Assessment of left ventricular function in horses with aortic regurgitation by 2D speckle tracking

Background Aortic regurgitation (AR) may lead to left ventricular (LV) dilatation, cardiac arrhythmias and heart failure. Close follow-up of horses with AR is therefore paramount to detect onset of cardiac decompensation. The aim of this study was to examine whether two-dimensional speckle tracking (2DST) can be used to detect altered myocardial function in horses with chronic AR compared to control horses. Speckle tracking was performed on short axis and long axis images of the LV in 29 healthy Warmblood horses and 57 Warmblood horses with AR. Radial, circumferential and longitudinal strain, strain rate and displacement were measured for each segment separately and the average was calculated over all segments. Data generated from the apical segments were not included in the analysis. Results Radial (SR) and circumferential (SC) strain were significantly higher in horses with moderate AR (average SR 75.5 +/- 24.3%, SC 19.3 +/- 3.2%) but not in horses with severe AR (SR 65.5 +/- 26.2%, SC 16.3 +/- 3.5%), compared to control horses (SR 54.5 +/- 18.0%, SC 16.8 +/- 3.0%). Longitudinal strain did not show significant differences, but longitudinal displacement (DL) was larger in horses with moderate (average DL 29.5 +/- 4.1 cm) and severe AR (DL 32.4 +/- 6.1 cm) compared to control horses (DL 25.7 +/- 4.0 cm), especially in the interventricular septum. Diastolic longitudinal strain rate was lower in early diastole in horses with severe AR (0.93 +/- 0.18/s) compared to controls (1.13 +/- 0.13/s). Conclusions 2DST is able to detect altered myocardial motion in horses with AR, which showed significantly higher radial and circumferential strain. Further research is needed to determine whether these findings contribute to a more accurate diagnosis and prognosis in clinical cases.