The duration of ventricular diastole relative to the cardiac cycle length is much shorter (46%) in varanids than in mammals (>70%).
Atrial systolic pressures were high (15–20 cmH2O), and atrial contraction was apparent in pressure waveforms from the ventricular cavum arteriosum and cavum pulmonale. Atrial contraction coincides with the short period of ventricular diastole and represents the filling agent for the ventricular cava.
Increased central venous flow coincides with ventricular contraction, which by reducing the intrapericardial pressure will promote the expansion and filling of the atria and central veins, implying a suctional element of cardiac filling.
Inspiration during spontaneous breathing will reduce central venous pressure, steepen the pressure gradient towards the heart and aid flow towards central veins. There is a positive correlation between the systolic level of central venous pressure and cardiac cycle duration.
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JOURNAL ARTICLE| 01 November 1984
Venous Return and Cardiac Filling in Varanid Lizards
1Department of Zoophysiology, University of Aarhus, DK-8000 Aarhus C, Denmark
WARREN W. BURGGREN
2Department of Zoology, University of Massachusetts, Amherst, MA 01003, U.S.A.
Accepted: 11 May 1984
Online Issn: 1477-9145
Print Issn: 0022-0949
© 1984 by Company of Biologists
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KJELL JOHANSEN, WARREN W. BURGGREN; Venous Return and Cardiac Filling in Varanid Lizards. J Exp Biol 1 November 1984; 113 (1): 389–399. doi: https://doi.org/10.1242/jeb.113.1.389
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