Pulsed-wave Doppler evaluation of intracardiac blood flow in 30 clinically normal Standardbred horses.

Pulsed-wave Doppler echocardiography was performed on 30 clinically normal 1- to 6-year-old racing Standardbreds. There were 13 females, 13 geldings, and 4 stallions. Cardiac disease was not detected with M-mode, 2-dimensional real-time or pulsed-wave Doppler echocardiography. Normal flow velocities for right and left atrial outflow, right and left ventricular outflow, the aorta, and pulmonary artery were determined. Peak flow velocities for right and left atrial outflow occurred during the rapid filling phase and were higher toward the mitral valve (mean, 0.70 +/- 0.24 m/s) than toward the tricuspid valve (mean, 0.49 +/- 0.17 m/s). Peak flow velocities in the right and left ventricular outflow tracts were similar (means, 0.81 +/- 0.10 m/s and 0.75 +/- 0.39 m/s, respectively). Peak flow velocities in the pulmonary artery (mean, 1.09 +/- 0.42 m/s) and aorta (mean, 1.01 +/- 0.29 m/s) were similar, although flow peaked earlier in systole in the aorta than in the pulmonary artery.