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- Author or Editor: Rikke Buhl x
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Abstract
Objective—To assess whether physical training induces cardiac hypertrophy and valvular regurgitation in maturing Standardbred trotters and to establish a prediction model for the size of the left ventricle.
Design—Longitudinal observational study.
Animals—53 Standardbred trotters.
Procedures—Each horse underwent 2-D, M-mode, and color flow Doppler echocardiography at 5.5 years of age; previously, each horse had been examined at 2, 2.5, 3, and 3.5 (time of maturity) years of age. Horses were or were not in training or racing for variable periods during the entire assessment period; data for a given horse were assigned to 1 of 2 groups on the basis of the horse's status at the fifth examination (racing [n = 40] or not racing [13]). At each examination, left ventricular (LV) internal diameter in diastole (LVIDd), LV mass, and mean and relative LV wall thicknesses were measured. Prevalence and severity of tricuspid, pulmonary, mitral, and aortic valve regurgitation were determined.
Results—During the assessment period, LVIDd, LV mass, and mean LV wall thickness increased; body weight was significantly associated with those variables. Prediction of LV mass was possible when sex and weight were included in the model. Prevalence of valvular regurgitation increased for all valves. An increased risk of development of tricuspid and pulmonary valve regurgitation for horses in racing was observed.
Conclusions and Clinical Relevance—The LV mass and prevalence of valvular regurgitation increased (indicative of development of exercise-induced cardiac hypertrophy and valvular regurgitation) in young horses, even during the latter part of the assessment period, when maturity was attained.
Abstract
Objective—To evaluate changes over time in echocardiographic measurements in young Standardbred racehorses undergoing training and racing and determine whether there was any relationship between cardiac dimensions and racing performance.
Design—Longitudinal observational study.
Animals—103 horses.
Procedure—2-dimensional and M-mode echocardiography was performed 4 times at 6-month intervals.
Results—Significant cardiac enlargement took place during the study period as indicated by increases in left ventricular internal diameter in diastole (LVIDd), estimated left ventricular muscle mass (LV mass), and mean wall thickness attributable to eccentric left ventricular hypertrophy. Estimated body weight was positively correlated with left ventricular size, and males had significantly larger LVIDd and LV mass than did females. Horses that were racing regularly had larger LVIDd and LV mass than did unraced horses. A significant relationship between left ventricular size and racing performance was observed. The relationship was strongest at the time of the fourth examination.
Conclusions and Clinical Relevance—Results suggest that age must be taken into account when interpreting results of echocardiography in young Standardbred racehorses because significant cardiac enlargement takes place with age and training. A larger heart was found in horses that were racing, and size of the heart was correlated with athletic performance of the horse. (J Am Vet Med Assoc 2005;226: 1881–1887)
Abstract
Objective—To evaluate the incidence and development of valvular regurgitation and its effect on racing performance in Standardbred trotters from 2 to 3.5 years of age.
Design—Longitudinal observational study.
Animals—103 horses.
Procedure—Horses were examined via echocardiographic imaging 4 times at 6-month intervals. Twodimensional and M-mode echocardiographic examinations were performed in each horse, and color Doppler imaging was used to detect and evaluate regurgitant blood flow at each valve.
Results—For all cardiac valves, the frequency of valvular regurgitation increased significantly during the 18-month study period. Regurgitation was mild in all valves in which it was detected, and no progression in severity was observed at any valve. Tricuspid regurgitation was more prevalent in horses that raced regularly and was diagnosed more frequently in males and horses with larger left ventricular mass and left ventricular internal diameter during diastole. No relationship between racing performance and valvular regurgitation was observed.
Conclusions and Clinical Relevance—The incidence of valvular regurgitation increased during the study period, and it was common at 3.5 years of age. It was not possible to determine whether the increase was a result of maturity or training. The study revealed that there is a high prevalence of mild valvular regurgitation at this age, but apparently, the regurgitation had no effect on racing performance in this age group. Whether regurgitation will progress or influence future performance is not known. (J Am Vet Med Assoc 2005;227:1630–1635)
Abstract
OBJECTIVE
To determine whether administration of trimethoprim-sulfadiazine (TMS), detomidine (DET), or TMS plus DET would be associated with changes in ECG repolarization parameters in horses.
ANIMALS
9 healthy adult horses.
PROCEDURES
Each horse received 4 treatments in a blinded, randomized, crossover study design as follows: TMS, 16 to 24 mg/kg, IV; DET, 0.015 to 0.02 mg/kg, IV; TMS plus DET; and saline (0.9% NaCl) solution. Surface ECG traces were obtained over 24 hours, and repolarization parameters were measured at predefined time points after each treatment and compared with a 2-way ANOVA for repeated measures.
RESULTS
Heart rate–corrected QT intervals (QTc) were significantly increased after administration of DET (mean ± SD difference in QTc, 36.57 ± 23.07 milliseconds; increase of 7%) and TMS plus DET (44.96 ± 29.16 milliseconds; increase of 9%), compared with baseline (before treatment) values and values after administration of saline solution. Saline solution and TMS alone did not affect QTc.
CONCLUSIONS AND CLINICAL RELEVANCE
Administration of DET or TMS plus DET was associated with a significant and possibly clinically relevant prolongation of QTc, with prolongation of 7% to 9%, a range that is considered as a risk factor for the development of cardiac arrhythmias in people. Results were unexpected because DET is considered to be a safe sedative for horses.
Abstract
OBJECTIVE To evaluate heart rate, heart rate variability, and arrhythmia frequency as well as changes in cardiac biomarker values and their association with heart rate in horses before and after an endurance ride.
DESIGN Cross-sectional study.
ANIMALS 28 Arabian horses competing in a 120- or 160-km endurance ride.
PROCEDURES ECG recordings were obtained from each horse before (preride) and after (recovery) an endurance ride to evaluate changes in heart rate and the SD of normal R-R intervals (SDNN) during the initial 12 hours of recovery. Frequencies of supraventricular and ventricular premature complexes before and after the ride were evaluated. Blood samples were obtained before the ride and twice during recovery. Hematologic analyses included measurement of serum cardiac troponin I concentration and creatine kinase isoenzyme MB activity.
RESULTS Heart rate was significantly increased and SDNN was decreased during the recovery versus preride period. Frequency of ventricular premature complexes increased during recovery, albeit not significantly, whereas frequency of supraventricular premature complexes was not significantly different between preride and recovery periods. Serum cardiac troponin I concentration and creatine kinase isoenzyme MB activity were significantly increased in the recovery versus preride period. No associations were identified between cardiac biomarkers and velocity, distance, or mean heart rate.
CONCLUSIONS AND CLINICAL RELEVANCE Heart rate increased and SDNN decreased in horses after completion of an endurance ride. These and other cardiac changes suggested that prolonged exercise such as endurance riding might have cardiac effects in horses. Additional studies are needed to clarify the clinical relevance of the findings.
