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.
Interruption of aortic arch in two foals. Two foals with a history of normalcy at birth developed a lack of exercise tolerance and weakness in the first few days of life. Weakness, inability to rise, and reluctance to suckle were common complaints. Physical examination of both foals revealed a cardiovascular abnormality, with a loud systolic murmur audible over both thoracic walls. Additional diagnostic techniques were blood gas analysis, radiography, cardiovascular catheterization, and necropsy. Necropsy findings were ventricular septal defect, atrial septal defect, patent ductus arteriosus, and congenital absence of the aortic arch....
Artifact production with micromanometers used to record intracardiac pressure and sound. In horses experimental right and left heart catheterization using a catheter with two microtransducers 9 cm apart, usually in a transvalval position produced pressure and sound artifacts that confounded the diagnosis. Most were probably due to malpositioning resulting in movement through a valve during recording or impingement on the valve cusps or the chordae tendineae or lodgement in the apex of the heart. The recognition of these artifacts is particularly important in studies of large animals in which catheter siting cannot be monitored by radiography.
The influence of neuroleptanalgesia on the serum activity of muscle enzymes in ponies. The serum activities of creatine kinase (CPK), aldolase (ALD) and alpha-hydroxybutyrate dehydrogenase (HBD) were determined in a group of Welsh Mountain ponies before and after a 30 minute period of neuroleptanalgesia induced by i.v. injection of Immobilon and terminated by i.v. injection of Revivon. There were slight but significant increases in the serum activities of CPK and HBD following neuroleptanalgesia, but no change in the serum activity of ALD. It is suggested that this form of neuroleptanalgesia may be associated, in ponies, with a degree of reversible myocardial hypoxic change, pos...
Regional blood flow to the stomach and small intestine in ponies. Studies on regional blood flow to the stomach and small intestine were performed in 9 anesthetized ponies. Carbonized microspheres (15 +/- 5 micron in diameter) labeled with 85Sr were injected into the left atrium to determine blood flow distribution. In 4 ponies, the regional flows to mucosal-submucosal layers of the stomach and the small intestine were also measured. The nonglandular region of the stomach received the least blood per 100 g of tissue, and the duodenum received the greatest. The regional blood flow to the duodenum was significantly higher than that to the glandular stomach reg...
Effect of exercise on systemic blood pressure and heart rate in horses. Carotid loops were prepared in 3 horses several months prior to the experiments. Systemic blood pressure was recorded at rest and during exercise by insertion of a plastic cannula into the carotid artery. The pressure transducer was fixed at the neck of the animal. The blood pressure signal was transmitted by telemetry. When the horses were standing under the rider, the following results were obtained: heart rate 38 +/- 5 beats-min-1, systolic pressure 115 +/- 15, disstolic pressure 83 +/- 10, mean pressure 97 +/- 12, and pulse pressure 32 +/- 9 mm Hg. During steady gallop at a mean speed of 5...
Paroxysmal atrial fibrillation in a racehorse. A 4-year-old thoroughbred stallion with a history of loss of racing form was studied over a period of approximately 7 months. At the initial examination he showed positive T waves in 1 chest lead and wandering of the pacemaker. This was followed by an episode of paroxysmal atrial fibrillation which disappeared spontaneously and was replaced by significant T wave changes in all the chest leads. During a period when these changes persisted, there was progressive lengthening of the P wave and the P-R interval. Because the last ECG showed evidence of intra-atrial block, first degree A-V block and ...
The clinician’s approach to equine cardiology. The author considers some of the difficulties the clinician may be faced with when giving an opinion on a horse with a cardiac abnormality. The 3 types of cardiological cases presented to the practitioner are described. The first 2 categories both exhibit a reduction in performance either with loss of bodily conduction or without it. The third group, which is the most troublesome for the clinician, involves the horse which shows a cardiological abnormality but is otherwise apparently normal.
Cardiological problems in equine medicine. This paper outlines the major problems in evaluating and assessing prognosis in horses with minor cardiac abnormalities. It emphasises that progress will only be made if adequate data on the "natural history" of equine cardiac disease can be collected. This will necessitate a long-term study of suitable cases and will require the collaboration of specialist institutions and general practitioners if it is to be successful.
Pacing techniques in assessing cardiac function in the horse. The problem of transitory cardiac arrhythmias in equidae is discussed particularly with regard to the referral of suspect cases to specialist institutions for second opinion. Recently developed electro-stimulation techniques designed to uncover problem arrythmias, are briefly described and their potential in the analysis of cardiac electrical function under varying conditions is reviewed. The author cautions on the too rapid evaluation of the techniques for this purpose while remaining optimistic of the potential of electro-stimulation in the objective analysis of cardiac electric parameters.
The legal responsibilities of the veterinary surgeon arising from advances in equine cardiology and in the prescription of drugs for racehorses. The paper examines the responsibilities of the veterinary surgeon in relation to the advances more recently made in the field of equine cardiology. Notwithstanding such advances it is stated that the normal established legal principles apply, in particular in relation to the preparation of certificates, namely that the veterinary surgeon must be sufficiently expert to give the opinion sought, that he must make himself fully aware of the purpose for which the certificate is required and that he must make clear the nature and limitations of any examination carried out.
