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Topic:Heart Rate
Heart rate in horses is a physiological parameter that reflects the number of heartbeats per minute. It is an important indicator of cardiovascular function and can be influenced by factors such as exercise, stress, excitement, and health status. Monitoring heart rate provides valuable insights into the horse's physical condition and can aid in assessing fitness levels or detecting potential health issues. In equine practice, heart rate is often measured using stethoscopes, heart rate monitors, or electrocardiograms. This page compiles peer-reviewed research studies and scholarly articles that explore the determinants, measurement techniques, and implications of heart rate variations in equine health and performance.
Cardiac arrhythmias identified in horses with duodenitis/proximal jejunitis: six cases (1985-1988). During a 3 1/2-year period, cardiac arrhythmias were identified in 6 of 67 horses diagnosed with duodenitis/proximal jejunitis (DPJ). Arrhythmias were detected by auscultation of irregular cardiac rhythm and subsequently were characterized by electrocardiographic evaluation. Arrhythmias included frequent second-degree atrioventricular block, ventricular ectopic depolarizations, and atrioventricular conduction disturbance. In 4 horses, arrhythmias resolved with recovery from the primary problem. One horse died suddenly 66 hours after admission, and another was euthanatized at 72 hours after adm...
Diaphragm does not produce ammonia or lactate during high-intensity short-term exercise. To ascertain whether costal diaphragm engages in ammonia and lactate production (like limb muscles) during high-intensity short-term exercise, experiments were carried out on six healthy trained ponies in which phrenic venous catheters had been implanted 5-9 days earlier. Simultaneous anaerobically obtained blood samples from abdominal aorta and the phrenic vein at rest and during 4 min of exertion at 32 km/h and at a 7% grade were analyzed for blood-gas variables as well as lactate and ammonia concentrations using standard procedures. At rest, heart rate was 47 +/- 4 beats/min and the diaphra...
Clinical exercise testing in the normal thoroughbred racehorse. To evaluate normal cardiorespiratory and metabolic responses of Thoroughbred horses to a standardised treadmill exercise test, we examined 28 horses ranging in age from 1 to 4 years. The group consisted of eight yearlings, eight 2-year-olds and twelve 3 and 4-year-olds. All horses except the yearlings were in training, and either racing or ready to race, at the time of examination. None of the horses had histories of performance problems. On the first day the horses received a full physical examination, resting electrocardiogram, upper respiratory tract endoscopy and either one or two acclimat...
Failure of subtotal arytenoidectomy to improve upper airway flow mechanics in exercising standardbreds with induced laryngeal hemiplegia. Upper airway flow mechanics and arterial blood gas measurements were used to assess the efficacy of subtotal arytenoidectomy for treatment of induced left laryngeal hemiplegia in horses. Measurements were collected with the horses at rest, and trotting or pacing on a treadmill (6.38 degrees incline) at speeds of 4.2 and 7.0 m/s. Experimental protocols were performed after right common carotid artery exteriorization (baseline), after left recurrent laryngeal neurectomy (LRLN), and after left subtotal arytenoidectomy. At baseline, increasing treadmill speed progressively increased peak inspirato...
Doxapram infusion during halothane anaesthesia in ponies. Doxapram, 0.05 mg/kg bodyweight/min, was infused during the second hour of 2 h halothane anaesthesia in six ponies. Two of the ponies were anaesthetised on a second occasion as controls and given 5 per cent dextrose in place of the doxapram. Respiratory depression typical of halothane anaesthesia in ponies developed in the first hour of anaesthesia and continued during the second hour in the control animals. During doxapram infusion arterial carbon dioxide tension decreased and pH increased. Arterial blood pressure increased but there was no change in pulse rate, the electrocardiogram or arter...
Time-related responses to a constant-dose halothane anaesthesia in dorsally recumbent ventilated ponies. Haemodynamic and respiratory responses to halothane were investigated in dorsally recumbent, ventilated ponies during 2 hours. Normocapnia was maintained using intermittent positive pressure ventilation. Compared to the base line values at 30 minutes of constant dose halothane, no significant changes in heart rate, systemic blood pressure, cardiac output, cardiac index, stroke volume and left ventricle work were observed during a 2 hours anaesthesia. Arterial oxygenation increased initially (greater than 300 mm Hg) but tended to decrease non-significantly during the rest of the anaesthesia. Bl...
