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  • Author or Editor: Nikolaus G. Kriz x
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Objective—To investigate the effects of deconditioning on cardiac dimensions and indices of cardiac function in horses.

Animals—Thirteen 3-to 4-year-old Standardbred geldings.

Procedure—All horses had echocardiographic measurements performed at the conclusion of 9 months of intense training and at weeks 1.5, 4, 8, and 12 of deconditioning. Direct echocardiographic measurements included interventricular septal thickness, left ventricular internal dimensions, left ventricular freewall thickness, left atrial dimension, aortic diameter, diameter of the pulmonary artery, slopes of the mitral valve, heart rate, preejection period, and ejection time. Derived indices of cardiac function included fractional shortening, fractional area change, and cardiac output.

Results—Cardiac dimensions did not change significantly for the first 4 weeks of deconditioning but decreased significantly by week 8 and continued to decrease until week 12. Indices of cardiac function increased significantly during the first 10 days of deconditioning, remaining stable until week 4 of deconditioning. After week 4, indices of cardiac function decreased significantly until week 12.

Conclusions and Clinical Relevance—Deconditioning resulted in a general reduction in cardiac dimensions and indices of cardiac function over 12 weeks. However, results of the study reported here indicate that following an intense period of training, cardiac function may be maintained during the first 4 weeks of deconditioning. Results indicate that trained horses may rest for up to 4 weeks without a substantial reduction in cardiac capacity as reflected by echocardiographic indices. (Am J Vet Res 2000;61: 1553–1560)

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in American Journal of Veterinary Research


Objective—To determine the prevalence of various types of heart murmurs in Thoroughbred racehorses and assess their association with performance by echocardiography and review of the horses' race records for the preceding 2 years.

Design—Clinical and retrospective study.

Animals—846 Thoroughbred racehorses.

Procedure—Cardiac auscultations were performed by 3 individuals; for 30 horses, Doppler echocardiographic examinations were also performed. Statistical analyses of race records for 753 horses were performed to assess association of heart murmurs with performance.

Results—Heart murmurs were detected by cardiac auscultation in 686 of 846 (81.1%) horses. Systolic murmurs over the heart base were most common; 365 (43.1%) horses had systolic murmurs that were loudest over the pulmonary valve area, and 232 (27.4%) horses had systolic murmurs that were loudest over the aortic valve area. Systolic murmurs over the tricuspid valve area were detected in 241 (28.5%) horses, whereas systolic murmurs over the mitral valve area were detected in only 32 (3.8%) horses. Diastolic murmurs were much less common than systolic murmurs. Review of race records did not reveal a significant association between murmurs and performance.

Conclusion and Clinical Relevance—Results suggest that heart murmurs are a common finding in racehorses; most of these heart murmurs do not appear to be clinically important. (J Am Vet Assoc 2000;216:1441–1445)

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in Journal of the American Veterinary Medical Association