Pulsed wave Doppler echocardiography in normal horses.

This study establishes reference values for Doppler-derived variables from healthy Thoroughbred horses, using two-dimensional (2-D) images to guide the Doppler sampling site. Significant differences were found between measurements taken from different locations and in horses with certain heart murmurs. These findings may be useful in evaluating heart function in horses.

Objective and Methodology

• In this investigation, the team of researchers aimed to establish reference values for certain variables derived from pulsed wave Doppler echocardiography in a group of 40 healthy Thoroughbred and Thoroughbred cross horses.
• The team collected readings from different locations in the horse’s heart, using standard two-dimensional (2-D) images to guide the site of Doppler sampling. This ensured an accurate alignment with blood flow.

Results and Observations

• Significant differences were observed in the heart’s tricuspid inflow velocities during rapid filling (E) and atrial contraction (A), depending on the site from which the readings were taken. The velocities were higher when recorded from a right parasternal angled view than from a right parasternal long-axis view.
• In eight horses, the peak tricuspid inflow velocity during atrial contraction (A) was higher than during rapid filling (E).
• The peak acceleration of blood flow was observed to be significantly higher in the aorta (average 8.01 m/s/s) than in the pulmonary artery (4.45 m/s/s).
• There were significant differences in the pre-ejection period, ejection time and acceleration time between these two blood vessels.

Conclusions and Potential Implications

• Horses that exhibited functional ejection murmurs had a lower peak aortic acceleration and a longer acceleration time than horses without such murmurs.
• Horses that had filling murmurs over the left hemithorax had elevated peak mitral E velocities when compared to those without the murmurs.
• The measurements taken from the Doppler waveforms were repeatable, indicating that these reference values can be reliably used in future assessments of ventricular function in this species.