The ratio of cardiopulmonary blood volume to stroke volume as an index of cardiac function in horses

A method was developed for determining the ratio of cardiopulmonary blood volume to stroke volume, in horses. The radioisotope 99 Tc (technetium 99m pertechnetate) was injected into the jugular vein as a bolus, which was then detected in the right and left ventricles consecutively by a scanning device consisting of a Na I crystal, a collimator, an amplifier and a discriminator. The radiocardiogram (RCG) and the ECG were recorded simultaneously by a two-channel writing device. The ratio of cardiopulmonary blood volume to stroke volume (cardiopulmonary flow index = CPFI) was then determined from the RCG and ECG tracings. Five categories of horses were examined, viz. Thoroughbreds in training, showjumpers in training, horses not in training, horses with cardiovascular disease and horses with chronic lung disease. The mean CPFI of the above categories were respectively 7.0 +/- 0.39, 7.3 +/- 0.45, 6.7 +/- 0.61, 9.8 +/- 1.30 and 6.2 +/- 0.47. The mean CPFI of the subjects with heart disease was significantly greater than the mean values of the other four categories (P less than 0.001). It was concluded that the CPFI was a reproducible physiological parameter in horses and that the value was significantly increased in our series of subjects with heart disease.     

Haemodynamic effects of small volume hypertonic saline in experimentally induced haemorrhagic shock

A comparison of the haemodynamic benefits of small volume hypertonic saline (2,400 mOsm/litre) versus isotonic saline (300 mOsm/litre) was conducted in 12 adult horses using a haemorrhagic shock model. The horses were anaesthetised and intravascular catheters placed for the measurement of haemodynamic data. Mean systemic arterial pressure was then reduced to 50 to 60 mmHg by controlled haemorrhage and maintained at that level for 40 mins. Cardiac output, stroke volume, mean systemic arterial pressure, plasma volume and urine production decreased significantly following blood loss. Hypertonic or isotonic saline was administered randomly by intravenous infusion and haemodynamic data recorded for a 2 h period. Treatment with hypertonic saline produced rapid elevations in cardiac output, stroke volume, mean systemic and pulmonary arterial pressures, cardiac contractility and urine output, and was accompanied by expansion of the plasma volume. The changes in cardiac output and stroke volume were maintained for the duration of the recording period, whereas increases in mean systemic arterial pressure were not as remarkable. Infusion of isotonic saline caused only transient increases in cardiac output and mean systemic and pulmonary arterial pressure, and cardiac output; urine output and plasma volume did not change. This study indicates that hypertonic saline produces haemodynamic improvements in experimentally induced haemorrhagic shock in horses.     

Comparison of Systolic Cardiac Function Before and After Treatment of Atrial Fibrillation in Horses With and Without Additional Cardiac Valve Insufficiencies

Clinical, electrocardiographic and echocardiographic examinations were conducted before therapy and 4 days after conversion to normal sinus rhythm in 15 horses with a history of atrial fibrillation of 2-6 months duration. Seven horses showed no other signs of cardiac disease. Four horses suffered additionally from mitral valve insufficiency, while six horses had aortic valve insufficiency, including two of the four horses with mitral valve insufficiency, but none had signs of congestive heart failure. Doppler echocardiographic estimates of various variables were made for assessment of systolic heart function. These included heart rate, stroke volume, cardiac output and cardiac output per kg of body weight (heart index). After conversion to normal sinus rhythm, the horses without heart valve insufficiency showed a statistically significantly decreased heart rate (-24%) and cardiac output (-3%), but an increase in stroke volume (+8.4%) and heart index (+9%). The horses with heart valve insufficiency experienced a statistically significant decrease in heart rate (-21%) after conversion to normal sinus rhythm, but showed an increase in all other variables. Cardiac output increased statistically significantly by 20%, stroke volume by 54% and heart index by 58%.     

