Assessment of left ventricular size and function in horses using anatomical M-mode echocardiography

ObjectiveTo study the applicability of anatomical M-mode (AMM) for assessment of left ventricular (LV) size and function in horses, evaluate agreement with conventional M-mode (CMM), determine reliability, and establish reference intervals for AMM measurements.Animals98 horses; 13.1 ± 5.6 years; 538 ± 78 kg.MethodsTwo-dimensional and M-mode recordings were analyzed retrospectively. Standard LV dimensions and indices of LV function, including time intervals, were measured in CMM and compared with AMM studies in long-axis (lx) and short-axis (sx) views.ResultsThe percentages of measureable cycles were 99%, 97%, and 90% for routine LV studies in CMMsx, AMMsx, and AMMlx mode. For time intervals, ≥ 93% of cycles could be measured using AMM compared to a maximum of 77% using CMM. AMMsx measurements agreed well with CMMsx measurements for LV studies; the agreement of AMMlx with CMMsx was markedly lower. The LV ejection time and the duration of electromechanical systole, but not the LV pre-ejection period and the index of myocardial performance, showed fair agreement between methods. Intraobserver and interobserver measurement variabilities were low for most variables.ConclusionsAMM can replace CMM for assessment of LV dimensions in horses, but is not recommended for measurement of time intervals.