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This Article Full Text Full Text (PDF) All Versions of this Article: 291/4/H1670    most recent 00097.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Syme, D. A. Articles by Jones, D. R. Search for Related Content PubMed PubMed Citation Articles by Syme, D. A. Articles by Jones, D. R.

Wave reflection effects in the central circulation of American alligators (Alligator mississippiensis): what the heart sees

¹Department of Biological Sciences, University of Calgary, Calgary, Alberta; ²Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, Newfoundland; and ³Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada

Submitted 23 January 2006 ; accepted in final form 12 May 2006

A large central compliance is thought to dominate the hemodynamics of all vertebrates except birds and mammals. Yet large crocodilians may adumbrate the avian and mammalian condition and set the stage for significant wave transmission (reflection) effects, with potentially detrimental impacts on cardiac performance. To investigate whether crocodilians exhibit wave reflection effects, pressures and flows were recorded from the right aorta, carotid artery, and femoral artery of six adult, anesthetized American alligators (Alligator mississippiensis) during control conditions and after experimentally induced vasodilation and constriction. Hallmarks of wave reflection phenomena were observed, including marked differences between the measured profiles for flow and pressure, peaking of the femoral pressure pulse, and a diastolic wave in the right aortic pressure profile. Pulse wave velocity and peripheral input impedance increased with progressive constriction, and thus changes in both the timing and magnitude of reflections accounted for the altered reflection effects. Resolution of pressure and flow waves into incident and reflected components showed substantial reflection effects within the right aorta, with reflection coefficients at the first harmonic approaching 0.3 when constricted. Material properties measured from isolated segments of blood vessels revealed a major reflection site at the periphery and, surprisingly, at the junction of the truncus and right aorta. Thus, while our results clearly show that significant wave reflection phenomena are not restricted to birds and mammals, they also suggest that rather than cope with potential negative impacts of reflections, the crocodilian heart simply avoids them because of a large impedance mismatch at the truncus.

blood pressure; blood flow; impedance; pulse wave velocity; harmonics