Myocardial Function of Horses Under Sedation with Romifidine Using Two-Dimensional Speckle Tracking

Two-dimensional speckle tracking echocardiography (2DST) provides the assessment of the left ventricle deformation parameters strain (St) and strain rate (SR). The objective of this study was to evaluate St and SR under the influence of romifidine in healthy horses and horses affected with heart disease. The study subjects were 45 privately owned horses. Valvular insufficiencies were identified by color Doppler in 21 out of 45 horses. Dimensional changes were identified in 13 of these 21 horses. These dimensional changes included dilatations of the left ventricle (130 ± 8.95 mm) and/or the left atrium (141 ± 4.8 mm). The other 24 horses were without echocardiographic findings and had normal heart dimensions. Based on clinical signs, echo-, and electrocardiographic examinations, 24 horses were categorized as group 1 (healthy), 13 as group 2 (heart disease without dimensional changes), and 8 as group 3 (heart disease with dimensional changes). The radial St and SR were assessed in the left ventricular free wall and the interventricular septum using 2DST. After application of romifidine, a significant reduction of St and the systolic peak of SR were found in all three groups. Group 3 showed the most significant reduction of these parameters (41.5%). The reduction of St and SR under romifidine showed a reduced myocardial function, which is more obvious in horses with cardiac dilatation. It can be assumed that heart disease with myocardial dilatation leads to decreasing myocardial function, which becomes more obvious after romifidine application and of clinical importance in horses with severe heart disease and cardiac dilatation.     

Effects of dobutamine on cardiovascular function and oxygen delivery in standing horses

Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10 min of dobutamine infusion (2 µg kg⁻¹ min⁻¹). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observed with dobutamine compared with baseline measurements. Arterial and mixed venous haemoglobin and oxygen content, as well as mixed venous partial pressure of oxygen increased. No significant changes in cardiac output, stroke volume, systemic vascular resistance, arterial partial pressure of oxygen, or oxygen consumption, delivery and extraction ratio were detected. Concluding, dobutamine increased systemic blood pressure without detectable changes in stroke volume, cardiac output or systemic vascular resistance in conscious horses.     

马运动候选基因的研究进展

马的运动性能是由环境和遗传因素共同决定的。研究表明,马身体构造和优异的运动能力很大程度上受控于基因。随着马基因组序列的公开和分子遗传学工具的快速发展,科学家发现与能量代谢、胰岛素信号转导、心肺功能及肌肉力量等相关的基因与马运动能力表型密切相关。同时这些基因也与人类的某些疾病有关。文章仅就与马运动能力密切相关的候选基因的研究成果作一综述,旨在为我国尽早开展相关研究、培育出品质优良的新型马种及对某些疾病的防治提供理论参考。     

Stress Response of Three-year-old Horse Mares to Changes in Husbandry System During Initial Equestrian Training

For initial training, horses are often transferred from group housing to individual boxes, which is a potential stressor. In this study, salivary cortisol concentrations, locomotion activity, and heart rate (HR) were analyzed and the HR variability (HRV) variables standard deviation of beat-to-beat interval (SDRR) and root mean square of successive RR differences (RMSSD) were calculated in 3-year-old mares (n = 8). Mares were transferred abruptly from a group stable with access to a paddock to individual boxes without a paddock and were studied from 4 days before to 5 days after changing the stable. Mares underwent routine equestrian training for young horses. On the days before mares were moved to individual boxes, cortisol concentrations showed a diurnal rhythm with values approximately 0.6 ng/ml in the morning and a decrease throughout the day. When horses were moved to individual boxes, cortisol concentrations increased to 1.8 ± 0.2 ng/ml within 30 minutes and did not return to baseline values within 6 hours (0.7 ± 0.1 ng/ml, P < .05 over time). On the following days, a diurnal rhythm was re-established but at a higher level than before the change of stable. Locomotion activity was higher when mares had access to a paddock than when kept in individual boxes. Heart rate increased for approximately 60 minutes when mares were separated from their group. In conclusion, separating young horses from their group and individual stabling are perceived as stressful.     

Hemodynamic Effects of Atropine, Dobutamine, Nitroprusside, Phenylephrine, and Propranolol in Conscious Horses

The authors investigated the cardiovascular effects of low doses of nitroprusside, dobutamine, and phenylephrine and a beta-adrenergic blocking dose of propranolol in conscious, healthy horses with and without prior atropine administration. A parasympathetic blocking dose of atropine produced significant increases in heart rate and arterial pressures, and decreased stroke volume, ejection fraction, pulse pressure, and right-ventricular end-diastolic pressure and volume. Cardiac output was not changed by atropine administration. Nitroprusside reduced arterial pressures to a greater extent in atropinized horses but increased heart rate in both atropinized and non-atropinized horses. Dobutamine increased mean arterial pressure in both non-atropinized and atropinized horses but increased heart rate, diastolic arterial pressure, and systemic vascular resistance only in atropinized horses. Propranolol did not affect any of the hemodynamic variables that were measured. Phenylephrine, in the presence of beta-adrenergic blockade, increased mean arterial pressure and reduced cardiac output. This study showed that low doses of nitroprusside, dobutamine, and phenylephrine produce significant hemodynamic effects in conscious, healthy horses and that these effects are modified by prevailing parasympathetic tone.     