Studies on left ventricular isotonic function in conscious and anaesthetized ponies. The effects of thiopentone-halothane and thiopentone-ether anaesthesia on left ventricular isotonic function were assessed in Welsh Mountain ponies from measurements of left ventricular stroke work, minute work, stroke power, mean ejection rate and tension-time index.
All of these variables were affected similarly during anaesthesia, an initial marked reduction being followed by a progressive return towards control levels in the later stages of anaesthesia. Quantitative differences between the effects of each agent were evident, the depression which occurred during halothane anaesthesia bei...
Coronary arterial anatomy of the small pony. Ventricular weights and coronary arterial distribution and diameters were determined in 10 small adult ponies (139 +/- 32 kg). Combined ventricular weights averaged 0.52% of the body weight, with an average of 77% of the total ventricular weight being the left ventricle. The pony is right coronary predominant, with the interventricular subsinusoidal branch of the right coronary artery and interventricular paraconal branch of the left coronary artery providing comparable blood supply to the left ventricular free wall and septum.
Nonsteroidal anti-inflammatory drugs: a review. New applications in hypersensitivity reactions of cattle and horses. Nonsteroidal anti-inflammatory drugs inhibit the biosynthesis of kinins and prostaglandins and stabilize leukocyte lysosomal membranes. Nonsteroidal anti-inflammatory drugs also weakly block the biosynthesis of histamine and serotonin, and pharmacologically antagonize kinins, prostaglandins and slow-reacting substance of anaphylaxis. Nonsteroidal anti-inflammatory drugs effectively control both cardiovascular and respiratory manifestations of hypersensitivity in cattle and horses. This, coupled with the contrasting lack of effectiveness of "antiamine" drugs, suggests that bio-amines such as hi...
Cardiac output, left ventricular ejection rate, plasma volume, and heart rate changes in equine laminitis-hypertension. Acute laminitis-hypertension was produced experimentally by carbohydrate overloading of the gastrointestinal tract in 8 horses, and the resulting hemodynamic changes were measured. Statistically significant (P less than 0.01) increases in cardiac output, left ventricular ejection rate, heart rate, and arterial pressure were related to statistically nonsignificant changes in peripheral resistance and a delayed (Obel grade 3 plus 24 hours) decrease in plasma volume. When compared with control values, the doubling of cardiac output and left ventricular ejection rate simultaneous with little or no...
Echocardiography in the horse. Echocardiograms were obtained from 25 standing, clinically normal horses, using an ultrasonic recording device. The echobeam penetrated the right thoracic wall in the area of the 4th to 5th intercostal space, with a frequency of 2.5 mHz. Measurements of left ventricular wall thickness generated a mean value of 3.2 +/- 0.18 (SEM)cm, whereas the left ventricular chamber diameter in diastole was 9.3 +/- 0.30 cm and in systole was 5.7 +/- 0.23 cm. The aortic root dimensions had a mean of 7.7 cm, with a SEM of 0.16. Mitral valve closing slope (E-F) was calculated to be 17.7 +/- 0.87 mm/second, and ...
A method for indirect measurement of arterial blood pressure in the horse. A method using the Doppler ultrasound principle for indirect determination of arterial blood pressure in the horse is described. The method is simple and suitable for field situations. Validation studies show that systolic and diastolic blood pressure measurements bear a close relationship to true values obtained by direct measurement.
Exercise studies in horses: 1. A simple telemetry system for recording excercise ECGs in horses. A robust low cost portable radiotelemetry system is described for the horse and its method of operation and advantages briefly discussed. The equipment consisted of 2 electrodes forming a bipolar lead, a transmitter, a receiver and a writing device. The sitting, application and immobilising of the electrodes was a most important factor in obtaining good quality recordings. ECGs were recorded at all paces and also while jumping and the results proved satisfactory.
Treatment of atrial fibrillation in three racehorses. Three young Standardbred pacers with atrial fibrillation were treated with quinidine sulphate (QS) by stomach tube. They were given 10g QS every 2 hours until cardioversion was achieved. Total doses varied between 20 and 30 g. No premedication was given nor any follow up treatment after return to sinus rhythm. All horses were given 3 months rest after the treatment, and when electrocardiographed then, and at 6 months, showed normal sinus rhythm. As all 3 horses won races after cardioversion and showed subsequent normal electrocardiograms it seems likely that atrial fibrillation can occur witho...
Exercise studies in horses: 2. The cardiac response to exercise in normal horses and in horses with chronic obstructive pulmonary disease. The relationship of velocity (v) to heart rate (HR)and of kinetic energy (KE) to heart rate, were investigated in 6 normal horses and in 6 horses with chronic obstructive pulmonary, disease (COPD). Radiotelemetry was used to determine the heart rate while subjects were ridden on a 400m track. Velocity was measured by stop-watch between 2 markers 50 m apart at the end of the track. Kinetic energy was calculated from the formula KE =1/2 Mv2, where M = mass of horse, rider, saddle and bridle (KG) and V = velocity (metres per second). In all subjects, the relationship of velocity to heart rate was...