Effect of age on isoproterenol-induced maximal heart rate in horses. The effect of age on maximal heart rate induced by IV infusion of isoproterenol was studied in 19 healthy, sedentary, normothermic horses ranging in age from 0.25 to 9.90 years. Isoproterenol was administered IV (1.0 micrograms/kg of body weight/min) for 3 minutes, and the heart rate attained during the last 30 seconds of the infusion was determined. Linear regression of the maximal heart rate on age suggested that the rate decreased with age in a trend described by the equation: maximal heart rate (beats/min) = 209.63 - 3.28 x age (years). The regression coefficient (r) for this relation was ...
Effect of hypertonic vs isotonic saline solution on responses to sublethal Escherichia coli endotoxemia in horses. Cardiovascular responses to sublethal endotoxin infusion (Escherichia coli, 50 micrograms/ml in lactated Ringer solution at 100 ml/h until pulmonary arterial pressure increased by 10 mm of Hg) were measured 2 times in 5 standing horses. In a 2-period crossover experimental design, horses were either administered hypertonic (2,400 mosm/kg of body weight, IV) or isotonic (300 mosm/kg, IV) NaCl solution after endotoxin challenges. Each solution was administered at a dose of 5 ml/kg (infusion rate, 80 ml/min). Complete data sets (mean arterial, central venous, and pulmonary arterial pressures, pul...
Evaluation of 25%, 50%, and 67% nitrous oxide with halothane-oxygen for general anesthesia in horses. Twenty-five percent, 50%, and 67% nitrous oxide was administered to 12 horses anesthetized with halothane and oxygen. Compared to halothane-oxygen alone, there was no significant difference in heart rate, systolic, diastolic, or mean blood pressure values, arterial pH, PaCO2, or plasma bicarbonate values when nitrous oxide was included. A significant linear reduction in PaO2 values could be correlated with N2O:O2 concentrations. The halothane level required to maintain surgical anesthesia was reduced when nitrous oxide was administered, but it was not affected by changing the nitrous oxide con...
Halothane-sparing effect of benzodiazepines in ponies. The halothane-sparing effect of 2 benzodiazepines, diazepam and temazepam, were investigated in ponies by measuring the minimum alveolar concentration (MAC) for halothane before and after drug administration. The MAC value for halothane decreased 29% and 16% when either 0.044 mg/kg of diazepam or 0.044 mg/kg of temazepam, respectively, was administered intravenously. Heart rate, respiratory rate, systolic and mean arterial blood pressure, and expired CO2 were also measured. No differences were present in these variables before and after drug administration nor were differences noted between th...
A comparative study of interval and conventional training in thoroughbred racehorses. Eight horses with previous racing experience were used in a comparative study of training methods for Thoroughbred racehorses. They were randomly assigned to two groups of four horses each. One group was trained using an interval training method (IT) and the other using conventional training (CT) methods. Peak heart rates, heart rate recovery curves, peak plasma lactate levels, plasma lactate clearance rates and run times were used to evaluate differences in the training methods. Peak heart rates, heart rate recovery curves, and run times were not significantly different between the groups. Ho...
Application of a standardised treadmill exercise test for clinical evaluation of fitness in 10 thoroughbred racehorses. Clinical exercise stress testing is an important diagnostic tool for evaluating exercise intolerance and degree of fitness in human athletes. The purpose of this paper was to describe the methodology necessary to perform a clinical exercise test and report the results of performance evaluations on 10 Thoroughbred racehorses using this test. The test utilised an open flow gas analysis system for ease of use with untrained horses and a fast time response lactate analyser for rapid data analysis. Exercise test measurements used to evaluate fitness included peak oxygen consumption (mean VO2peak = ...
Effect of show jumping on heart rate, blood lactate and other plasma biochemical values. This study investigated some physiological responses to exercise performed by a horse during show jumping. The effects of jumping on heart rate (HR), blood lactate (LA) and some other blood values were studied in nine normal horses participating at the Belgian Junior Championship. Venous blood was sampled before and immediately after the show jumping and was analysed for packed cell volume, LA, blood glucose (GLU), total plasma protein, bicarbonate, sodium, potassium (K+), chloride, calcium and activities of plasma lactate dehydrogenase, creatine phosphokinase (CK) aspartate amino transferase ...
Methodology and repeatability of a standardised treadmill exercise test for clinical evaluation of fitness in horses. This paper describes the methodology necessary to perform a clinical exercise test and the expected variability in an individual horse's exercise test measurements based on comparing the results of two repetitions of the test with six horses. The exercise test measurements were obtained with an open flow respiratory gas analysis system, fast time response lactate analyser and an on-board heart rate monitor during an incremental inclined treadmill exercise test. With the exception of peak venous lactate concentration (LACpeak), the results indicate that the mean variability in peak oxygen consu...
