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Topic:Heart
The equine cardiovascular system, particularly the heart, is fundamental to maintaining the health and performance of horses. The heart is responsible for pumping oxygenated blood throughout the body, supporting vital functions and physical activity. In horses, the heart's structure and function are adapted to meet the demands of both rest and exertion, with notable features such as a large cardiac output and efficient blood circulation. Conditions affecting the equine heart, such as arrhythmias, valvular diseases, and myocardial disorders, can significantly impact a horse's well-being and athletic capability. This page aggregates peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of the equine heart, as well as diagnostic and therapeutic approaches to managing cardiac health in horses.
A survey of cardiac auscultatory findings in horses. Auscultation was used to examine 545 horses for cardiac murmurs and some arrhythmias. The most significant finding was the high prevalence of right-sided holosystolic or pansystolic plateau-type murmurs compatible with a diagnosis of tricuspid regurgitation in National Hunt racing Thoroughbreds of all ages (16.4%). This condition was found in 4.7% of flat-racing Thoroughbreds, 3.7% of non-racing Thoroughbreds and Thoroughbred crosses, and in none of the ponies examined. High prevalences of left-sided early systolic murmurs (53%), left-sided early diastolic murmurs (23%), right-sided early dias...
Determination of the optimal treadmill slope for reproducing the same cardiac response in saddle horses as overground exercise conditions. The purpose of this study was to define the most suitable treadmill slope for reproducing the same heart rate response as in horses being ridden on a track. Seven French saddle horses were exercised first on a level turf track and then on a treadmill. On the track the exercise test consisted of four periods of three minutes of increasing speeds at the trot and the gallop (96 to 600 m/minute). The treadmill exercise tests consisted of seven steps of increasing slope (0 to 9.6 per cent) at the trot (252 m/minute), followed, after an active recovery period at the walk with a 0 per cent slope, by ...
Reconstitution of horse heart myoglobin with hemins methylated at 6- or 7-positions: a circular dichroism study. The reconstitution kinetics of horse heart myoglobin, as met-cyano derivative, with two synthetic hemins in which the 6- or the 7-propionate is replaced by a methyl group, has been investigated by circular dichroism, in order to gain information on the heme re-orientation process following the heme insertion into the globin pocket. The results obtained confirm that the preferred heme orientation places the sole propionate into the position occupied by the 6-propionate in the crystal structure, supporting the importance of the salt bridge occurring between this propionate and the basic CD3 resi...
Cardiovascular effects of thoracic compression in horses subjected to euthanasia. Six horses scheduled for euthanasia were instrumented for the measurement of blood flow by thermodilution, pulmonary arterial, right atrial and arterial blood pressures and collection of arterial blood for pH and blood gas analysis. The horses were anaesthetised with intravenous (iv) thiamylal sodium (10 mg/kg) and placed in right lateral recumbency. After euthanasia with an overdose of pentobarbitone sodium (100 mg/kg, iv) and loss of the electrocardiogram and arterial pulse pressure, thoracic compression at rates of 40, 60 and 80 compressions/min was instituted. Thoracic compression was acco...
Pharmacokinetics of digoxin administered to horses with congestive heart failure. Nine horses with (naturally acquired) congestive heart failure were treated with 2.2 micrograms of digoxin/kg of body weight by the IV route, followed by 11 micrograms/kg administered orally every 12 hours thereafter. Furosemide was administered IV concurrently with IV administered digoxin every 12 hours. Serum concentration of digoxin was measured after the first (IV) and seventh (orally administered) dose. After IV administration, digoxin disposition was described by a 2-compartment model, with a rapid distribution phase (t1/2 alpha = 0.17 hour), followed by a slower elimination phase (beta ...
Furosemide attenuates the exercise-induced increase in pulmonary artery wedge pressure in horses. Right atrial (RA), right ventricular (RV), pulmonary artery (PA), and pulmonary artery wedge (PAW) pressures were examined, using catheter-mounted micromanometers, in 8 healthy horses at rest and during galloping on a treadmill at belt speeds of 8, 10, and 13 m/s. The in vivo signals from the micromanometers were matched with those from conventional fluid-filled catheter transducers leveled at the scapulohumeral joint. Thirty minutes after completing control exercise measurements, furosemide was administered IV at a dosage of 1 mg/kg of body weight, and resting, as well as exercise, measuremen...
