Comparison of the Repeatability of Echocardiographic Measurements from Different Modes and Views in Horses of Various Breeds and Sizes

The objective of this study was to compare the repeatability of echocardiographic measurements obtained from different echocardiographic modes and views in healthy adult equids of various sizes, breeds and thorax shapes.
Ten, free of cardiac disease, equids (body weight: 120 to 662 kg; age: 1 to 26 years) from various breeds were used in this study. Each animal was submitted to a standardized echocardiographic and Doppler protocol 3 times at 1 day interval. This protocol included the measurements of left and right ventricular, aortic, pulmonary, and left atrial parameters obtained from different views using the bidimensional (2D) or the motion (M) modes, and the measurement of several parameters of blood flow obtained from the pulsed wave Doppler mode. Repeatability of each measurement was estimated on the basis of the residual variance using a linear model and the coefficient of variation of repeated measurements. A two by two comparison of the repeatability of measurements performed in different views was performed using the residual variances in a variance ratio F test.
Results showed that repeatability of echocardiographic or Doppler measurements in equids of various sizes, breeds and thorax shapes are comparable to previously reported results in thoroughbred and standardbred horses. Left ventricular morphologic parameters showed a good repeatability in the classic M-mode right parasternal short axis (Sax) view at the level of the chordae tendinae, but the 2D-mode right parasternal long axis (LAx) four- chambers view appeared to offer an interesting alternative to measure them. This latter view also allowed obtaining the mostre repeatable measurement of right ventricular internal diameter. The left atrial diameter was maximal and most repeatable in the 2D-mode left parasternal long axisLAx four- chambers angled view, and the repeatability of the aortic diameter was best in the 2D-mode right parasternal long axisLAx five-chambers view. Finally, aortic systolic time intervals were more repeatable when measured from the Doppler mode as compared to the M-mode.
ThusIn conclusion, best repeatability of echocardiographic measurements in horses could be optimized following an echocardiographicthe following protocol in equids:
1-M-mode right parasternal short axis view at the level of chordae tendinae, to measure left ventricular morphologic parameters, and 2D-mode right parasternal long axis four-chamber as an alternative view.
2-2D-mode right parasternal long axis five-chambersre, to measure the aortic diameter.
3-2D-mode left parasternal long axis four-chambersre angled view, to measure the left atrial diameter.