Cardiorespiratory drift during exercise in the horse. The purpose of the present study was to measure the time-course and degree of cardiovascular and respiratory 'drift' during constant submaximal exercise in the horse. One Thoroughbred and four Morgan mares were instrumented for simultaneous measurement of respiratory and blood gases which also enabled cardiac output (Q) to be calculated. Data were collected at rest, and at 10, 20 and 30 mins during a constant workload which elicited an initial exercising heart rate (HR) of 150 beats/min, and an approximate 15-fold increase in oxygen consumption (VO2). Significant cardiac and respiratory drift ...
Effects of treadmill elevation on heart rate, blood lactate concentration and packed cell volume during graded submaximal exercise in ponies. Six ponies performed a standardised exercise test on a motorised treadmill at each of three randomly assigned treadmill elevations (1, 4, or 7 degrees). The exercise test consisted of four, 4 min increments of increasing treadmill speed from 1.0 to 3.4 m/sec. Heart rate, blood lactate concentration, and packed cell volume (PCV) were determined, during the last min of each exercise level, and at 4 and 12 mins post exercise. Regardless of treadmill elevation, no differences were observed in pre-exercise heart rate (49 +/- 2) beats/min), lactate (1.2 +/- 0.1 mM), and PCV (0.32 +/- 0.01 litres. Du...
Standardized exercise test and daily heart rate responses of thoroughbreds undergoing conventional race training and detraining. Ten healthy sedentary male Thoroughbreds with previous race training experience were studied for 14 weeks. Horses were trained for 9 weeks, using a program designed after those used commonly in the United States. Horses were trained conventionally by slow trotting (250 m/min) for 2 weeks and galloping (390 to 450 m/min) for 4 weeks, followed by 3 weeks of galloping (440 to 480 m/min) and intermittent sprinting exercises (breezes) at distances between 600 and 1,000 m (900 to 950 m/min). The horses were then pasture rested for 5 weeks. A standardized exercise test (SET) involving an 800-m gallop...
Pulmonary artery, aortic and oesophageal pressure changes during high intensity treadmill exercise in the horse: a possible relation to exercise-induced pulmonary haemorrhage. This study investigated changes in packed cell volume (PCV), pulmonary artery and aortic pressures, and the interaction between oesophageal pressure and pulmonary artery and aortic pressures during strenuous exercise in the horse. It was hypothesised that oesophageal pressure changes summate with pulmonary artery and aortic pressures during exercise and contribute to exercise-induced pulmonary haemorrhage (EIPH). Acute treadmill exercise (10 m/sec, 3 degrees incline) produced increases in heart rate (HR) from 50 to 202 beats/min; mean pulmonary artery pressure (PAP) from 28 to 80 mmHg; mean ao...
Isoproterenol-induced maximal heart rate in normothermic and hyperthermic horses. The heart rate (HR) induced by maximal beta-adrenergic activation, which was elicited by infusion of isoproterenol, was studied in 8 healthy horses before (control) and after hyperthermia was induced by IV administration of 2,4-dinitrophenol (DNP). Isoproterenol was administered IV at 1.0 micrograms.kg-1.min-1 for 3 minutes, and the HR was determined during the final 30 seconds of the infusion. As the rectal temperature increased (P less than 0.001) from 38.2 +/- 0.1 C (mean +/- SEM; normothermic control) to 40.1 +/- 0.1 C at 60 minutes after DNP administration, the isoproterenol-induced HR al...
Plasma theophylline concentration and lung function in ponies with recurrent obstructive lung disease. Six ponies with recurrent obstructive lung disease were studied during two separate 60 min periods while receiving constant equal volume infusions of either aminophylline or sterile water. Dynamic lung compliance, pulmonary resistance, respiratory rate, tidal volume, blood gas tensions and heart rate were measured. Plasma samples were obtained for determination of theophylline concentrations before, and at 10 min intervals during, the infusion period. Excitability was assessed subjectively at these same time periods. The plasma theophylline concentrations in ponies were well predicted by a pre...
Renal and systemic hemodynamic responses to sustained submaximal exertion in horses. We investigated the effects of 1 h of sustained submaximal exertion on the renal and systemic hemodynamics of six horses. The horses ran on a treadmill at a speed that produced heart rates of 55-60% of each horse's maximum heart rate. Exertion produced heart rates of 121 +/- 6.6 and 126 +/- 6.1 (SE) beats/min after 15 and 60 min, respectively. Cardiac output increased significantly (P less than 0.05) from 70.1 +/- 3.1 to 246.2 +/- 4.7 ml.min-1.kg body wt-1 after 15 min of exertion and thereafter did not change. There was no significant change from rest in p-aminohippuric acid and creatinine cl...