[M-mode echocardiography in dressage horses, class S jumping horses and untrained horses]. Heart structures of 45 warmblooded horses were measured by M-mode-echocardiography. The current training level of 15 dressage horses (group I) and 15 show-jumping horses (group II) was category "S". In the third group were 15 untrained horses. Four standardized transducer positions were determined for the m-mode echobeam, calibrated according to the two-dimensional real time technique. End systolic and end diastolic diameters of left ventricle, right ventricle, aortic root, interventricular septum and left ventricular wall, as well as motion pattern of heart wall, mitral valve and aortic valve...
Pulmonary artery wedge pressure increases with high-intensity exercise in horses. Using catheter mounted microtip manometers, right atrial, pulmonary artery, and pulmonary artery wedge pressures were studied in 8 horses while they were standing quietly (rest), and during galloping at treadmill speeds of 8, 10, and 13 m/s. At rest, mean (+/- SEM) heart rate, mean right atrial pressure, mean pulmonary artery pressure, and mean pulmonary artery wedge pressure were 37 (+/- 2) beats/min, 8 (+/- 2) mm of Hg, 31 (+/- 2) mm of Hg, and 18 (+/- 2) mm of Hg, respectively. Exercise at treadmill belt speed of 8 m/s resulted in significant (P < 0.05) increments in heart rate, right at...
Effect of xylazine on the arrhythmogenic dose of epinephrine in thiamylal/halothane-anesthetized horses. The effect of xylazine on the arrhythmogenic dose of epinephrine (ADE) was studied in 9 horses. Anesthesia was induced by administration of guaifenesin (50 mg/kg of body weight, IV) followed by thiamylal (4 to 6 mg/kg, IV) and was maintained at 1 minimal alveolar concentration (MAC) of halothane (0.89%). Base apex ECG and facial artery pressure were recorded. Epinephrine was infused in a sequence of arithmetically spaced increasing rates (initial rate 0.25 micrograms/kg/min) for a maximum of 10 minutes. The ADE was defined as the lowest epinephrine infusion rate to the nearest 0.25 micrograms/...
Cardiopathological observation on a case of persistent ventricular tachycardia in a pony mare. A 20-year-old pony mare with persistent ventricular tachycardia (VT) was examined cardiopathologically. At necropsy, the heart was enlarged and rounded with both ventricular dilatation. In a longitudinal section of the ventricular septum, a large grayish white patchy lesion (5 x 25 mm) was detected in the relatively higher portion. Microscopically, the lesion was extensive myocardial fibrosis located in the vicinity of the proximal part of the left bundle branch. Partially the fibrotic lesion was in contact with the branch. Such a lesion might play an important role in creating a suitable back...
[B-mode, M-mode and Doppler sonographic findings in mitral valve insufficiency of horses]. B- and M-mode echocardiography was performed on 38 horses. 34 patients had systolic heart murmur with the point of maximal intensity over mitral valve. Additionally, 17 of these patients were examined with the pulsed wave doppler echocardiography (Vingmed 200). In 26 patients with cardiac murmur and in 4 patients without cardiac murmur a mitral valve insufficiency was diagnosed by echocardiography. In 8 horses with a systolic murmur over mitral valve M- and B-mode evaluation could not reveal a haemodynamic importance of the murmur. The diagnosis of MVI was based on a dilation of left atrium wi...
Distribution of coronary collateral blood flow at different levels of collateral growth in conscious ponies. Coronary collateral growth was stimulated in chronically instrumented conscious ponies by a previously validated intermittent coronary occlusion method. Changes in regional myocardial function (sonomicrometry) and reactive hyperemia (Doppler method) were used to monitor collateral growth and to program measurements of regional myocardial blood flow (microsphere method). A serial analysis of the transmural and lateral distributions of collateral blood flow was performed at the native and three superimposed levels of collateral growth. Results in nine animals undergoing an average of 553 +/- 188...
