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First published online September 16, 2005
Journal of Experimental Biology 208, 3637-3643 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01789
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Stroke volume and cardiac output in juvenile elephant seals during forced dives

Sheila J. Thornton1,*, Peter W. Hochachka1,{dagger}, Daniel E. Crocker2, Daniel P. Costa3, Burney J. LeBoeuf3, Daniel M. Spielman4 and Norbert J. Pelc4

1 Department of Zoology, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia V6T 1Z4, Canada
2 Department of Biology, Sonoma State University, 1801 East Cotati Avenue, Rohnert Park, CA 94928-3609, USA
3 Department of Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
4 Department of Radiology, Stanford University, Lucas Center for MR Imaging and Spectroscopy, Stanford, CA 94305, USA

* Author for correspondence (e-mail: thornton{at}zoology.ubc.ca)

Accepted 11 July 2005

The aim of this study was to examine the effect of forced diving on cardiac dynamics in a diving mammal by evaluating cardiac output and heart rate. We used MR Imaging and phase contrast flow analysis to obtain accurate flow measurements from the base of the aorta. Heart rate (fH) and cardiac output () were measured before, during and after dives in four restrained juvenile northern elephant seals, Mirounga angustirostris, and stroke volume (VS) was calculated (VS=/fH). Mean during diving (4011±387 ml min-1) and resting (6530±1018 ml min-1) was not significantly different (paired t-test; P<0.055). Diving was accompanied by a 20% increase in VS over the pre-dive level. Pre-dive, post-dive or diving fH was not significantly correlated with VS during any state. Diving VS correlated negatively with the bradycardic ratio (diving fH to pre-dive fH). In this study, the degree of bradycardia during diving was less than in previous pinniped studies, suggesting that the reduction in vagal input may contribute to the observed increase in VS.

Key words: diving, elephant seal, Mirounga angustirostris, cardiac output, stroke volume, magnetic resonance imaging


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[Abstract] [Full Text] [PDF]


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