Left Ventricular Radial and Circumferential Wall Motion Analysis in Horses Using Strain, Strain Rate, and Displacement by 2D Speckle Tracking

Background Noninvasive assessment of left-ventricular (LV) function is clinically relevant, but is incompletely studied in horses. Objectives To document the feasibility, describe the techniques, and determine the reliability of 2D speckle tracking (2DST) for characterization of LV radial and circumferential wall motion in horses. Animals Three Standardbreds, 3 Thoroughbreds; age 8-14 years; body weight 517-606 kg. Methods Observational study. Repeated 2-dimensional echocardiographic examinations were performed in unsedated horses by 2 observers and subsequently analyzed by 2DST. Test reliability was determined for segmental and for averaged 2DST indices (including strain, strain rate, displacement, and rotation) by estimating measurement variability, within-day interobserver variability, between-day interobserver variability, and between-day intraobserver variability. Variability was expressed as coefficient of variation (percent) and the absolute value below which the difference between 2 measurements will lie with 95% probability. Results 2DST analyses were feasible in 16 of 18 echocardiographic studies. The automated tracking was accurate during systole but inaccurate during diastole. Reliability was higher for radial compared to circumferential measurements. For radial strain, radial systolic strain rate, and radial systolic displacement, the test-retest variabilities ranged between 2.4 and 33.1% for segmental and between 4.1 and 16.1% for averaged measurements. Conclusions and Clinical Importance Systolic radial motion of the LV at the chordal level could be reliably characterized in horses by 2DST. Circumferential measurements were less reliable. Diastolic measurements were invalid because of inaccurate tracking. The clinical value of LV wall motion analysis by 2DST in horses requires further investigation.