Abstract: Background – Studies assessing operator/measurement variability of left ventricular wall thickness (LVWT) on serially obtained echocardiograms of cats with equivocal/mild wall thickening are rare. Objectives – We sought to evaluate the intraoperator (between-day) and interoperator measurement variability (reproducibility) of LVWT in cats. Animals – 10 cats with equivocal or mild wall thickening (LVWT 5 to 6.5 mm). Methods – Prospective reproducibility study. Cats underwent 9 echocardiograms by 3 operators on 3 different days within 1 week. LVWT of the interventricular septum (IVS) and free wall (LVFW) was measured from right parasternal long-axis (Lx) and short-axis (Sx) views with two-dimensional echocardiography (2D) and Sx M-mode. Reproducibility was quantified using coefficients of variation (CV) and 95% reproducibility coefficients (RC). Results – Intraoperator and interoperator CVs for maximum LVWT_2D (MaxLVWT_2D [6.3 and 6.6%, respectively]) were less than maxLVWT_M-modeSx (12.5 and 13.3%, respectively). CVs for LVWT_2DLx (5.5 - 8.2%) were less than LVWT_2DSx (10.4 - 10.6%). An ANOVA model revealed a significant effect of operator for MaxIVS_2DLx, MaxLVFW_2DLx, IVS_2DSx, LVFW_2DSx, IVS_M-modeSx, and LVFW_M-modeSx, and day for MaxIVS_2DLx (P < 0.05). Intraoperator and interoperator RCs for maxLVWT_2D were 0.9 and 1.0 mm, respectively, and maxLVWT_M-modeSx were 1.8 and 1.9 mm, respectively. Conclusions – Results suggest LVWT measurements by 2D are less variable than M-mode. LVWT_2DLx measurements are less variable than LVWT_2DSx. A change in maxLVWT_2D and maxLVWT_M-modeSx exceeding 0.9 mm and 1.8 mm, respectively, are likely beyond expected intraoperator variability. Clinicians should be mindful of measurement variability when judging progression/regression of LVWT on serial echocardiograms.