Cardiac Power Output during Dobutamine Stress Test in Horses

Although echocardiography has greatly improved the diagnostic possibilities in equine medicine, determining the prognosis remains a difficult task. In humans, maximal cardiac power output (CPO) has been described as a powerful indicator of exercise capability and outcome in heart disease. The aim of the study is to describe the measurement of CPO by echocardiography and by thermodilution in healthy horses. Six healthy horses were studied. Cardiac output (CO) was measured by thermodilution and Doppler echocardiography at rest and during a pharmacologic stress test consisting of 35 μg/kg atropine followed by incremental steps 2, 4, 6, and 8 μg/kg/min of dobutamine infusion. Mean arterial pressure (MAP) was measured invasively by a catheter introduced into the transverse facial artery. CPO was calculated as the product of CO and MAP. Baseline CPO measured by thermodilution and by Doppler echocardiography was 10.7 ± 3.3 and 13.7 ± 4.5 watts, respectively. CPO increased significantly with pharmacologic stimulation and reached maximal CPO of 66.4 ± 3.6 and 60.4 ± 5.1 watts when measured by thermodilution and Doppler echocardiography, respectively. This study describes an estimation of CPO in horses. Further studies should demonstrate the usefulness of CPO as a predictive indicator in horses suffering from cardiac disease.     

Long-term Electrocardiography Recording with Holter Monitoring in 15 Donkeys

The heart rates (HR) and rhythms of 15 healthy donkeys of various ages, both sexes, and various breeds were analyzed throughout 24-hour Holter monitoring. The animals were evaluated at rest in their daily environment without the presence of investigators causing stress, using a three-channel digital Holter recorder. Analysis revealed a maximal HR range from 62.5 to 93.7 beats/min (mean, 72.50 ± 7.51 beats/min), whereas the minimal HR ranged from 29.7 to 42.2 beats/min (mean, 34.90 ± 4.22 beats/min). The daily mean HR was 47.55 ± 3.70 beats/min. The daytime mean HR was 49.39 ± 2.77 beats/min, whereas the night time rate was 46.22 ± 4.38 beats/min. Sinus bradycardia and sinus tachycardia were detected in 7 and 10 of 15 studied donkeys, respectively. Cardiac dysrhythmias due to high vagal tone such as sinoatrial heart block and second-degree atrioventricular heart block were occasionally recorded in 1 and 3 donkeys, respectively. A higher mean HR and fewer cardiac dysrhythmias were observed in donkeys than in horses and ponies at rest. These findings could be justified by differences in the autonomic nervous system tone.     

Cardiopulmonary effects of hypercapnia during controlled intermittent positive pressure ventilation in the horse.

The cardiopulmonary effects of eucapnia (arterial CO2 tension [PaCO2] 40.4 +/- 2.9 mm Hg, mean +/- SD), mild hypercapnia (PaCO2, 59.1 +/- 3.5 mm Hg), moderate hypercapnia (PaCO2, 82.6 +/- 4.9 mm Hg), and severe hypercapnia (PaCO2, 110.3 +/- 12.2 mm Hg) were studied in 8 horses during isoflurane anesthesia with volume controlled intermittent positive pressure ventilation (IPPV) and neuromuscular blockade. The sequence of changes in PaCO2 was randomized. Mild hypercapnia produced bradycardia resulting in a significant (P < 0.05) decrease in cardiac index (CI) and oxygen delivery (DO2), while hemoglobin concentration (Hb), the hematocrit (Hct), systolic blood pressure (SBP), mean blood pressure (MBP), systemic vascular resistance (SVR), and venous admixture (QS/QT) increased significantly. Moderate hypercapnia resulted in a significant rise in CI, stroke index (SI), SBP, MBP, mean pulmonary artery pressure (PAP), Hct, Hb, arterial oxygen content (CaO2), mixed venous oxygen content (CvO2), and DO2, with heart rate (HR) staying below eucapnic levels. Severe hypercapnia resulted in a marked rise in HR, CI, SI, SBP, PAP, Hct, Hb, CaO2, CvO2, and DO2. Systemic vascular resistance was significantly decreased, while MBP levels were not different from those during moderate hypercapnia. No cardiac arrhythmias were recorded with any of the ranges of PaCO2. Norepinephrine levels increased progressively with each increase in PaCO2, whereas plasma cortisol levels remained unchanged. It was concluded that hypercapnia in isoflurane-anesthetized horses elicits a biphasic cardiopulmonary response, with mild hypercapnia producing a fall in CI and DO2 despite an increase in MBP, while moderate and severe hypercapnia produce an augmentation of the cardiopulmonary performance and DO2.     

