Table 4.7 Guidelines for measuring cardiac dimensions and a range of values obtained in normal adult Thoroughbred horses. All measurements made using leading-edge to leading edge technique (cursor placed at transducer side of thin hyperechoic endocardial echoes for near and far endocardial surfaces) except PV, AoV and LAD measurements (inner edge of endocardial surface). Five measurements of good quality frames which strictly meet measurement criteria should be measured at resting rates in unsedated animals, and the mean value calculated. Evaluation should not be made on measurements alone. If measurements cannot be certain to be accurate they should be interpreted with caution.


Dimension Image Plane Measurement Guidelines Average (cm) Max Min
LVDS RCSx M-mode
(Figure 4.4, Figure 4.12, Figure 4.13)
Standard R chordal M-mode image with cursor through mid-point of ventricle from nadir of septal motion to LVFW 7.5 9.1 5.8
LVDd RCSx M-mode Standard R chordal M-mode image IVS-LVFW at onset of R wave 11.9 13.5 9.7
IVSs RCSx M-mode Standard R chordal M-mode image IVS thickness at nadir of septal motion 4.2 5.2 3.2
IVSd RCSx M-mode Standard R chordal M-mode image IVS thickness at onset of R wave 2.9 3.7 2.3
LVFWs RCSx M-mode Standard R chordal M-mode image Greatest LVFW thickness 3.8 4.6 3.2
LVFWd RCSx M-mode Standard R chordal M-mode image LVFW thickness at onset of R wave 2.2 2.6 1.7
LAD LLx 2DE
(Figure 4.17)
Maximul dimension of left atrium dorsel to valve annulus at end-diastole 12.8 14.5 11.3
AoV RLx 2DE
(Figure 4.10)
Width at sinus of Valsalva, at end-diastole 8.7 9.7 7.8
PV ROx 2DE
(Figure 4.11)
Width at base of valve at end diastole 6.1 8.0 5.2
LVDs LCSx M-mode M-mode cursor through junction of IVS and LVFW smallest dimension, minimum ventricular diameter 7.4 9.5 5.7
LVDs LCSx M-mode M-mode cursor through junction of IVS and LVFW onset of R wave, maximum ventricular diameter 36.9 45.0 28.0
FS% (R) RCM-mode (LVDd-LVDs)/LVDd x 100 36.9 45.0 28.0
FS% (L) LCM-mode (LVDd-LVDs)/LVDd x 100 38.0 47.0 27.0

Key:LVDs - Left ventricular diameter at end-systole, LVDd - Left ventricular diameter at end diastole, IVSs - Interventricular septal thickness at end-diastole, LVFWs - Left ventricular free-wall thickness at end-systole, LVFWd - Left ventricular free-wall thickness at end-diastole, LAD - Left atrial diameter at end systole, AoV - Aortic valve diameter, PV - Pulmonary Valve diameter, FS% - Fractional shortening, RCSx - Right chordal short-axis, LCSx - Left chordal short-axis, LLx - Left long axis, RLx - Right long axis, ROx - Right oblique-axis, 2DE - Two-dimensional image.

Adapted from Long, K.J. (1992) Two-dimesional and M-mode echocardiography. Equine Vet, 4:303-10, and Patteson, M.W. (1993) Echocardiographic studies in the horse.PHd thesis, University of Bristol. Maximum and minimum values are derived from 78 clinically normal Thoroughbred and Thoroughbred-cross horses; values outside this range are not necessarily abnormal but are uncommon.