Measurement of cardiac function by transthoracic echocardiography: day to day variability and repeatability in normal Thoroughbred horses.

The research article outlines a study aimed at understanding the effectiveness and accuracy of transthoracic echocardiography in monitoring cardiac function variability in Thoroughbred horses over time. The study focused mainly on assessing the repeatability of measurements from various echocardiographic indices.

Research Methodology

• The study included several echocardiographic indices of ventricular function that varied from 2-dimensional and M-mode echocardiography to pulsed Doppler echocardiography.
• The variables researched included aortic diameter, pulmonary artery diameter, left ventricular internal diameter in systole and diastole, left ventricular fractional shortening, estimated ejection fraction, maximum velocity and acceleration of aortic and pulmonary arterial blood flow, left and right ventricular velocity time integral, estimated cardiac output, left and right ventricular ejection time and pre-ejection period, and heart rate.
• Other variables like maximum velocity of early rapid right ventricular filling, late right ventricular filling due to right atrial contraction, maximum deceleration, and time for deceleration of early rapid filling were also assessed.
• Seven mature Thoroughbred horses were analyzed, where the horses’ management regimes and environment were standardized and an echocardiographic examination was undertaken at the same time daily for six consecutive days.

Findings and Conclusions

• Two statistical measures of repeatability, the intraclass correlation coefficient (rI) and the 95% confidence intervals for error-free value of a single measurement, were calculated for each variable.
• According to the study, measurements derived from 2-D and M-mode echocardiography were found to have better repeatability for individual horses compared to those from Doppler echocardiography.
• It was also found that Doppler echocardiographic variables often presented wide 95% confidence intervals for error-free value.
• The research therefore cautions users about the limitations of attributing serial changes measured through Doppler echocardiography to effects of a treatment or disease in an individual horse. This showcases the need to use these measurements with care due to their wider range of potential error.