Comparison of heart rate and heart rate variability obtained by heart rate monitors and simultaneously recorded electrocardiogram signals in nonexercising horses

Heart rate (HR) and heart rate variability (HRV) are often determined with Polar heart rate monitors (HRMs; S810i; Polar, Kempele, Finland). The aims of this study were to compare data from horses obtained by Polar HRMs and a portable Televet electrocardiogram (ECG; 100 version 4.2.3; Kruuse, Marslev, Denmark) device and to determine appropriate recording times in horses (n = 14). Correlations were calculated and a Bland-Altman analysis was carried out to examine agreement between recording systems. For beat-to-beat (RR) interval, uncorrected and corrected data were highly correlated irrespective of the recording system and recording time (r > 0.99, P < 0.001). For HRV variables, standard deviation of RR interval and root mean square of successive RR intervals, correlations higher than 0.9 were obtained between uncorrected and corrected ECG but not Polar data. The RR interval, HR, and HRV from corrected Televet and Polar data at no time differed between the recording systems. However, with the increase in recording time, the RR interval decreased (P < 0.001). Thus, for comparisons, recording intervals of similar length should be chosen. Correlations among RR interval, HR, and HRV variables obtained by ECG and HRMs were highly significant at all recording times (r > 0.9, P < 0.001). Correlations increased with increasing recording time. Bland-Altman graphs showed a strong agreement between HRMs and ECG and mean RR intervals, HR, and HRV variables were close to identical. In conclusion, Polar HRMs are as adequate as ECG recordings in horses. Owing to a low HR in stationary horses, recording times below 2 minutes will underestimate changes in HR and HRV.     

Change in Some Physiologic Variables Induced by Italian Traditional Conditioning in Standardbred Yearling

The goal of this study was to quantify the effect of a traditional Italian conditioning method (CM). Six Standardbred yearlings were kept in standardized conditions for 140 days. From T1 (day 1) to T10 (day 10), the horses were hitched for 30 minutes/day to accustom them to a cart. From T11 to T70, they were jogged or exercised for 30 minutes/day at a slow trot (4.4 ± 0.3 m/second) and from T71 to T140 for 40 minutes/day (5 m/second ± 0.3 m/second). Every 15 days, the horses performed fast exercise for a distance of 5,000 m with increased speeds. Blood samples were collected before and after daily training (DT) every 21 days (P1…P7), to measure the following variables: erythrocytes (RBC), hemoglobin (Hb), packed cell volume (PCV), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), total protein (Pt), albumin, aspartate amino transferase (AST), alkaline phosphatase (ALP), creatine kinase (CK), lactate dehydrogenase (LDH), urea, creatinine, glucose, triglycerides, and blood lactate. A three-step standardized exercise test (SET) also was performed. Analysis of variance was used to study differences during the training. Tukey's post-hoc test was used for statistical multiple comparison (P ≤ 0.05 and 0.01). Lactate level did not show an increase over 4 mmol/L in all periods. Glucose was higher at P1 than P7. There was no correlation between method of conditioning and the level of CK, LDH, or AST. Conditioning method induced an increase in triglycerides for the change in exercise metabolism supply. According to SET, conditioning method induced an increase of SVO2_max (speed [m/second] reached to a theoretical maximal oxygen consumption), V₄ (speed [m/second] reached at a lactate content of 4 mmol/L), V₂₀₀ (speed [m/second] at 200 beats/minute) and HR₄ (heart rate [beats/minute] at 4 mmol/L of lactate). We concluded that the Italian conditioning method used in this study improved the fitness of horses.     

