Two-Dimensional Speckle Tracking for Quantitative Right Ventricular Wall Motion Analysis in Horses Affected by Equine Asthma

The aim of the present study was to evaluate the right ventricular (RV) wall motion by two-dimensional speckle tracking (2DST) in healthy horses and in severe asthmatic horses. Twelve warmblood horses were examined, of which six horses were clinically healthy and six horses suffered from severe equine asthma. 2DST echocardiographic examination was performed on the right ventricular myocardium in a standardised right-long-axis-view. The right ventricular free wall and the interventricular septum were divided into 3 myocardial segments each. Myocardial velocities, strain, strain rate and displacement parameters were measured in all 6 right ventricular myocardial segments. The early diastolic filling velocity at the transverse plane of the basal right ventricular (basRV) segment was significantly (P = 0.041) decreased in asthmatic horses compared to healthy horses. In the longitudinal plane of mid right ventricular (midRV) segment, the early diastolic filling (E) and late diastolic filling (A) velocities were significantly higher in asthmatic horses compared to healthy horses. Strain at the longitudinal plane of the basRV segment was significantly (P = 0.045) increased in asthmatic horses. Strain rate at the transverse apical right ventricular (apRV) segment during late diastolic filling stage was significantly (P = 0.041) lower in severe asthmatic horses. In general the differences happen at the level of the right ventricular free wall and not at the level of the IVS and there is an impact on the early and or late diastolic and not on the systolic function. In conclusion, 2DST is able to quantify right ventricular myocardial function in healthy horses and may be helpful in detection of myocardial alterations due to equine asthma.