Use of Tissue Doppler Imaging in horses - exercise stress echocardiography with Tissue Doppler Imaging in healthy horses and horses with cardiac disease

The evaluation of performance capacity with exercise test is of particular importance in horses with mild to moderate valvular regurgitations as a possible exercise intolerance, and a detrimental cardiac function is often first detected after exercise. Aim of the study was the comparison of myocardial velocities evaluated with Tissue Doppler imaging in healthy horses and horses with a cardiologic disease. 20 adult warmblood horses without cardiovascular diseases and 40 horses with valvular regurgitation or atrial fibrillation were examined. The examination included a clinical examination and standard electro- and echocardiographic examinations at rest. Additionally, the left ventricular septum (IVS) and the left ventricular free wall (LVW) were evaluated with tissue Doppler imaging at rest and after lung exercise. The peak systolic (S), early diastolic (E-Wave) and late diastolic (A-Wave) myocardial velocities were analysed with colour-coded Tissue Doppler and imaging (TVI) and with PW-Tissue Doppler Imaging respectively. Horses with atrial fibrillation (n =15) showed an increase of systolic myocardial velocities at rest (TVI: IVS: control: -3.92 +/- 1.54 cm/s, AF: -6.66 +/- 3.26 cm/s, p < 0.0001, LVW: control: 7.14 +/- 1.18 cm/s, AF: 10.03 +/- 3.10 cm/s, p < 0.0001) and after exercise (PW: IVS: control: -13.37 +/- 3.84 cm/s, AF: -17.15 +/- 3.93 cm/s, p < 0.005, LVW: control: 13.53 +/- 3.66 cm/s, AF: 17.95 +/- 3.50 cm/s, p < 0.001) compared to the healthy control horses. Furthermore, the group of horses with atrial fibrillation had higher early diastolic myocardial velocities then the control horses (TVI: IVS: control: 12.34 +/- 2.91 cm/s, AF: 16.70 +/- 6.13 cm/s, p < 0.001, LVW: control: -17.32 +/- 5.25 cm/s, AF: -22.25 +/- 5.19 cm/s, p < 0.01). Horses with mitral valve regurgitation (n =15) also had higher systolic myocardial velocities, but only at rest compared to the healthy control horses (PW: IVS: control: -8.36 +/- 1.78 cm/s, MVI: -10.99 +/- 3.13 cm/s, p < 0.005), while horses with aortic valve regurgitations (n = 10) had higher early diastolic myocardial velocities at rest (PW: IVS: control: 17.06 +/- 3.85 cm/s, AVI: 20.30 +/- 3.59 cm/s, p < 0.05), but higher late diastolic velocities after exercise compared to the healthy control horses (TVI: LVW: control: -8.62 +/- 3,7 cm/s, AVI: -11.86 +/- 2.05 cm/s, p < 0.05). The myocardial analysis with Tissue Doppler imaging was feasible at rest and after exercise. The increase of myocardial velocities in the horses with cardiovascular disease is probably the result of an increase in contractility due to increased filling pressure of the ventricle in the presence of adequate ventricular capacity.