Changes in cardiac dimensions and indices of cardiac function during deconditioning in horses.

The research explores how a lack of training, or deconditioning, affects the heart dimensions and function in horses. The study found that while there are no significant changes observed in the initial 4 weeks of deconditioning, noticeable reductions in cardiac dimensions and function occur from the 8th week onwards.

Study Design and Methodology

• Thirteen standard-bred geldings aged 3 to 4 years were used in the study.
• Echocardiographic measurements were taken after 9 months of intensive training and then at various intervals (1.5 weeks, 4 weeks, 8 weeks and 12 weeks) during a deconditioning period.
• The parameters studied included aspects such as interventricular septal thickness, internal dimensions of the left ventricle, left ventricular freewall thickness, left atrial dimension, aortic diameter, diameter of the pulmonary artery, mitral valve slopes, heart rate, preejection period, and ejection time.
• The researchers also calculated indices of cardiac function such as fractional shortening, fractional area change, and cardiac output.

Research Findings

• While the cardiac dimensions did not experience a noteworthy change in the first 4 weeks of deconditioning, reductions were evident by the 8th week and continued to take place until the 12th week.
• The indices of cardiac function significantly increased within the first 10 days of deconditioning, however, this stabilized until the 4th week of deconditioning. After this point, the indices decreased significantly until the 12th week of the deconditioning period.

Conclusions and Implications

• The research showed that deconditioning in horses generally led to a reduction in cardiac dimensions and indices of cardiac function over 12 weeks.
• However, it was also noted that following an intense training period, cardiac function was maintained during the first 4 weeks of deconditioning.
• The findings suggest that trained horses may be given a break from training for up to 4 weeks without a significant reduction in cardiac capacity, as indicated by echocardiographic indices. This could have important implications for training schedules and overall equine health.