cardiac catheterization, are useful in se...
Cardiovascular response to exercise and training in the horse. The quality of the overall response to exercise in the horse is very similar to that seen in man and laboratory animals; differences are mainly quantitative and persist when relative body weight is taken into account. The apparently greater flow capacity of the equine muscle bed during maximal whole-body exercise implicates the extent of central circulatory adaptations as the limiting factor in performance but implies a role for increase in arteriolar capacitance/muscle capillarity as an appropriate response to intense endurance training. The blood oxygen-carrying capacity of the horse is ofte...
Diagnosis and treatment of cardiac arrhythmias. Cardiac arrhythmias are probably more common in horses than in any other domestic animal species. The most frequent clinical complaint associated with cardiac arrhythmias is exercise intolerance. Physical examination is characterized by auscultation abnormalities such as fast or slow heart rate, irregular rhythm, extra sounds, long pauses, or abnormal heart sounds. The electrocardiogram is used to make a definitive diagnosis of the dysrhythmia. Other laboratory and cardiac function tests are employed to determine the etiology and to assess the significance of the arrhythmia. Antiarrhythmic the...
Pharmacology and pharmacokinetics of drugs used to treat cardiac disease in horses. The rational therapy of cardiovascular disease in horses requires a thorough knowledge of the pharmacology and pharmacokinetics of several specific drugs (digitalis, digoxin). Calcium solutions, dopamine, and dobutamine are frequently used to treat congestive heart failure in horses. Quinidine, procainamide, lidocaine, and propranolol are used to treat a variety of supraventricular and ventricular arrhythmias. Furosemide, a highly potent loop diuretic, is used to eliminate edema and promote diuresis. A thorough understanding of the applied pharmacology, dosage recommendations, toxicity, and pr...
Acquired cardiovascular disease. This article reviews the etiology, clinical findings, and significance of diseases of the heart valves, myocardium, pericardium, and great vessels of the horse. Each valve is considered separately from the point of view of murmur production. In addition, the role of the cardiovascular system in the etiology of sudden and unexpected death is considered.
Arterial thrombosis as the cause of lameness in a foal. A 3-day-old foal was examined because of forelimb lameness. Brachial artery occlusion was diagnosed. The foal was euthanatized. Necropsy revealed brachial artery thrombosis and an atrial septal defect.
Differential diagnosis of equine respiratory noises. EXAMINATION of a horses 'wind' has long been a requirement at the time of sale. More recently the respiratory system has been the subject of investigation in the assessment of poor performance, although an examination for these purposes must be pan of a full clinical examination with special attention paid to the respiratory and cardiovascular systems. The differential diagnosis of adventitious respiratory sounds heard at exercise is considered here.
Regional blood flow changes in response to near maximal exercise in ponies: a review. In recent years, increasing attention has been focused on the physiological responses of the horse to maximal exercise. Cardiovascular response in near maximally exercised galloping ponies (heart rate 225 +/- 7 beats/min; whole body oxygen consumption 122 +/- 12 ml/min/kg) comprised a marked increase in blood flow to the cerebellum, myocardium, diaphragm and the working muscles, while renal blood flow decreased precipitously. Cerebral and brainstem perfusion did not vary from resting values. Transmural homogeneity of myocardial blood flow persisted during near maximal exercise. It was reported...
Enhanced prostacyclin biosynthesis and decreased thromboxane formation by 3-dimethylamino 5-(2′,6′-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89). The effects of 3-dimethylamino 5-(2',6'-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89) on the biosynthesis of PG I2 and TX A2 using horse aorta and horse platelet microsomes as sources of enzymes and arachidonic acid as substrate, were investigated. PC 89 (1.10(-6) M- 1.10(-3) M) dose-dependently - enhanced the biosynthesis of PG I2: the AD50 was 6.8 X 10(-6) M +/- 1.2 X 10(-9) M, the Vmax did not vary significantly with concentrations: PC 89 increased the affinity of enzyme for substrate - but inhibited TX A2 biosynthesis (ID50 = 3.31 X 10(-3) M +/- 4.8 X 10(-7) M): this inhibiting act...