Arginase distribution in tissues of domestic animals. 1. A new colorimetric method was used for determination of arginase in different tissues of some domestic animals. 2. In all species studied liver was the richest source of arginase. 3. Significant differences were observed in the specific activity of arginase in livers from different species. 4. In all species, besides liver, kidney and brain also contained significant levels of arginase. 5. In the dog, in addition to the three organs mentioned above, lung, heart, spleen and skeletal muscle showed some arginase activity. 6. In sheep and cattle significant arginase activity was observed in the...
Cardiac cycle length variability in ponies at rest and during exercise. We evaluated cardiac cycle length variability in ponies at rest and during strenuous exercise with and without premedication with atropine. In the absence of premedication, cardiac cycle length at rest was 1,112 +/- 53 ms, the individual cardiac cycle length standard deviation (SDCL) was 75 +/- 23 ms, and the individual cycle length coefficient of variation (CVCL) was 6.32 +/- 1.62. Exercise significantly decreased (P < 0.05) all three indexes (290 +/- 9 ms, 5 +/- 1 ms, and 1.65 +/- 0.20, respectively). Atropine premedication significantly reduced resting cardiac cycle length (685 +/- 46 ms...
Postsurgical ventricular tachycardia in a horse. A 2-year-old Thoroughbred racehorse developed ventricular tachycardia after elective laryngoplasty and ventriculectomy were performed while anesthesia was maintained with halothane. During surgery, the horse became febrile and developed transient mild hypercarbia. The horse was treated with an IV infusion of quinidine gluconate. Continuous electrocardiographic monitoring was used to evaluate cardiac rhythm during treatment, and conversion was achieved after 12 hours of IV infusion. The inciting cause for the arrhythmia was not determined.
Vegetative endocarditis in an Appaloosa gelding. A 5-year-old Appaloosa gelding was presented with a history of intermittent multiple joint swelling, weight loss, and anemia. Physical examination and clinical pathology revealed a grade IV/VI holodiastolic murmur, louder on the left, and a marked hyperproteinemia. Echocardiography of the heart demonstrated a large vegetative lesion on one of the aortic valve cusps. Blood cultures did not elucidate the causative organism, and the disease was refractory to empiric antibiotic therapy. The horse was euthanized after approximately 2 months of therapy.
Standardised imaging technique for guided M-mode and Doppler echocardiography in the horse. Eighteen echocardiographic images useful for diagnostic imaging, M-mode echocardiography, and Doppler echocardiography of the equine heart were standardised by relating the position of the axial beam to various intracardiac landmarks. The transducer orientation required for each image was recorded in 14 adult horses by describing the degree of sector rotation and the orientation of the axial beam relative to the thorax. Repeatable images could be obtained within narrow limits of angulation and rotation for 14 of the 18 standardised images evaluated. Twenty-seven National Hunt horses were subse...
Constrictive pericarditis in a mare: attempted treatment by partial pericardiectomy. Chronic constrictive pericarditis was diagnosed in a 6-year-old Thoroughbred mare based on the clinical findings of right congestive heart failure, hyperechoic pericardium without pericardial effusion, and a dip-and-plateau shape of the right ventricular pressure curve with equilibration of the diastolic pressures in all cardiac chambers. Treatment was attempted by partial pericardiectomy using a right lateral thoracotomy approach. Because of severe epicardial involvement recurrence of the constrictive pathology was noted 6 weeks after the surgical procedure. However, in selected cases in whic...
Total synthesis of horse heart cytochrome C. A strategy based on complexation-assisted condensation of large synthetic protein fragments and mitochondria-mediated stereospecific heme insertion has been utilized to assemble a functional molecule corresponding to native horse heart holocytochrome c. This original approach offers the unique opportunity of selective modifications both in the C-terminal and in the N-terminal regions of the apoprotein and may represent an useful alternative to site-directed mutagenesis, particularly when D-amino acids, chemically and/or isotopically modified or other unnatural amino acids have to be introduced...
