Echocardiographic Left Ventricular Structure and Function in Healthy, Non-Sedated Southern Sea Lions (Otaria flavescens)

Abstract

The goal of this study was to test transthoracic echocardiography as a method to characterize heart morphology and function in the southern sea lion (SSL) (Otaria flavescens) for health evaluation. Four clinically healthy captive SSLs (mean weight 110 ± 17.5 kg) were trained to be examined by transthoracic echocardiography at Mar del Plata Aquarium in Mar del Plata, Argentina. Two-dimensional guided M-mode images were obtained using a portable cardiovascular ultrasound system equipped with a 1.5 to 3.5 MHz convex 3S phased-array transducer. The mean left ventricular internal dimension at enddiastole 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 the end of the expiration and the beginning of the next inspiration. We successfully demonstrated that the in vivo structure and function of the SSL heart can be safely and effectively evaluated by transthoracic echocardiography in captive trained animals. These data have clinical and research implications for evaluating diseases of the cardiopulmonary system in pinnipeds.

Ultrasound images of the ascending aorta of anesthetized northern fur seals and Steller sea lions confirm that the aortic bulb maintains continuous blood flow

“…These results indicate that the entire Asc Ao is enlarged—not only the AB. The Asc Ao we measured in Steller sea lions (4.72 cm) is similar to aortic root diameters measured in bottlenose dolphins ( Tursiops truncatus ; 4.34 cm) (Chetboul et al, 2012) and southern sea lions ( Otaria flavenscens ; 4.78 cm) (Castro et al, 2018), suggesting that a large diameter aorta may be an adaptation for an aquatic lifestyle.…”

Comparative electrocardiogram in two anesthetized pinnipeds, the South American fur seal (Arctocephalus australis) and the Southern sea lion (Otaria byronia), with analysis of ECG parameters allometry

“…The cardiac morphology of SAFS is structurally similar to other mammals, with some changes that may be associated with their adaptation for breath‐hold diving (Guimarães et al, 2014; Pérez et al, 2008), but there are no similar anatomical studies for the SSL. In previous reports, our research group has provided one echocardiographic description of the left ventricular structure and function in the SSL (Castro et al, 2018) and detailed ECG descriptions of anesthetized SSL and SAFS adult females (Dassis et al, 2016, 2019). Electrocardiogram patterns of both species resembled the ECG tracing of terrestrial and marine mammals (Meijler & Meijler, 2011).…”