Changes in digital venous pressures of horses moving at the walk and trot. Blood pressures from the catheterized lateral digital vein of the fore-limbs of 6 clinically normal horses were measured at rest, at the walk, and at the trot. Digital venous pressures were compared with the phases of the stride and weight-bearing forces, using electrogoniometry and a force platform. Rapid increases in digital venous pressures to maximal values were observed immediately before maximal forces during the support period of the stride. At the trot, increases in peak vertical forces were paralleled by increases in peak digital venous pressures. Seemingly, the hydrodynamics of the d...
Common ventricle with separate pulmonary outflow chamber in a horse. On the basis of clinical and laboratory examinations, a ventricular septal defect or a variant of the tetralogy of Fallot was suspected in a 3-year-old filly with a history of poor growth rate and exercise intolerance. The filly was euthanatized and found to have a 3-chambered heart (cor triloculare biatriatum). The heart had 2 normally formed atria and a large common ventricle into which the right and left atrioventricular orifices opened and from which the aorta arose. There was a small separate chamber from which the pulmonary trunk originated. This chamber communicated with the common vent...
Antagonism of xylazine-pentobarbital anesthesia by yohimbine in ponies. Effects of yohimbine on xylazine-pentobarbital anesthesia were evaluated in ponies. Five minutes after the IV injection of xylazine (1.1 mg/kg of body weight), pentobarbital sodium (12.7 mg/kg, IV) and additional xylazine (2.2 mg/kg, IM) were given and produced anesthesia in 12 ponies for 64.0 +/- 16.4 minutes (mean +/- SD) as well as immobilization for 89.8 +/- 34.2 minutes. Eleven ponies were given yohimbine (0.1 mg/kg, IV) 50 minutes after pentobarbital dosing. In these 11 ponies, durations of anesthesia and immobilization were shorter, 52.0 +/- 1.4 and 65.5 +/- 14.8 minutes, respectively. ...
Observations on seven cases of mitral insufficiency in the horse. Observations on seven cases of mitral insufficiency are described. Three of the horses had recent histories of cardiac failure and formed a separate group in which there were marked haemodynamic changes which varied in relation to heart rate but were associated with pulmonary hypertension, elevated right ventricular pressure and low peak left ventricular pressure. In the other four horses the heart appeared to be compensating at rest but to be unable to cope with severe exertion. On auscultation, a widespread pansystolic murmur and a prominent third heart sound were characteristic of the left ...
Cardiopulmonary effects of prostacyclin infusion in anesthetized horses. Prostacyclin was infused IV into 6 horses anesthetized with halothane. Three dosage rates (10, 30, and 100 ng/kg of body weight/min) were evaluated in each horse. Facial and pulmonary artery pressures, heart rate, cardiac output, blood temperature, and arterial and mixed venous pH, PCO2, and PO2 were measured. Arterial blood was collected for determination of glucose, lactate, and PCV. Mixed venous blood was sampled for assay of 6-keto-prostaglandin F1 alpha and catecholamines. Infusion of prostacyclin at 10 ng/kg/min had no effect on the variables measured, whereas the 30 ng/kg/min dosage dec...
Intensive care of the neonatal foal. The basic concepts of diagnosis and treatment in the abnormal neonatal foal are presented. Methods of restraint, sedation, and general nursing care are discussed, as well as more specific techniques of respiratory and circulatory system support.
Cardiovascular disease in the equine neonate. Cardiac disease in the equine neonate occurs infrequently. Murmurs are often heard in foals and are not considered significant unless they persist beyond 4 days of age. Congenital cardiac defects are the most common form of primary cardiac disease in the foal, with ventricular septal defects occurring most frequently. Other neonatal foal diseases such as ruptured bladders, white muscle disease, neonatal respiratory distress syndrome, and septicemia have secondary cardiac involvement.
Flunixin meglumine attenuation of endotoxin-induced damage to the cardiopulmonary vascular endothelium of the pony. Endotoxic shock was induced in 5 ponies by intraperitoneal injections of 20, 40, 60, 80, and 80 micrograms of Escherichia coli endotoxin (LPS)/kg of body weight at 0, 6, 12, 18, and 24 hours, respectively. At 24 hours, the ponies also were given 20 micrograms of LPS/kg via catheter in the left ventricle of the heart. A 2nd group of 4 ponies was given 1.1 mg of flunixin meglumine (FM)/kg, IV, at 6, 12, 18, and 24 hours just before the corresponding LPS injection. Two hours after the 24-hour LPS injection, the ponies in both groups were anesthetized, the lungs were perfused with fixative, and po...