Influence of exercise on horses' limb volume, measured by an optoelectronic device

This study tested for the first time an optoelectronic device (Perometer*) measuring limb volume of horses. An analysis of its application was performed regarding the influence of different types of physical exercise on the volume of the extremities. 40 horses were divided into four groups often horses, each group being exposed to exercise, differing in kind and duration of lunging, horse-ridden and riderless. The volume measurement was performed by determining the inactive value (I) after a twelfe-hour standing period, the load value (II) immediately after exercise and recovery value (III) one hour after exercise. The results showed a highly significant decrease in limb volume of 5.7% between values (I) and (II), as well as a highly significant increase of 68% between (II) and (III). The volume changes observed in male horses were significantly higher than in female horses. Volume changes in horse-ridden groups were higher than riderless ones, but not significant. There were fewer leg volume changes at low ambient temperatures (1-12 degrees C) compared to high temperatures (23-31 degrees C), but these were not statistically significant. Well-trained horses showed lower volume changes than less trained horses (not statistically significant). The Perometer is a fast and reliable tool for measuring limb volume of horses. The ICC (Interclass Correlation Coefficient) calculated a high measurement reproducibility of 0.996. A variance analysis showed no significant differences between the three repeated leg measurements. Thus, the Perometer can be used for monitoring and quantifying edema and documenting limb volume changes resulting from training, wearing compression stockings or bandages, manual lymph drainage.     

Effects of saffan on cardiopulmonary function in healthy cats.

The effects of saffan on cardiopulmonary function were evaluated in eight healthy adult cats. Measured values were cardiac output by thermodilution, heart rate by electrocardiogram, arterial blood gases, respiratory rate and systolic, diastolic and mean arterial blood pressures by arterial catheterization. Calculated values included cardiac index, stroke volume and systemic vascular resistance. Statistical analysis employed paired t-tests comparing pre saffan anesthetic induction and post saffan anesthetic parameters over a 120 minute time sequence. Thirty min after saffan induction, significant depression in cardiac output was evident while stroke volume was significantly depressed at 45 and 60 min, systolic blood pressure at 15 min and respiratory rate at 5, 10 and 15 min. No significant changes occurred in cardiac index, heart rate, arterial blood gases, diastolic and mean arterial blood pressure or systemic vascular resistance. It was concluded that saffan causes significant depression of cardiopulmonary function in normal adult cats.     

Influence of a constant rate infusion of dexmedetomidine on cardiopulmonary function and recovery quality in isoflurane anaesthetized horses

ObjectiveTo investigate the influence of a dexmedetomidine constant rate infusion (CRI) in horses anaesthetized with isoflurane.Study designProspective, randomized, blinded, clinical study.AnimalsForty adult healthy horses (weight mean 491 ± SD 102 kg) undergoing elective surgery.MethodsAfter sedation [dexmedetomidine, 3.5 μg kg^?1 intravenously (IV)] and induction IV (midazolam 0.06 mg kg^?1, ketamine 2.2 mg kg^?1), anaesthesia was maintained with isoflurane in oxygen/air (FiO₂ 55–60%). Horses were ventilated and dobutamine was administered when hypoventilation [arterial partial pressure of CO₂ > 8.00 kPa (60 mmHg)] and hypotension [arterial pressure 70 mmHg] occurred respectively. During anaesthesia, horses were randomly allocated to receive a CRI of dexmedetomidine (1.75 μg kg^?1 hour^?1) (D) or saline (S). Monitoring included end-tidal isoflurane concentration, cardiopulmonary parameters, and need for dobutamine and additional ketamine. All horses received 0.875 μg kg^?1 dexmedetomidine IV for the recovery period. Age and weight of the horses, duration of anaesthesia, additional ketamine and dobutamine, cardiopulmonary data (anova), recovery scores (Wilcoxon Rank Sum Test), duration of recovery (t-test) and attempts to stand (Mann–Whitney test) were compared between groups. Significance was set at p < 0.05.ResultsHeart rate and arterial partial pressure of oxygen were significantly lower in group D compared to group S. An interaction between treatment and time was present for cardiac index, oxygen delivery index and systemic vascular resistance. End-tidal isoflurane concentration and heart rate significantly increased over time. Packed cell volume, systolic, diastolic and mean arterial pressure, arterial oxygen content, stroke volume index and systemic vascular resistance significantly decreased over time. Recovery scores were significantly better in group D, with fewer attempts to stand and significantly longer times to sternal position and first attempt to stand.Conclusions and clinical relevance A dexmedetomidine CRI produced limited cardiopulmonary effects, but significantly improved recovery quality.     