Tracheobronchial perfusion during exercise in ponies. Tracheobronchial circulation during exercise has previously not been examined. Therefore blood flow to the trachea and bronchi (up to 7th generation of branching) was studied in seven healthy adult ponies at rest and during the 3rd and 10th min of exercise performed at a treadmill speed setting of 25 km/h. The ambient air temperature varied from 19 to 20 degrees C and humidity from 35 to 45%. To determine blood flow radionuclide-labeled 15-microns-diameter microspheres were injected into the left ventricle via a catheter advanced from the left carotid artery (exposed using local anesthesia), a...
Haematological, biochemical and physiological changes in horses and ponies during the cross country stage of driving trial competitions. The haematological, biochemical and physiological changes associated with the cross-country stage of driving trials were studied in horses and ponies competing in singles, pairs, tandems and teams at five, five-section and two, three-section events. Heart rates were monitored continuously and sometimes exceeded 200 beats/minute. The highest maximum, mean and recovery heart rates were found after the most severe competitions. Rectal temperatures were also highest after the most severe events and in some animals exceeded 41 degrees C. Respiratory rates were very variable. Blood taken five minute...
Effects of acetazolamide on metabolic and respiratory responses to exercise at maximal O2 uptake. Changes in blood gases, ions, lactate, pH, hemoglobin, blood temperature, total body metabolism, and muscle metabolites were measured before and during exercise (except muscle), at fatigue, and during recovery in normal and acetazolamide-treated horses to test the hypothesis that an acetazolamide-induced acidosis would compromise the metabolism of the horse exercising at maximal O2 uptake. Acetazolamide-treated horses had a 13-mmol/l base deficit at rest, higher arterial Po2 at rest and during exercise, higher arterial and mixed venous Pco2 during exercise, and a 48-s reduction in run time. Ar...
Inspiratory and expiratory muscle perfusion in maximally exercised ponies. The present study was carried out on seven healthy ponies to examine the extent of blood flow in various inspiratory and expiratory muscles at rest and during maximal exertion as well as to determine the proportion of cardiac output needed to perfuse respiratory muscles during these conditions. Tissue blood flow was studied with 15 micron-diameter radionuclide-labeled microspheres injected into the left ventricle during steady conditions. The inspiratory and expiratory muscles comprised 2.41 and 3.05% of body weight, respectively, and received 6.17 and 3.75% of the cardiac output at rest. With...
Effect of high PaCO2 and time on cerebrospinal fluid and intraocular pressure in halothane-anesthetized horses. The effects of different arterial carbon dioxide tensions (PaCO2) on cerebrospinal fluid pressure (CSFP) and intraocular pressure (IOP) were studied in 6 male halothane-anesthetized horses positioned in left lateral recumbency. Steady-state anesthetic conditions (1.06% end-tidal halothane concentration) commenced 60 minutes following anesthetic induction with only halothane in oxygen. During atracurium neuromuscular blockade, horses were ventilated, and respiratory rate and peak inspiratory airway pressure were maintained within narrow limits. The CSFP and IOP were measured at 3 different leve...
A preliminary study on the effects of atropine sulphate on bradycardia and heart blocks during romifidine sedation in the horse. Romifidine (STH 2130-Cl or Sedivet) is an alpha 2-agonistic imino-imidazol sedative for intravenous use in horses recently developed by Boehringer Ingelheim, Vetmedica GmbH. An exploratory study was done in nine warm-blood horses, randomly divided into three groups, which received different dosages of romifidine (0.04, 0.08 and 0.12 mg/kg of body weight (BWT) intravenously (i.v.)) with at least one week's interval between tests. Romifidine induced a marked bradycardia accompanied by second degree atrioventricular (AV) block and some sinus blocks at all tested dosages. A placebo (NaCl 0.9% i.v....
Digital processing of equine exercise electrocardiograms. We have developed and used a system for recording and analyzing the electrocardiogram (ECG) of the horse during exercise. The system consists of a commercial ECG transmitter telemetering a Z lead (base-apex) ECG from an exercising horse. The received data are then remodulated at an audio frequency and stored on a audio cassette recorder. Exercise protocols of up to 10 minutes are digitized using a Macintosh II computer. For rhythm analysis, a computer program to identify the various waves of the ECG uses a modification and refinement of the integrated-squared-derivative (ISD) technique. This t...
