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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.
Blood flow in the hypertrophied right ventricular myocardium of unanesthetized ponies. To examine the effects of right ventricular (RV) hypertrophy on regional myocardial blood flow and coronary vascular reserve, hemodynamics and myocardial blood flow (15-micrometers radio-nuclide-labeled microspheres) were studied in 12 unanesthetized adult ponies before and during intravenous isoproterenol HCl infusion (1 microgram.kg-1.min-1). Six ponies served as controls, whereas in each of the others the main pulmonary artery (PA) had been banded 35-90 days prior to the study. Marked RV hypertrophy was present in PA-banded animals. In these ponies, there was a significant increase in RV sy...
Ultrastructural observations in ponies after treatment with monensin. Ultrastructural studies were made of myocardium, diaphragm, appendicular muscle, liver, and kidney of 3 ponies acutely poisoned with a single oral dose of monensin (4 mg/kg of body weight). These ponies developed severe signs of toxicosis and were killed 28 to 72 hours after treatment. Severe mitochondrial damage (swelling) and lipoidosis in myocardial tissues were observed in 2 of the 3 ponies; similar, but less severe, changes were observed in the 3rd pony. The hepatocytes of the 3 ponies were characterized by increased amounts of smooth endoplasmic reticulum, large numbers of lipid droplets...
Ischaemic myocardial fibrosis and aortic strongylosis in the horse. The hearts and aortas of 2076 unselected horses of all ages were examined immediately after slaughter. Focal zones of fibrosis, observed in the myocardium of 14.3 per cent of hearts examined, were found in both atria and ventricles and were unrelated to age. Microscopically the majority of lesions involved myocardial fibre lysis and replacement fibrosis, although acute infarction was present in some cases. Intramyocardial arterioles in or adjacent to the lesions exhibited occlusive arteriosclerotic changes whereas those elsewhere remained patent. The evidence strongly suggests that the myocard...
[Practolol test for adrenergic beta receptor blockade in veterinary electrocardiographic diagnosis]. The receptor theory of the action of catecholamines as well as the synthesis and production of beta-adrenolytics gave new perspectives for the treatment of circulatory diseases and enabled to use the beta-adrenergic blockade in electrocardiographic diagnosis. The aim of this work was to study whether it is possible to modify the oral method of administration used in human beings, into intravenous one, and what an information could be obtained as to actual heart condition after practolol injection. The results can be summarized as follows:--Practolol-Polfa injected intravenously in amounts of 3...
Multiple atrial dysrhythmias in a horse. A variety of atrial dysrhythmias including paroxysmal atrial tachycardia, atrial tachycardia with 2nd-grade atrioventricular block, atrial fibrillation, and atrial flutter developed in a 5-year-old Quarter Horse gelding. Quinidine and propranolol were not successful in restoring normal sinus rhythm. Sinus rhythm was re-established during digoxin therapy, but later reverted to atrial dysrhythmia. At necropsy, multiple, discrete pale areas were found on both atria and the interatrial myocardium. Histologic examination of these lesions demonstrated myocytolysis and replacement by fibrous connecti...
Echocardiography in assessing mitral valve motion in 3 horses with atrial fibrillation. Echocardiography is a non-invasive, safe means of assessing intracardiac structures and their motion. In the normal motion of the mitral valve there is anterior motion noted during atrial systole. In 3 horses with atrial fibrillation the mitral valve motion had no anterior motion to correspond with atrial contractions. Quinidine returned the electrocardiogram of one horse to a sinus rhythm after which echocardiography demonstrated the reappearance of the anterior motion of the mitral valve.
Recent experience with heart transplantation. The major factors contributing to the recommencement of clinical heart transplantation in the United Kingdom last year were the steadily improving results from Stanford University, the clarification of the diagnosis of brain death, and advances in preserving donor hearts. Twelve men aged 16 to 52 years received heart transplants at Papworth Hospital from January 1979 to July 1980. Six had cardiomyopathies and six ischaemic heart disease. The donors were aged 16 to 35 (mean 21) years. A combination of road and air transport was used to transport the heart to Papworth in seven cases. The total d...
Pathogaenicity of Toxoplasma gondii oocysts to ponies. Nine ponies were fed 100,000 infective Toxoplasma gondii oocysts and were given corticosteroid injections before and after feeding the T gondii oocysts. Titers to the Sabin-Feldman dye tests (1:2 to 1:16,384) developed within postinoculation days (PID) 7 to 21 and antibodies persisted to PID 133. Toxoplasma organisms were isolated from the tissues of 4 ponies (heart of 4, brain of 2, spinal cord of 3, diaphragm of 1, skeletal muscle of 1, liver of 1, kidneys of 1) killed between PID 36 and 63, but not from 5 ponies killed between PID 117 and 150. Seemingly, ponies are one of the more resistant...