Subspecies Studies: Pharmacokinetics and Pharmacodynamics of a Single Intravenous Dose of Xylazine in Adult Mules and Adult Haflinger Horses

This study reveals the different effectiveness of xylazine in mules compared with horses. Fourteen adult mules (mean body weight ± standard deviation, 466 ± 89 kg) and six adult Haflinger horses (483 ± 39 kg) chosen from a single livestock operation in Germany received 0.6 mg of the α₂-agonist xylazine administered intravenously per kilogram of body weight. Principal pharmacokinetic and pharmacodynamic parameters were determined while the animals received a routine dental treatment. To objectively assess the depth of sedation, a variety of behavioral and clinical parameters were assessed and transferred to a scaled score system. Compared with the Haflinger horses, the depth of sedation in mules differed significantly between 10 and 45 minutes after xylazine administration. In the mule, sedation was good during the first 10 minutes, moderate at 15 minutes, and insufficient at 30 minutes. In the horse, sedation was excellent during the first 15 minutes, moderate at 30 minutes, and insufficient at 45 minutes. Moreover, significant (P < .05) subspecies differences in the pharmacokinetics of xylazine were detected between the mules and the horses. Data analysis followed the two-compartment model, which had a correlation with the measured data of R² = .99. Values for t_1/2β (half-life during elimination), mean residence time, mean residence time_(0-tz) (residence time on last measuring time point above limit of quantification), k₂₁ (velocity constant for distribution from peripheral to central compartment), β (velocity constant during elimination), and B (relative y-intercept) varied significantly between the two subspecies.     

Pharmacokinetics and Effects of Alkalization after Intravenous Administration of Eltenac in Horses

Eltenac (ELT) [4-(2,6-dichlorophenyl)amino-3-thiophene] is a non-steroidal anti-inflammatory drug (NSAID) that was developed for veterinary use in horses and cattle. The pharmacokinetics of ELT was evaluated in horses at 0.5 mg/kg body weight (BW) after single IV injection after 5 days of repeated IV administration and after a single IV injection in horses previously subjected to 250 mg/kg BW of sodium bicarbonate (NaHCO₃) as an alkalization treatment. The aim was to determine whether blood and subsequent urinary alkalization could modify the pharmacokinetics of ELT. Drug quantification was performed with serum and urine using high performance liquid chromatography with UV-visible detection. The results were also integrated with cyclo-oxygenase-inhibition literature data to review the dosage scheme of ELT in horses. After a single intravenous administration, ELT was characterized by rapid distribution (mean t½_λ1 = 0.18 ± 0.07 hour) and a short elimination half-life (mean t½_λ2 = 2.9 ± 0.68 hour). The volume of distribution was small (V_dss = 253.51 ± 47.55 mL/kg), which is likely because of the high percentage of drug protein binding (approximately 97%). The AUC_0-∞ and Cl_B were 6.92 ± 0.84 h*μg/mL and 73.2 ± 10 mL/h/kg, respectively. Repeated administration did not cause either accumulation or modification of the pharmacokinetic profile. The in vitro effective concentrations were maintained for a 6-hour period. The alkalization procedure appeared to accelerate drug elimination, as ELT was quantifiable only for 6 hours; however, the drug clearance was not significantly modified. Thus, the administration of alkaline compounds to accelerate the elimination of ELT is not completely confirmed.     

Behaviour of the heart rate of horses with auricular fibrillation during exercise and after treatment.

Cardioversion through varying quinidine sulphate treatments was achieved in 3 riding horses with auricular fibrillation. The horses were subjected to continual telemetric ECG registration before and after reversion in a uniform exercise-tolerance-test. A comparison of the heart rate curves showed a strong decline of the heart beat frequency during the exercise phase after synchronisation. The decrease in heart rate during exercise was greater than 30% in all 3 patients. Anti-arrhythmic treatment is, therefore, recommended for horses with auricular fibrillation and without concurrent heart disease.     

Biokinematics under Competitive Racing Conditions in Young Standardbred Trotters: A Preliminary Report

With the aim of evaluating equine performance in competitive trotter horses under normal racing conditions data of stride length, stride frequency and mean horses speed were obtained from 50, 2-year-old Italian winner fillies during the racing and the sprint laps of competition. The enhancement of speed in the sprint lap was obtained by increasing both stride length and stride frequency. Stride frequency for the racing and the sprint laps were (mean ± SD) 133.63 ± 3.93 and 138.97 ± 6.62 strides per minute, respectively and Stride length for the racing and the sprint laps were 7.17 ± 0.17 and 7.30 ± 0.11 m, respectively; mean speed was 48.18 ± 1.09 km/hr. The usefulness of the kinematic assessments is discussed as is its potential reference for future indicators of performance.