Page 995 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

970 CHAPTER 8

VetBooks.ir 8.7 8.8

Fig. 8.7 Right-sided, long-axis view, highlighting Fig. 8.8 Left-sided, long-axis view. Image taken from
the aorta. Image taken from the right 4th ICS aiming the left 5th ICS aiming across the thorax. LV = left
across the thorax. Slight rotation of the probe is ventricle; LA = left atrium.
necessary to have a true long-axis view of the aorta.
RV = right ventricle; RA = right atrium; LV = left
ventricle; Ao = aorta; LA = left atrium.

8.9 8.10

Fig. 8.9 M-mode image of a left ventricle. Image Fig. 8.10 Continuous-wave Doppler image of right
taken from the left 5th ICS in a normal horse. The AV valvular regurgitation (RAVVR). Image taken
small image shows the long-axis view from which the from the right 4th ICS of a 4-year-old Standardbred
M-mode image was collected. In this case, M-mode gelding with moderate RAVVR. Colour-flow Doppler
of the left ventricle was collected for the evaluation is used to locate the most intense regurgitant jet and
of left ventricular function. Left ventricular internal then continuous-wave Doppler to assess the flow
dimensions in diastole and systole were collected and velocity. This can then be used to calculate pressure
then ejection fraction and fractional shortening were differential across the valve.
calculated.

been detected. A fairly accurate assessment of flow determined. Pulsed-wave or colour-flow Doppler
velocity is possible with ventricular septal defects echocardiography is used to assess the extent and
(VSDs) because parallel positioning of the ultra- direction of intracardiac and extracardiac shunts as
sound beam is possible. Without accurate assess- well as valvular regurgitation. Valvular stenosis is
ment of flow velocity, pressure gradients cannot be extremely uncommon in the horse.