Studies on the physiopathology of chronic obstructive pulmonary disease in the horse. II. Right heart haemodynamics. Pressure curves obtained by cardiac catheterization of the pulmonary artery, right ventricle and right atrium of 9 horses and ponies with chronic obstructive pulmonary disease (COPD) were compared with those similarly recorded from 6 clinically normal control subjects. The mean pulmonary peak systolic, pulmonary minimum diastolic and ventricular peak systolic pressures of the COPD subjects were significantly higher (P less than 0,01) than the corresponding mean pressures of the clinically normal control subjects. The mean pressure calculated from pressure curves obtained from 8 Thoroughbreds i...
Cardiorespiratory adjustments to tethered-swimming in the horse. The cardiorespiratory and metabolic responses to various levels of tethered-swimming were evaluated in 5 sedentary horses. Cardiac output (Q) and heart rate (HR) correlated highly (r = 0.89 and 0.94 respectively) with work effort (WE) expressed as kg pulled . kg body wt-1 . 10-2. While swimming, stroke volume (SV) was reduced at the lowest workloads, but increased with increasing WE so that at the highest workloads it had returned to the on-land standing SV. Pressures in the pulmonic as well as on both sides of the systemic circulation were considerably elevated by this form of exercise, altho...
Relationship between QRS-duration (heart score) and racing performance in trotters. Heart scores increased with age and training. Yearlings had average heart scores of approximately 90 milliseconds (msecs). This increased to approximately 110 msecs in 5-year-old horses, after which there was only slight further increase. In horses 4 years or older, regression analysis revealed a highly significant correlation between heart score and kilometre time. In younger horses the level of significance was less. There was a positive correlation between heart scores and earnings in races. Thus, horses with heart scores above 115 msecs had won considerably more than horses with lower hear...
Electrocardiography in the horse. (A report of findings in 138 horses). Over a period of approx. 3 years, electrocardiograms (ECG) were recorded from 138 horses referred as patients to the Medical Clinic. Of these, 22 horses (approx. 16 per cent) has ECG alterations. The 22 ECG's revealed a total of 29 ECG abnormalities. The most frequent ECG alteration was incomplete AV block, that was seen in 9 horses (31 per cent of the ECG abnormalities). Abnormal (i.e. broad, tent-like and, sometimes, inverted) T waves and deviations of the ST segment were seen each in 5 ECG's from 7 horses, 3 of which had both abnormalities which were associated with severe underlying diseas...
Ventricular defibrillation with myocardial electrodes in the dog, calf, pony, and pig. The defibrillation effectiveness of 4-msec rectangular wave shocks was evaluated using myocardial electrodes with 25-kg dogs and (nominally) 100-kg calves, ponies, and pigs as part of an evaluation of the suitability of these animals as models for automatic implanted defibrillator research. The percent success of defibrillation attempts in dogs ranged from 44% with 4-A, 6-J shocks to 93% with 8-A, 16-J shocks. The success achieved in calves with scaled electrodes was uniformly lower and reached a maximum of 28% with 23-A, 107-J shocks. Pigs defibrillated with scaled electrodes at a success lev...
Persistent right aortic arch associated with a persistent left ductus arteriosus and an interventricular septal defect in a horse. In this article a description is given of the clinical and postmortem findings of a persistent right aortic arch in association with a persistent left ductus arteriosus and a ventricular septal defect in a horse.
Assessment of myocardial function in the horse. 1. Theoretical and technical considerations. The paper discusses the various parameters which are currently used in attempts to assess the contractile efficiency of the myocardium in various species. These procedures depend upon accurate recording of intracavity pressure. The response of a catheter-mounted microtransducer compared with a fluid-filled catheter manometer system is illustrated to show the advantage of the former in providing a true representation of pressure changes.
Phonocardiography in the horse: 2. The relationship of the external phonocardiogram to intracardiac pressure and sound. The paper describes observations during individual cardiac cycles on the changing pressures and sounds recorded from the various chambers of the heart and aorta, related to phonocardiograms from an external microphone hand-held over the cardiac area. The majority of the first sound appears to arise from the left side of the heart after the AV valves have closed and the second sound is a consequence of sudden deceleration of blood against already closed semilunar valves. Systolic murmurs at the aortic root may be benign from increased flow and turbulence at the peak of ejection but these may no...
