Echocardiographic Assessment of Left Ventricular Function in Healthy Horses and in Horses with Heart Disease Using Pulsed‐Wave Tissue Doppler Imaging

Background Assessment of left ventricular (LV) function by tissue Doppler imaging (TDI) is not well established in horses with heart disease. Objectives To describe the use of pulsed-wave (PW) TDI for the assessment of LV function, establish reference intervals, investigate effects of mitral regurgitation (MR), aortic regurgitation (AR), and primary myocardial disease (MD), and provide proof of concept for the use of PW TDI in Warmblood horses with heart disease. Animals Thirty healthy horses, 38 horses with MR, 25 with AR, 8 with MD. Methods Echocardiograms were retrospectively analyzed. Reference intervals were calculated. PW TDI indices of healthy horses and horses with MR, AR, and MD were compared by one-way ANOVA and Dunnett's test. Results A complete set of PW TDI variables could be obtained in 94 of 101 horses. Variables corresponding to isovolumic intervals were most difficult to measure. Valvular regurgitation influenced variables describing isovolumic contraction and ejection. Horses with MD had significantly shortened ETm (−118.5 [−154.1 to −82.9] ms; mean difference [95% CI of difference of means]), increased PEPm/ETm (0.11 [0.05 to 0.17]), prolonged IMPm (0.28 [0.18 to 0.37]), increased S1 (8.9 [5.2 to 12.6] cm/s), and decreased E1 (−2.6 [−4.7 to −0.5] cm/s), Em (−14.2 [−19.9 to −8.5] cm/s), and Em/Am ratio (−1.6 [−2.6 to −0.6]). Conclusions and Clinical Importance Pulsed-wave TDI might be useful for detection of LV dysfunction in horses with primary MD. The clinical value of TDI in horses with MR and AR remains uncertain.