Feasibility, Within-Day and Between-Day Variability of Transthoracic Echocardiography in Sloths (Bradypus Variegatus and Choloepus Hoffmanni)

Bradypus variegatus (Xenarthra, Bradypodidae) and Choloepus hoffmanni (Xenarthra, Megalonychidae) are sloths from the tropical rain forest of the Caribbean and Pacific regions of Costa Rica. Because of their unique physiology and behavior, sloths have intrigued scientists, and several studies have already been conducted regarding blood pressure and heart rate variations. However, the use of transthoracic echocardiography (TTE) in these species has never been reported. The aim of the present study was therefore to determine the feasibility, and then the within-day (repeatability) and between-day (reproducibility) variability of TTE in sloths. A total of 36 TTE examinations (including a total of 1080 measurements) with continuous ECG monitoring were performed on 4 different days by a trained observer on 6 healthy, adult, sedated Choloepus hoffmanni (sexually intact females, age, mean ± SD [minmax] 5.1 ± 1.3 years [4.0-7.5]) from the Costa Rica Animal Rescue Centre. Standard transthoracic M-mode and two-dimensional mode measurements included left ventricular (LV) end-diastolic and endsystolic diameters and thicknesses, the LV fractional shortening, the E point-to-septal separation, the left atrium-to-aorta ratio, and the right atrial width-to-the left atrial width ratio. Pulsed-wave Doppler parameters included peak systolic aortic and pulmonary flow velocities as well as early and late diastolic mitral flow velocities. A general linear model was used to determine the within-day and between-day coefficients of variation (CV). The main results were the following: all measurements could be performed at each TTE examination. Most within- and between-day CV values (90%) were <15%, the lowest being observed for the right atrial width-to-left atrial width ratio (2.2%). These results suggest that TTE is feasible and reliable in sloths, and therefore can be part of the cardiovascular exploration in these species. Further studies are now required to determine the corresponding reference intervals.