The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output [RESEARCH ARTICLE]

Morten Smerup, Mads Damkjaer, Emil Brondum, Ulrik T. Baandrup, Steen Buus Kristiansen, Hans Nygaard, Christian Aalkjaer, Cathrine Sauer, Rasmus Buchanan, Mads Frost Bertelsen, Kristine Ostergaard, Carsten Grondahl, Geoffrey Candy, J. Michael Hasenkam, Niels H. Secher, Peter Bie, and Tobias WangGiraffes – the tallest extant animals on Earth – are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. The pressure which may exceed 300 mmHg has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It remains enigmatic, however, how the normal-sized giraffe heart generates such massive arterial pressures.We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4&plusm...

Source: Journal of Experimental Biology - December 7, 2015 Category: Biology Authors: Smerup, M., Damkjaer, M., Brondum, E., Baandrup, U. T., Kristiansen, S. B., Nygaard, H., Aalkjaer, C., Sauer, C., Buchanan, R., Bertelsen, M. F., Ostergaard, K., Grondahl, C., Candy, G., Hasenkam, J. M., Secher, N. H., Bie, P., Wang, T. Tags: RESEARCH ARTICLE Source Type: research