Noninvasive Assessment of Systolic Left Ventricular Torsion by 2‐Dimensional Speckle Tracking Imaging in the Awake Dog: Repeatability, Reproducibility, and Comparison with Tissue Doppler Imaging Variables

Abstract

Left ventricular (LV) torsional deformation plays an important role in myocardial function. However, it has never been assessed in the awake dog, because magnetic resonance imaging and sonomicrometry have been the only methods available so far. Two dimensional speckle tracking echocardiography (STE), a new ultrasound imaging technique, provides a repeatable and reproducible noninvasive assessment of systolic LV wringing motion in the awake dog. Six healthy dogs were used to determine the repeatability and reproducibility of STE variables (study 1). These variables also were prospectively assessed in a population of 35 healthy dogs (study 2). Peak LV basal and apical systolic rotations were measured by STE from right parasternal short-axis views using automatic frame-to-frame tracking of gray-scale speckle patterns. Systolic LV torsion (LVtor, degrees ) was defined as apical rotation relative to the base. All within-day and between-day coefficients of variation were <20% (6.8-18.0%). Amplitude of apical systolic rotation was significantly higher (P < .001) than the basal value (5.4 +/- 3.2 degrees and -3.1 +/- 1.3 degrees , respectively). Global LVtor was significantly correlated with systolic longitudinal LV myocardial velocity gradient assessed by tissue Doppler (P < .05), but not with either systolic radial LV myocardial velocity gradient or the ratio of early mitral inflow velocity to early mitral annular velocity (Em/Ea). Speckle tracking echocardiography is a repeatable and reproducible method for assessing systolic LV torsional deformation. The combination of these new STE indices with tissue Doppler variables could provide a new approach for quantifying canine LV systolic function.