Echocardiographic Left Ventricular Structure and Function in healthy non-sedated Southern Sea Lions (Otaria flavecens)

Abstract

The goal of this study was to test transthoracic echocardiography as method to characterize heart morphology and function in the Southern Sea lion (SSL) for health evaluation. Four clinically healthy captive SSLs (mean weight 110.0 ± 17.5 kg) were trained to be examined by transthoracic echocardiography at Mar del Plata Aquarium (Mar del Plata, Argentina). Two-dimensional guided M-mode images were obtained using a portable cardiovascular ultrasound system equipped with a 1.5-3.5 MHz convex 3S phased-array transducer. The mean left ventricular internal dimension at end-diastole was 73 ± 5.8 mm, the mean interventricular septum thickness and posterior wall thickness at end-diastole were 9 ± 1.1 mm and 8.9 ± 2 mm, respectively. Fractional shortening and ejection fraction were 44.6 ± 1.7% and 74.4 ± 1.7%, respectively. The left atrial diameter-to-aortic root index was 0.92 ± 0.03. The most suitable position for obtaining good quality images was the left lateral recumbency (with slight inclination to 45°), with the probe placed on the left side of the thorax, ventrally just near the sternum, at the level of the caudal portion of the left pectoral fin. The best acoustic window in relation to the breathing cycle occurred between inspirations. We successfully demonstrated that the in vivo structure and function of the SSL heart can be safely and effectively evaluated with the use of transthoracic echocardiography in captive trained animals. These data have clinical and research implications for evaluating diseases of the cardiopulmonary system in pinnipeds.